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Subwoofer Plate amp shot - Options?

ScooterMcTav

ScooterMcTav

I know less than I think
So a few months back I picked up a PSB Subsonic 6i locally, purchased with the knowledge it is not working.

After ordering parts, and paying my local electronics guy to solder them on, it is still not working - likely as the crummy glue smeared everywhere is causing continued shorts somewhere on the plate amp. Based on Internet research, it appears this is an extremely common failure.

That being said, it has a nice driver, and an excellent front ported cabinet. So I am considering a number of options. FYI, the original plate amp was a class D 225W continuous power BASH MOSFET amp.

It seems I have a few options, priced from highest to lowest:

- Blow the larger dollars for the "right" plate amp
- Save some scratch on a lower powered plate amp
- Purchase an outboard sub amp and treat the sub as a passive
- Set up a second amp I already own with pre-ins to drive the sub, and put a low pass filter between the speaker outs and the woofer

Welcome the thoughts and experiences of others in doing something like this.
 
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I know nothing of this sub, but it sold for about $750. You will be hard pressed to find a 225 watt bash amp with a 24 db per octave crossover. parts express is where I would look for cheap. Have you talked to the sub manufacturer, the sometimes have fair deals for replacement, although they may not honor it due to the fact you had someone work on it. Sometime when they have a known defect they have a program to make it right.
 
I know my experience is limited to the mildly anecdotal, but it didn't take me long to tire of plate amps as they never seemed to last for me, and I drive my speakers like an old man. If you've got a HT receiver or a relatively modern preamp, you've got subwoofer control function available to you. It's just a matter of laying hands on a cheap, Craigslist power amplifier (easier said than done in Manitoba, I suppose).
I've had two different Kenwood power amps that I bought on the cheap on subwoofers in two home theaters and both have outlasted previous plate amps.
 
I had the same problem with one of my 4 REL Q201e subs . I purchased a Crown XLS 2502 amp drilled some holes in the plate amp installed binding posts on 2 of my subs. The Crown has a built in low pass . I would find another matching sub and set both up the same way .
 
I have a PSB Alpha SubSonic 5i that ended up with this same dilema.
After much thought I decided to go the "convert it to passive" route.

The conversion is still in progress,but here's how I'm approaching this:
My plan was to add it to my basement workbench system that's powered by a NAD 3140 integrated that feeds some Optimus Pro7AV.
Now a while back I picked up the 3140's matching NAD 2140 power amp just in case I wanted to bridge both amps and bump up the wpc of that rig.
I thought "hey,why not bridge just that 2140 power amp and use that to power the converted passive sub" ???
Thus the seed of a plan formed.

I bought one of those adjustable low pass active crossover boards with Hz/level controls,and a DPDT switch for polarity.
Those will be mounted to a blanking panel for the telco rack all this is mounted in.

I gutted the plate amp & I intend to use a single +/- pair of the binding posts for the speaker inputs for the +/- speaker leads from that bridged 2140.
Plan is to block off any remaining openings on the former plate amp (so now it's just a block-off plate).

Got all the parts now,just need to get off my @ss and find the time to get it all finished.

And yeah those PSB subs have some nicely designed cabinets & drivers so IMHO it's worth doing SOMETHING with it.

FWIW

Bret P.
 
Freddymac2 said:
I know nothing of this sub, but it sold for about $750. You will be hard pressed to find a 225 watt bash amp with a 24 db per octave crossover. parts express is where I would look for cheap. Have you talked to the sub manufacturer, the sometimes have fair deals for replacement, although they may not honor it due to the fact you had someone work on it. Sometime when they have a known defect they have a program to make it right.
Click to expand...

Unfortunately, these plates are not provided under any manufacturer program - the failure rate was so high, the part supply was exhausted. But I have looked at the PE plate amps,and am just sad even with this route I lose the front volume and crossover controls.

Porkloin said:
I know my experience is limited to the mildly anecdotal, but it didn't take me long to tire of plate amps as they never seemed to last for me, and I drive my speakers like an old man. If you've got a HT receiver or a relatively modern preamp, you've got subwoofer control function available to you. It's just a matter of laying hands on a cheap, Craigslist power amplifier (easier said than done in Manitoba, I suppose).
I've had two different Kenwood power amps that I bought on the cheap on subwoofers in two home theaters and both have outlasted previous plate amps.
Click to expand...

I would likely use it with my Marantz 7.2 HT receiver, so could run its sub pre to a second amp which drives the sub. Not a bad idea. This is actually a free option, as a I have plenty of gear around.

enginedr said:
I had the same problem with one of my 4 REL Q201e subs . I purchased a Crown XLS 2502 amp drilled some holes in the plate amp installed binding posts on 2 of my subs. The Crown has a built in low pass . I would find another matching sub and set both up the same way .
Click to expand...

Kind of thinking something this way too, but was looking at subwoofer specific outboard amps.

