View Full Version : seeking help from speaker drive unit experts
Hi All , I am looking to embark on a project and am totally clueless as to what I need so am seeking the help of those with knowledge of drive units
and enclosure design,
Basically I want to build a pair of single drive unit speakers with a frequency range from 20hz to 55hz in a cabinet with the dimensions H39cmXW39cmXD27cm, I would like the drivers to be as fast as possible
any ideas anybody
cheers
Paul
Stratmangler
04-10-2014, 19:29
Best of luck!
You'll struggle in your quest, especially with the miniscule cabinet dimensions you've mentioned.
walpurgis
04-10-2014, 19:30
Are you sure it's 20Hz to 55Hz you want? That's a subwoofer.
A realistic full range response might be 45Hz to 18kHz.
Why have you chosen those cabinet dimensions?
Stratmangler
04-10-2014, 19:33
Well spotted Geoff.
I must read posts more thoroughly :doh:
I thought it said 20Hz to 55KHz.
Hi Geoff, yes that's right basically I want to build a pair of passive subs in cabinets of the size quoted (don't mind if they are ported) with
that frequency response . Is it possible?
cheers
Paul
walpurgis
04-10-2014, 19:43
No. Not with conventional drivers in boxes that size. Actively driven with equalisation the right units may get you down to about 30Hz.
If you've got wooden suspended floors you could try a pair of passive 'Shakers' to give that earth moving bass sensation.
http://www.bassshakers.com/
No. Not with conventional drivers in boxes that size. Actively driven with equalisation the right units may get you down to about 30Hz.
does that not equate to the same as active subs ala REL if so they are too slow sounding if you know what I mean.
If you've got wooden suspended floors you could try a pair of passive 'Shakers' to give that earth moving bass sensation.
they look like a great way of inducing nausea, fools and their money:doh:
http://www.bassshakers.com/
I could increase the height by a small amount (not W and D though) if it would help and 30hz would probably be low enough
cheers
Paul
walpurgis
04-10-2014, 20:00
Would it not be easier to buy an active sub? Going passive means bigger boxes and more problems integrating them with the main speakers.
I have tried half a dozen different active subs including ridiculous priced REL's and cant find anything that gives me the sound I am after.
I figured getting rid of the electronics and using a driver with a natural roll off might work better, but as I said I am clueless with cone speakers.
cheers
Paul
walpurgis
04-10-2014, 20:11
What about getting main speakers that give you the bottom end you want?
Sadly I cant afford them:(
Light Dependant Resistor
04-10-2014, 20:33
Hi All , I am looking to embark on a project and am totally clueless as to what I need so am seeking the help of those with knowledge of drive units
and enclosure design,
Basically I want to build a pair of single drive unit speakers with a frequency range from 20hz to 55hz in a cabinet with the dimensions H39cmXW39cmXD27cm, I would like the drivers to be as fast as possible
any ideas anybody
cheers Paul
Acoustic suspension http://en.wikipedia.org/wiki/Acoustic_suspension is the principle to follow where smaller cabinet size must be used. The best example I can think of that gets very low in frequency other than the single driver early acoustic Research models, is the galeGS401a with 2x 8 inch drivers however it is 60.5cm in length, but nearly satisfies the other dimensions you ask for
http://0339436.netsolhost.com/WordPress/gs401-speaker/
The AR7 would easily satisfy the dimensions they are single driver, and owning a pair they are not sub woofer capable, but offer the best low frequency for cabinet size dimensions I can think of, and sound great.
So my advice is to use acoustic suspension, which means a floppy speaker driver, and see what you can achieve. It looks like your cabinet already exists, as you are very specific with its dimensions.
Other than that an active electronics based acoustic suspension model with well defined frequency 20-55 cutoffs, but expense would be much greater, and would require amplifiers and crossover outboard.
Cheers / Chris
walpurgis
04-10-2014, 20:39
A thought crosses my mind. You could try a small quarter wave tuned acoustic column (not transmission line). Basically a pipe around eight feet long (can be folded to make a compact unit) with a small low resonance dual coil bass driver to energise it. That potentially could reinforce the bottom end in the manner you want.
