Advice on eBay Amp Modules and PSU's please. [Archive]

DarrenHW

03-04-2016, 14:12

I'm in the process of DIY'ing a couple of subs and currently using an amp board. I'd like to experiment with a MiniDSP and power amp to allow for digital crossover, room correction, custom EQ, etc... I've looked at various pro power amps but I'm put off by XLR's and case fans so feel a MiniDSP with power amp offers the best solution and would like members opinions and suggestions from the vast array of amp modules and power supplies available from eBay.

I'm currently thinking of using this: http://www.ebay.co.uk/itm/111512871515?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT an assembled LJM L50.

http://i.ebayimg.com/00/s/NTU0WDE2MDA=/z/dKUAAOSwh-1W5WWH/$_57.JPG

with this: http://www.ebay.co.uk/itm/111862254814?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT an assembled 1200w SMPS.

http://i.ebayimg.com/00/s/NTcwWDg1OA==/z/dLQAAOxyVaBS1giP/$_57.JPG

The sub is a 4ohm LAB12 http://www.eminence.com/pdf/LAB_12C.pdf

I know the amp is a bit of a beast, but can an amp be too powerful? Looking at prices on eBay there is certainly very little financial advantage in using a less powerful module and the power supply requirements don't seem that crazy to me?

What's the opinion on using a SMPS, they seem to be quite popular in commercial amp boards? I know they can inject noise into the mains but the subs will not be plugged into my HiFi radial circuit, they will however both be plugged into the same ring main and if this project is successful I plan on adding a few more. In researching this (i.e. looking at what's commercially available and attempting to copy it) I've come across quite a few threads where users of commercially available subs complain of hum associated with big toroidals and a SMPS seem like a good way to avoid this.

I'm still in the process of putting together a list of viable hardware and not emotionally invested in one solution over another. If anyone has experience or opinions of the above, alternative suggestions etc... I'd be grateful for the input.

Puffin

03-04-2016, 17:19

I have built an LJM L12 Mosfet amp which has been reliable and very good sounding. This LJML50 appears to use the same Mosfets IRF9140 and the complementary IRFP140 drivers. I would be surprised if this did do 500w, it would depend on the PS. Are you intending to drive 4 or 8 Ohm speakers. What wattage do you need? How sensitive are the speakers. I could be wrong but I suspect you will need a split rail PS I am bit sure that an SMPS would be suitable. Others may say otherwise.

DarrenHW

04-04-2016, 07:47

Thanks for the reply Rob, I was hoping you'd chip in :).

I have built an LJM L12 Mosfet amp which has been reliable and very good sounding. This LJML50 appears to use the same Mosfets IRF9140 and the complementary IRFP140 drivers.

I think it was a thread you started that introduced me to LJM, which helped me to narrow down the available choices on eBay.

I would be surprised if this did do 500w, it would depend on the PS.

I too share your skepticism, the eBay listing for the amp states:

"Output power: 500W 8R 1000W 4R mono, supply voltage + - 50V DC, plus AC12-0-12.

400W 8R, 800W 4R mono, supply voltage + -45V DC, plus AC12-0-12.

300W 8R, 600W 4R mono, supply voltage + -38V DC, plus AC12-0-12."

and the power supply states:

"Main Output +/- 52 V (DC) [52 to 55]"

However, I don't think my power requirements are that high, I'm currently using a Monacor SAM 300-D (300w Class D Amp Plate) which integrates well with the volume control at half mast.

Are you intending to drive 4 or 8 Ohm speakers. What wattage do you need? How sensitive are the speakers. I could be wrong but I suspect you will need a split rail PS I am bit sure that an SMPS would be suitable. Others may say otherwise.

I'm using a Lab 12C:

"Power Handling (RMS)500 Watts
Power Handling (max)1000 Watts
Impedance4 ohms
Frequency Response25 to 120 Hz
Sensitivity88.9 dB 1W/1m"

Do you have an alternative suggestion for the power supply?

Puffin

04-04-2016, 08:44

I too share your skepticism, the eBay listing for the amp states:

"Output power: 500W 8R 1000W 4R mono, supply voltage + - 50V DC, plus AC12-0-12.

400W 8R, 800W 4R mono, supply voltage + -45V DC, plus AC12-0-12.

300W 8R, 600W 4R mono, supply voltage + -38V DC, plus AC12-0-12."

The voltage of an AC 12-0-12 tranny after rectification will be 16 - 18vdc. To get +/- 45 you would need secondaries of over 30vac (after rectification 42 - 45vdc)

Below is a list of the electric wattage current draw from differing size transformers and the Amps output.

https://www.cybermarket.co.uk/shop/power-supplies/voltage-conversion-help.html
200Va 140 Watts 0.58 Amps
300Va 210 Watts 0.88 Amps
400Va 279 Watts 1.15 Amps
500Va 350 Watts 1.46 Amps
600Va 420 Watts 1.75 Amps
700Va 490 Watts 2.04 Amps
1000Va 700 Watts 2.92 Amps
1500Va 1050 Watts 4.38 Amps
2000Va 1400 Watts 5.83 Amps
2500Va 1750 Watts 7.29 Amps
3 kVa 2.1 kWatts 8.75 Amps
4 kVa 2.8 kWatts 11.67 Amps
5 kVa 3.5 kWatts 14.58 Amps
6 kVa 4.2 kWatts 17.50 Amps
7 kVa 4.9 kWatts 20.42 Amps

I found this below on Diyaudio :-

http://www.diyaudio.com/forums/power-supplies/285885-toroidal-transformer-help.html

1. Would these Torods be suitable for powering the Chinese Naim 140 clone kits found on Ebay?
2. If so which would be preferred the 500va or 330va?
3. I am assuming these are a dual secondary voltage source 25 Volt X 2 to power the supply's for both channels from the single Toroidal?

If my assumptions are incorrect please put me on the correct path and recommend a toroidal transformer setup suitable for the Naim 140 2 channel amp.
Thank you.

Avel Y236801 500VA 25V+25V Toroidal Transformer - Parts Express

Avel Y236750 330VA 25V+25V Toroidal Transformer

The 330va should be fine as you will be looking at around 40 to 50 watts RMS from those supply voltages.

DarrenHW

04-04-2016, 10:29

Thanks Rob, I'm struggling to keep up :scratch: so I've looked back to my Quad 405 for inspiration. The 405 tranny (I believe) has ~35v secondaries through a bridge rectifier, 2 x 10000uF and outputs 50v. Am I over simplifying things here or could a simple circuit like this be implemented?

I'm also struggling with the Watts = Amps x Volts formula. CPC had this tranny: http://cpc.farnell.com/multicomp/mcfe500-35/transformer-500va-2-x-35v/dp/TF01407, 500 VA, 2 x 35V, 7.14 A. If I multiply 240 (volts) x 7.14 (amps) = 1713.6w :scratch: surely I'm not getting this right?

Puffin

04-04-2016, 10:52

Darren, I have built a lot of power supplies for my Gainclones and other stuff. These require a split rail supply (say +28vdc - 0 - -28vdc to 32v +/-) the simplest way is to use a twin secondary tranny and join the centre wires of the two pairs to make the 0v (voltage reference) I can't see from the pic of the board you have posted where the PS connects, but I would suspect that it requires a split rail supply (most do)

Then you then connect the separate wires to each ac side of the bridge rectifier and then take the dc + & - to the inputs on the amp and then connect the 0v leads to the board. Now......your board may already have rectification built in, if so than you connect the secondary ac wires to wherever it says and the 0v as well.

Your 405 seems to follow what is normal and I suspect is a split rail supply.

So far as the CPC tranny is concerned is it correct to multiply mains voltage by amps to calculate the current draw? EDIT : Yes, it seems it is.

When I was building amps I only really gathered enough knowledge to make something that worked:eek: Perhaps the adage a little knowledge........However they all worked and still do.....and I lived!

This worth a read re: real world power consumption.

http://www.diyaudio.com/forums/solid-state/168253-power-amplifiers-power-consumption.html

My understanding is that when you listen to music you are often only using a handful of watts (music power) UNLESS YOU WANT TO GO DEAF

DarrenHW

04-04-2016, 14:04

Thanks for the link, I'll read it and get back.

DarrenHW

06-04-2016, 17:22

I've read the above links (and many more threads to boot!) and I'm now going round in circles. I thought my original plan using a SMPS would give me a simple plug and play option with plenty of power on tap but I guess that was too simple. I really just can't get my head around why this isn't a viable option which only highlights how little I know about electronics and why I could only take this on in kit form.

I originally intended on using a Class D amp board and maybe I should look at this again. There are a few simple Class D modules that have onboard regulation and just need a tranny plugging in, they don't deliver the same amount of power but that only leaves me questioning whether I really need that amount of juice?

