View Full Version : Going Active?
I am thinking fully going active its not like I do not have a lot of resolution but heck as been said we can always do with even more headroom and scare everybody:)
I do not want it sounding clinical or sterile
I only really need to go two way as already got active dsp on the bass
So i need to think of the right amps (i cannot afford to go down Marco route, for me it will have to be t-amps)
The Behringer DCX2496 would seem to suit my needs
I am totally open to ideas on how I could achieve this
Reid Malenfant
25-05-2012, 19:04
Can you link to the specs on your sub & amp John? I'd like to see what this thing does :)
I'm assuming the DSP is already a part of it...
As far as the amp I open to different t-amps
http://www.behringer.com/EN/Products/NU1000DSP.aspx for bass
These are my main drivers
http://www.hawthorneaudio.us/catalogs/index.php?main_page=product_info&cPath=3&products_id=1
Reid Malenfant
25-05-2012, 19:35
Ok, I remember that from Scalford :D
I'll look into the delay etc but I have had thoughts..
I have a DCX2496 here that has been hit by the ugly stick on numerous occasions, it's kind of battered :lol:
However, it works just fine!
Now having had a think after the to-ing & fro-ing of our PMs, I should be able to set the DCX up for you if you want to borrow it. All you'd need to do is match in the volume levels of bass to mid & then mid to treble. It'll be that easy.
What I can do is set the DCX to 3 way, so you connect you duke nukem amp to the bass output of the DCX, however, I can set it so it's full range on the bass output! This will allow you to use the DSP on the amp & also get the mid output delayed by the correct amount. I can do similar with the midrange & give it no high pass filter. This would be exactly what you have there I'm guessing?
If you let me know a few things I'll be able to set up the DCX so you don't have to, it'll be a case of plumbing it in & trying it out & seeing what you think.
What I need to know is the crossover frequency from midrange to tweeter. I also need to know the distance between the front plate of the magnetic assembly of the bass side of the 15" coaxial & the front plate (which will likely be at the back) of the tweeter which is part of the coaxial driver. Distance in mm will be fine.
Give me that & i'll set it up & post it out to you :cool:
I get back to you on the crossover stuff
A bit confussed about what you want from the speaker side of things
Would that be the centre of duel concentric to the centre of the bass drivers sorry i am not so bright
Hey John.
I’ve had a go at this in the past and I didn’t think it was an easy or cheap to do well.
You should at least avoid some of the problems I had by having open baffles.
Often overlooked for sealed monitors with internal amps is the feckin heat!
A couple of things to think about though.
An adjustable crossover or a fixed Linwitz Riley 24dB?
My preference would be for a fixed crossover using the best components you can afford. The problem is then establishing the best crossover points for your kit. Unfortunately the same values for a passive crossover don’t seem to translate directly to an active set up.
Apparently a good rule of thumb is three times the wattage of each driver. :eek:
Don’t hang me for it mate; this is from the man.
What gets forgotten is when using a single amp to drive multiple drivers; each driver can call on power from the amp that isn’t being used by other drivers. Active systems can’t do this so you can’t afford not to have amps easily capable of handling any demand a driver may make. This is one of the reasons good active pre-built systems seem to be seriously overpowered. It’s nothing to do with going loud really, just making sure there is plenty of peak power.
The hardest part I found apart from the expense was deciding whether to stick with a limited low frequency main driver and try to integrate a sub; never got that right, or just to have limited bass.
A popular combo seems to be D class for bass and A/B class for mid and hi.
I have no idea what you have atm or what set up may suit it.
Just a couple of thoughts before you get some horrendous underpowered adjustable lash up.
Good luck. :)
Thanks John plenty to ponder and perhaps this is not going to be as easy as I thought
This is from Darrel in response to the xover
Figure around 1200 Hz for the high pass to the tweeter to be on the safe side. We bring the mid woofer in under this. Play around with different slopes also.
Reid Malenfant
25-05-2012, 20:03
I get back to you on the crossover stuff
A bit confussed about what you want from the speaker side of things
Would that be the centre of duel concentric to the centre of the bass drivers sorry i am not so bright
Sorry John I didn't really make myself clear.
Imagine your coaxial driver without the tweeter for a minute. The front plate on the magnet would be the one at the front, which the voice coil for the bass driver is sat inside. It's the steel plate glued onto the ferrite (I'm assuming) magnet. There is a back plate at the rear (forget about that). It's the one that is sandwiched between the speaker chassis & the magnet which is the one I'm talking about.
In the case of the tweeter it'll most likely be reversed, the front plate will likely be the steel plate furthest from you in your listening position. Again the tweeter voice coil will be sat inside the front plate of the magnetic assembly of the tweeter unit.