Something like this may be suitable. http://www.ebay.co.uk/itm/Black-134-mm-30-W-Dual-Voice-Coil-Bass-Mid-Range-Driver-8-Ohm-Electrovision-/321165570343?pt=UK_ConElec_SpeakersPASystems_RL&hash=item4ac6f5b127
You can connect both channels to it and get a summed bass output. You can also tuck it out of sight in the listening room (not right in a corner though). A tuned column depends on the air in it being excited at and around its resonant frequency. Bigger is better, but the tube width can be pretty small, even 100mm may be enough, it depends on what level of output you expect. An inductor in series with commoned negatives can provide roll off at a chosen point.
walpurgis
04-10-2014, 20:50
In a small sealed cabinet, Isobaric loading works well. The Linn Sara had a remarkable bass extension (the rest was a bit questionable though). I remember hearing deep, tight bass coming from these compact speakers many times.
thanks chaps , lots for me to read there, think I will leave it for tomorrow as I'm just back from enjoying a Fullers LP or3
cheers
Paul
The Grand Wazoo
05-10-2014, 08:09
Not intending to piss on your cornflakes or to discourage your admirable spirit of adventure Paul, but I really think you're going to waste time and money and only find out how not to build a subwoofer here. You've tried numerous designs from people who do this as their job and you admit that you have almost no experience or knowledge in this field. In which case, how on earth are you going to improve on what you've already heard?
I think it might be time to investigate alternative methods of removing the pelt from the pussy.
Firebottle
05-10-2014, 08:26
I'm thinking the same thing Paul, REL are very good subs in my opinion which is why mine is based on the same approach.
:cool: Alan
20Hz to 55Khz from a single driver in a small cab?
As Montgomery Scott would say 'I cannae change the laws of physics, Captain.'
Technics did a range of speakers in the 'nineties that used (I think) some variety of coupled -cavity bass loading to achieve deep bass from relatively small cabs. They got pretty good reviews although I am damned if I can recall the model numbers - SB something, obviously. I've been looking for some second-hand for years but never seen any.
If you want 20Hz without a sub then you need something like that or maybe a transmission line but they are still going to need to be big-ish. And a full range driver that capable is going to cost a bomb.
If it could be done then professional designers would already be doing it, I would suggest.
walpurgis
05-10-2014, 09:44
Apparently it's a pair of subs that's wanted Martin. 20Hz to 55Hz.
It ain't going to work in the specified box size, not as a passive setup anyway.
I don't know if this would fill the bill, but it certainly looks interesting:
http://www.audio-talk.co.uk/phpBB2/viewtopic.php?t=5794&highlight=
Light Dependant Resistor
05-10-2014, 09:53
Not intending to piss on your cornflakes or to discourage your admirable spirit of adventure Paul, but I really think you're going to waste time and money and only find out how not to build a subwoofer here. You've tried numerous designs from people who do this as their job and you admit that you have almost no experience or knowledge in this field. In which case, how on earth are you going to improve on what you've already heard?
I think it might be time to investigate alternative methods of removing the pelt from the pussy.
Chris whilst you are answering honestly there is still much enjoyment to be had with bass reproduction, and its wrong to shut out /close off ideas that have been provided by members that are close to meeting what could provide enjoyment for Paul, so let me expand:
I think it might become apparent that not many pieces of music contain 20-55Hz, but reduced db at these frequencies is still lots and lots of fun, whilst many more pieces of music contain 35Hz upward. This is whyI think good result can be had with a single driver acoustic suspension loaded in the modest cabinet size he has in mind, Why because distortion is so low with acoustic suspension, it will integrate well with other speakers doing higher frequencies and provide a reasonable result to assist low frequency reproduction.
Maybe this will be enough to help Paul enjoy his music choices this is what AOS is about I think. Rather than ' because it won't do 20Hz or 30Hz don't try " I recall being thrilled by AR7's on stands with bass reproduction, so small cabinet acoustic suspension is both cost effective and will deliver reasonable result. Isobarik by design has to be 2 speakers in the one cabinet, but if Pauls requirements can be expanded to 2 drivers isobarik is very impressive too, but at much higher cost namely cabinet design and mounting drivers internally with precise spacing.
Shanes post #20 I am getting excited about, as this may be a good way of extending bass with ESL57's.
