Built in subwoofer plate amp is dead. Any reason not to use an external amp?

[swechsler]

The subwoofer in question is an NHT SW10 Mk II. All the sub will do is produce a loud hum when the gain knob on the back is turned all the way clockwise. I pulled the amp and looked for obvious issues (leaky caps, broken boards) and didn't any. The sub is connected to an HT receiver with a sub out, so I really don't need any of the controls on the sub's amp. I have several unused power amps sitting on shelves in my storage area, so I'm thinking I could wire one of them in using the NHT's high level inputs, and inside the cabinet, wire the input directly to the driver. I prefer this idea since it doesn't require modifications to the cabinet, and if at some later date I find a replacement amp (or decide to get this one repaired) I can get it back to stock appearance fairly easily.

I know that plate amps are available, but I suspect using any of them would require making severe changes to the cabinet. I could also get the amp repaired, but it looks like repair costs would approach the working value of the sub. In addition, budget is tight right now; my entire team at work has been laid off in favor of cheaper offshore workers (in Warsaw, of all places).

The amps I'm thinking of using are commercial amps from Crown, QSC or Rane. Any caveats? Any reason not to do this?

 

[jlovda]

Aside from the obvious high pass and low pass filters, do OEM plate amps have some equilization built in or are they flat? This could also mean an underdamped high pass filter with a bump.

 

[djnagle]

No reason what so ever. I just built two more subs and I am using the Behringer iNuke 3000 with built in DSP. I have way more tuning capability with the DSP than any plate amp.

 

[jblnut]

There are only two kinds of subs with plate amps - those that are still working, and those that have failed. The vibration from the sub driver is slow death on all of those components.

Best thing you can ever do is use a separate amp....

jblnut

 

[jdmccall]

I have a Dayton Titanic III 10" sub in which the plate amp failed. I was told parts to repair it were no longer available. So I pressed my Onkyo M-282 into service. Bass management is done in the AVR anyway in this system, so it all works out fine.

 

[swechsler]

Thanks guys. I'm assuming that the NHT doesn't have any built-in EQ, so I figure I'm good to go.

 

[Freddymac2]

swechster, do you eat the frogs you whisper to? My wife loves legs. Most good subs have boost built in and sharper crossover cut off than any AV unit would have.

 

[cassette]

I have had NHT repair the plate amp for one of my SW-10s. They had great service, but it wasn't cheap. I bought another SW10 with a bad plate amp and Parts Express has one that drops in and even uses the same screw holes. If I recall correctly, it is slightly less powerful than the original one from NHT, but the price was right and it was a simple fix.

A

 

[transmaster]

All of the anti-vibration potting on my Kilpsch subwoofer is what caused me to purchase a new plate amp. All that was wrong will the old one was a damaged RCA jack. But it was potted with a goop I could not clean off so I could solder in a new one.

 

[WaynerN]

Parts Express (Dayton) has a sub woofer amp that has cross-over pot, phase, speakers outputs, HI level inputs, line level inputs and LFE inputs.

https://www.parts-express.com/dayton-audio-sa230-230w-subwoofer-amplifier--300-813

 

[swechsler]

Most good subs have boost built in and sharper crossover cut off than any AV unit would have.

This is what I'm trying to clarify. I don't care about the crossover because I wasn't using it, but do good subs actually artificially boost the bass? If so, how is it that drop-in plate amps work well? The amount of boost needed would vary from system to system, wouldn't it?

And again, I would prefer to avoid spending money, especially since I already have the external amps.

ETA: I see a few PE plate amps are sold both in a boosted and non-boosted version. That doesn't really clarify my situation, though, although it does confirm that at least some subs use a LF boost circuit.

 

[cnolanh]

OP, you're getting good advice here. I have powered two different subs (one passive and one with a failed plate amp) with this flexible little Dayton APA150:
https://www.parts-express.com/dayton-audio-apa150-150w-power-amplifier--300-812
Beyond sub duty, it also functions nicely as a full-range stereo or mono amp when needed.