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Velodyne ULD subwoofer Servo Cable Question

@Bill Ferris
It sounds like you have a bit of experience with these subs. A while back I picked up a 1987 ULD15S4 (5-pin servo input) -- sans the servo amplifier. A little later I picked up a 1993 ULD15B (RCA servo input) -- before I realized that there were two different incompatible series.

I downloaded what schematics I could find but do not have adequate information to make a determination as to how to go about interfacing the two units at their servo connections.

FYI, I'm an electronics engineer so I won't have any problem understanding the information -- it's just that I can't find the information.

Do you or anyone here have what information is needed to be able to interface these two units? I saw a reference somewhere to a three wire connection to the servo in the older unit -- so I don't know if it makes them inherently incompatible. I do understand the need to recalibrate.

Grateful for any input. This unit looks like a worthwhile effort.
 
CoastinHome said:
@Bill Ferris
It sounds like you have a bit of experience with these subs. A while back I picked up a 1987 ULD15S4 (5-pin servo input) -- sans the servo amplifier. A little later I picked up a 1993 ULD15B (RCA servo input) -- before I realized that there were two different incompatible series.

I downloaded what schematics I could find but do not have adequate information to make a determination as to how to go about interfacing the two units at their servo connections.

FYI, I'm an electronics engineer so I won't have any problem understanding the information -- it's just that I can't find the information.

Do you or anyone here have what information is needed to be able to interface these two units? I saw a reference somewhere to a three wire connection to the servo in the older unit -- so I don't know if it makes them inherently incompatible. I do understand the need to recalibrate.

Grateful for any input. This unit looks like a worthwhile effort.
Click to expand...

I wish I could be of some help with the electronic aspects of these Servo based subwoofers, but all my 4 non Din connected type ULD 15 versions have only needed their surrounds replaced, & thankfully no electronic servicing has yet been required by me yet.

At least I know my models subwoofer`s electronics are calibrated to their specific amp, and when I purchased my last 2 used from Audio Classics in 2000, I made sure to not mix up the amps from their specific subwoofers by tagging both the amp and subwoofer to avoid any problems/issues as I unpacked them..

I wish I could be of some help in this area for you, CoastinHome, Sir.

Good luck.

Kind regards, Billy Ferris
 
Hi!

So I'm getting some popping from the woofer itself intermittently when playing music or when just sitting idle. I have the ULD-15 and have had the foams redone. With that being said, should I try to replace the servo cord to see if that solves the issue? Or would my issue becoming from something else. The Amp itself also has a slight hum coming from it as well. I'm trying to see if I can keep using this or if I should move on to something else, witch I really don't want to do.
 
@limberpine
I've spent many hours researching the ULD-15 and communicating with the company's new owner in Germany this past month. The only documentation to be found for these older subs is a nearly unreadable and incomplete schematic set for the ULD-15 Series 2. I couldn't turn up anything for the Series 1 unit.

I've laid out the schematics and studied the circuit design for the Series 2 controller -- and now I understand how this complex servo controller system works -- but I still don't have the documentation needed for the accelerometer circuit used in the earlier subwoofer. So mine might be a lost cause as well.

I bought mine from Goodwill -- minus the servo amplifier. The cabinet is in great shape and the foam surround on the driver appears to be in perfect condition. Once I understood how the system works, however, I finally concluded that it's owner must have replaced the surround on the driver and thereafter was never able to get it to work quite right.

This unit uses a Piezo accelerometer glued to the driver cone. It's part of a feedback system that must be properly calibrated within the servo amplifier. If you've had the foam surround redone you've changed the characteristics of the driver and the feedback loop will need to be recalibrated -- perhaps again as the surround breaks in. Also, it's critical that the driver is properly sealed to the cabinet. If there is an air leak in the cabinet the servo will have a real time with that.

The other issue is if you have bad capacitors in the Servo amplifier resulting in an unacceptably high DC offset on the output, the servo is going to struggle to mitigate that.

First, ground the input of the servo controller to see if the hum goes away. If it doesn't you're probably in a bit deep with needing attention to the servo amplifier unless you are comfortable rebuilding the amplifier yourself. I don't know that anyone services these. I did encounter one company that specializes in Velodyne subwoofer repair but the ULD series was not on their list.

Let me know which series you have and I can possibly make some more suggestions.
 
CoastinHome said:
@limberpine
I've spent many hours researching the ULD-15 and communicating with the company's new owner in Germany this past month. The only documentation to be found for these older subs is a nearly unreadable and incomplete schematic set for the ULD-15 Series 2. I couldn't turn up anything for the Series 1 unit.

I've laid out the schematics and studied the circuit design for the Series 2 controller -- and now I understand how this complex servo controller system works -- but I still don't have the documentation needed for the accelerometer circuit used in the earlier subwoofer. So mine might be a lost cause as well.

