Hey guys i haven't been online here at Diyaudio.com for quite some time and i was looking at my old thread in subwoofers. I was wondering if anyone can suggest some websites and literature for a Servodrive subwoofer, I am looking to build one and my countless internet searches have alas turned up nothing. Any help would be appreciated Thank You a Bass junky Teenager
Posting twice in an hour's going to make people NOT want to help you. Given that you're going to be waiting on shipping, assembly, etc, relax and you'll get better feedback. Your impatience shows in that you haven't searched sufficiently to find anything, as servo subs have been discussed extensively in this and other forums.
You seem to be expecting this to be a free tech support forum for you, where people will spoonfeed you. I looked at the wikipedia entry for subwoofers, and there's a company that makes servo kits within there.
Spend the time and do your own homework young man!
You seem to be expecting this to be a free tech support forum for you, where people will spoonfeed you. I looked at the wikipedia entry for subwoofers, and there's a company that makes servo kits within there.
Spend the time and do your own homework young man!
You probably won't find much info on ServoDrive on this site; most of the diy activity surrounding them occurred on the old Bass List. Just as well, as your attitude pretty much ensures that you won't get much help on this site now.
If you can't find the Bass List archives and make sense of them, I find it unlikely that you would be able to pull off the project anyway.
BTW - this is not a rhythmic style servo sub. The ServoDrive used a mechanical servo motor to drive the diaphragms.
If you can't find the Bass List archives and make sense of them, I find it unlikely that you would be able to pull off the project anyway.
BTW - this is not a rhythmic style servo sub. The ServoDrive used a mechanical servo motor to drive the diaphragms.
dwk123 said:
Yep, where's a moderator when you need one.......
Having built two kits with another two unassembled that I probably should have sold along with them while the 'iron was hot', I seriously doubt even an advanced diyer would be able to properly replicate its belt system close enough to withstand high power for any useful length of time, at least not without some spectacular failures along the way to getting it right.
GM
Sound Physics Labs is where the info on the Servodrive sub is,unfortunately,their site is down for revamping at the moment.
I heard the Servo subs at a speaker show some years back,and they were quite impressive...,however,I would suggest that you would be better off to build a tapped horn instead.Much easier and less expensive.
If you haven't read the The Collaborative Tapped Horn thread,now is the time to start.
Good Luck!
I heard the Servo subs at a speaker show some years back,and they were quite impressive...,however,I would suggest that you would be better off to build a tapped horn instead.Much easier and less expensive.
If you haven't read the The Collaborative Tapped Horn thread,now is the time to start.
Good Luck!
Ok, not sure about servo subs, but I know of a similar technology which involves driver motion correction.
Get a DVC driver, hook one coil up to an amp, they other coil up to a circuit that looks at the input to the amp, and the 2nd voice coil, compares the positions, then makes adjustments to the sound going into the amp
Theoretically, this is a good idea
Never heard it in practice though
BTW - patience is a virtue.
Get a DVC driver, hook one coil up to an amp, they other coil up to a circuit that looks at the input to the amp, and the 2nd voice coil, compares the positions, then makes adjustments to the sound going into the amp
Theoretically, this is a good idea
Never heard it in practice though
BTW - patience is a virtue.
Hope this post achieves better than the standard 50% true content.
Middle '50s a guy from RCA labs (once a very important speaker lab) proposed "motional feedback" which reads the speaker voice coil and feeds it back to the amp. I've worked with this and it can be a monumental bass improvement. But hard to make a stable commercial speaker system.
A variant is getting a speaker with two voice coils (some woofers come that way). Should be easier to set up than the RCA way.
Footnote: these systems must be sealed boxes or infinite baffles because only in that way does the output bear much relationship to the cone motion which MF controls. MF grabs and flattens freq response (and can lower it as far as you wish and even flatter through and below resonance of the box) as well as impulse response and distortion. No kidding.
Later, Philips glued $.75 accelerometers to their speakers and sold a bunch for a few years. You can create all kinds of acoustic pick-up systems but, if you ask me, the idea is plain daft due to phase shift, distortion in pick-up device, etc.
Recently, folks have tried to drive cones using servo motors. Sounds nifty to me but like swatting flies with a baseball bat.
Middle '50s a guy from RCA labs (once a very important speaker lab) proposed "motional feedback" which reads the speaker voice coil and feeds it back to the amp. I've worked with this and it can be a monumental bass improvement. But hard to make a stable commercial speaker system.
A variant is getting a speaker with two voice coils (some woofers come that way). Should be easier to set up than the RCA way.
Footnote: these systems must be sealed boxes or infinite baffles because only in that way does the output bear much relationship to the cone motion which MF controls. MF grabs and flattens freq response (and can lower it as far as you wish and even flatter through and below resonance of the box) as well as impulse response and distortion. No kidding.
Later, Philips glued $.75 accelerometers to their speakers and sold a bunch for a few years. You can create all kinds of acoustic pick-up systems but, if you ask me, the idea is plain daft due to phase shift, distortion in pick-up device, etc.
Recently, folks have tried to drive cones using servo motors. Sounds nifty to me but like swatting flies with a baseball bat.
I have used Servodrive subs for concert systems, nightclub installs even put four into one of those awful SPL competition vans once for a guy...
Servodrive subs only work well in a very limited range 20-60hz and only at what i would consider to be low power for a sub. they can only handle about 400 watts each before the circuit breakers trip open. they have a tendency to sound quite sloppy, but they are what i would consider to be a true subwoofer. Most pro concert PA subs don't go down below 40 very well and that's where the servos shine! crossed to take over only for the very lowest of the lows they are ungodly! but i would never use them without another LF box to take over the main LF duties.