As AOS is about having fun with sound and sound equipment, here is a very small list of readily available music with very impressive bass to test speakers with. Madonna, track Rain, Elton John live in Australia track Candle in the Wind, Genesis Trick of the tail Los Endos.
Cheers / Chris
Apparently it's a pair of subs that's wanted Martin. 20Hz to 55Hz.
It ain't going to work in the specified box size, not as a passive setup anyway.
Oh I see. I should read more carefully. Dipoles with digital signal processing not a bad suggestion, fiendishly complex though. Well for me anyway.
The Grand Wazoo
05-10-2014, 10:09
Chris, I'm not trying to discourage exploration at all and if Loo goes into it in order to enjoy the experience, learn from it and is prepared for a possibly disappointing outcome, then that's great and I'll cheer him on all day long. On the other hand, if he just wants to build something without fuss, and for it to be his perfect solution to hifi heaven, then I fear there will be tears.
Chris whilst you are answering honestly there is still much enjoyment to be had with bass reproduction, and its wrong to shut out /close off ideas that have been provided by members that are close to meeting what could provide enjoyment for Paul, so let me expand:
I think it might become apparent that not many pieces of music contain 20-55Hz, but reduced db at these frequencies is still lots and lots of fun, whilst many more pieces of music contain 35Hz upward. This is whyI think good result can be had with a single driver acoustic suspension loaded in the modest cabinet size he has in mind, Why because distortion is so low with acoustic suspension, it will integrate well with other speakers doing higher frequencies and provide a reasonable result to assist low frequency reproduction.
Maybe this will be enough to help Paul enjoy his music choices this is what AOS is about I think. Rather than ' because it won't do 20Hz or 30Hz don't try " I recall being thrilled by AR7's on stands with bass reproduction, so small cabinet acoustic suspension is both cost effective and will deliver reasonable result. Isobarik by design has to be 2 speakers in the one cabinet, but if Pauls requirements can be expanded to 2 drivers isobarik is very impressive too, but at much higher cost namely cabinet design and mounting drivers internally with precise spacing.
Shanes post #20 I am getting excited about, as this may be a good way of extending bass with ESL57's.
As AOS is about having fun with sound and sound equipment, here is a very small list of readily available music with very impressive bass to test speakers with. Madonna, track Rain, Elton John live in Australia track Candle in the Wind, Genesis Trick of the tail Los Endos.
Cheers / Chris
I'd second that, but would also throw in a "however"
However, in this case, is that one would normally start by selection of the driver and then design the cabinet around that. You could be making a rod for your own back by starting with a cab which might restrict quite appreciably the choice of drivers.
I'd also suggest that whilst acoustic suspension would be the easier way to go for a small enclosure, matching the sensitivity to your main drivers may ultimately dictate which driver, hence cabinet design you go for. If looking for an acoustic suspension design, there a number of vintage drivers which can be had used which might work well (Goodmans 12 inch 4 Ohm drivers for example) but your main challenge would be looking at anything like 20Hz. I can't think of any drivers offhand which will yield 20Hz in a small acoustic enclosure.
You could get away with a smaller longer throw driver (low "Q") using a ported enclosure. A way to experiment and have a bit of fun in the virtual realm would be to download something like WinISDBeta freeware which includes a library of drivers that you can model. You may find something that would suit your box.
The other thing already highlighted is getting one with a natural rolloff at 55Hz, or more specifically it would need to be between -3dB and -6dB down at your chosen crossover point depending on the slopes desired. That's a big ask, and I'm not sure if you'll find any driver which meets that criteria. At the very least you'll be needing a simple first or 2nd order roll off. I'm happy to help you with getting into the right ballpark filter values.
