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KSW-150: Possible problems???


stepher

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Hi all,

Happy holidays to everyone!!!

I have a KSW-150 10" @ 150W (supporting a set of KG 2.5s). I'm original owner. I've had some minor problems along the way (hum because of a cold solder joint on one of the filter caps, for example), but the sub has performed flawlessly, otherwise (there's a reason I won't settle for less than Klipsch :)

Within the last 6 months I've notice what sounds like "clipping" at higher volumes (I expect it could also sound like voice coil problems for the sub speaker, but it doesn't sound quite that "scritchy", if you know what I mean). When I first noticed this, it seemed to be related to HD/surround sound (it was very obvious during some intensive room-filling, low-end material on the movie Oceans...environmental flick, not the George Clooney ones ;) since I never noticed it when playing 2-channel programs (CD, etc.). My initial thought was it might be something in the receiver decode circuitry causing the problem. However, the other day out of curiosity I cranked up the sub during 2-channel play and discovered the "clipping" noise was there, just at much higher volume levels than during surround sound material (why I never noticed it).

I've done minimal testing on the sub speaker itself. Since it's a down-firing unit, I did flip over the box and carefully pressed the speaker in ~1/4" and heard no rubbing or "scritching" noises (associated with a loose voice coil). I plan to test the coil with a DMM, tho I'm expecting that may not be much of an indicator except for a catastrophic failure (which doesn't seem to be the case, yet). I read somewhere about performing a "battery" test by momentarily connecting a 1.5V battery across the speaker pins and listening for some sort of "wooomfp" (sans "scritching" and "clipping" sounds). Any input on the wisdom of doing this.

I'm hoping it may still be a clipping issue, but related to the amp/power supply. Only problem is I'm not sure what normal is supposed to be (i.e. supply voltages both with and without loading, etc.). Schematics don't seem to be available (readily or otherwise) so I have no roadmap. I have looked at the LFE signal (from the receiver) using a scope during both single LF tone and the Oceans video and saw nothiong obvious (makes me want to eliminate the receiver as a culprit). I suppose I could get ambitious and look at the output of the sub amp to see if the clipping is occuring there. I'd be grateful to anyone with knowledge or experience with these kinds of subs for any suggestions in this area.

Cheers....Steph
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Happy Holidays to you.

If you can press in on the driver and it feels smooth then the voice coil is most likely fine. If the noise has a fast paced "clack" sound then it may be the suspension bottoming out on the driver itself. It would be normal to hear this more in a movie with a strong LFE track as you describe. The drivers suspension is weaker now than it was when it was new and easier to bottom out.

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Appreciate the input.

After I saw your posting, I went and did another pressing on the cone and pushed it beyond the 1/4",
close to a half inch, and no sound at all, not even any sense of bottoming out. Feels fairly firm, too. I know the sound you mention. I've heard it in other speakers I've blown...cheap ones, fortunately :) I also took a closer look at the rolled rubber edging and it shows no signs of
tears or any wear and appears to be solidly attached both to the paper cone and the frame. In fact, other than a bit of dust, it looks almost as new as the day I bought it.

I hadn't thought about it being just an age-related issue, but what you say makes sense. I've had it over 10 years, prob'ly closer to 13. I think the speaker is of the K1049 series.

I still plan to look at the sub amp audio circuitry with a scope and check the power supply under load, just to be sure. If one of the filter caps dried up or a diode got leaky, or a bypass cap went bad, it could still be an electronic issue (certainly easier to fix than the speaker).

So, assuming it is an age thing, any suggestions other than replace or rebuild (or keep the volume lower) to fix it.

Thanks and cheers....Steph

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I'd relegate it to a possible second system in a smaller room (if that's even a possibility). There's no way I's spend any serious money on a 10 year old sub. If you can fix it with a cap, or with some inexpensive part, it would be worth it to repair it. Subwoofer technology has come so far in the last 10 years (especially in the drivers) that I'd have to look at something new, but that's just me. Everyone's situation is different

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Thanks for the help.

I did some prelimiinary checking and the replacement speaker looks to be about $140 or so. So, your point's well-taken about not fixing/replacing the speaker. I'll troubleshoot the sub amp and if that doesn't solve it, I'll figure where to go from there.

Just out of curiosity....is this kind of "old age" something that is somewhat common to subs or speakers in general? I expect that subs might be susceptible because of the focus on lower frequencies.

Thanks again and cheers....Steph

I'd relegate it to a possible second system in a smaller room (if that's even a possibility). There's no way I's spend any serious money on a 10 year old sub. If you can fix it with a cap, or with some inexpensive part, it would be worth it to repair it. Subwoofer technology has come so far in the last 10 years (especially in the drivers) that I'd have to look at something new, but that's just me. Everyone's situation is different

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Don't have a definite answer but I can speculate. I would think that any speakers suspension would loosen over time just by the nature of how it works. I would also think that a driver mounted horizontally would be even more succeptible to suspension sag because of the way it "hangs" off the suspension. The fibers of the spider most likely free up to a certain extent. I'll bet if you could measure the Fs of the speaker now it would be much lower than when it was new.

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