Originally Posted by Rob Morse
Resurrecting subwoofers in this condition is not often practical. The reality is you have a beat up cabinet and need a replacement driver and amp assembly. The cost of purchasing these components is fairly high. Repairing the amplifiers would be difficult as the schematics are not available since the those amps are still used in current production pieces.
With regards to creating your own, my ability to advise is quite limited. When we assemble our subwoofers care is taken to match the drivers and amplifiers to work together. It is advised you are cautious and realize you operate at your own risk when creating a Frankenstein subwoofer from miscellaneous components. Any safety agency approvals the devices once carried are null and void once you start mixing components.
Thank you very much Rob for your response. Regarding electronics repair, this is what I did in the military, and as a hobby off and on for 30 years or so. I have gone as far as reconstructing or duplicating snapped circuit boards. So, replacing the bad capacitors, testing the power supply section is fairly straight forward. However, both of these amps use what appears to be an accelerometer glued to the speaker cone to provide the feedback to the preamp stage of the plate amp, or on the Digital Drive plate amp, there is a more advanced controller board with an onboard computer on it. This is the part of the amplifier which I imagine is your trade secret. The actual amplifier module on these plate amps appears to be a fairly straightforward amplifier. However, I was somewhat surprised to see that both of these amps rectify AC line current straight from the input plug with no power supply transformer... safety is definitely an item to keep an eye on here. With this in mind, I can see how you would make a recommendation to stay wall away from the amplifier module. I was also surprised to see that you are only using six 1000uf capacitors to filter the power supply for a 1250 watt rms output stage. Although at the ~170 VDC used by the module, your amp would only be pulling about 7-8 amps, but that still results in quite a bit of power supply ripple. Perhaps this is possible due to the Class D amp. All my experience has been with older style Class A or B amps years ago.
Anyway, on the Digital Drive plate amp, there are two jumper blocks, neither one is labeled that I could see. On the left is a block with five or six jumper positions and no jumpers in place. On the right side, there is one with two jumpers positions and a jumper on the right pair. Are these used as a proprietary connector to program the controller module at the factory to match the driver installed in the box, or are they there to set additional options ... Perhaps there is an option to disable the accelerometer feedback. I believe that I have the accelerometers for each plate amp, but would prefer to just disable or bypass the accelerometer function for testing the amps prior to investing in a replacement driver, even though I considered gluing one to a standard 15" driver, but doubt that would work well since the dampening and excursion would not match the intended driver at all.
I do realize that these plate amps are probably not worth the time to fix up. I may just toss them out and build a DIY sub following a proven plan. But on the other hand, I may see if I can fix them up just for the challenge to see if I can do it. I may even scope the 10 or so pins going between the pre-amp or controller boards and the amplifier module and just build a new pre-amp section to drive the amplifier module, just to see if it can be done.
As far as building a franken-sub. I suppose you could call it that. I prefer to call it a learning experience whether the plate amps are repairable or not.
P.S. I know it may be a long shot. But could you provide part numbers and a ball park figure for how much the 15" drivers to match these two plate amps would cost? That would help me decide if I want to resurrect or just experiment with these plate amps.
Thank you very much - JZ