I bought mine from Goodwill -- minus the servo amplifier. The cabinet is in great shape and the foam surround on the driver appears to be in perfect condition. Once I understood how the system works, however, I finally concluded that it's owner must have replaced the surround on the driver and thereafter was never able to get it to work quite right.

This unit uses a Piezo accelerometer glued to the driver cone. It's part of a feedback system that must be properly calibrated within the servo amplifier. If you've had the foam surround redone you've changed the characteristics of the driver and the feedback loop will need to be recalibrated -- perhaps again as the surround breaks in. Also, it's critical that the driver is properly sealed to the cabinet. If there is an air leak in the cabinet the servo will have a real time with that.

The other issue is if you have bad capacitors in the Servo amplifier resulting in an unacceptably high DC offset on the output, the servo is going to struggle to mitigate that.

First, ground the input of the servo controller to see if the hum goes away. If it doesn't you're probably in a bit deep with needing attention to the servo amplifier unless you are comfortable rebuilding the amplifier yourself. I don't know that anyone services these. I did encounter one company that specializes in Velodyne subwoofer repair but the ULD series was not on their list.

Let me know which series you have and I can possibly make some more suggestions.
Click to expand...


Thanks! I have the ULD-15 made in 1986. Ground the input?

Also, I can send you the video of the noise if you want to DM me your email address.

I'm not comfortable rebuilding the amp myself and talked to a place locally who works on them but they essentially said its $100 to look at it and most likely something is broken that they can no longer get parts for, so that doesn't seems like a good road to go down.

Also talked to a guy who builds subs here in Portland, OR and he suggests cutting the wires to bypass the servo and installing a plate amp on the side of the box.

Thanks for any help!
 
<<I have the ULD-15 made in 1986.>>

That would be a Series 1 unit. I haven't had any luck finding documentation for it.

<<Ground the input?>>

Divide and conquer. Want to first make sure that your hum is not coming from the preamplifier or a ground loop etc. You're just disconnecting the RCA inputs to the servo amp and shorting center conductor to outer conductor on each input. If the hum goes away you're probably in better shape.

I would otherwise tend to agree with the sub builder in Portland about installing a plate amp on the side of the box. Problem is that the driver has a specific set of characteristics which optimize it for use with a servo system. It has an extremely low resonant frequency. It also has modifications to the cone. Before you commit to a direction, try the subwoofer connected to a different high power amplifier. That will let you hear what the sub sounds like without the servo. You'll probably be very disappointed. You would do much better to replace the driver as well if you are leaving the servo out of the loop.

Sounds like you're stuck about the same place that I am with this unit.
 
CoastinHome said:
<<I have the ULD-15 made in 1986.>>

That would be a Series 1 unit. I haven't had any luck finding documentation for it.

<<Ground the input?>>

Divide and conquer. Want to first make sure that your hum is not coming from the preamplifier or a ground loop etc. You're just disconnecting the RCA inputs to the servo amp and shorting center conductor to outer conductor on each input. If the hum goes away you're probably in better shape.

I would otherwise tend to agree with the sub builder in Portland about installing a plate amp on the side of the box. Problem is that the driver has a specific set of characteristics which optimize it for use with a servo system. It has an extremely low resonant frequency. It also has modifications to the cone. Before you commit to a direction, try the subwoofer connected to a different high power amplifier. That will let you hear what the sub sounds like without the servo. You'll probably be very disappointed. You would do much better to replace the driver as well if you are leaving the servo out of the loop.

Sounds like you're stuck about the same place that I am with this unit.
Click to expand...

Thanks for your help. I will try shorting the inputs and see what happens.

Yeah, I really like this sub, like alot, but if it doesn't end up working I'm also at a loss at what I should move to. Any suggestions?
 
I don't have any suggestions on what subwoofer to move to. I'm a low-budget hobbyist and don't keep up with these things. I'm the guy who would spend a whole lot of time researching how to repair an old subwoofer, sharing what I learn, and as likely as anything never getting back to the project. I have quite an investment of time in studying schematics and trying to secure complete documentation -- and have come to the conclusion that I'm stuck with where I am at on this subwoofer. If I had your amplifier I would at least have a starting place as it Is the correct amplifier for my woofer. But still no documentation.

That said, I've repeatedly heard good comments about the REL subwoofers -- so if your budget allows I have the strong impression that that a great place to start.

If you are working with more limited means and your servo amplifier is failing you and you don't have the expertise to repair it and recalibrate it yourself, I would first suggest that you try the subwoofer with a standalone amplifier to get a feel for what to expect from it without the servo. My guess is that you will end up with that plate amplifier (or other suitable outboard electronics) and a replacement driver to get anywhere close to back to where you were. It's too bad these aren't serviceable. A tech can probably get the hum out of the amplifier -- but proper documentation showing how to recalibrate it is a must.
 