Qwin

06-04-2016, 18:57

I would leave this alone Darren.
Looking at the specified power requirements, the PCB connections and writing printed on the PCB - This board requires two power supplies.

One +/- DC supply of between 38-0-38 Vdc and 50-0-50 Vdc the actual voltage supplied will dictate the power output of the amp.

Additionally one +/- AC supply of 12-0-12 Vac.

I think you are struggling to see this, so maybe a bit too much to take on as a first build.
To be honest I can't understand why it would be made this way but check out the number of connections on the board. The voltage requirements are printed near by, actually for the ac input it says Min 12-0-12 max 18-0-18 on the board.
On the ebay add you can see on the pictures he has connected to all the power input points (6), both AC and DC so its not as though there is an option to use on board rectification, it needs both forms of supply to work.

Its clear as mud as to what is going on with the design, but the spec and pictures are consistent in what they are suggesting.

There are simpler things to try as a first project, Connexelectronic (Hong Kong I think) do a class D power amp module with on board SMPS, it is available in 300w or 500w versions. You simply connect the mains voltage and input from a pre amp and connect it to a speaker. Its a single channel device so two modules required for stereo.
Check it out http://connexelectronic.com/product_info.php/cPath/39_47/products_id/151

Also available from their French distributer who has other modules that may be of interest to you:
http://www.audiophonics.fr/en/amplifier-boards/irs500smps-mono-amplifier-class-d-500w-4-ohms-p-10092.html

DarrenHW

07-04-2016, 07:25

I would leave this alone Darren.
Looking at the specified power requirements, the PCB connections and writing printed on the PCB - This board requires two power supplies.

One +/- DC supply of between 38-0-38 Vdc and 50-0-50 Vdc the actual voltage supplied will dictate the power output of the amp.

Additionally one +/- AC supply of 12-0-12 Vac.

I think you are struggling to see this, so maybe a bit too much to take on as a first build.
To be honest I can't understand why it would be made this way but check out the number of connections on the board. The voltage requirements are printed near by, actually for the ac input it says Min 12-0-12 max 18-0-18 on the board.
On the ebay add you can see on the pictures he has connected to all the power input points (6), both AC and DC so its not as though there is an option to use on board rectification, it needs both forms of supply to work.

Its clear as mud as to what is going on with the design, but the spec and pictures are consistent in what they are suggesting.

Thank you Ken, you're absolutely right, I didn't realise the board required two power supplies. After reading your post and looking back through the listing I can see that now and completely agree that it's way too much for me to take on.

There are simpler things to try as a first project, Connexelectronic (Hong Kong I think) do a class D power amp module with on board SMPS, it is available in 300w or 500w versions. You simply connect the mains voltage and input from a pre amp and connect it to a speaker. Its a single channel device so two modules required for stereo.
Check it out http://connexelectronic.com/product_info.php/cPath/39_47/products_id/151

Also available from their French distributer who has other modules that may be of interest to you:
http://www.audiophonics.fr/en/amplifier-boards/irs500smps-mono-amplifier-class-d-500w-4-ohms-p-10092.html

Thank you for the suggestion, this is more what I'm looking for. I had looked at the Connexelectronic SMPS range and saw the IRS500SMPS but as I couldn't find any evidence of anyone using one I thought I'd misunderstood what it was, it looks ideal for both my application and non-existent skill set.

Thanks for putting this in a language I can understand :).

tubehunter

07-04-2016, 08:26

Sound great for the price.

Happy Days

http://www.ebay.co.uk/itm/271730743485?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Qwin

07-04-2016, 09:37

Thanks for putting this in a language I can understand :).

Your welcome Darren - I've had another look at the board you were considering and I can see there is an on board rectifier next to the +/- 12vac inputs on the centre of the upper edge of the PCB, so that makes sense. There is not enough information supplied for my liking, in terms of how much current has to be on tap with your power supplies etc. I think leaving this one alone is a wise move.

The Connexelectronic stuff is not very good in this respect either, documentation is non existent. I am looking at putting their IRS400SMPS modules for bass duties and their LM3886SMPS (Gainclone) modules for mid and tweeter on my active Yamaha NS-1000m speakers. I contacted them and they said this combination was ideal for a three way active set up and could be built into the speaker cabinet if I wished. I have one of the LM3886SMPS modules on test at the moment, it seems well made, has lots of safety devices built in, like DC detection/shut down on the speaker outputs, short circuit protection, under/over voltage protection etc. It also came with a full set of leads to plug into the PCB sockets, so I just had to connect these and I was in business. It gives out the tiniest amount of hum if you put your ear to the speakers, but this is a lot less than my Nakamichi AV Power amp, so nothing to worry about.

Quite a few people have built power amps using Hypex modules and used Connexelectronic SMPS's to power them, in preference to Hypex's own, the Hypex SMPS are very good but expensive, if they are being used to supply top notch and quite expensive modules like these, they must be pretty good SMPS's.

I think a pair of these amplifier modules with on board SMPS would get the job done for you. ;)

DarrenHW

07-04-2016, 15:51

Sound great for the price.

Happy Days

http://www.ebay.co.uk/itm/271730743485?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Thanks for the suggestion Duncan, I'm not sure it would have enough welly for the main sub's but they do look like a potential bargain for the 8" drivers I have, do you know if it's 200w into 4 or 8ohm?

P.S. When did you stop hating OP Amps? :D

Your welcome Darren - I've had another look at the board you were considering and I can see there is an on board rectifier next to the +/- 12vac inputs on the centre of the upper edge of the PCB, so that makes sense. There is not enough information supplied for my liking, in terms of how much current has to be on tap with your power supplies etc. I think leaving this one alone is a wise move.

The Connexelectronic stuff is not very good in this respect either, documentation is non existent. I am looking at putting their IRS400SMPS modules for bass duties and their LM3886SMPS (Gainclone) modules for mid and tweeter on my active Yamaha NS-1000m speakers. I contacted them and they said this combination was ideal for a three way active set up and could be built into the speaker cabinet if I wished.

None of the eBay modules seem to have great documentation, I guess it's not a problem if you're familiar with amplifier design (which I suppose is the market their aimed at) but it would be a lot easier to make a decission if proper documentation was available. One of the attractions of the LJM amps is that they have an account on DIYAudio, I think the Connexelectronics account has been banned.

I have one of the LM3886SMPS modules on test at the moment, it seems well made, has lots of safety devices built in, like DC detection/shut down on the speaker outputs, short circuit protection, under/over voltage protection etc. It also came with a full set of leads to plug into the PCB sockets, so I just had to connect these and I was in business. It gives out the tiniest amount of hum if you put your ear to the speakers, but this is a lot less than my Nakamichi AV Power amp, so nothing to worry about.

The safety features are a plus, although I've read a couple of posts that suggest some onboard safety devices are useless (not necessarily aimed at Connex). What's your opinion on these, have you had a chance to test?

Have you had a chance to listen to the LM3886SMPS, if so how would you compare it to the Nak?

Quite a few people have built power amps using Hypex modules and used Connexelectronic SMPS's to power them, in preference to Hypex's own, the Hypex SMPS are very good but expensive, if they are being used to supply top notch and quite expensive modules like these, they must be pretty good SMPS's.

I think a pair of these amplifier modules with on board SMPS would get the job done for you. ;)

It was the Hypex modules that first opened my eye's to this. Zu Audio use a Hypex UcD 400 and the Lab12 in their sub's and of all the commercial sub's I've looked at this had the greatest appeal. I agree Hypex amps have a good reputation so using them in conjunction with Connex SMPS's speaks volumes. I take it you have no concerns using a SMPS?

DarrenHW

07-04-2016, 16:36

I think a pair of these amplifier modules with on board SMPS would get the job done for you. ;)

I've just ordered a pair.

Qwin

07-04-2016, 21:07

Hi Darren
I've no doubt that the Hypex SMPS are better, they are supposed to run absolutely silent, but the Connex. are not too far behind, if I just needed one I would buy Hypex, but as I need several or with them on board the amp modules, it starts to mount up. I've not tested the safety features so don't know how effective they are.