Bret, your idea is interesting as well. However I do have an old Rotel RX-600 that has a pre/power section, and it might be a good fit here. Power amps are a bit scarce here, and for the price, might as well pick up a plate amp.

I like Porkloin's idea just for the zero cost factor, so we'll give that a try.
 
The BASH concept is pretty cool, but it doesn't seem like it was tested for reliability.. I don't know if the failure rate is due to poor quality components, underrated components, or just a poorly designed amp. I have both a BASH 300 and 500 from PE. The 300 is 3 years old and still working, and the 500 is brand new. Both have no name capacitors, and I have a Boston PV800 (mfd in 2003) with a BASH amp, still working, but everyone else seems to have failing amps, especially Klipsch subs and their computer speaker system.
 
Did you ever look at the construction of the average subwoofer plate amp -vs- an old A/B external amp? The average (note the word "average") plate amp doesn't have the big, honking heat syncs that strain your back to lift, a big wadd of capacitance and is crammed into a big, vibrating box (to those of you that popped in here while perusing Amazon for robotic female companionship,this is not always a good thing). Some of the plate amps at PE even have their own heat holding plastic enclosures to intensify that issue. I'm amazed that they last for more than a year of the abuse that bass heads like to dole out.
Unfortunately, even with the subwoofer controls built into modern receivers, the precedent of the plate amp is insurmountable. The external amp for subwoofers will remain the realm of guys like me that gave some shaky derelict from Craigslist 20 bucks for an old Kenwood amp that's still churning 35 years after it's manufacture.

I have no recollection where I got that sheet of aluminum as I've started to balk at materials pricing as of late, but it was still cheaper than a plate amp. The terminal plate I found (new) for a couple of bucks in an electronics surplus store.

IMG_0726.JPG
 
Porkloin said:
Did you ever look at the construction of the average subwoofer plate amp -vs- an old A/B external amp? The average (note the word "average") plate amp doesn't have the big, honking heat syncs that strain your back to lift, a big wadd of capacitance and is crammed into a big, vibrating box (to those of you that popped in here while perusing Amazon for robotic female companionship,this is not always a good thing). Some of the plate amps at PE even have their own heat holding plastic enclosures to intensify that issue. I'm amazed that they last for more than a year of the abuse that bass heads like to dole out.
Unfortunately, even with the subwoofer controls built into modern receivers, the precedent of the plate amp is insurmountable. The external amp for subwoofers will remain the realm of guys like me that gave some shaky derelict from Craigslist 20 bucks for an old Kenwood amp that's still churning 35 years after it's manufacture.

I have no recollection where I got that sheet of aluminum as I've started to balk at materials pricing as of late, but it was still cheaper than a plate amp. The terminal plate I found (new) for a couple of bucks in an electronics surplus store.

View attachment 1017614
Click to expand...

The idea with BASH, and Class D, is you use a switch mode power supply, and because the design is thermally efficient, you don't need huge heatsinks.. They don't need a big wadd of capacitance since a SMPS operates on different principals than a conventional design.
 
Plate amps in subs are a bad idea in the first place. They will literally shake themselves to death.

Put a block-off plate over the hole with a speaker terminal and put/use the amp in a separate enclosure. This is what I did the second time my Sunfire broke down. Since putting the amp in its own enclosure and making a block-off plate for tthe cabinet, no problems.

In fact, the amp runs cooler and the cabinet has a bit more internal volume.

My amp is actually located in my bedroom closet behind the wall.

Sunfire_003.JPG


With the speaker in the living room.

Sunfire_004.JPG
 
I picked up an older Sonance component sub amp on ebay for $50. The external speaker inputs didn't work but it's in a seperate pre/amp system so it didn't matter. I never bothered to look up the specs but it will drive a jbl 12" to moderate level no problem.
 
Sometimes Apex Jr has plate amps. I have no experience with them, other than occasionally looking at the website, so caveat emptor.
 
ScooterMcTav said:
I would likely use it with my Marantz 7.2 HT receiver, so could run its sub pre to a second amp which drives the sub. Not a bad idea. This is actually a free option, as a I have plenty of gear around.
Click to expand...
If you've run your Audyssey utility on the old subwoofer amp, you may have to re-do it for the new amp. If you haven't done it, it would be worth looking into. I pretty much hated my subwoofer at the other end of the room from the front speakers. It sounded out of place. I'm sure the Audyssey adjusted the phase issues, which are pretty obvious to me over the distance of 10 feet. I manually upped my volume level a couple of notches (Denon 3808) and the crossover point by 20 Hz, but the Audyssey did most of the correction for me. I doubt that I could do as well twisting the knob on a subwoofer amp.
 
Unless the gain of the external amp is the same as the plate amp was dialed in, then certainly the levels will need to be reset/recalibrated if you want it back the same way.

I like the trim levels in my pre/pro to be roughly centered around 0dB. So, after I run the cal I go back in and see where the levels ended up. If the trims are more than a few dB above or below 0dB I'll turn down or turn up the gain/level on the sub or external amp accordingly and then run the cal and check it again.
 
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