some great reply's gent's , I think a big problem may have been in my original post due to its lack of explanation as to what I was hoping to achieve from this project, I shall endeavour to explain it better, basically I am a long term 20yr+ Quad esl user (57's and 63's) and have only ever used a few pairs of conventional speakers so my knowledge of them is very limited even just as an end user. Recently I decided to put an office system together and in doing so I resurrected a pair of Rehdeko's from the loft .Well blow me
it was love at first hear. I had totally forgotten how these speakers sounded and just loved it. Consequently they have found their way into my main system and are sounding great BUT... they are a bit light in the lower registers very much like a Quad 57 in the way they just stop at a certain frequency .So what I wanted to do was make a simple pair of passive units to fill in the void, the 20hz was just a reference to the lower end I was wanting to fill. I am sure down to 35 or even 40hz would be fine and the 55hz was where the Rehdeko's drop off . The cabinet size emulates that of the main speakers and would also fit with my 57 stands so it seemed practical but if it is totally unacheiveable I am happy to look at alternatives . and just to echo a comment Chris (LDR) made Shane's post number 20 looks very interesting ,anybody got experience of the design.
hope that lot makes some sense
cheers
Paul
awkwardbydesign
07-10-2014, 11:42
Shane's post number 20 looks very interesting ,anybody got experience of the design.
Ask Jazzman53 on the Wigwam or Audiotalk. He built them after all.
I don't really frequent other forums , I have read his blog and he does not have much detail other than construction and states himself that he is no expert , what I need help with if I go ahead with a pair is, driver recommendations as in matching sensitivity and load , Jazzman's speakers are 4ohms I would need to build a pair that are 8ohms also I have no idea about limiting their frequency range ,and intergrating them into my system. any Ideas
cheers
Paul
Magna Audio
08-10-2014, 07:44
Having had great success modelling and simulating horns from tapped 20Hz upwards using Hornresp, I would look at getting a good sub simulator / modelling aid.
A quick search for subs threw up this one. I'm not recommending it as I've never used it but the basics looks a bit similar to Hornresp. You put in your T&S of your driver and then play with sizes etc until you get the freq range you want.
There may even be a wizard that gives you the driver spec that will do what you want and then you can hunt for such a driver.
You will end up trying lots of drivers T&S - hours of fun:) With a simulator / model you do get pretty close to what the model says when you've built it and measure the response - in my experience.
It will show you how far away from your perfect size / freq you are likely to be.
http://www.ajdesigner.com/fl_subwoofer/subwoofer.php
Hi Steve. thanks for that, looks useful
cheers
Paul
Ninanina
10-10-2014, 21:22
I resurrected a pair of Rehdeko's from the loft
I wish I had a pair of Rehdeko's in my loft....always wanted a pair...:doh:
BTH K10A
10-10-2014, 21:33
A clone of a Sunfire SDS8 Subwoofer may fit the bill
walpurgis
10-10-2014, 22:19
A clone of a Sunfire SDS8 Subwoofer may fit the bill
Funny you should say that. I'd had thoughts along the same lines.
walpurgis
10-10-2014, 22:26
How about a mini dual voice coil car subwoofer driver?
Something like this: http://www.ebay.co.uk/itm/Lanzar-MAXP64-6-5-Sub-600w-Max-4-Ohm-/171242484300?pt=UK_In_Car_Technology&hash=item27ded8f24c
How about a mini dual voice coil car subwoofer driver?
Something like this: http://www.ebay.co.uk/itm/Lanzar-MAXP64-6-5-Sub-600w-Max-4-Ohm-/171242484300?pt=UK_In_Car_Technology&hash=item27ded8f24c
Shows what I know as I was thinking more along the lines of that nice pair of Fane units of yours
A clone of a Sunfire SDS8 Subwoofer may fit the bill
Spooky, a friend has offered me a loan of an SDS12 which I am going to take him up on , apparently its a 600w monster:rolleyes:
what I just don't get with these active subs is the huge power ratings why would you ever need 600w or even 200watts when most
domestic systems are probably 50 to 100 watts/channel at most .
cheers
Paul
Paul Lange
11-10-2014, 12:54
I suspect that you could find an enclosure / speaker combination that would do the trick (after a bit of tuning) but find that it is difficult integrate the sub into your system. I also suspect that you may end up with a sub that has the required output at 20hz and 55hz but a large peak in output between these two points which will have to be reduced with a filter of some kind.
Achievable but not straight forward.
:
what I just don't get with these active subs is the huge power ratings why would you ever need 600w or even 200watts when most
domestic systems are probably 50 to 100 watts/channel at most .
cheers
Paul
I'd guess because reproducing low frequencies takes a lot of power, and the louder you want them the more power it takes. No point having a sub that will do 20Hz but so quietly you won't hear it (or feel it). I suppose the exception would be those huge horn subwoofers built into the floors or whatever but for a cone in a box to go really low and be audible you need power.