I've been listening a lot to the LM3886smps module, as two channels of midrange, with the other four channels being covered by the Nakamichi on the 3 way active Yamaha's. They hold their own and I would say each sounds slightly different as opposed to one being better. I like the way the Gainclone does the midrange and vocals a lot. For the last few days I have been listening to the Gainclone module as a stand alone 2 channel power amp, being fed from my new Pro-Ject Pre Box RS and using a pair of old stand mount Tannoy M20 Mercury speakers and it sounds damn good. Got JazzFM on in the background as a freesat optical digital signal fed into my DAC and the piano solo is sounding so clear and tonally accurate.
I really rate this module, a stereo amp and power supply on a 100mm square board and it trounces something like a Quad 306 for transparency, realism and clean bass.
As Jez Arkless put it recently "Shockingly good for a "car radio chip" are those LM3886 They are a prime example of how sometimes in this game one can get lets say 85% of the performance that it's even possible to get for little money.... but then to get another 10% you need to add at least a nought to the cost"
Rod Elliot (ESP) described them as "Audiophile items with a caveat", that being you don't drive them to close to clipping, as the protection circuitry kicks in early and adds noise as it approaches activation.
Using SMPS over a linear supply is controversial, but I read a couple of threads from Gainclone builders who had tried just about every option and combination available and thought they sounded better using a SMPS.
Gainclone Chip Amps and class D for bass, using SMPS's offers a compact solution that is light weight and generates little heat, what's not to like.

Liking it a lot in fact, no hesitation in using LM3886SMPS to drive mid and tweeters on the Yamaha's, if the IRS400SMPS bass module sounds as good as the Nakamichi I will be well pleased. Be interested in your impression of the more powerful IRS500SMPS - If that's what you ordered?

DarrenHW

08-04-2016, 07:34

Hi Ken,

Yes, I ordered 2 x IRS500SMPS.

I know what your saying about the cost multiplier, I'm going to attempt to integrate 6 subs, front left, front right (both 12" sealed ~100 litre), rear left, rear right (both 8" sealed ~ 25 litre), centre (I'm thinking 10" sealed ~ 50 litre) and a dedicated AV sub (minimum 12" ported ~100 litre). This may sound ridiculous but I have had nothing but positive results adding a sub to these channels, obviously the frequency range is increased and bass response is improved but the biggest benefit is the "bed" that the bass provides which the other frequencies seem to "ride" on, improving the surround illusion. I don't know how well this is going to work, it wasn't my original plan but the more I've read the more compelling the argument is for one sub per channel. I should add at this point that I am probably what is referred to as a "bass head" primarily due to my exposure to Marco's Tannoys!

I know the Gainclone's have a strong following and they seem ideal for your application. When researching the above Peerless drivers I came across this http://mjanyst.weebly.com/audio.html where they have been used to power the subs!?! I agree the choice of a SMPS for audio is controversial (this was the concern I had when starting this thread, now I'm really glad I did!) but it's encouraging that they are considered by some to be the best option. I plan on strapping the amp / psu to the exterior of my subs so low heat, weight and size are all desirable attributes for me too.

I will report back with my impressions of the IRS500SMPS but this will not be in comparison to the Nak as I do not use it for subwoofer duties. A couple of months ago when the amp plate in my existing sub died I borrowed a REL Seri S5 which opened my eyes to what a sealed sub could do. Since the 44's made themselves at home in my lounge I've fancied trying a sealed sub and I'm very glad I did, integration with the 44's was good and after a little tweaking the sub audibly disappeared. I was offered a very good deal (for a sub with a RRP of £1600) but there were two factors that dissuaded me from buying it; i, it didn't go low enough for AV meaning I'd have to buy another ported sub, and, ii, it lacked a little slam compared to the 44's, rightly or wrongly I put this down to the ABR. With the expense I'd have gone too if I bought the Rel and added a ported sub I decided the DIY route would be worth investigating. My current objective is to build two sealed subs as helpers for the 44's with the primary focus being music and the benchmark being the Rel. Hopefully I can drag Marco round to help me setup the subs and I'm sure he'll be far more capable of reporting back on the sonic attributes of the amps than me.

Qwin

08-04-2016, 09:32

Sealed Woofer/Sub the more I hear this type of speaker the more I like it.

I recently came across an article saying the bass on the Yam NS-1000m didn't go that deep and started to roll off at about 50Hz. The Celestion 66's start to roll off closer to 60Hz, so why do both these speakers sound so full bodied. Its because they both are good in the upper bass, which is most of what we hear in music tracks, also the bass on sealed or ABR systems rolls off a lot slower than ported so more of the deeper bass is still at an audible level. In this respect the F3 (Minus 3dB) quoted figure can be misleading when comparing ported against sealed.
I researched the figures for the Yamaha's and Troels Gravesen confirmed this 50Hz roll off, both in simulation using T&S parameters for the bass driver in its stock enclosure volume and also with actual measured response of the speakers.
I went to the Wigwam Show a couple of weeks back and for me, one of the stand out moments was listening to a DIY lash up, the guy (Looper) is very good at programming and had written his own FIR filters for a DSP 3 way active system. He had used a 12" driver in a 90L sealed cabinet which he happened to have. Me and Gordon (Halfway Tree) just looked at each other, this was some of the best bass in the show, tight deep and tuneful. We asked what drivers he had used, the bass were Skytronic 902-222 he said they were 12" car speakers meant for ported boom boxes, but when he did the T&S numbers they were better suited to sealed cabinets of around 100L 120L being optimum. When he said he bought the pair, new off ebay for £47 I was gob smacked. I may buy some of these drivers they calculate as an F3 of about 32Hz in a 100L sealed cabinet. Like I say the sound stopped me in my tracks for the shear quality of the bass.

walpurgis

08-04-2016, 09:59

An ABR equipped speaker is a reflex type. The ABR taking the place of the bass port. They should not be regarded as a sealed, 'infinite baffle' speaker. Their characteristics are not the same and the bass curve using an ABR will be much the same as that produced using a reflex port, assuming the speakers are otherwise similar and similarly tuned.

Qwin

08-04-2016, 13:48

Because of the increased loading/damping compared to ported, I have always found ABR to react more like a sealed cabinet, but it is more like a halfway house I suppose. Like sealed I found ABR has less interaction with the room. The bass curve on Celestion 66's (ABR) is more like sealed than ported and is what triggered my comment. Most reflex designs drop off a cliff after the initial roll off, once port velocity has dropped they contribute zero to the output so the drop off is rapid. With infinite baffle and to a lesser degree ABR, they tend to roll off more gradually, these are generalised observations and there are always going to be exceptions, but that's how it comes across to me. :)

walpurgis

08-04-2016, 15:06

Posted by me three years ago.

http://theartofsound.net/forum/showthread.php?20759-Which-Tannoys-folks/page42

Qwin

08-04-2016, 18:59

Yep, Celestions own figures for the 66 from their brochure, which has been posted on my website for some time as well. Hump in the mid bass then steady roll off from 100Hz to 40Hz with a -4dB point at 50Hz. By the time it falls off the cliff at 40Hz its over 10dB down and contributing little.

Infinite baffle tend to start to roll off early but gently so its not that dissimilar in this respect.
It's not uncommon for ported designs to drop off the cliff just below the -3dB reference point.
This in my opinion is why Infinite baffle designs tend to sound as though they have more bass than the F3 figure would suggest and I would include the 66's ABR design in this camp, how many times have you heard people say 66's have great bass. With an F3 close to 60Hz you would not expect that, even taking the mid bass hump and emphasis into account. That's my perspective on this phenomenon, I'm not asking anyone to agree with this, just offering a point of view.

walpurgis

08-04-2016, 19:25

It should be born in mind that the response shown on the graph is not strictly representative of that obtained under normal listening conditions. Back in the seventies (and possibly still), it was more or less standard that a response sweep test would be made in an anechoic chamber. This usually produced an appearance of curtailed bass extension in the results.

Qwin

08-04-2016, 20:18

I think this was done in Celestions own anechoic chamber, I know they had one, so its highly probable, plus I think I read it somewhere.

DarrenHW

09-04-2016, 07:02

I went to the Wigwam Show a couple of weeks back and for me, one of the stand out moments was listening to a DIY lash up, the guy (Looper) is very good at programming and had written his own FIR filters for a DSP 3 way active system. He had used a 12" driver in a 90L sealed cabinet which he happened to have. Me and Gordon (Halfway Tree) just looked at each other, this was some of the best bass in the show, tight deep and tuneful. We asked what drivers he had used, the bass were Skytronic 902-222 he said they were 12" car speakers meant for ported boom boxes, but when he did the T&S numbers they were better suited to sealed cabinets of around 100L 120L being optimum. When he said he bought the pair, new off ebay for £47 I was gob smacked. I may buy some of these drivers they calculate as an F3 of about 32Hz in a 100L sealed cabinet. Like I say the sound stopped me in my tracks for the shear quality of the bass.

I know exactly what you mean, I was not expecting the results I achieved with the Rel, what really surprised me was how it filled gaps I was unaware of, the improvement to vocals for example was a revelation!