If you can measure the distance in mm between the centre of the bass top plate & centre of the tweeter top plate I'll be able to set the delay on the midrange so it sounds coincident, rather than just coaxial. They'll be time aligned in other words :)
Reid Malenfant
25-05-2012, 20:05
This is from Darrel in response to the xover
Figure around 1200 Hz for the high pass to the tweeter to be on the safe side. We bring the mid woofer in under this. Play around with different slopes also.
Is that with a 12dB/octave slope?
If so & I recommend you go linkwitz/riley minimum phase 24dB/octave it can safely be lowered.
Let me know what slope the passive is & I'll have a better idea what to do :)
Ok I understood the last bit so be ab;e to give the measurements tommorow
Figure around 1200 Hz for the high pass to the tweeter to be on the safe side (from the designer of the drivers) mid bass is set underneath this
Hi Mark I am waiting for Darrel to come back to me around the last question
The length between the top of tweeter to the top of the bass drive unit is 330mm
Reid Malenfant
26-05-2012, 17:22
Hi Mark I am waiting for Darrel to come back to me around the last question
The length between the top of tweeter to the top of the bass drive unit is 330mm
:scratch:
Umm, maybe if you look at this picture & then try again we'll get somewhere :)
Once again, I want the distance between the centre of the top plate of the 15" midrange driver & the centre of the top plate of the coaxially mounted tweeter :lol:
Look at the pic & then go & measure it again :cool:
6768
Mark it might be best if I call u I am even more confussed
ahh think I got it using your red lines as measurement than its 80cm as I put a collar pushing the tweeter further back did was a subtle but noticable improvement at the time a few people on the Hawthorne forum have done this
Reid Malenfant
26-05-2012, 18:00
I hope you mean 8cm or 80mm :)
Reid Malenfant
26-05-2012, 19:05
That's better :D
Yes wait for Darrel to get back to you on the crossover slope of your speaker. Take it from me though that going to a steeper slope IE 24dB/octave you'd be able to lower the crossover frequency & keep the tweeter safer than it is now!
I'm not suggesting you lower it by much, but I'd suggest dropping it to 1KHz as this will give the 15" less upper frequency work to do (a good thing imo) & as the rolloff would be steeper the tweeter will still see less lower frequencies :)
Just to give you an idea of how safe a tweeter can be with a steep rolloff, I used to use a Focal T90K down to 1.25KHz with a 24dB slope xover, when it'd normally only be happy with a minimum of 3KHz with a 12dB rolloff passive xover.
The speakers were used at party volume levels & it was the Kef B139 bass drivers that expired, the midrange & tweeters never showed any signs of distress.
Wish I never sold them, but I built another set of speakers using them & sold them for £600 :eyebrows:
awhile back i had to replace one of the tweeters after sending everything at full volume for a second
Reid Malenfant
26-05-2012, 19:28
That was probably due to the amp clipping. The thing is with an active system it doesn't matter too much if you clip the bass/midrange amp as the tweeter will still be getting nice clean sine waves from it's own amp :)
Tweeters really don't generally get a lot of power at all, though they can handle a load of power on transients, maybe 10 times or more there continuous power rating.
I had to laugh when looking at the thread John (welder) posted about the Questeds. The tweeters are very high quality domes, but nothing out of the ordinary & yet they were being fed by an amp that could generate 450W RMS :eek:
As I say, they'll take very high transient peaks of clean power, but not a lot continuously, they definately don't like clipping amps :rolleyes:
I found this on the Hawthorne forum it should answer the question
http://www.hawthorneaudio.us/forums/search.php?keywords=active+slope&sid=2815a544a09ea60caa1cc680d9cab8c6
For amps I was thinking Bantam Golds for mid/bass and the mini t for the treble as the compression driver is 105db but after reading John's thoughts I might go for 2 Bantam golds
In the past i really loved the treble response of the amptastic but it does not really control the mid/bass on my drivers
I don’t know if this helps John but this is the basic crossover design I used when I had a go.
http://sound.westhost.com/project09.htm
There are probably many who won’t agree with me but imo not all speakers are suitable for active conversion.
If you are very familiar with the sound of your speakers and like their character then in my limited experience going active can markedly change the character which won’t necessarily be to your taste. Sure you can make the electronics work but getting them to sound as you want requires a bit more than this ime.
Ah thanks that is what I was thinking
How I was thinking of working around this was using a Berhinger and some Bantam golds as the |Bantam has a 60 day money back grantee in the worst case scenrio I can always return and continue wit a passive design. Ironically before I got the Duets I was considering getting ATC actives but never regretted my choice so perhaps trying this is wasted energy;now a bit confussed as to if it worth the effort
I’m not trying to dissuade you from having a go John; I’m just trying to stress that going active is far from simple.