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CoastinHome said:
I don't have any suggestions on what subwoofer to move to. I'm a low-budget hobbyist and don't keep up with these things. I'm the guy who would spend a whole lot of time researching how to repair an old subwoofer, sharing what I learn, and as likely as anything never getting back to the project. I have quite an investment of time and studying schematics and trying to secure complete documentation and have come to the conclusion that I'm stuck with where I am at on this subwoofer. If I had your amplifier I would at least have a starting place as it Is the correct amplifier for my woofer. But still no documentation.

That said, I've repeatedly heard good comments about the REL subwoofers -- so if your budget allows I have the strong impression that that a great place to start.

If you are working with more limited means and your servo amplifier is failing you and you don't have the expertise to repair it and recalibrate it yourself, I would first suggest that you try the subwoofer with a standalone amplifier to get a feel for what to expect from it without the servo. My guess is that you will end up with that plate amplifier (or other suitable outboard electronics) and a replacement driver to get anywhere close to back to where you were. It's too bad these aren't serviceable. A tech can probably get the hum out of the amplifier -- but proper documentation showing how to recalibrate it is a must.
Click to expand...


It's weird. I thought someone on here posted that they had the service manual for these. I found this.
 

Attachments

That's a retyped portion of the service manual - perhaps for the original series since there is no mention of a Series2. That will be helpful to a tech if the amplifier is working properly and it's simply a matter of recalibration. If it's not working properly you really need at least the schematics. That's the part that I was unable to locate.

You had mentioned popping sounds -- on page 9 the manual suggests that you may have a DC output on the binding posts. I mentioned in a previous post that this will confuse the servo.

Unfortunately, this manual does not provide information on how to test the servo amplifier separately from the woofer cabinet. On the Series 2 model apparently you can replace the (RCA) servo return cable with a 1.2 K resistor to at least get the amplifier to power up without the servo return. I don't know yet how that is done on the earlier model -- for lack of a schematic.
 
I just started working my way through the manual. Although there's no mention of this being a Series 2 manual, on page 4 it mentions:

"The servo connection between the Velodyne amp and driver is made with a single RCA cable."

So this partial manual is for the Series 2 -- But may be useful for calibration of a properly working Series 1 amplifier.
 
Nope...That is pages 13 through 25 of the Series 2 schematics. Those are the schematics I said I carefully studied.

Velodyne's new owner searched their records for me this past month. That's all they could come up with -- exactly that file down to the exact file size.
 
@limberpine

I spent another long evening researching what the options are with this 35-year-old subwoofer. I'm approaching it from the perspective of a hobbyist with an engineering degree but, for lack of documentation, have hit the wall on what I can do with my combination of a Series 1 cabinet with a refoamed woofer and an incompatible Series 2 servo amplifier -- and insufficient documentation to allow me to interface the two.

I really like the form factor of the woofer box; its that which provides the inspiration on this project -- but my investment in this woofer is as a learning tool and not as need for a subwoofer. I have a properly working FSR-1500 (which also came from Goodwill).

Of course your mileage may vary and if you have the budget and are interested in making use of the ULD-15 furniture, I'm convinced that the best path is replacement of both the driver and amplifier. Of course there are countless options, but here's some information I encountered in my research which presents as a good starting place:

Here's an enthusiastic review of the ULD-15 with a drop-in replacement driver -- you'll notice from 15 years ago. Apparently this driver is again in current production as a budget series driver for the newly reformed company. This driver seems like a solid bet, but depending on budget and how far you want to take this you might start with the box volume and fitment data and consider other options.

Adire Audio Tempest 15" Subwoofer
https://forum.audiogon.com/discussions/velodyne-uld-15-repair/post?highlight=velodyne+uld&postid=1181996#1181996

Here's the driver on the company's website:

Adire Audio Tempest ADTM15D4 15" DVC Subwoofer
https://www.adireaudio.com/product/tempest-15/

If it were my system I would prefer the use of a standalone subwoofer amplifier over a plate amplifier and associated labor and damage to the the furniture aspect of the ULD-15.

If you've already got the crossover and filtering built into the other components in your system you have a much wider range of choices of amplifiers. Of course it's a different situation if you need the subwoofer amplifier to additionally provide the crossover and tailoring functions. Here's an example of a rackmount subwoofer amplifier which offers those provisions:

Dayton Audio SA1000 Subwoofer Amplifier

Hope this all helps... And let me know if you are abandoning your Series 1 servo amp.
 
Dave Sanford said:
Bill & VonDrake - A quick update to let you both know that the MIDI/DIN recommendation worked! I ordered a 30' MIDI Cable made from Mogami 2948 Cable from Pro Audio LA in Glendale, CA. Cable shipped from stock same day and I had it 2 days later. Connected to my ULD15 and ServoAmp, and beautiful deep, pounding bass emerged. Thanks for your correspondence and recommendations!
Click to expand...
Things like this just spin positive energy into our world when people help out each other. So glad it worked out,enjoy!
 
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