F3 @ ~32Hz at that sort of money is amazing value! How did you get that figure, if I put these values (http://www.discoworld.dk/manuals/skytronic/thielesmall_902127.pdf) into Winisd with a 100l sealed cabinet I get F3 @ ~42Hz? (I'm not questioning your calculations, more trying to understand where mine are wrong :scratch:.)

Qwin

09-04-2016, 09:43

The calculations were done by someone else, very lengthy calculation pages using Mathcad but in French, with lots of tables showing the effect of variables, so I hope I was understanding it correctly, using an on-line translator. I have found the T&S Parameters so might do the numbers myself later.
I think in French it was an ideal (empty) box with Qtc 0.707 @ 132L and F3 of 30.4Hz

Coming down in size to around 100L but allowing for it being well stuffed to give a virtual 120L moved it to an acceptable Qtc of around 0.77 and F3 of approx 32Hz.
I jotted these figures down for future reference. The chap at Wigwam said the figures seemed a fairly close match to what he had come up with. He reckoned 120L was ideal.
He put it in a 90L box because he had an old pair of knackered Goodmans Magisters and recycled their 90L cabinets. The drivers sounded very nice in these but I don't know if he had any data for the performance, either calculated or measured. I wish I could have spent longer with him but only found his room 15 minutes from the close of the show. I have since found his blog on the web so might follow up.

All I can say with certainty is it sounded deep and clean and very musical, you know, the kind of sound you could just sit and listen too for a long while. They went way deeper than my NS-1000M or 66's, I'm talking some of the best bass I have ever heard South of £10k. He was in a small room and they were pretty loud without any noticeable room effects, which plagued many exhibitors. This may have been partly due to the DSP filters he had written, but he did say he wasn't using room correction on the day. The results he was getting for the price of the drivers was mind blowing, regardless of cost, one of the best sounds of the day for me.
They are cheap enough that I might get some to play about with.

This was his stack:

https://therationalaudiophile.files.wordpress.com/2014/10/lh-speaker.jpg?w=158

Qwin

09-04-2016, 13:21

Darren - I just ran the T&S parameters through an on line calculator and it seems to agree with your results.
I got 119.6L as an empty sealed box, F3 of 41.85Hz, for Qtc of 0.707
If you account for a reasonable amount of stuffing increasing the virtual volume by 15 to 20L max, roughly 100L for F3 around 42Hz.

Not as deep as suggested but still well below what my Yamahas achieve, Troels Grevesen measured their in room response " As can also be seen the NS1000 really doesn't do much below 50 Hz"
This was using the stock 50L cabinet, I like the Yamaha's but I'm realistic about their bass output.

I just ran the Yams T&S Parameters through the same calculator and came up with a graph rolling off from 100Hz and F3 of 53Hz, remarkably similar to Troels measured results.

DarrenHW

10-04-2016, 17:39

All I can say with certainty is it sounded deep and clean and very musical, you know, the kind of sound you could just sit and listen too for a long while. They went way deeper than my NS-1000M or 66's, I'm talking some of the best bass I have ever heard South of £10k. He was in a small room and they were pretty loud without any noticeable room effects, which plagued many exhibitors. This may have been partly due to the DSP filters he had written, but he did say he wasn't using room correction on the day. The results he was getting for the price of the drivers was mind blowing, regardless of cost, one of the best sounds of the day for me.
They are cheap enough that I might get some to play about with.

I know where you're coming from, I've heard 66's in my lounge but they pale in comparison to the Rel and my (MD500 modded) 44's, subsequently I no longer plan on sourcing a pair of ABR's and building a pair of 66 clone cabinets. It' wasn't just the depth or impact of the bass that won me over but the sheer scale delivered without any negative effect to the musicality.

Darren - I just ran the T&S parameters through an on line calculator and it seems to agree with your results.
I got 119.6L as an empty sealed box, F3 of 41.85Hz, for Qtc of 0.707
If you account for a reasonable amount of stuffing increasing the virtual volume by 15 to 20L max, roughly 100L for F3 around 42Hz.

Well at least that confirms I'm using the software correctly, after reading your post and inputting the figures I found I couldn't understand how I had such different results. I used Winisd to run the numbers but I've not spent much time with it, there is a crossover section but I've not read up on how to use it yet. The figures I quoted don't take into account the effect of adding a high pass filter lower down the frequency range, from what I've read though I would be surprised if the Skytronics couldn't achieve that sort of output with the right crossover, which as you say for the money is phenomenal!

Not as deep as suggested but still well below what my Yamahas achieve, Troels Grevesen measured their in room response " As can also be seen the NS1000 really doesn't do much below 50 Hz"
This was using the stock 50L cabinet, I like the Yamaha's but I'm realistic about their bass output.

I just ran the Yams T&S Parameters through the same calculator and came up with a graph rolling off from 100Hz and F3 of 53Hz, remarkably similar to Troels measured results.

What I really like about the addition of a sub/s is that I think you keep the character of your stereo speakers, I've been running a Kef 30B (sealed) with B&O RL60.2's in my kitchen system for over 6 months, I still have the character of the RL's the Kef just fills in what's missing down to about 40Hz and really helps to fill the room with sound. When I heard 66's in my lounge I felt they weren't as fast as the 44's and I put this down to the ABR's in the 66's (again I don't know if I'm correct in this assumption). The ability to keep the speed of the 44's whilst improving the frequency response through the addition of subs is what appeals to me about this approach.

Qwin

10-04-2016, 20:16

Firebottle

11-04-2016, 06:53

This would have a smaller sealed box sat on top holding a 5" full range driver covering everything above 300Hz. ..

You will definitely need two subs with that high a crossover Ken IMO.

I appreciate the problems with only one, even with such a low crossover frequency setting that I use (38Hz), as I think you can 'feel' where the pressure wave is coming from even if you can't locate it L and R in the usual fashion.

I do love what a sub does though and wouldn't be without it. One of the better descriptions I read recently was that it provides the foundation for the music to play from.

:cool:

Qwin

11-04-2016, 07:38

Hi Alan - No subs with that set up, a 12" Woofer crossing at 300Hz.
I heard the Skytronic 12" in a 90L cabinet crossing at this frequency, at the Wigwam show and was very impressed with the results. It was paired with a 4" Peerless Mid (no longer made) and a tiny Monacor Tweeter in a separate cabinet, as per my picture a few posts back. I was thinking along similar lines but using a full range mounted on top instead, to keep the drivers close together for time alignment. You Probably got confused with my ramblings, which jumped about topic wise, lots of things I would like to try.

I might get round to trying subs again one day, my room does not allow free space for the sound to get away from the cabinet and I get poor results using a ported sub, which I just sold on, but a sealed pair with directed output might be better. On many of the single sub set ups I have heard, yes they were omnidirectional in that you could not pin point them in the room, but they didn't sound part of the stereo image either and I tired very quickly of the overall presentation. It's tricky to get right but I appreciate what they can offer.

DarrenHW

11-04-2016, 08:59

I'm not a big fan of the classic arrangement, using a single sub.
It certainly has never worked for me, in three different houses (rooms) using a different main speaker each time.

I had the pleasure of listening to a diy 3 way plus two subs that worked really well.
He had forward firing subs and had the main speakers sat on top with them styled and proportioned to look like one cabinet, looked like an additional woofer at the bottom and looked really smart. The subs were sealed box and not ported.

Balls to the omnidirectional effect of subs, this was his approach, treat them like another driver, must say I did like the results.

One thing, he pushed home to me, that you must use a crossover of some kind to cut off the bass output from the main woofers and hand the rest of the signal over to the subs from this point. If you let the woofers roll off naturally, in most cases it will be too slow and muddy what the sub is doing, he used a 24dB/octave filter to do this and on his powered subs had the ability to bypass the on-board filters and just use the pre filtered input from his crossovers to feed the subs plate amps.

There was something very logical with this approach and I promised myself if I ever dabbled with subs again, I would try and copy this.

I'd not thought about this, it does make sense although I don't know whether this could be achieved with a passive crossover in the main speakers?

I've been tempted to build some that would sit under the NS-1000m, with exactly the same width to give the same visual effect that he achieved. I think someone else has done this already with the Yammies.

I'm thinking of using this approach as well, not only does it save space but replaces speaker stands providing what I believe could be a more inert footing for the main speakers. The only concern I have with this is the effect on / of rear wall reinforcement, I don't know how rear wall reinforcement can be optimised with the reduced flexibility of placement this would allow. I'm hoping that the use of DSP for the subs would make it possible to optimise the placement for the mains and adjust the subs to suit.

