Nice inexpensive experiment, great results

DangerBoy

Active Member
At my cabin I have a Panasonic SA-PMX9 micro stereo system that is a few years old. These systems were fairly good and fairly well reviewed at the time they came out (https://www.whathifi.com/panasonic/sc-pmx9db/review). I was never all that satisfied with the speakers though. They were a bit muddy and lacked punch but what can you expect with a well featured system that only cost ~$450 - $500 CAD?

I decided I wanted to get a better set of speakers for the system but didn't want to spend a lot, maybe $150 - $175 CAD at most so I purchased a used set of PSB Image 2B bookshelf speakers which I think originally retailed at about $400 and were also well reviewed in their day.(http://www.audioreview.com/product/speakers/floorstanding-speakers/psb-speakers/image-2b-b25.html). I think I picked the pair up in real nice condition for about $110 or $120 CAD. One of the first things I did after I got them was to check out the crossovers to see what they had on them for Caps. They had three 10% spec non-polarized electrolytics 1.5 uF, 8.0 uF and 12.0 uF. I decided to try upgrading them to audio grade Polypropylene caps. To stay within budget I went with Dayton 5% Poly caps, 1.5 uF, 8.2 uF and 12.0 uF. I purchased them from Solen.ca here in Canada because the shipping cost was so much cheaper than buying from a US vendor. I can't remember what it cost me for all 6 caps but it wasn't very much.

The poly caps were quite a bit larger than the original electolytics so I had to solder the two larger caps to the back side of the circuit board as shown in the photos.

Sonically, I'm VERY pleased with the result. The speakers sound noticeably better than they did with the original caps and waaaaaaaaaaaaaaay better than the Panasonic speakers that came with the system. Highs are really crisp and clean, there's lots of detail in the highs and mids and the imaging is good too. The PSB woofers are surprisingly good as well and deliver pretty good bass with plenty of punch although the butyl surrounds came unglued from the bezels on both woofers so I'm wondering if that's a common fault with these speakers. That was a quick, easy and inexpensive fix, however, (see this thread for how I fixed them (http://audiokarma.org/forums/index....uick-speaker-surround-gluing-question.826128/). I'm curious to see how they'd sound hooked up to a better system but I don't see that happening anytime soon as these babies are staying out at the cabin for the foreseeable future.

The bottom line here is that if you're looking for a decent pair of bookshelf speakers at a budget price and happen to come across some PSB Image 2Bs at a bargain price, buy 'em, throw some inexpensive audio grade caps in 'em and you'll be a real happy camper. They're definitely worth modding and you'll get a set of speakers that sound as good as something that would cost you many times more from a store. I'm pretty pleased with how the Daytons sound in them but you might get even better results with some other brands but be mindful of the diameters, as the cut-out on the back of the cabinets on these speakers don't give you a whole lot of extra clearance.

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The 1.5 uF Cap glued on top of a resistor.

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The 8.2 uF and 12 uF caps soldered and glued to the underside of the circuit board. Note the short length of red wire used to extend the one lead from the 12 uF capacitor.
 
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Update to my previous post: I just went through listening to Afrocelt Sound System Vol. II CD on it and during the play I experimented with some of the Panasonic's preset EQ modes and tweaked a couple of them and finally arrived at what to my hearing was a perfect setting. I would now rank the sound of these modified bookshelf speakers as powered by this decent micro stereo system as "astonishing" or "incredible" considering the money spent on the system. For what I spent on the speakers and the mods, the results I got were incredible. I encourage others to look for a set of these speakers used and do some cap mods on them. It will be a great investment. :rockon:
 
It can be a challenge fitting new film caps when the crossover is mounted to the speaker terminals.

Normally, it is best to keep some clear air space around resistors. There is a reason most crossover resistors are rated at 5 or 10 watts. If you crank the speakers the resistors may get warm.

If the hot glue does not melt and drip down over the resistor after you pump some power through the speakers, you are likely fine.
 
No evidence of that happening so far and I've been playing them at high volume for the last few hours straight. I'll keep that tip in mind for next time though.
 
With 10% total harmonic distortion that amp is going to ruin those speakers at the "high volume for the last few hours straight." Sounds like your having fun!
 
With 10% total harmonic distortion that amp is going to ruin those speakers at the "high volume for the last few hours straight." Sounds like your having fun!

I see that's what they put in the spec sheet for THD but that must be a mistake or a misprint. No modern amp has 10% THD. The amp doesn't distort at all. It's clean and clear even at the volumes I like to listen at and I like listening at a fairly high volume. I have no concerns whatsoever about the amp damaging those speakers.

I really am confused about that 10% THD rating. They must've slipped a few decimal points or something. That was considered a "high end" micro system a few years ago... :wtf:
 
Well after further research I stand corrected. Distortion will not harm speakers. Thanks bowtie427ss!
The 10% thd rating on that amp was the FTC(federal trade commission) rating of continuous musical output. The RMS rating is at 1% which seems to be average.
 
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