I'd guess because reproducing low frequencies takes a lot of power, and the louder you want them the more power it takes. No point having a sub that will do 20Hz but so quietly you won't hear it (or feel it). I suppose the exception would be those huge horn subwoofers built into the floors or whatever but for a cone in a box to go really low and be audible you need power.
In a nutshell...this.
As frequency drops, so does loudspeaker impedance. Partly because the voicecoils are in effect acting as inductors. As impedance drops, so the current required to maintain SPL increases. Therefore, a speaker delivering say 30Hz with a 4 Ohm load takes twice the power needed to deliver the same SPL at 8Ohms, typically from around 1KHz upwards.
The second factor is that our hearing sensitivity is non-linear (read up on the Fletcher-Munson effect), meaning that at bass frequencies, especially at lower volumes, our hearing isn't that sensitive. So for an aurally flat hearing response, bass needs tilting upwards (what loudness buttons on older amps achieve), hence for serious bass, you (generally speaking) need serious wattage. Even for moderate volumes, most speaker systems need more than twice the power input for low bass than they do at a KHz.
You may read about "flat speaker response" and conclude it's no good because of the above, but that's a different thing entirely. A flat response simply means that a speaker is capable of passing 20Hz to 20Kz very linearly, with little deviation from a reference SPL and this is a good thing. If it couldn't do that, then a note, say, played on a trombone which was mic'd rising in pitch from its lower frequency range to upper frequency say all recorded at the same SPL level in the studio, couldn't be reproduced to sound the same. In other words the level of play back would vary with frequency when the live mic feed may have recorded something very different. Flat response in this context is just one aspect of accuracy.
The good ol' Beeb developed a response curve for broadcast monitors (most famously the LS3/5a) which had a dropped midrange so that at moderate listening levels, they could part compensate for hearing sensitivity. Some manufacturers do the same thing today. This is fine as a compromise but the effects vary with loudness so usually a defining SPL level is set for a flat hearing response (75 to 85dB nearfield is quite normal).
Thanks for the explanation Paul although I still don't quite get how a pair of well endowed (driver wise) speakers can do good bass on the end of an average power amp
but a sub with a similar sized driver needs a mega watts amp, right this evening has been spent in the company of Ben and his Sunfire SDS12 which is a twin 12"
one passive sub with a 600w amp, well I don't think I want bass anymore ,not bass like this thing produces anyway:mental:
I feel like I've spent the evening in the engine room of a north sea trawler in a heavy storm . We did eventually manage to tame the beast and got a nice level going
but it still sounded detached from the main speakers ,even Ben who was convinced it would integrate seamlessly was surprised at the slight detached delay effect.
I am beginning to think there may be something to do with my room that active subs don't like ,or maybe its the single sub set up.
Anyway I am left thinking that I don't have a cat in hells chance of coming up with anything that's likely to be effective:(
Cheers
Paul
Magna Audio
12-10-2014, 08:30
I get 105dB/w out of my taped horns - but that's horns for you. I still need more current to them (the drivers are rated 650W) than the rest of the system that is up in the 110 - 115dB / region (depending on drivers).
One thing you will find as you approach say 30-90Hz at full SPL - you will probably need room mode correction as somewhere in this range or even slightly above it you will excite the room. DSP is the way to go unless you want to change your room to a recording studio stuffed full of traps etc. There are quite sensible ones like Antimode (i used them before going full DSP X/O). They really worked for me. I got full bass down to 20Hz but not the massive room boom at 35Hz that made some material interesting, shall we say. They were very clever in the way they set themselves up with test tones.
Doing it manually with a measuring mic was no problem - I have a -18dB cut on one of the Tapped horns at 35Hz! Now they are nice and flat.
Here's a before and after Antimode DSP in my room (it was working between 20Hz and 100Hz)..
http://i727.photobucket.com/albums/ww272/speedysteve7/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page27/with_withoutdsp.jpg (http://s727.photobucket.com/user/speedysteve7/media/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page27/with_withoutdsp.jpg.html)
Later with manual correction in the DSP X/O I could remove the bump above that.