So many possible projects to consider, I have a sketch pad full of ideas for a 100L sealed woofer using the skytronic driver, or for 9/10Hz lower bottom end, the SB-Acoustics 12". This would have a smaller sealed box sat on top holding a 5" full range driver covering everything above 300Hz. Google the PRV 5MR450-NDY-4 professional mid range made in Brazil, 160-16,000Hz so it almost works as a full range, with 225watts RMS into 4 ohm setting it apart from most full range drivers. There is a long thread on diyaudio about this driver and Vic at Transfi-Audio, who designed and makes my linear tracking tone arm swears by this driver in his open baffle designs. Back to the sketch pad..............

I looked into OB's and was advised to adopt Vic's approach (at the time he was using Alpair P12's), I spoke to Vic about implementing this in a 5/7 speaker setup but attempting this in my room would have been quite a gamble. As much as I want to pursue the OB route it won't be in this house, I won't live here forever but as long as I do I'm sticking with the Celestions, I just don't have the time or energy to start over.

DarrenHW

11-04-2016, 09:08

You will definitely need two subs with that high a crossover Ken IMO.

I appreciate the problems with only one, even with such a low crossover frequency setting that I use (38Hz), as I think you can 'feel' where the pressure wave is coming from even if you can't locate it L and R in the usual fashion.

I do love what a sub does though and wouldn't be without it. One of the better descriptions I read recently was that it provides the foundation for the music to play from.

:cool:

Hi Alan, We spoke about your sub at Marco's but I can't remember the details, I'd be interested in the specifics if you'd like to share? Your post also reminded me I've been so wrapped up with work I haven't bought a copy of Sade's Soldier of Love, come to think of it I don't think I've bought any music so far this year :(

Firebottle

11-04-2016, 10:11

Hi Darren, my sub is a copy of the REL Stadium.

I made the MOSFET power amp and filter unit myself, then bought an enclosure kit that matched the size of the Stadium.
After experimenting with some cheap 10 inch woofers in an isobaric configuration I fitted a single 10 inch 'car sub' driver.

This was purchased a long time ago from a shop in Soho Road, Handsworth, for something like £22 if memory serves me correctly.
You can get good performance from the 'car sub' drivers.

:)

DarrenHW

11-04-2016, 11:15

I made the MOSFET power amp and filter unit myself

Thanks Alan, was your filter along the lines of the KMTech PCB's?

Qwin

11-04-2016, 11:26

I'd not thought about this, it does make sense although I don't know whether this could be achieved with a passive crossover in the main speakers?

I looked into OB's and was advised to adopt Vic's approach (at the time he was using Alpair P12's), I spoke to Vic about implementing this in a 5/7 speaker setup but attempting this in my room would have been quite a gamble. As much as I want to pursue the OB route it won't be in this house, I won't live here forever but as long as I do I'm sticking with the Celestions, I just don't have the time or energy to start over.

Yes Darren, it can be done in the passive crossover. You need a bandpass filter similar to your midrange filter, so it cuts off the higher frequencies getting to the woofer but also cuts of the very low frequencies, so the woofer only sees the band left in the middle. Eg. combining say a low pass of 500Hz with a high pass of 80Hz. You then use a low pass filter set at the same 80Hz frequency to pass what's left below this to the Sub.

As an alternative, you could use the subs own low pass filter and set it to the same 80Hz value as the band pass on your woofer. At least if you use your own filters you can pick the slope etc. Very easy to experiment with all of this in a DSP environment and create suitable filters. This is why many of the better subs have the ability to bypass their on-board filters and allow users to use their own.

I think Vic has tried most of the Alpair drivers, but his latest OB trials are with the PRV driver, he was telling me yesterday that he preferred it, "super efficient and to my ears smoother than the Alpairs" he also mentioned the PRV doesn't flap about in OB use like the Alpairs do. I was considering this driver in a small sealed box, the thread on Diyaudio has examples and measurements for this type of application and even sound bites of the results. Too many possible directions to follow at the moment, I'm working a lot of them through on paper and looking at costs, at this point I don't know which, if any, I will mock up. This is what happens after going to a show, I end up with lots of things I want to try out and maybe put my own slant on. :)

Edit: You could use multiple PCB's from KMTech to achieve these filters and I think they do a three way plus sub as a single board. My original layout for the Yammies had an output for a sub, the filters were cascaded so all of the bass could be handled by the Yammies or by changing some jumper leads, it would cut the lower bass to the Yammies and send this to a separate output socket for the sub.

DarrenHW

11-04-2016, 13:37

Yes Darren, it can be done in the passive crossover. You need a bandpass filter similar to your midrange filter, so it cuts off the higher frequencies getting to the woofer but also cuts of the very low frequencies, so the woofer only sees the band left in the middle. Eg. combining say a low pass of 500Hz with a high pass of 80Hz. You then use a low pass filter set at the same 80Hz frequency to pass what's left below this to the Sub.

As an alternative, you could use the subs own low pass filter and set it to the same 80Hz value as the band pass on your woofer. At least if you use your own filters you can pick the slope etc. Very easy to experiment with all of this in a DSP environment and create suitable filters. This is why many of the better subs have the ability to bypass their on-board filters and allow users to use their own.

I see, that's my lack of knowledge coming into play again, I thought the crossover arrangement was proportional to the cabinet / woofer relationship, I've still got a lot to learn.

I think Vic has tried most of the Alpair drivers, but his latest OB trials are with the PRV driver, he was telling me yesterday that he preferred it, "super efficient and to my ears smoother than the Alpairs" he also mentioned the PRV doesn't flap about in OB use like the Alpairs do. I was considering this driver in a small sealed box, the thread on Diyaudio has examples and measurements for this type of application and even sound bites of the results. Too many possible directions to follow at the moment, I'm working a lot of them through on paper and looking at costs, at this point I don't know which, if any, I will mock up. This is what happens after going to a show, I end up with lots of things I want to try out and maybe put my own slant on. :)

I do find full range drivers a tempting proposition mainly due to their simplicity and size. I know there are arguments for and against but to me it seems the positives outway the negatives.

Edit: You could use multiple PCB's from KMTech to achieve these filters and I think they do a three way plus sub as a single board. My original layout for the Yammies had an output for a sub, the filters were cascaded so all of the bass could be handled by the Yammies or by changing some jumper leads, it would cut the lower bass to the Yammies and send this to a separate output socket for the sub.

I have considered taking the Celestions active but again it comes down to time and energy or the lack there of. The biggest factor for me is that due to space considerations I can't use the same speakers for all AV channels which really is the path I want to follow, another reason I'm interested in FR drivers.

Firebottle

11-04-2016, 14:31

Thanks Alan, was your filter along the lines of the KMTech PCB's?

No this was years ago, the filter is based on an MF10 filter chip and a variable clock circuit.

DarrenHW

11-04-2016, 14:36

Still way beyond my level of understanding, I just wondered whether there was an easier way to implement the crossover.

Qwin

11-04-2016, 14:51

Qwin

11-04-2016, 15:11

Still way beyond my level of understanding, I just wondered whether there was an easier way to implement the crossover.

Your trying to achieve something complicated so there is no easy solution if you can't design your own passive crossover (which I couldn't do, its harder than it looks).
Going the active DSP route, you would have so many channels, its hard to say if any off the shelf solution, either hardware or software, would be suitable.

If you kept your speakers passive for mid/tweeter and used one amp channel to drive this, you could use an ASP like KMTech's boards to actively separate Woofer and Sub frequencies at line level, you would need an amp channel for the woofer, and presumably the Sub would be built in, that's about as simple as you can, get it down to, if you want to cut the woofer off early. You need to insert some form of band pass filter.
Otherwise just stick to what you have and let the Sub work with the natural roll off of the woofer.
If you were talking 2 channel I would say persevere with clipping the signal to the woofers, but doing this for multi channel with multiple subs is never going to be easy.

DarrenHW

11-04-2016, 17:37

Going fully active with an AV set up means a lot of amp channels, maybe a combination of passive for mids/tweeters and active for woofers, separating out the lower bass in the active crossover to allow subs with built in amplification. Still end up with a lot of amps. You could always look at the Professional gear and use active mid field speakers with everything on board and feed them from a line level receiver with no power amplification and acting purely as a multi channel decoder/pre amp. The higher end AV stuff seems to go that route these days, splitting the receiver/Power amp functions into separate boxes.

Your trying to achieve something complicated so there is no easy solution if you can't design your own passive crossover (which I couldn't do, its harder than it looks). Going the active DSP route, you would have so many channels, its hard to say if any off the shelf solution, either hardware or software, would be suitable.

If you kept your speakers passive for mid/tweeter and used one amp channel to drive this, you could use an ASP like KMTech's boards to actively separate Woofer and Sub frequencies at line level, you would need an amp channel for the woofer, and presumably the Sub would be built in, that's about as simple as you can, get it down to, if you want to cut the woofer off early. You need to insert some form of band pass filter.
Otherwise just stick to what you have and let the Sub work with the natural roll off of the woofer.
If you were talking 2 channel I would say persevere with clipping the signal to the woofers, but doing this for multi channel with multiple subs is never going to be easy.

