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Proac problem: tweeters or crossover?

Recently, something moved me to listen closely to the tweeters, and when I couldn't hear anything I hooked up the speaker cable just to the tweeter binding posts. I can't say there was no sound at all, because there was the faintest of recessed, tinkly sound that didn't seem to vary much with the level of the volume control.

I called up Modern Audio and they told me just to get the Scanspeak D2010s from Madisound. I soldered them in this morning. Now the new tweeters are a bit louder than before, but not nearly as loud and not as strong on the higher frequencies as I would have expected. They still sound subdued, recessed and tinkly/jangly, but not as much as before, and there's a bit more change in level when varying the volume control. This is as always with the cable hooked up only to the tweeter binding posts.

So...is this how they're meant to sound, or is there a problem with some component in the crossovers? If there is, it must be the same in both speakers' crossovers. I wish the result of the change-over had been less ambiguous: either virtually no sound, or a great improvement. Instead, it falls somewhere in between, but the result makes me think that I haven't solved the problem.

BTW, the Response 2.5s must be ~17 years old. Custom yew finish bought new from Accutronics in Ann Arbor in 1998/99. The mid-woofers still sound great.

Does anyone know what a Proac tweeter driven in the way I've described should sound like when it's functioning correctly?
128x128twoleftears
twoleftears's avatar
twoleftears OP
5,313 posts
 
For anyone coming across this thread I thought I'd add the following information.

I recently had a very useful conversation with an highly knowledgeable technician. He expressed surprise that both speakers were equally affected, until he enquired as to whether they had been in storage for any length of time. Indeed, they had gone essentially unused for quite a while before being brought back into service recently. According to him, while electrolytic capacitors can just fail with age, they are more likely to go bad if they are not juiced or goosed from time to time with some signal from your amplifier. Who knew? He added that the effect of capacitors going bad is like soldering a resistor into the signal path, resulting in a much lower level signal to the tweeters and just a faint sound coming out of them, which is exactly what I am experiencing.

They'll be off to him for repair soon, and I'll report back in due course.
ctsooner
2,480 posts
 
Good luck and keep us posted.
timlub
2,039 posts
 
Hello Twoleftears,
I haven't chimed in before now because I saw that Peter has given you solid advice on what to look at... I'm replying now to give a quick response to your last post. Proac doesn't use any electrolytics in that speaker. An experienced tech would look these up and tell you that. Just don't want you to go down a road of a lot of expense without solving this.
Tim
twoleftears's avatar
twoleftears OP
5,313 posts
 
Yes. I realized that shortly after I posted. In the tech's defense, we only had a telephone call, so it wasn't "eyes on". I gather that the Ansar Supersounds are polypropylene. I'm assuming, unless someone can tell me otherwise, that polypropylenes can go bad too and act in the same way (essentially, as a resistor) as electrolytics.

I find this theory about the problem highly plausible, because when I went back and tested the newly installed new tweeters again, the sound level was back to where it had been when I realized I had a problem, i.e., there was just a very faint, throttled sound coming from the tweeters, pretty much no matter what the volume on the amplifier was set at.
timlub
2,039 posts
 
I have seen a bad Polypropylene cap, but it was bad from the factory, I've never seen one go bad. I would suggest, you go more the way that Al suggested, get a test tone cd and a decent mic and measure frequencies at about a 3ft away... turn your volume up until you measure 90 db or so, then without changing your volume, change the frequencies and measure... I'd probably check from 2k to 5k in 500hz brackets. All should range from 87 to 93.
If it all falls in that range, your tweeters are fine. I think we all have been tricked into thinking there are problems... on the other hand, if it measures weird then at least you have a frequency that gives a barometer of where to look. Odd things happen, you could have gotten tweeters with the wrong diaphrams...
If you plan on continuing in the speaker game, I would highly recommend purchasing a LCR meter
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