What's wrong with this $$$ speaker?

[cdwitmer]

I need to repair a nice pair of Pioneer 3-way speakers that cost the equivalent of US$2000 when they were built in 1986. At the time, these were Pioneer's best consumer-use speakers (excluding the TAD line). I just reconed the woofers, and all the transducers sound excellent. The problem is intermittent loss of sound from one enclosure (all three transducers go silent simultaneously). The problem is almost certainly in the crossover network, but I am not sure if it is a degraded passive component (such as a capacitor) or a bad connection due to a loose wire, bad solder, etc. (BTW, I know the problem is the network because it persists 1) regardless of what amp I use, and 2) even after swapping the drivers between the two cabinets.)

The problem is intermittent. When it occurs, it occurs in the first few minutes of operation, and with continued operation, it usually disappears. Rather than noise occurring, there is loss of sound from the loudspeaker. For example, this morning I decided to test the problem by playing only the offending loudspeaker. At first, no sound would come out at all. Then, after a few seconds, I got clean sound -- without any distortion that I could notice -- for about three minutes. At that point, I lost sound momentarily. I could hear the sound rapidly fading out and disappearing altogether, in the space of no more than a second. Then, after a second or two of silence, it came back and I could listen for the next 90 minutes straight without a single glitch. This is a very typical pattern. It seems almost as if "warming up" solves the problem. Does this suggest anything? This loudspeaker has a rated efficiency of 90dB, and I never play loud, so I think at most I am putting a watt or two into these speakers most of the time. I wonder if that is enough to cause a thermal "warming up" effect of any components. (It is interesting that this problem was not occurring at all during the warm summer months, but started only recently, so temperature differences may be involved.) At any rate, if anyone can offer insights, I'd be grateful. BTW I do not have very much in the way of diagnostic or measuring equipment -- just a cheap analog multi-tester. THANKS!

Christopher Witmer
Tokyo

[Bill Fitzpatrick]

Insights would be more free flowing if a schematic was offered.

[cdwitmer]

Thanks, Bill. Sorry, no schematic on hand, although maybe I can sweet-talk Pioneer into faxing me one. The xover network is kind of a pain to get at. (In fact, I'm not sure just how I am going to remove them from the cabinets to work on them, in light of my previous experiences disassembling Pioneer loudspeakers to cannibalize the xovers for parts.) About the only other information I have is that the loudspeaker uses a DVC "Watkins woofer" to extend the bass (and it does so very nicely.) The xovers are more complicated than anything I have ever built myself, and include some rather massive components. I think the caps say Elna on them, although it has been a while since I stuck my head inside to check.

[simon5]

If you shake the enclosure or the wires at the back, does the sound stop and/or come back?

Complete loss of sound, probably a loose wire or a very bad solder IMHO.

Did you check the speakers terminals? Tried to bypass them?

[cdwitmer]

Shaking the enclosure is a bit beyond my ability, as it is all I can do to lift the thing. I suppose I could bypass the terminals, but only by removing something from the cabinet, as it is a sealed enclosure. I also suspect it is either bad solder or a loose wire somewhere, as I it is hard to imagine this kind of a pattern of failure in a passive component . . . although I am far from an expert in this area, by any means. One possibility I continue to suspect is that some component (probably a capacitor) is starting to go bad, and it occasionally shorts out. It still seems odd to me that something in the network could be bad at the beginning of a listening session and then get better as the listening continues, since there shouldn't be much heat generated in the network to begin with.

BTW, in follow-up to Bill's question, Pioneer refused to give me a schematic for the crossover.

Rather than trying to chase down such an oddball problem on my own, I may take the coward's way out and have a repairman mess with it. Not that I am keen on spending money, but I suspect I could spend a lot of time trying to locate the problem.

Anyway, I appreciate the answers and hope anyone with a suggestion will chime in.

Thanks!

Christopher Witmer
Tokyo

[BobEllis]

just a thought, but did you check the offending speaker connected to a different amp, or the other channel of your current amp? It might not be the speaker at all.

[Stocker]

If you can get to the crossover and pull it out, try to do so. Head to your favorite parts house and get replacements for all the electrolytic capacitors, and re-flow all the solder joints. Vibration could have caused a hairline crack after all the years.

BTW, it is not a Bad Thing to operate the speakers at less than full-volume with one driver (carefully) hanging out so you can shake wires. Oh yes, check the quality of the wiring and internal connections in the box.

Be sure to tell us all what happens.

P.S. do not wimp out and take it to a repair shop unless you like supporting the local economy for its own sake. You can very likely find and fix this yourself.

[Greg B]

That definitely sounds like a loose connection or a cold solder joint. Check all the soldering and reflow any that look suspicious. Check all jacks and use deoxit or whatever on any mechanical connections. (audiophiles - I don't even want to hear about it!)


I've also had loose lead connections inside capacitors. You can't really fix this without replacing the cap. Seems doubtful this is your problem, since all drivers stop. Just FYI.

GB

[jo-briggs]

Surely, if all 3 drivers drop out at the same time, it can't be the actual xover elements, as they separates the signal it three. Have you swapped the speaker leads at the amplifier end?

1) If the same speaker drops out the problem is on that channel from the amp output to the speaker.
2) If it changes it is likely the Amp, and probably the output connection.
3) If it doesn't change sides, swap the speaker leads at the speaker end, if it changes sides it is likely to be the banana/whatever connectors you use on the leads.
4 If it is still the same speaker, it is probably the connection between the inputs on the back of the speaker and the connection on the xover board.

If I've stated the bloomin' obvious, and you've done all this, then I apoligise, but a few simple checks should be gone through before pulling things apart and re-soldering/replacing parts that may not need it.

[Greg B]

Surely, if all 3 drivers drop out at the same time, it can't be the actual xover elements, as they separates the signal it three.

Could be, if there's a dead short across something. But yeah, it's most likely in one of the things you mention.

GB