The FR AV setup is not a project that I'll be starting for quite a while, it is my long term plan but certainly not something I'll be undertaking this year. In a nutshell I'm thinking of going with active 2 way speakers 1 x full range, 1 x woofer (both channels controlled and x-over via MiniDSP), with AV subs as required (again using MiniDSP which with a splitter would give me the option of 4 subs but only on the .1 channel). If I were to do this tomorrow I'd be looking at something like the Goldwood GW-1858 (which I believe Vic uses in his OB's) which if memory serves me correctly can get down below 30Hz in a H frame. The amp for the FR wouldn't need to be a monster possibly something like a Gainclone and the woofer could be powered by something Class D (in place of the popular iNuke). Maybe I'm oversimplifying things here but this project will be a while in the making so plenty of time for more research. This is part of my motivation to familiarise myself with amp modules, active x-overs, DSP etc... but for my attention is only on the subs.

DarrenHW

15-04-2016, 17:49

Firebottle

15-04-2016, 18:41

The mains input is at the other end by the look of it Darren.

Yes definitely, with another look, the 400V reservoir cap is at the other end :thumbsup:

DarrenHW

15-04-2016, 18:51

The mains input is at the other end by the look of it Darren.

Yes definitely, with another look, the 400V reservoir cap is at the other end :thumbsup:

Sorry Alan, I've not made it clear, I'm not sure where the audio input goes, the mains input is so well labeled even I couldn't get it wrong :).

Qwin

15-04-2016, 20:07

The IRS500SMPS's have arrived, the dimensions are on the site but it was still a surprise to see them in the flesh:

http://i1324.photobucket.com/albums/u606/drtwas/IMG_6045_zpsyajrwc0x.jpg (http://s1324.photobucket.com/user/drtwas/media/IMG_6045_zpsyajrwc0x.jpg.html)

Despite being a simple module it still has me confused as to how to hook up the input. The board is labeled +In and -In which I'm assuming is where I connect to (red and black arrows) but the Ground label on the board made me question whether this is correct, I think this is just for a balanced input but I'm not certain.

http://i1324.photobucket.com/albums/u606/drtwas/IMG_6047_zpsvub1ax3j.jpg (http://s1324.photobucket.com/user/drtwas/media/IMG_6047_zpsvub1ax3j.jpg.html)

I'm also not sure what connector to the left is, it looks like it could be for an optional switch (it does "ON" above it). I've emailed Connex asking for some documentation so hopefully this will have the answers. I'm a big believer in RTFM, I just need the FM!

Hi Darren - Yes, its balanced input on this model, says so in the product description on their website. So connect the audio input as you have shown for unbalanced RCA, connect signal to + (red arrow) and the Coax shield/Ground to the - (black arrow).

The "ON" is difficult to see, but some of these modules have a standby facility, I think it is more likely relating to the LED next to it, which looks like the "ON" light.
Also according to the spec. this model has connections for adding a volume pot to control the gain level, I can't see any other connections on the board, so the bridged pins and third pin are probably Input/Output/Ground for connecting a pot. Screw some stand off's on each corner of the board to lift it clear of your work surface, connect the mains only and power the unit up. See if the LED next to the word "ON" lights up, on my Gainclone version it is a Green one of incredible brightness, takes a couple seconds to come on due to the soft start.

For a switch, just switch your mains supply going into the big green terminal block at the other end, I switch both poles. You wont get clicks or bangs as the soft start/stop works well. On my Gainclone version I can switch the module on off at the supply while all my other gear is "hot" and it produces no noise at all through the speakers.

Wait for Connexelectronic to respond, as they are usually pretty quick, but I am pretty sure they will confirm what I have said.

DarrenHW

16-04-2016, 06:30

Thanks Ken, your suggestion that the other connector is for a pot and it's the LED that's labeled makes more sense. I'm still waiting on a response from Connex but I'm in no rush as I won't have time to hook up the amp for a couple of days.

Qwin

16-04-2016, 08:56

Yeh, slow but steady is the way to go.
I read the spec again for this module and it has an auxiliary power out, of -15/0/+15Vdc so there will be another small 3 pin socket somewhere on the board. There wouldn't be any reason to bridge the pins on this, but it makes sense to bridge the input/output when a pot is not in place, adding more weight to the theory that the connector near the "ON" lettering is for a pot.

When I asked a question before buying my module, it was answered after a couple of days, time differences etc mean it is going to take at least two days, It's the same when I talk to Burson in Australia.

I also had to work out what the connections were for on my board. Using a multimeter helped identify the Auxiliary power. The speaker connection and power inputs were fairly obvious, with a bit of thought, looking at the specified features and what sockets I had left, I managed to work it out. It didn't stop me getting the audio input connections the wrong way round though, on my 2 channel (unbalanced) it has three pins, left/right/ground, I presumed on the harness provided it would be black for left, red for right and yellow for ground - WRONG! the yellow was for left channel and black is for ground. My speaker output was green for right, yellow for left and a black on each channel for ground, so watch out for unexpected colour schemes.

From my experience it looks like their colour scheme on the harnesses is red for input signal, green for output to speaker and black for grounds(-).
But don't bank on it.
You did get harnesses supplied with yours, didn't you?

On the seven pin socket, the four pins on the right are for Ground, Shut Down, Mute and Thermal warning, these can be left for now, you can consider using these features once you have the unit working correctly in its basic form. I wouldn't put it straight into a case, make a lash up to experiment with, until you are sure what everything does and how to wire it. Take a look at my Gainclone lash up on my NS-1000m Tweaks thread. I fed this straight from my pre amp and connected up an old set of speakers till I was happy with it. Once done, I put it into my active set up, with a bit of confidence that I wasn't going to blow any of the active crossover components or the Yamaha drivers.

DarrenHW

26-04-2016, 16:29

It's been awhile since my last update, sorry for not responding to your last post Ken, I've been flat out at work.

I hooked up one of the boards yesterday as illustrated above using the supplied harnesses, everything was fine but there was quite a lot of hum. I checked out all the usual suspects but could only eliminate it by connecting the ground from the harness (along with the negative) to the negative of the RCA. I don't know whether this is something I should be doing or not, I've not heard back from Connex but as I bought the boards second hand from DIYAudio (I didn't mention this in my email to Connex) I've no real cause to complain.

I'm connected to the Sub Out from the Oppo to a MiniDSP and into the IRS500SMPS. I've only implemented a basic crossover in the MiniDSP but initial results are encouraging, I'm leaving everything to settle in for the next couple of days as I won't have any free time but I'm hoping for a long weekend so spend some time familiarising myself with the MiniDSP software, here's hoping anyway!

Qwin

27-04-2016, 09:36

Not sure from your description how you have connected things.

Any chance you could put up a sketch of the connections you've made?

DarrenHW

06-05-2016, 07:52

The RCA is wired like this;

http://i1324.photobucket.com/albums/u606/drtwas/Ground_zpsnnweqrb6.jpg (http://s1324.photobucket.com/user/drtwas/media/Ground_zpsnnweqrb6.jpg.html)

the two wires running to the sleeve being the -In and GND from the board, without the ground connected hum was quite audible.

The bank holiday didn't yield as much free time as I'd hoped but I was able to spend some time configuring the MiniDSP. I currently have the cut off frequency at 35Hz with a LR 48db filter, I arrived at these settings using the MiniDSP coefficients calculator with the Lab12 specs and then tuning by ear. I'm torn between using a LR and Butterworth filter, the LR seems to give slightly deeper bass with slightly more impact, where as the BW filter seems to integrates better with the main speakers.

Within the filtered frequency range the sub is doing a very good job of disappearing giving little audible clue to it's location and integrating very well with the mains. Outside (and above) the filtered frequency range the sub is audible at times. I believe this is cabinet resonance of some sort, the cabinet is constructed completely from MDF and is only screwed together to allow me to make changes to the cabinet. Anyone who's worked with MDF will know it's far from the best material for a screw fixing so this is one potential cause, there is also a lot of room for improvement in the bracing I have applied and the construction of the feet. My next step is to create a 25 litre cabinet, this is not intended for the Lab12 but I'll cut a baffle to allow me to install the Lab12. Being a smaller cabinet, applying adequate bracing shouldn't be as much of a challenge and will also allow me to hear the difference cabinet volume makes.

