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Old 22nd January 2009, 08:12 PM   #1
M5Sime is offline M5Sime  United Kingdom
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Smile B&W Tweeter Replacement?

Hello all,

I have just joined your forum with the hope that some of you might be able to make an audiophile suggestion for replacing a B&W metal dome tweeter pair for the P5 series.

These have a degrading issue of the ferro fluid that seems to be well known and B&W have NO SPARES left for this series.

They are as follows:

* 3 way, 4th order, twin-vented box design
* 1 x 25mm metal dome - tweeter
* 1 x 165mm Kevlar®- bass/midrange
* 1 x 165mm Cobex® - bass
* Frequency Response: 42Hz – 20kHz ±2dB on reference axis
* Sensitivity: 90dB spl (2.83 V @1 m)
* Impedance: 8 ohms
* Dimensions: 35.5H x 8"W x 9"D

As these units are no longer available and B&W have not been able to suggest something from their range, then what might be a good replacement?

I am hoping to press B&W for some ideas.. See enclosed pic for what these look like...

Any thoughts on an external Nautilus tube for example??

BR

Simon
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Old 22nd January 2009, 08:17 PM   #2
badman is offline badman  United States
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Can you remove the tweeter faceplate and dome? If so you can use something to 'wick' the ferrofluid out, and put fresh in, if I understand the problem correctly.
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Old 22nd January 2009, 10:27 PM   #3
M5Sime is offline M5Sime  United Kingdom
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Quote:
Originally posted by badman
Can you remove the tweeter faceplate and dome? If so you can use something to 'wick' the ferrofluid out, and put fresh in, if I understand the problem correctly.

Thanks for the quick response.. The issue is the fluid hardens apparently. Is it possible to dismatle, clean and find new fluid?

Sounds like a surgeon's job...

The issue was to do with reaction to the glue they used, over quite some years..

Br

Simon
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Old 23rd January 2009, 02:27 PM   #4
M5Sime is offline M5Sime  United Kingdom
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Default High Quality Aftermarket drivers

Guys

I have been doing some more research and have seen that companies like SEAS make high quality drivers. I guess the challenge is in matching the new with old..

If the old tweeter was a metal dome, ferro fluid cooled 25mm unit, and in a small enclosure then this is a starting point?

Appreciate your ideas/suggestions on a good quality driver

Br

Simon
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Old 25th January 2009, 07:32 PM   #5
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This is a difficult problem to solve. For a drop-in replacement to work and sound like the original tweeter, it needs (at least) the same impedance profile, frequency response, harmonic distortion characteristics, and acoustic center. I'd be surprised if you found a tweeter that fits these criteria. (I would be surprised if acoustic centers of tweeters didn't match, but impedance, FR, and HD vary quite a bit.)

If it were my problem, I would measure responses and impedances of all three drivers in-box (or at least the tweeter), and then draw up the B&W crossover in a simulation program such as SoundEasy or Speaker Workshop. This would allow me to figure out what final response the original tweeter had. Then I'd purchase a tweeter (see www.zaphaudio.com or other sites for suggestions on good tweeters), and modify the crossover to get the desired response.

Short of doing that, you could hope that someone else has gone through this process with these particular drivers and can advise you. Otherwise, I don't know how you can come up with satisfactory results...

If you drop in a different tweeter as a replacement without any modifications to the crossover, you are likely to run into trouble. Differences in raw, infinite-baffle frequency response can in principle be minimized by comparing specifications, but different impedances will change the interaction with the crossover, leading to nulls, peaks, and/or poor phase tracking around the crossover frequency. Also, the harmonic distortion profile of the drivers will likely be different, leading to a different sound. Oh, and the off-axis response might be different, too (especially if you get a different size tweeter), which will change the sound both on- and off-axis.

Eric
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