Take for example the constant debate about amp and speaker interaction. If you believe that all amps sound the same, no problem (1)
If you believe that all amps can be made to sound very similar given a particular drive unit; you’ve got problems (2)
If you believe that an amp can seriously change the sound of any drive unit and certain types of amps give certain types of sound then given you may have 3 pairs of drive units and six amps (3) :eek::doh:…………..then of course there is the matter of what components in the active crossover influence the sound and which op amps to use etc etc.
A bantam may for example sound fine through a passive crossover but if you’re in camp 2 or 3 and you change the sonic characteristics of the crossover……..
It should seem obvious, there is a lot more to building good speakers than doing the maths, I think everyone would agree with that and for an active set up, there are a lot more variables if your swapping amp types per drive unit pair and messing about with crossover slopes.
Ali Tait
27-05-2012, 22:43
I found this on the Hawthorne forum it should answer the question
http://www.hawthorneaudio.us/forums/search.php?keywords=active+slope&sid=2815a544a09ea60caa1cc680d9cab8c6
For amps I was thinking Bantam Golds for mid/bass and the mini t for the treble as the compression driver is 105db but after reading John's thoughts I might go for 2 Bantam golds
In the past i really loved the treble response of the amptastic but it does not really control the mid/bass on my drivers
I use two Golds on my OB's John, along with a DCX2496. Works very well to my ears, and have had nothing but positive comments from visitors.
I still will go adhead with this everything I am doing I am able to undo and I guess for me it will tell me once and for all if active will work in my system.
Reid Malenfant
29-05-2012, 17:38
Right John, I have set up the DCX as best as I can for you given the information I have.
The thing I'd like to know is how much delay the DSP in the Inuke adds to the proceedings. I'm guessing that it'll be similar to other DSP based amps, so I have given all outputs except the bass output which you'll plug the Inuke into 1.46mS of delay. If you happen to have the user manual there John please take a look as somewhere it must give some idea of the delay caused by the DSP. I'm not on about any that is added, I just want the delay of the DSP itself as they do delay stuff due to the processing - it takes time :eyebrows:
Don't worry, the bass output is actually set to full range :) The mid output is set to go down to below 20Hz & roll off at 1.19KHz. The tweeter output rolls in at 1.19KHz & as well as the 1.46mS delay it also has a delay of 80mm to allow for the spacing between the mid & treble driver voicecoils.
The inputs are input A & input B on the back panel. If you regard input A as left channel, then outputs 1, 2 & 3 are left bass, mid & treble respectively.
Likewise regard input B as right & outputs 4, 5 & 6 as right bass, mid & treble.
I have left all gain settings flat, no doubt you'll be able to use volume controls to balance things up. If you need to do it via the DCX then I'll help you out.
Digital delay function 0 - 300 ms
I have function where I can control the amount of digital delay which is set at 100ms at present
I probarly play around with the settings Mark
Even if this does not qork I just go all mono blocks with this type of set up
Thanks very much
Reid Malenfant
29-05-2012, 18:53
I know there is variable delay available, but it's not that which I want. What I want is the delay that the audio waveform gets going through the DSP processor, as it's got to have some as DSP isn't instant, it takes time to process :D
The DSP adds about 1.4mS of delay on my PLM14000, it can't help it as running through the DSP takes time, again like you I can add delay etc, but I don't.
Now why have you set a delay of 100mS??? :scratch: That is a delay that'll put the sub about 33 Meters away :scratch: Either you made some kind of mistake or your room is the size of a big sports hall :eyebrows:
Because it sounded great with tabla, bass and drums and also sounds awesome on prog metal
I set it back to zero
The Behringer manual does not mention anything else on delay
Reid Malenfant
29-05-2012, 19:33
The Behringer manual does not mention anything else on delay
Very odd, after all it does take time to do anything via DSP :scratch: As I say, the DSP in my Lab Gruppen states the delay time & even the 8033 (bass DSP units) state how long they take to process & the output delay caused by this...
Anyway, I have added a good ball park guesstimate of processing time :lol:
By the way just playing Koryojang and agree at zero more acurate with how the drums are intergrating
Reid Malenfant
29-05-2012, 19:47
By the way just playing Koryojang and agree at zero more acurate with how the drums are intergrating
:thumbsup: You'd only need to add delay if your subs were nearer you than the main speakers. The whole idea is to align every driver so that they appear to be radiating from the same plane in front of you. This may result in adding a delay to certain things, but if your drivers are all in virtually the same vertical plane, then it'll be quite small.