Servos require a lot of maintenance as well. the metal rods from the belt/motor system connect to rubber stoppers glued to the cone center. with heavy hard use the rubber tears or cracks and then they make a horrendous sound much like a blown woofer.
Brushes need to be replace on the motors and the motors need to be cleaned of brush dust. the circuit breakers can fail if your constantly up against them. and its a little strange to hear the fan motors kick on high after the breaker has opened!
The system i had ran 4 servodrives per side x-over at 45hz on a crown MA5000VZ and 2 JBL double 18 sub boxes on a Crown MA3600VZ(per side) with various flying rig top cabs.
Of note, Micheal Jackson on a tour used 16 servodrive subs running on a Crown Macro-Tech 10,000! that's almost 10kw of power! the sound guy had a DBX subharmonic synth unit connected to a volume pedal. for effect, he would stomp on that pedal and shake the hell out of the building! a crew member friend said that in concert, he never ran it past 1/3 volume but during soundchecks he would try and shake the lighting guys out of the rafters!!!! (I don't know if there is any truth to that hahahah)
Zc
Servodrive subs only work well in a very limited range 20-60hz and only at what i would consider to be low power for a sub. they can only handle about 400 watts each before the circuit breakers trip open. they have a tendency to sound quite sloppy, but they are what i would consider to be a true subwoofer. Most pro concert PA subs don't go down below 40 very well and that's where the servos shine! crossed to take over only for the very lowest of the lows they are ungodly! but i would never use them without another LF box to take over the main LF duties.
Servos require a lot of maintenance as well. the metal rods from the belt/motor system connect to rubber stoppers glued to the cone center. with heavy hard use the rubber tears or cracks and then they make a horrendous sound much like a blown woofer.
Brushes need to be replace on the motors and the motors need to be cleaned of brush dust. the circuit breakers can fail if your constantly up against them. and its a little strange to hear the fan motors kick on high after the breaker has opened!
The system i had ran 4 servodrives per side x-over at 45hz on a crown MA5000VZ and 2 JBL double 18 sub boxes on a Crown MA3600VZ(per side) with various flying rig top cabs.
Of note, Micheal Jackson on a tour used 16 servodrive subs running on a Crown Macro-Tech 10,000! that's almost 10kw of power! the sound guy had a DBX subharmonic synth unit connected to a volume pedal. for effect, he would stomp on that pedal and shake the hell out of the building! a crew member friend said that in concert, he never ran it past 1/3 volume but during soundchecks he would try and shake the lighting guys out of the rafters!!!! (I don't know if there is any truth to that hahahah)
Zc
We seem to have 2 completely threads going here...
1/ ServoDrive, which is Tom Danley's (patented i believe) rotary motor to rod driver cone subwoofers (thanx for the pictures guys). With these you'll pretty much need to be very handy with mechanics or find someone selling off some (of the very limited production) used
2/ feedback controlled (servo) subwoofers. The easy way out here is to buy a Rythmic kit.
Perhaps mulletdude can tell us which he is really after.
dave
1/ ServoDrive, which is Tom Danley's (patented i believe) rotary motor to rod driver cone subwoofers (thanx for the pictures guys). With these you'll pretty much need to be very handy with mechanics or find someone selling off some (of the very limited production) used
2/ feedback controlled (servo) subwoofers. The easy way out here is to buy a Rythmic kit.
Perhaps mulletdude can tell us which he is really after.
dave
Zero Cool said:
Servodrives work great up to 80Hz+/- I'd never run them up to 100-120.
I wouldn't run them at 20Hz either 28Hz is their -3dB in groups of 4.
I would never describe them as sloppy sounding. Though I own the BT7's perhaps you owned the SDL-5's which were maintenance nightmares. I think perhaps you never had them combining well with the upper boxes.
My BT7s have no breakers, just an inductor resistor , and a filter for the fans bridge rectifier. The Servo also has a ballist resistor.
The big problem most people have with the BT7 (Mostly DJ's and people not in the know) is that running the BT7s amps into clipping caused too much HF energy to make it to the Motor, causing the belts to slip and overheat, and the motor to burn up.
I have 8 of the beasts, all of them are doing quite well for their age. I had one refurbished, and replaced the pads on 1 when I got them used.
I'm not sure why you think they can't handle enough power, remember that 4 of them is ~110dB efficient with just 1kW they put out 140dB 142dB at rated power, and 145dB peak.
How many subwoofers do you know that can put out 142dB @ 30Hz with only 1.6kW of power???
I love my BT7's
Back to the OP Mullethead.
Do you mean servodrive or servo feedback, two totally different things.
Hey guys good input so far i am after the first one with a motor driving the diaphragms any more specific input would be appreciated.
.edit. um ifsomeone wouldnt mind explaining exactly how one of these works i have done quite extensive research on the internet and i can only find the servo feedback subs which are not what i am looking for
.edit. um ifsomeone wouldnt mind explaining exactly how one of these works i have done quite extensive research on the internet and i can only find the servo feedback subs which are not what i am looking for
Mullet Dude,
As far as I know the only one here on DIY audio that has an authoritatve knowledge of Servomotor drive speakers, is Tom Danley.
He posts here often, also at www.prosoundweb.com
He may or may not be willing to share some information with you.
I think he was using Low inertia DC servomotors. I have no idea what that means, perhaps it means they don't rely on inertia to keep moving, but can change acceleration force rapidly?
As far as I know the only one here on DIY audio that has an authoritatve knowledge of Servomotor drive speakers, is Tom Danley.
He posts here often, also at www.prosoundweb.com
He may or may not be willing to share some information with you.
I think he was using Low inertia DC servomotors. I have no idea what that means, perhaps it means they don't rely on inertia to keep moving, but can change acceleration force rapidly?
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