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nordy
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B&W CDM1: Poor treble

Hello,

my pair of CDM1 - bought in 1998, seldom and always played with low levels - has a very weak treble response.
Testing with white noise shows a sharp frequency cut off below 8 kHz, whereas nominal cross-over is 3 kHz.

A German B&W-group manager told me the tweeters' ferrofluid might have become thick so the coils would not be able to swing easily enough.
He told me this would be the result of thermal overload due to too high amplifier output.

But I never listened to the speakers with high levels, so misuse cannot be the reason for the problem, which now occurs since 1 year on both tweeters.

Believe me the speakers' sound is awful.
After purchase they sounded much brighter and clearer, only the upper bass region was too much emphasized.

If the reason is thick ferrofluid it must be a failure by manufacturing, have you heard about such problems ?

If it's not the bipolar electrolytic capacitors - do they relly use such cheap stuff ? - might have lost some capacity that may increase the crossover frequency considerably.

What do you think about this ?
I would deeply appreciate your postings.

Many greetings from football crazy Germany (good luck for both the English and the German team).

Peter from Wolfsburg (Germany, the Volkswagen town)

CECE
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Re: B&W CDM1: Poor treble

Why not swap it with the one from the other side to see if it does the same thing, then you know, then you can order a replacement tweeter. That VW factory is supposed to be the world's biggest car factory under one roof....All I buy are VW's or Audi.

Logan
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Re: B&W CDM1: Poor treble

The problem with the CDM1 speakers I had was too much treble. The quality was fine but the quantity was excessive in relation to other frequency bands, and in the end wore me out. I think you need to have a dealer look over yours.

nordy
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Re: B&W CDM1: Poor treble

Hello DUP,

  • Why not swap it with the one from the other side to see if it does the same thing, then you know, then you can order a replacement tweeter. That VW factory is supposed to be the world's biggest car factory under one roof....All I buy are VW's or Audi.

The problem occurs on both tweeters so there is no normal tweeter to compare with.
You are right, the VW factory in Wolfsburg is the biggest one in the world under one roof.
More than 40.000 workers and employees do their job there.

Best regards Peter

nordy
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Re: B&W CDM1: Poor treble *DELETED*

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nordy
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Re: B&W CDM1: Poor treble

Hello Logan,

  • The problem with the CDM1 speakers I had was too much treble.

It is true, something is wrong with my tweeters but what ?

I don't want to buy new ones before there is evidence of the kind of failure.
I don't trust in the B&W manager's advice completely.
I deeply doubt the theory of overheated coils and thick ferrofluid, because I never played the speakers loud.

I have some experience in self-building speakers.
I sold two Dynaudio D 28 and two D54 speakers the other day on E-bay, both 30 years old and stressed the whole time with high pop levels, but playing absolutely well after all decades.
They have ferrofluids as well.
If one of those speakers would have been damaged I could believe in overheat as cause for failure but not here.

If the ferrofluids really have become thick there must be a manufacturing or material cause for it and B&W is liable for this defect.

Regards Peter

nordy
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Re: B&W CDM1: Poor treble

Hey guys,

I'm very lucky, because i got my pair of CDM 1's repaired now.
Both tweeters have been substituted for new ones because the ferrofluid in the voice coil gaps had dryed out.
First an coil overheating was assumed as responsible for it by the mechanic , but when measuring a normal coil-DC-resistance of 4.9 ohms a technical failure within the 10-years warranty was considered to be causal.

I'm very happy with the clear sound of the speakers now.

Thanks to B&W for the 10 years warranty.

Best Regards

Peter from Germany

Jeff Wong
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Re: B&W CDM1: Poor treble

Hi Peter - Glad to hear you got it sorted out and are enjoying the sound you paid for.

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