And the DIY bitsphase_accurate said:
http://wanderkolonie.org/servod.htm
😀
With the latest super woofers available,im not sure if the contrabass type units will be so useful - But they still win with THD and thermal constant.
Actually there was a comparison of a number of subwoofers and the Contrabass wasn't the best. Velodyne (which was a servo) and Genelec were clearly superior in distortion.
http://www.ultimateavmag.com/features/604way/
I'm very impressed with the Rythmik kit and driver, which also has a very impressive appearance!
http://www.ultimateavmag.com/features/604way/
I'm very impressed with the Rythmik kit and driver, which also has a very impressive appearance!
paulspencer said:
Paul,
Thanks for the link. I had a hunch feeling that Contrabass does not have the best distortion because there is no feedback mechanism. I could be wrong. But here is what I think. While the servo motor provides a very linear BL profile, the main source of distortions in a subwoofer comes from spider nonlinearity, which contrabass does not solve. Also the resolution of steps in servo motor can affect low level distortion. That means, the distortion is lowest at highest SPL level. That clearly puts Contrabass to applications other than home use. Again, this is my hunch feeling and I can be wrong without doing further investigation.
Brian D.
Rythmik Audio
Brian, as you can see on the link (you have to go through a few links), the Contrabass has lower distortion as SPL goes up, to a point, then distortion increases. The strength of the Contrabass was shown to be very high output in the LFE range, with decent distortion performance and acceptable size.
Regarding the DirectServo kit, I'm a little surprised I don't hear of more diyers using them, seems a great chance to get some impressive technology on a diy sub - best of both worlds.
Couple of Q's to Brian:
* what if someone wants to have a small box - say 1 cu ft? Does the kit cater to that either by being able to use settings that are suitable on the LT or by altering the LT circuit?
* have you considered a 15" version? I feel a 12" sealed sub with 1" xmax is fairly limited in output (I have 2 x AV12 in sealed boxes and find them adequate, but would like to later put them in vented boxes when I get around to it)
Regarding the DirectServo kit, I'm a little surprised I don't hear of more diyers using them, seems a great chance to get some impressive technology on a diy sub - best of both worlds.
Couple of Q's to Brian:
* what if someone wants to have a small box - say 1 cu ft? Does the kit cater to that either by being able to use settings that are suitable on the LT or by altering the LT circuit?
* have you considered a 15" version? I feel a 12" sealed sub with 1" xmax is fairly limited in output (I have 2 x AV12 in sealed boxes and find them adequate, but would like to later put them in vented boxes when I get around to it)
Paul,
1) The kit can be used for that size. The trade-off is lower SPL output. The frequency response is still flat because of the servo feedback. We don't need LT with the servo. That is something I didn't make clear.
2) There is no excuse for not having a 15" driver and I am working on it. However, I would like to emphasize 15" drivers simply need more enclosure volume to show the advantage. For a 2 cu ft sealed box, it is very diffcult for a 15" driver to beat a 12" driver with the same amplifier size. It is hard to explain in a few words but it is all related to physics.
Brian
Rythmik Audio
1) The kit can be used for that size. The trade-off is lower SPL output. The frequency response is still flat because of the servo feedback. We don't need LT with the servo. That is something I didn't make clear.
2) There is no excuse for not having a 15" driver and I am working on it. However, I would like to emphasize 15" drivers simply need more enclosure volume to show the advantage. For a 2 cu ft sealed box, it is very diffcult for a 15" driver to beat a 12" driver with the same amplifier size. It is hard to explain in a few words but it is all related to physics.
Brian
Rythmik Audio
Isn't everything in DIY? We're proud to be with the crowd that knows hifi is governed by the laws of physics and not the marketing babble of some company. Wouldn't it be nice to see all those nonsense rave reviews of silly products go away if we could just get all people, but particularly magazine journalists, to understand even the basic laws of physics? Oh wait, that means Bose will go out of business faster than you can blink an eye.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
I want to use a dayton 12" woofer . A box of 3.0 CF gives an f3 of 27hz
now if i add a servo to this . do you think I should build active or passive ?
now if i add a servo to this . do you think I should build active or passive ?
fcotton, why would you even try? There is a kit right in front of you with a driver that is probably better than any of the Dayton drivers anyway, and it's not a simple matter of just grabbing a servo and whacking it on! I've heard of a number of one off attempts to diy a servo sub, this kit is the only successful implementation I've heard of.
Hear, hear, I'm with Paul on this one, if you have to ask whether a passive or active servo sub will sound better you obviously don't have clue (sorry). The idea of a servo sub is having a transducer, either piezo-electric or a MEMS device, attached to your woofer cone and feeding the resulting signal from it back to the amplifier. All in an attempt to lower THD and flatten the SPL curve and cause for a low-end extension of the frequency curve. Hence a servo sub is an active sub by definition, there's no such thing as a passive servo sub (unless you buy into some manufs marketing babble).
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
The problem arises from the terminology: Some call MFB subs servo subs and some call the ones that use a servo motor servo subs.
Regards
Charles
Charles,
He specifically mentioned in his last post he'd like to use a 12" Dayton woofer and wondered whether he should add a active or passive servo, hence my reply.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
He specifically mentioned in his last post he'd like to use a 12" Dayton woofer and wondered whether he should add a active or passive servo, hence my reply.
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
I agree that Servo subs can have very low distortion. I have a Genesis 900 sub which uses a 15 inch aluminum cone driver with a 500 wpc Class D plate amp. I owned it for many years and it was very good with bass. I contacted Genesis and they told me that they can modify how the accelerometer is attached consequently further lowering distortion. I was a little sceptical, but I sent my driver off to them.
A few weeks later I got the modified driver back and it popped it in. Wow!!! what clean tight bass, in fact it was breathtaking. The bass even mated seamlessly with Lowthers which can have very, very clean bass when mounted in the right cabinet.
I think that the improved accelerometer mounting places a higher demand on the plate amp to control the driver because about 6 months later, while playing the chinese drums CD by Burmeister, the amp died. I shipped it back to Genesis, but they could not fix it. Instead they are redesigning a new amp for these subs.
No box sub that I ever heard could match the low distortion numbers and sound as clean as a servo sub. Genesis is a first class company for producing bass using servos (the Genesis 200 speakers, which use eight 8 inch bass drivers per side produces the best bass I have ever heard for home use). I believe that the only ways to have truly great bass is a servo sub, a horn sub, infinite baffle and open baffle bass.
Retsel
A few weeks later I got the modified driver back and it popped it in. Wow!!! what clean tight bass, in fact it was breathtaking. The bass even mated seamlessly with Lowthers which can have very, very clean bass when mounted in the right cabinet.
I think that the improved accelerometer mounting places a higher demand on the plate amp to control the driver because about 6 months later, while playing the chinese drums CD by Burmeister, the amp died. I shipped it back to Genesis, but they could not fix it. Instead they are redesigning a new amp for these subs.
No box sub that I ever heard could match the low distortion numbers and sound as clean as a servo sub. Genesis is a first class company for producing bass using servos (the Genesis 200 speakers, which use eight 8 inch bass drivers per side produces the best bass I have ever heard for home use). I believe that the only ways to have truly great bass is a servo sub, a horn sub, infinite baffle and open baffle bass.
Retsel
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