Thought I'd share this as you might get into some of these issues...
If you are filling in below 55Hz only you might be able to get away with just one sub - bass at that freq isn't terribly directional but it depends on room, you etc...
DSP is very useful for tuning at a listening position (it needs re-tuning if listening position is shifted) but in reality, there's very little music information below 40Hz on most music unless you're into pipe organ.
For most purposes, a loudspeaker system that delivers clean, well integrated, articulate and detailed bass to say 40Hz will be far more enjoyable than something that booms and lags to 20Hz. Subs are notoriously difficult to integrate in some systems and rooms.
They cannot be treated as a bolt on to be positioned anywhere. The same time alignment and sensitivity matching along with slope matching with the main speakers mid-woofers needs great care otherwise the results can become a boomy blurry mess, usually with audible overhang or lag. It's unlikely that a single evening tuning by ear will do the trick. A mic is really needed to see where the sub is actually rolling off and at what level compared with the main speakers. Ideally, the sub should be close to the firing plain of the main speakers although some believe it doesn't matter where it's placed (it does matter...a lot). DSP can then be useful to reduce the specific frequencies causing boom at the listening position. Most decent active subs have variable time delay/level controls built in, so DSP isn't necessarily needed to tune them but can be borrowed to learn where to set the controls.
It's all a compromise. Sometimes better to find some speakers that offer a good compromise than start down the sub-route (ie find some whos lower frequencies start rolling off to coincide with lower bass boom areas..although this wont cure overhang).
Thanks for the explanation Paul although I still don't quite get how a pair of well endowed (driver wise) speakers can do good bass on the end of an average power amp
but a sub with a similar sized driver needs a mega watts amp,
There is bass and then there is bass. Even big speakers will not do a lot below 40Hz which is fine for almost all music but if you play music with a fair amount content below 40Hz like organ or some electronica then you awill be missing out.
Shame you are so far away I would offer to come round and have a crack at integrating the sub, I've done a few by ear over the years. Best I have heard is a Velodyne that had built in DSP. The trick is always to tune the sub so you can't hear it at all. Counter-intuitive but there you go. Doesn't always work, though ;)
walpurgis
12-10-2014, 10:21
Concentrating on getting a deep bass end is probably a mistake. Years ago I used to seek out and build speakers that would deliver proper deep notes, but these days I just listen for transparency and 'musicality'. There is little truly deep bass on most recordings in any case, so a roll-off (not cut-off) below say 50 Hz still gives an enjoyable speaker.
Magna Audio
12-10-2014, 16:44
There is bass and then there is bass. Even big speakers will not do a lot below 40Hz which is fine for almost all music but if you play music with a fair amount content below 40Hz like organ or some electronica then you awill be missing out.
Shame you are so far away I would offer to come round and have a crack at integrating the sub, I've done a few by ear over the years. Best I have heard is a Velodyne that had built in DSP. The trick is always to tune the sub so you can't hear it at all. Counter-intuitive but there you go. Doesn't always work, though ;)
Sorry cannot resist to show what a there "there is bass and then there is bass" solution might look like...
A pair of these in a reasonable sized room, properly EQ'd, give the latter but oh so right and enjoyable on all music and vols:)
http://i727.photobucket.com/albums/ww272/speedysteve7/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page32/tappedbracing2.jpg (http://s727.photobucket.com/user/speedysteve7/media/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page32/tappedbracing2.jpg.html)
This was taken while prepping for the transportation to Scalford hifi show 2012.
Sorry cannot resist to show what a there "there is bass and then there is bass" solution might look like...
A pair of these in a reasonable sized room, properly EQ'd, give the latter but oh so right and enjoyable on all music and vols:)
http://i727.photobucket.com/albums/ww272/speedysteve7/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page32/tappedbracing2.jpg (http://s727.photobucket.com/user/speedysteve7/media/hifi/Conical%20horn%20project/Horn%20thread%20on%20Wam/page32/tappedbracing2.jpg.html)
This was taken while prepping for the transportation to Scalford hifi show 2012.
very impressive Steve
I bet I could get a pair of them either side of the bay window , wonder how long it would take her indoors to notice em if painted the same colour as the walls
cheers
Paul
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