PSW202 + Blown Amplifier = Frankensub

johnchabin

I'm one of the many owners of the PSW202 who went through the blown amplifier issue (bad caps & bad IC). Rather than spend any time or money on repairing the underwhelming and underpowered 50W amp that was part of this package, I opted for a little experiment:

I had an M&K Sound plate amp laying around for a DIY subwoofer project I have been planning, but just for grins I knocked out the back of the PSW202, replaced the back and installed the M&K.

180 watts RMS into 8 ohms @ .1% THD, 272 watts into 4 ohms @ 0.2% THD

With this install, I lost the port that was on the back of the original sub. I ran it this way for a while, but I thought a couple of 10" passive radiators might improve the bass extension. Boy, did it ever.

I always thought the sub had a decent punch, but the bass was sort of generic and not particularly musical. All bass sounded about the same. With 180 W and no port, I was hearing different notes in the bass I hadn't before. The passive radiators have given me the best of both worlds, IMO. Now for some tuning with weights to optimize this nutty idea.

I'm liking it so much I might just go with it for a while.

Tbone289

I like it! Are you using the original driver?

johnchabin

Yes, I generally think the Polk drivers are pretty good. I have a second PSW202, also with a blown amp. My original plan was to make a larger enclosure with both 202 drivers and the 180W plate amp, but this (above) was an easy and fun experiment. The Polk enclosure is pretty solidly built, to the point where it's maintained its rigidity even with a new back and two 9" holes cut in either side.

But before going through the trouble of building a custom enclosure, I'd want the driver specs which are not available as far as I know. And these drivers are 4 Ohm, so I'm more tham a bit hesitant wiring them in parallel resulting in 2 Ohms.

Now I'm considering a second one like the one above for another part of the room...

Tbone289

Yeah, I have a PSW-202 that I use daily in my 2channel rig, and I've found that it's built pretty well also (after disassembling to replace caps and IC). This looks like a great upgrade... Is the bass extension improved? I always felt that the weak amp and short excursion of the driver keep the 202 from reaching full potential. I would think the PRs help in this respect, while also tightening it up vs. the stock port.

I also have a PSW10, the 202's replacement, and feel that it was a huge downgrade from Polk's engineering dept. It's sloppy, has a foam surround, and the port isn't flared internally.

johnchabin

A word of caution. When the sides of this enclosure are cut, bracing is cut as well. I wasn't too worried since it's such a small box, but I have considered cross bracing the box internally (just in case) to reconnect the original bracing. Probably not to worry, as it is just a small 14" cube made of 3/4" MDF.

I don't know if the bass extension is improved (but I can feel it more, telling me it probably has), but the quality of the bass is improved. I really had 3 different subs here, the original with port, the middle one with the new amp and no port, and now the new amp and passive radiators. This one is my favorite so far.

I just finished Yo-Yo Ma performing Bach's Six Suites, and now have Led Zeppelin in the player. Both sound great.

Feels like a good match to the RTi8s with Sonicap update.

johnchabin

And all that said, I still would like to build a larger box with the same amp and both 202 10" drivers. I'd love some specs on these drivers to optimize enclosure size...

But this was fun.

thsmith

Looks like a fun project.

johnchabin

I rebuilt the blown amp in the second PSW202 with new caps and a new IC. It works. I was curious to perform an A/B test between the stock and modified to see if there is a real or perceived improvement.

What I can say is that in a much smaller room (my office) and in a corner, the PSW202 isn't bad at all. Pretty nice, really. The original location for this sub was a very large room, so is probably too much for this little 10" with the 50W amp.

I'd still like to put the M&K Sound amp on both drivers in a custom enclosure, then back out in the big room, but I'm not sure how to size the box without driver specs.

Joe08867

johnchabin wrote: »

I rebuilt the blown amp in the second PSW202 with new caps and a new IC. It works. I was curious to perform an A/B test between the stock and modified to see if there is a real or perceived improvement.

What I can say is that in a much smaller room (my office) and in a corner, the PSW202 isn't bad at all. Pretty nice, really. The original location for this sub was a very large room, so is probably too much for this little 10" with the 50W amp.

I'd still like to put the M&K Sound amp on both drivers in a custom enclosure, then back out in the big room, but I'm not sure how to size the box without driver specs.

You could always measure the cabs they are in now? You will need to separate them internally anyway.

johnchabin

I wonder if the small cubes they are in now really are designed to optimize sound quality, or are just as small as possible to make them more marketable. And if I'm not changing dimensions, why not just stack the boxes I have and call it good?

Or in opposite corners?

I have to be careful about money spent, because at some point I should just buy new drivers online and start from scratch...

Tbone289

johnchabin wrote: »

What I can say is that in a much smaller room (my office) and in a corner, the PSW202 isn't bad at all. Pretty nice, really. The original location for this sub was a very large room, so is probably too much for this little 10" with the 50W amp.

I agree. You can see from my sig that I use a 202 with RT3 mains for my 2-channel office setup. They blend very well musically. I had used a PSW10 before I fixed the amp in my PSW202, and it wasn't nearly as clean and musical, IMO.

johnchabin

I have the PSW202 with RTi4 mains.

My integrated amp has no sub out, so I use the left/right speakers through the sub, then to the RTi4s. Sounds is good, but I wonder if there's a better way (like channel A to speakers, channel B to sub).

I cross over the sub at 100.

Tbone289

Interesting. I've been planning to replace my RT3s with RTi4s if I can find a killer deal on a lightly used pair. Or, at least I'd like to try them out, because the RT3s sound pretty good. The RTi4s are worth it at the current $149 retail, but I'm going to wait it out...

I'm currently running my setup the same way, but have run them parallel in the past. In other words, run both the speakers and the sub inputs directly from the same amp outputs (channel A to speakers, channel A to sub), rather than running in series you have it now. I don't think it will matter much sound-wise unless it will allow you to shorten your wire runs. However, you may get cleaner signal to your RTi4s this way, since the signal is not being sent to the sub first. Polk recommends both setups.

I run the low pass filter at minimum (80Hz). The RT3s have pretty good low frequency output for their size. Anything above that starts to make the midbass sound a bit too full to me.

johnchabin

The RTi4s were rears for my surround sound system (RTi8 fronts). For political reasons, they haven't made it back into the living room, so now they live in my office. I think I might prefer the RTi4's 5.25" mid to the RTi8's 6.5". Not really a fair comparison because of room size. Both speakers need a subwoofer.

Anyway, this has given me the opportunity to listen to the RTi4 more closely. I can't compare them to the RT3s, but I give them a high recommendation.

And since this is a subwoofer thread, I should mention that the factory PSW202 with cap and IC repair is quite capable in a small room.

Tbone289

Hey John, does the integrated you're using have a pre-out/main-in loop? If so, there's another way you can hook up your sub with better results.

johnchabin

No pre-out/main-in loop, just a line input that allows me to use it as a power amp. It's a Pioneer A-35R.

Tbone289

OK. I just looked at the manual. That's a neat little amp.

Unfortunately, I see no way to connect your sub other than to the high-level (speaker) outputs. That leaves you with the three configurations we've already discussed.

1. Speaker "A" outputs to sub, sub outputs to RTi4s (as you have it)
2. Speaker "A" outputs to sub, Speaker "A" outputs to RTi4s
3. Speaker "A" outputs to RTi4s, Speaker "B" outputs to sub (or vice versa), as you mentioned above

I'm thinking #2 might be the best setup, and that amp should have no trouble with that setup since it's low impedance (4 ohm) stable.