Repairing a B&W tweeter

[NickXX]

Hi all,

I've unboxed some old B&W CDM7NTs and found that the tweeters no longer work on either L/R speaker. Before I put them away a couple of years ago they had been pushed in by my toddler, but I did think that this would only be cosmetic. I don't think it's the crossovers as the tweeters don't work with a direct connection to the speaker cable (is it ok to test this way?!).

I had purchased some new diaphragms which I think I'll be able to replace the old ones with, if a bit fiddly. Before I start though, will this likely fix it? Do diaphragms usually fail? The units themselves seem to be a big magnet (could this be a point of failure?) and the diaphragms. It's quite difficult to see in the picture but the underside of the diaphragm has a coil which is connected to the wiring terminals.







Appreciate any help as it's not something that makes immediate sense to me!

Thanks,
Nick

[gulls]

From your description changing the diaphragms should solve the issue as crossover failure is rare and you've already ruled out missing bi-wire links (etc) by testing the tweeter directly. However this is not advisable, tweeters should only see very high frequencies, using them without a crossover will overheat the coil almost immediately causing it to burn out. The failure of the tweeters is almost certainly related to being over driven (either by an under powered amplifier clipping/distorting or by excessive signal, the former is most common), even pushed in tweeters will produce some sound.

It's not that tricky to do, just take you time and if you get stuck DM me and I may be able to help.

[NickXX]

That’s great- thank you for your help! Would you advise checking the tweeter speaker wire connectors with another small speaker to rule out crossover failure for certain? Or could this potentially burn out the crossover?

[gulls]

A crossover is very unlikely to fail in the way that it will damage the tweeter, it is more likely ( but still rare) that there would be no output. Connecting a drive unit/speaker to the tweeters connections would be fine for a low level test

[NickXX]

You legend gulls- it works! Thanks for the help, I’ve had the speakers and spares in boxes for years as I was terrified at attempting it.

Was a very easy job- just soldering the 2 spots on each tweeter. The wires on the old connections seemed broken when I removed the old ones- seems odd that they both went, but they are 22 years old.

Forgot how good these sound, and they’re looking pretty again.

Edited by NickXX on Tuesday 22 August 14:27

[gulls]

That's great news, delighted to have been able to help!