I'm still encouraged by the results thus far and really do need to get some more hours on the components (maybe 20 hours at most on the MiniDSP and IRS500SMPS, 100+ hours on the Lab12) and address the cabinet issues before I can make a proper judgement on SQ. I can say without doubt that my DIY efforts fall short of the Rel Serie S5 but seem to be heading in the right direction. The Rel is a fully polished retail product, my screwed together MDF box is still a work in progress but it does dig slightly deeper and hit harder and faster, although whether I can elevate SQ to that achieved by the Rel remains to be seen.

Qwin

06-05-2016, 08:50

Wiring - Yes, this is the standard connection for RCA to Balanced.
What you label as sleeve should be connected to the Cold(-) and the Gnd balanced connections on the amp board.

Can't comment on the minidsp settings as I've never used it, but I might be dabbling with that soon.
I've just purchased the UMIKE-1 and downloaded REM to take some measurements and see what is going on with the Yamahas.
MiniDSP it is a great development tool for crossover design.

DarrenHW

06-05-2016, 10:21

Thanks for the clarification Ken :thumbsup:

I didn't mention in my previous posts how happy I am with the IRS500SMPS. Once connected properly there is no discernible hum, it runs at very low temperature, it has more than enough power and the soft start / anti thumb works very well.

The MiniDSP is a joy to use, real time changes make it very easy to dial in, how come your thinking about one? I caught up with your Yammie thread and I thought you were very happy with the KMTech / Burston combo, or is this for something else?

I'll most likely pick up a UMIK-1 myself, I haven't taken any measurements yet so I'm looking forward to what hear improvement can be made with room correction.

On a side note you have given me reason to reconsider the direction I'm taking with the subs, this current project was always intended for AV and as a learning tool for implementing stereo subs for the 44's. I can't help thinking instead of supplementing the 44's I'd be better off starting over with a FAST implementation of the PRV 5MR450-NDY-4. In the DIYAudio thread xrk971 says in a sealed cabinet he's crossing over to a single sub at 170Hz, my natural tendency would be to dismiss the suggestion of crossing over to 1 sub at so high a frequency but he is clearly far better educated in these matters than I am so I'd be a fool to dismiss this based on my own prejudice, what are your thoughts?

This is not something I'd consider for main speakers but it would be a good way to implement the surrounds. Solely for surround speaker purposes I'd rather partner a PRV 5MR450-NDY-4 with an 8" woofer to get down to ~80Hz and then cross to AV subs at the processor, is that just crazy? I've not done any real research into this but I've been spurred on as a friend brought a Fender Deluxe 85 and a bass guitar round the other day and this has re-ignited my desire to go H-frame OB for my mains.

Qwin

06-05-2016, 21:33

Thanks for the clarification Ken :thumbsup:

1). I didn't mention in my previous posts how happy I am with the IRS500SMPS. Once connected properly there is no discernible hum, it runs at very low temperature, it has more than enough power and the soft start / anti thumb works very well.

2). The MiniDSP is a joy to use, real time changes make it very easy to dial in, how come your thinking about one? I caught up with your Yammie thread and I thought you were very happy with the KMTech / Burston combo, or is this for something else?

3). I'll most likely pick up a UMIK-1 myself, I haven't taken any measurements yet so I'm looking forward to what hear improvement can be made with room correction.

4). On a side note you have given me reason to reconsider the direction I'm taking with the subs, this current project was always intended for AV and as a learning tool for implementing stereo subs for the 44's. I can't help thinking instead of supplementing the 44's I'd be better off starting over with a FAST implementation of the PRV 5MR450-NDY-4. In the DIYAudio thread xrk971 says in a sealed cabinet he's crossing over to a single sub at 170Hz, my natural tendency would be to dismiss the suggestion of crossing over to 1 sub at so high a frequency but he is clearly far better educated in these matters than I am so I'd be a fool to dismiss this based on my own prejudice, what are your thoughts?

5). This is not something I'd consider for main speakers but it would be a good way to implement the surrounds. Solely for surround speaker purposes I'd rather partner a PRV 5MR450-NDY-4 with an 8" woofer to get down to ~80Hz and then cross to AV subs at the processor, is that just crazy? I've not done any real research into this but I've been spurred on as a friend brought a Fender Deluxe 85 and a bass guitar round the other day and this has re-ignited my desire to go H-frame OB for my mains.

1). That's great news, my unit is quieter than the Nakamichi so good that yours is also quite.

2). I'm very sensitive to the sibilant distortion most three way speakers have at the crossover point, mid to tweeter. Still getting a bit on the Yammies which I'm trying to eradicate. I can borrow miniDSP to try and achieve this. But still they are the best I have had them.

3). Umik-1 is made to work with REW so straight forward set up as it's recognized by the software.

4).Spookey – Did I mention the PRV 5MR450-NDY to you?
I've been thinking of it mated with an AB Acoustics 12” woofer crossed at 300hz.
The PRV 8ohm is preferable to the 4ohm as it calcs in a bigger sealed box. Qtc 0.707 gives about 6.8L but only 1.5L or there about's for the 4ohm.
Be careful of crossing Subs at a high frequency. They tend to roll off quickly so the bass will not be deep if you do. The figure they quote for how deep they go, is usually based on the lowest crossover point they offer. The -3dB point of reference is directly related to the crossover point, as this moves up so does the -3dB frequency. Check out some of the frequency plots for subs taken at various crossover settings. In the example you quote, his diy sub is I believe, multi driver and is EQ'd in minidsp so characteristics may be considerably different. PRV recommend a crossover point of 290Hz or higher to achieve full output on the driver, which is too high for a sub and why I am considering a large woofer.

5). No not crazy, I was thinking the same, using a pair of 8” Scanspeak woofers crossing at 50Hz to a pair of BK subs. I even drew this up, all drivers including subs were in sealed cabinets for fast tight sound.

DarrenHW

07-05-2016, 08:19

1). That's great news, my unit is quieter than the Nakamichi so good that yours is also quite.

I don't have any complaints, even when hooked up to the Croft.

2). I'm very sensitive to the sibilant distortion most three way speakers have at the crossover point, mid to tweeter. Still getting a bit on the Yammies which I'm trying to eradicate. I can borrow miniDSP to try and achieve this. But still they are the best I have had them.

That is also a complaint I have with the 44's, I have considered hooking the MiniDSP up to the 44's and would / will do if I had more free time. After hearing the Beovox 5700's I agree with you that x-over is largely responsible for the resonance, it's still present with the 5700's but less obvious, until it is obvious then it's far worse. However as stereo speakers I find the 5700's boring and bloated in comparison but on ~75% of vocals I find it better which is why I use one as a centre speaker, still bloody sibilant though.

3). Umik-1 is made to work with REW so straight forward set up as it's recognized by the software.

Indeed, as I'm sure you know MiniDSP is fully supported in REW. Hook up the mic, run the measurement and export the file to MiniDSP. Some same it's problematic but as stated earlier I've not run any measurements so can't speak from experience.

4).Spookey – Did I mention the PRV 5MR450-NDY to you?
I've been thinking of it mated with an AB Acoustics 12” woofer crossed at 300hz.
The PRV 8ohm is preferable to the 4ohm as it calcs in a bigger sealed box. Qtc 0.707 gives about 6.8L but only 1.5L or there about's for the 4ohm.
Be careful of crossing Subs at a high frequency. They tend to roll off quickly so the bass will not be deep if you do. The figure they quote for how deep they go, is usually based on the lowest crossover point they offer. The -3dB point of reference is directly related to the crossover point, as this moves up so does the -3dB frequency. Check out some of the frequency plots for subs taken at various crossover settings. In the example you quote, his diy sub is I believe, multi driver and is EQ'd in minidsp so characteristics may be considerably different. PRV recommend a crossover point of 290Hz or higher to achieve full output on the driver, which is too high for a sub and why I am considering a large woofer.

Of course you did (post #28), do you think I came up with that on my own? :) When you said Vic's substituted the Alpairs it really piqued my interest, looking at the T/S it looks like a great match for the Goldwood GW1858 that he uses. A guy called Marin J. King (http://www.quarter-wave.com/Project08/Project08.html) says with the Goldwoods in an H-frame crossed at 350Hz;

"The H frame produces the deepest bass I have ever had in my home stereo
system. Granted I have never used a dedicated subwoofer, but most of the other
speakers I have designed and built have tended to reach down to about 40 Hz which
has always produced enough bass for the enjoyment of my acoustic jazz collection. But
the Goldwood GW-1858 goes well below 40 Hz without any of the bloat or one note bass
some speakers can produce; it is just an even growl into the 20 Hz range. I doubt I get
all the way down to the measured 22 Hz since the rear wave reflecting off the back wall
probably produces some cancellation of the lowest frequencies. A bigger room allowing
placement further from the rear wall would definitely improve this situation."