Glad we talked about this as I just realised I added extra delay to the treble section, when it needs to be the midrange in your speakers case...
I'll get that done now while I think about it :)
Just to let you know on the bass its going up to around 90hz with 18db slope
Reid Malenfant
29-05-2012, 20:10
Just to let you know on the bass its going up to around 90hz with 18db slope
I have left the settings to your 15" mid as full range down to below 20Hz, as I'm sure that's what it's getting right now.
So assuming you leave things as they are, the difference will be that you'll dump the passive xover & the 1.2KHz xover point will now be 24dB/octave Linkwitz/Riley. This will give perfect phase response as I have time aligned the things as well.
Just thought of something else to do - maybe :scratch:
I'm going to assume that when you take the passive xover out of the equation that you'll wire the mid (15") positive on the speaker to positive on the amplifier feeding it. I'm also going to assume you'll do the same with the tweeter.
As long as you do that the DCX is set right. The thing is with a 12dB slope as you have there the tweeter is often wired out of phase (connections reversed) from the passive xover to get things into alignment. It may not be the case with your system though. Just make a note of how they are wired before you pull off the passive xover, so you get it right again later!
But as long as you wire + to + etc then it's set, just needs the volume of each driver dialing in :)
Yes I was going to wire it as suggested, everything I do will be reversable so if this does not work for me I will go back to passive
48dB/octave anyone? :eyebrows:
Reid Malenfant
01-06-2012, 19:34
48dB/octave anyone? :eyebrows:
As long as it's Linkwitz/Riley there will be no phase problems, the DCX can do it ;)
48dB/octave slope well worth going for if you've got your drivers at a comfortable frequency handling range and they're half decent.
Reid Malenfant
01-06-2012, 19:47
I'd agree with that, not only will you increase the power handling of a tweeter to lower frequencies, but the sharper cutoffs will give less interaction between the drivers near the xover frequency & reduce comb filtering :)
I must confess, I’ve gone down the excessive power route allowing for 95 dB with 92 dB per Watt efficiency with my speakers (Seem to have lost a couple of dB from my last measurement:scratch:)
I'll put it down to better measuring :doh:
I’ve allowed 20 dB (approximately) headroom.
I’m beginning to understand why some studios need all that power given the monitors may be 3 or 4 metres away
Oh arr, almost forgot.
I've been recommended these guys if you're considering one amp per driver route and don't mind building your own boxes.
http://www.bkelec.com/Modules/Amplifiers.htm
I must say, I've heard a few beefy power maps over these last couple of weeks and once the SPL and channel output is matched properly I was fecked if I could pick one from another.
However, Pre amps and control units are another matter as has been the quality of the active crossover.
Reid Malenfant
01-06-2012, 20:21
I’m beginning to understand why some studios need all that power given the monitors may be 3 or 4 metres away
I nearly crapped myself with those Quested links you came up with, 450W RMS amp feeding a tweeter :eek: Ok, I know high frequencies aren't generally sustained, but still :scratch:
By the way, my head finally remembered some more superb active kit :) Genelec (http://www.genelec.com/?r=1).
Reid Malenfant
01-06-2012, 20:30
Looks like John (John) has received the DCX2496 (delivered at 09:49 apparently), he's probably having fun right now wiring it all in to his system :D
Perhaps explains why he's not about this evening :)
I heard some small genelec last week. Not over impressed tbh mate. Just lacked scale if that's the right word :scratch:
Have to wait for a few amps but looking forward to playing around
Suprised how light the unit is
That DCX is a useful bit of kit for experimenting with different slopes, frequencies etc. I’ll be using a similar bit of kit by Rane which I can borrow for a while.
I’m not going to be keeping the Rane. Once I’ve got all the messing about done I’ll build the crossover with decent components. I don’t really want another A/D to D/A converter in the chain and should I wish to do any DSP I can do it with software pre Dac on my server.
For those who don’t fancy building and/or love their valves this might be of interest.
http://www.marchandelec.com/xovers.html
What I haven’t quite decided on yet is whether to incorporate the amplifier enclosure into my speakers with a single active crossover channel included which is ideally what I would like but this may require fan cooling, or to build separate units a bit like my current external crossovers for the amps and put both channels of the crossover into a single box……decisions, decisions.
I should have the amps next week.
I want to mention again for anyone who is also considering going active with a set of speakers they know and like the presentation of, going active will make a fundamental difference to the sound. I’ve heard my speakers in active mode (easy to do with an external passive crossover) and it made a bigger difference to their presentation than any Dac, amp, source, change I’ve tried in the past.
I’m hoping to complete the project for around the grand mark which while not cheap is reasonable given the prices of Hi Fi equipment.
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