Sub project suggestions wanted..

shack

Thanks to a truly enjoyable transaction with dholmes I am now the proud owner of two new Polk PSW202 subs.

(a brief sidebar here - dholmes is a really nice guy. We live about 180 miles apart and he agreed to meet me somewhere in the middle to exchange the subs for cash. I now know I am jealous. In the short time we had to talk I found out that he may have the ultimate "mancave". His home theater is in a totally separate building from his house. Like he said, If he wants to crank it up at 3:00AM he can...and with rti150s that shouldn't be a problem. Thanks)

Since I got both at very reasonable price I am thinking of upgrading one while keeping the other stock to compare. I have one hooked up with a pair of Rt25is and they make a nice combo. For $229 MSRP they are built well and look and sound nice. Unfortunately they seem to be a little boomy. I'm not sure how I'm ultimately going to use these. I currently have the Dayton Titanic 10" sealed sub in my HT and it is excellent. I may consider using both of these in the HT and moving the Dayton with the RT25is for a 2 channel system. If I can tighten up the 202 I may use it in the 2 channel system.

Here are a couple of things I am considering. First off, when looking inside the port (I haven't cracked it open yet) there seems to be very little in the way of foam or polyfill in there. I might add a pound or two to see what that does. I also might consider bracing the inside of the box a little more. An amp upgrade is a possibility. Parts Express has a couple of plate amps to consider: this 120W Amp or this 250W Amp. Either one would probably be an upgrade from the current amp. I could maybe live with the stock amp if I could replace those %$#%^&$& spring clip speaker terminals since I may have to use the speaker level inputs in a 2 channel system (A note to Polk - PLEASE consider using the 5 way terminals on all of your speakers - It can't cost that much more and surely joe6pack - no offence Club Polk Guy - could figure out how to work them - the spring clips SUCK !).

These are my thoughts. Does anyone have any suggestions or comments before I start this little project? I would love to hear what someone like Ken S. would have to say but I know he probably can't give suggestions - warranty considerations and such. I know I'm voiding my warranty on at least one sub, but for what I paid that is no problem. I think I am starting out with a decent driver, box and amp (except for those clips!). I'm anxious to see if I can "improve" it just a little.

Dr. Spec

I have nothing constructive to offer, so I figured maybe a little humor wouldn't hurt. Why don't you install one of these in the 202 enclosure?

Dr. Spec

Sorry, forgot to add pic in my evil enthusiasm.

RuSsMaN

Fill and bracing sound like good places to start. Isolation might be something also, along the lines of a slate for it to sit on, and perhaps some weighted object on top.

Cheers,
Russ

Dr. Spec

Yes, Russ' advice is very good.

Sorry about the Adire crack. I LOVE that driver though. xMax = 37 mm one way - 3" peak to peak linear excursion. Can you say MOVE some air? Holy shista!

A little polyfill inside can fool the sub into thinking the enclosure is a bit bigger than it really is and might drop your F3 a tad. It will also help damp standing waves if they are present.

I'm not sure how you could internally brace such a small enclosure through the woofer hole, and it might not need it. Enclosure flex will definitely make a sub sound bad, that is true, but those little box enclosures that Polk makes seem pretty sturdy.

Elevating the sub a foot or two might take away some boom, if you can find a stand or shelf unit.

As for an amp upgrade, I don't really see the merit for such a small driver with limited power handling capability. I agree the spring loaded connectors are a PITA. I have to deal with them on certain parts of my equipment too.

Doc

kberg

Originally posted by Dr. Spec

Elevating the sub a foot or two might take away some boom, if you can find a stand or shelf unit.

Doc,

So if I elevate my Infinity BU2 (downfiring sub) from the carpet by such a distance and perhaps have it downfire on a piece of slate or other hard surface, I might improve the tightness of the bass response, and allow it to sound less "boomy"?

I touched on this in another thread but just wanted to be sure of what I might expect by doing this.

shack

Originally posted by Dr. Spec

As for an amp upgrade, I don't really see the merit for such a small driver with limited power handling capability.

Doc, What info do you have that this driver can't handle the additional power? Since it is a powered sub Polk doesn't give max power specs for the driver. You may be right. I'm not looking for more power necessarily just more clean power at any given output level. Wouldn't this tighten the sub up a bit? Am I "barking" (just one of the dog pack :rolleyes: ) up the wrong tree here?

