Advice on removal of resistor in B&W DM110 crossovers?

[CliffR52]

Well, since you didn't listen to the speakers before you worked on them, the tweeters may have been blown all along.

Measure their DC resistance while disconnected from the crossover.

Using the 200Ω scale, indicator displays "1" on left of LCD.
When I connected to terminals of an old driver the LCD displayed 7.9


When connected to the B&W tweeter remained on "1" on left of LCD.

 

[Galu]

If the reading is the same as when the multimeter probes are not connected to anything then the tweeters are open circuit.

 

[CliffR52]

Thanks Galu.


I guess the expression "I learned my lesson the hard way" comes to mind.
Visually the tweeters appear in good order, but, as you indicated, they can still be fried.
I took a risk when I bought the speakers, but at $30 or $40 the pair I think there are still options.

• Try to source replacement original tweeters.
• Select new or used similar tweeters of a different brand.
• Repair the existing tweeters.
• Part the speakers for spares.

Atleast we now know why they sound flat. 🙂

 

[Galu]

You can learn more positively from this, Cliff, by dismantling the tweeter as shown in the service manual.

Removing the four screws (part 12) allows access to the diaphragm/copper wire/voice coil former assembly (part 3/6/7).

You can then look to see if the voice coil is burned out or if there is an obvious break in the connecting copper wire.

I don't want to encourage you to spend even more money on these budget speakers, but the diaphragm/copper wire/voice coil former assembly is replaceable (see attachment) at a cost of around £30 the pair. However, it may prove fiddly to fit for someone with no previous experience. There are YouTube videos out there showing similar replacement jobs if you search for them.

 

[CliffR52]

Thanks Galu


The copper voice coil looks in very good condition.


It appears it's the wiring from the terminals to the coil which is the issue.
I can't get signal from the coil to the terminals.

 

[AllenB]

Doing some surgery I see Cliff. Keep up the good work 🙂

 

[CliffR52]

🙂🙂

 

[CliffR52]

I don't want to encourage you to spend even more money on these budget speakers.

Hi Galu.
Without working tweeters I was ready to give up on the B&W DM110's.
You wouldn't believe it. I found a pair of B&W TP26 Tweeters on someones hard rubbish the other day.
These were circa 1988 (originals 1986). What are the odds of that happening?
Apart from the rusty screws holding the plastic cover plate and diaphragm to the magnet body they appeared in very good condition.
The screws were replaced using parts from the faulty units.
I fitted and tested them with familiar tracks and am more than happy with their overall sound.
Another pair of speakers rescued from the tip.
Thanks for your and others input.
Cliff

 

[Galu]

The things you find when raking through other people's rubbish, Cliff!

Thanks for your thanks. 😎