Simple baffle construction, no need for stereo subs, ~$400 worth of drivers and a active crossover solution, if you've got the room what's not to like? Admittedly it would require an amp board per channel but so would stereo subs so really the total cost is still pretty low, the Nak's a bargain at £600 but still equates to ~£86 per channel.

4)5). No not crazy, I was thinking the same, using a pair of 8” Scanspeak woofers crossing at 50Hz to a pair of BK subs. I even drew this up, all drivers including subs were in sealed cabinets for fast tight sound.

Now I'm really quite excited, I feared I'd overlooked some simple yet fundamental reason why this wouldn't work, which Scanspeak driver are you looking at? I've looked at the 22W/4534G00 and it looks like a good partner. I'm really interested in the Goldwood GW-408D for surround speakers, it won't go as low (Fs 51.2Hz) ~60Hz after filter in a 20l cabinet, sensitivity is close at 91dB and it's a real bargain at $23.30! It also and has a bigger 10" brother GW-408D which I could use in a centre speaker which should get down to ~50Hz after filter in a ~50l cabinet, sensitivity is a bit high at 96dB but hopefully could be rectified via MiniDSP and again it's a bargain at $27.86. The only concern I have is xmax is a little limited at 3mm, I need to do more research into the implication of this but the ideal of having the same manufacturer of woofers is quite appealing.

Which BK subs are you looking at XXLS400?

Qwin

07-05-2016, 17:25

I was considering the XLS200 subs from BK, the XLS400's at 450mm deep, are 50mm too deep to fit on the step in my room floor.

This is what I was considering, note this is all to scale, the drivers are all in sealed cabinets, the subs have a 300mm square baffle.

http://www.jkwynn.co.uk/Pics/three_way_proposal.pdf

I am now leaning more toward the use of the PRV for mid/HF and crossed at 300Hz into the SB Acoustics 12" (6ohm) woofer. F3 of around 34Hz in a big sealed box. Note: The 8ohm version of this 12" is more suited to a ported design and only gets F3 of about 54Hz sealed.
This is a nice simple 2way crossing at 300Hz, which is well away from the area where I am hearing distortion.
For the three way in the PDF it is crossing at 300Hz and 50Hz. The beauty of the BK subs is you can bypass their internal filters and feed the plate amps direct, with the signal from your active crossover, and set the slopes and EQ as you prefer, or measure, either as analogue or as I was considering, minidsp.
Its a lot of money to pull out for the pair of subs and if I wasn't happy with the quality of the bass I would be spitting chips. Also the Scanspeak 8" woofers are well on the way to the price of the SB Acoustics 12" so the 2-way is a safer bet with a much smaller outlay. Bass wont be as deep, but may be more tunefull, and 35Hz or their about's will be good enough for me. According to Troels Grevesen's measurements the Yammies are only doing F3 of about 48Hz in room. The Yammies do some things so well, I could probably forgive the bass if I could iron out the sibilance issues. I couldn't do this completely on the 66's and still have a little on the Yammies. I'm hopping some measurements will give clues as to how I might achieve this and borrowing a minidsp to make multiple changes will make the testing easier.

Just noticed I'm repeating myself, blame the nice lunch I just had in Glasgow and the Pinot Grigio.:D

danilo

13-05-2016, 02:00

I've not done any real research into this but I've been spurred on as a friend brought a Fender Deluxe 85 and a bass guitar round the other day and this has re-ignited my desire to go H-frame OB for my mains.

Simply curiosity: Why would a Mediocre Fender inspire you to an H frame. Most all Fenders (guitar amps in general too) had open back sound boxes??
The openings are not very large though hardly H frame comparable.. more like breathing room.
As aside: Fender 85 is a Durable Contraption but general consensus maintains that it sounds like Crap. Not one of Fender's memorable products.
I have a '64 Bassman .. for over 45 years now. Far more representative of Leo Fender's work.
In truth wayy beyond my meagre guitar skills.. but it's Perfectly suited for annoying the neighbors.

DarrenHW

13-05-2016, 06:10

H-Frame OB's were a project I was considering a while ago, if you read the quote I did say re-ignited :). I know the Fender 85's nothing special and not an H-Frame but it was the first time I'd heard a open cabinet in my lounge and I enjoyed it's interaction with the room.

danilo

13-05-2016, 15:51

Thank you.
Agreed... OB's do have a way of intriguing .
I get the urge as well.. happily I've found that if I sit on it.. it fades.
My observations are that these only Look dead simple.. once one gets the baffling 'right',
then it's onto the myriad methods of replacing the Bass. Also there's the middle of the room issues. (roomate problems)
A sleeping dog problem.. for me.

Qwin

14-05-2016, 10:14

Darren - This is not relevant to your original topic, but might have some value in what you are trying to achieve overall.

As you know I have been looking at a sort of FAST two way. My main problem is the location of the speakers in my room, I only have one possibility and it is very space restricted. I would love to use a 12" bass in a large sealed enclosure (120 L) getting down to the mid 30's for F3 while maintaining Qtc of 0.707, but don't have the space.

Looking at the SB Acoustics 10" woofer (not sub driver), this calculates in an empty 33 L sealed box with Qtc 0.707 to F3 42.4Hz. This is fairly respectable and about 10Hz lower than the F3 on my Yamahas. This would give me a cabinet about the same size as my Yamaha's which fits nicely in my space, so its a contender.

I came across the Linkwitz Transform Circuit, don't know if you have heard of it? Siegfried Linkwitz developed it to increase the bass performance in his small sub woofer.
It changes the response, extending the F3 (realistically) by around an Octave. So if you were flat to say 50Hz you can insert this circuit and be flat to 25Hz without changing anything on the speaker. Their are a few pre requisites, it has to be a sealed enclosure, preferably a large driver with plenty of Xmax and with high power handling, it also has to be an active set up. It might be worth you looking at this, as I believe there are filters in miniDSP to implement it.

The 10" bass I was considering has a rating of 200w and Xmax of 11mm (22mm P-P coil travel) and I was considering just a modest improvement getting the F3 from around 42Hz to the mid 30's. I am looking further into this but there are some trade off's and if you try to do too much, run in to massive power requirements, amp power doubling for every 3dB you raise the target frequency as you bring it up to match the level of the rest of the response.

Google "Linkwitz Transform Circuit" it makes interesting reading.

DarrenHW

17-05-2016, 19:29

Hi Ken,

Yes, I am familiar with the Linkwitz Transform Circuit, there is a coefficients calculator for MiniDSP, select the filter type, input the T/S of your driver and it spits out values to copy and paste into the MiniDSP software. This was one of the first things I did when setting up the software and what I was talking about in post #50;

The bank holiday didn't yield as much free time as I'd hoped but I was able to spend some time configuring the MiniDSP. I currently have the cut off frequency at 35Hz with a LR 48db filter, I arrived at these settings using the MiniDSP coefficients calculator with the Lab12 specs and then tuning by ear. I'm torn between using a LR and Butterworth filter, the LR seems to give slightly deeper bass with slightly more impact, where as the BW filter seems to integrates better with the main speakers.

I abbreviated it to LR for Linkwitz Riley, which I suppose that wasn't very obvious.

I haven't spent any more time with the sub since then as I just don't have the free time and on that subject sorry for not replying to your earlier post, I completely missed it. I too would be looking at your FAST suggestion over the 2 way with BK subs, I may be wrong but I seriously doubt the XLS200 would output anything useful below 30Hz. If you could get the woofer into the mid 30's I don't think you'd really miss much, the only time I find the lack of depth obvious is watching films which for me was the main failing of the Rel, maybe the BK's go lower but I'd be surprised.

Qwin

18-05-2016, 10:21

Ah, I'm with you, I'm not familiar with miniDSP so you had lost me at "coefficients calculator".

Rod Elliot does PCB's to make a real world Linkwitz Transform circuit that can be wired in front or behind of an analogue active filter and this is what grabbed my attention.

The SB Acoustics driver I was looking at plots out at F3 approx 42.5Hz, Qtc 0.707 in a 33L sealed box. It has a gentle roll off so 10Hz down (32.5Hz) it is almost exactly at -6db. All the advice for using the transform seems to suggest not being too ambitious by setting your target frequency too low. Aiming at 32.5Hz for my F3 point would only require a 3dB lift at that frequency, which would double the power requirement in theory. This should be within the drivers capability, so it is an itch I may have to scratch at some point.

You would be surprised what the BK XLS200 can produce, they only quote a -6db figure which is 17Hz, this is only achievable with the crossover control at its lowest setting of 40Hz. Using a pair of them, with a bit of room reinforcement, I think an F3 of 25Hz would not be far from the mark. ;)

To be honest, my thoughts are moving away from subs. The idea of a wide range 5" driver mated with the woofer above for reasonably low bass, maybe adding the Transform circuit at a later date, is more appealing.