Thanks for the input.

Dr. Spec

Originally posted by kberg


Doc,

So if I elevate my Infinity BU2 (downfiring sub) from the carpet by such a distance and perhaps have it downfire on a piece of slate or other hard surface, I might improve the tightness of the bass response, and allow it to sound less "boomy"?

I touched on this in another thread but just wanted to be sure of what I might expect by doing this.

No, it's a matter of "uncoupling" the sub from the floor. If you have anything other than a slab on grade, it can couple to the floor and the opening below it and create a boomy resonance.

You can try the slate as a method of uncoupling, but bass waves, (as tour2ma stated) are difficult to get rid of and carpet doesn't really do a great job of absorbing them.

Dr. Spec

Originally posted by shack


Doc, What info do you have that this driver can't handle the additional power? Since it is a powered sub Polk doesn't give max power specs for the driver. You may be right. I'm not looking for more power necessarily just more clean power at any given output level. Wouldn't this tighten the sub up a bit? Am I "barking" (just one of the dog pack :rolleyes: ) up the wrong tree here?

Thanks for the input.

None - it's simply an educated guess that Polk wouldn't mismatch a driver and an amp in a self powered application. From a production cost and economics standpoint alone, it wouldn't make sense to match up a 50 watt amp with a 200 watt driver.

With that said, doubling the input power will give you a 3 dB increase in volume, assuming (and that's a big assumption) you are still within the safe operating limits of the driver.

So I guess the question becomes are you willing to spend $100 (plus s/h) for a PE amp on the outside chance the driver can safely take 100-120W and provide another 3 dB or so of output?

As for "cleaner power", the PE amp might have a higher damping factor than the Polk unit, and that might help. You'll hav to email both and ask for that spec.

I just think the other suggestions above make more sense to try first. The amp would be at the bottom of my list on the cost/benefit ratio aspect of things.

kberg

Originally posted by Dr. Spec


No, it's a matter of "uncoupling" the sub from the floor. If you have anything other than a slab on grade, it can couple to the floor and the opening below it and create a boomy resonance.

Aha - My system is in my family room which is on a slab and is carpeted, so boomy resonance shouldn't be an issue, if I understand you correctly.

shack

None - it's simply an educated guess that Polk wouldn't mismatch a driver and an amp in a self powered application. From a production cost and economics standpoint alone, it wouldn't make sense to match up a 50 watt amp with a 200 watt driver.

I figured that was your reasoning, but was just curious if you had additional info.

Well, I opened it up tonight (see pic below). Your thoughs on the bracing were correct. It is fairly well built for the price and not a lot of room for improvement. The driver is an decent but enconomy grade driver. There was a little polyfill in the bottom of the sub but not much.

TEST 1 - I started out putting about 16oz of polyfill (I read where you want about a lb. per cubic ft.). Too much. The sub went a little lower but it had to be cranked out full to get there. The sound became more muffled and not as clean IMO. For this test I had the original sub and the modified sub hooked up to a Sony receiver with A/B speaker switch using a set AR and Polk bookshelfs with speaker level inputs. This way I could go back and forth using the same material and get instant real-time comparisons. I proceeded to remove about half of the Polyfill so that the front part of the box was filled with the back half open. Lost some of the low extension but it still sounded muffled.

TEST 2 - Both subs in their original configuration. Since the Sony does not have pre-outs I left one sub hooked up with the speaker level method and then hooked the other sub up in the line level method using a set of audio out RCA jacks. Then I compared the two trying to make sure the crossovers and volume level matched as much as possible. This took a little more effort to do because I had to keep the sub hooked to the audio out jacks turned off until I was ready to switch. There was a marked difference in favor of the line level. Now this would be hard to do real world since there is no volume control of the sub from the receiver using this method.

Bottom line...These subs are good for what they are...and entry level sub with good performance at this price level. Better for music applications vs HT. Polk is getting as much out of this setup as possible. They just don't go low enough or loud enough for a serious HT setup. How I plan to use them is with the RT25is for a modest 2 channel rig. Maybe one or maybe both...I'll just have to play with it. I think that placement and method of hookup will have a lot to do with smoothing them out. I've got a little NAD integrated but if I use it I will have to use the speaker level method. I'll hook it up this weekend and see how it sounds. If that doesn't sound good I may be able to swap it for a Denon stereo receiver that has a sub out jack that may work better.