Repair/replace 30-year old B&W DM6 woofer?

jacques54 · 12th December 2005, 04:49 PM

Hello all,

My apologies if this issue has been covered extensively somewhere else, as in that case I haven't been able to find it back.

The woofer of one of my old faithful Bowers & Wilkins DM6 (bought back in 1976 or was it 1977) is dead. The current B&W dealer tells me to forget about them, no parts are available anymore, there's much better stuff now etc.

While there are definitely better speakers than this almost-30-year-old pair, I would consider to repair the faulty one. To what extent is it possible? My point of view would be that even a lesser-quality woofer might still be better than a dead one. Would any schematics be available?

I may be relatively comfortable with electronics, but maybe less with furniture-like items like loudspeaker cabinets. Among other things, I seem to remember from earlier days that it was not safe to test unmounted speaker drivers...

Any advice or pointers will be appreciated.

Best regards,

Jacques

RobWells · 12th December 2005, 10:32 PM

Hi Jacques,

You could ask these guys if they know of a replacement woofer:

http://www.wilmslow-audio.co.uk/

They are quite knowledgable..

The other option is to measure the TS parameters of the remaining woofer, and search for a close match (then replace both to get a proper pair)
Search for 'speaker workshop'

If these are the speaker I think they are they're way too cool to scrap..

edit: They weren't the ones I was thinking of, but hey..

Cheers,

Rob.

carlosfm · 12th December 2005, 11:44 PM

Quote:

Originally posted by jacques54
While there are definitely better speakers than this almost-30-year-old pair, I would consider to repair the faulty one. To what extent is it possible? My point of view would be that even a lesser-quality woofer might still be better than a dead one. Would any schematics be available?

Don't bother.
Don't miss this:
http://cgi.ebay.com/ws/eBayISAPI.dll...Pr4_PcY_BID_IT

0 bids... everyone is sleeping.

sreten · 13th December 2005, 11:19 AM

Hi,

first point of call is :

http://www.bwspeakers.com/downloadFi...DM6_manual.pdf

The purist would change both bass units.

You need 8 ohm units that model well into a 51 litre sealed box.

The only critical parameter is getting the correct sensitivity.

My calculations indicate 84dB/2.83V, for a bass unit in a 3-way
this equates to 90dB/2.83V measured in half space (usual).

The other issue is getting the form factor correct, you may be
better off fitting an 8" unit with an adaptor, possibly converting
the alignment to reflex or add an ABR on the back.

/sreten.

Puggie · 13th December 2005, 02:52 PM

Have you contacted B&W directly for parts? They do have some suprising new old stock on the shelves when I last called about replacement drivers for our series 80 801s.

jacques54 · 14th December 2005, 03:43 PM

All,

Thank you for the advice.

Some investigation revealed that it must be either one of these DM6 switches or a crossover component. I placed the supposedly faulty driver in the other cabinet where it behaves as it should. It is 30 years old but still acceptable with the refurbished Quad 405 (new capacitors & op-amps).

The circuitry isn't identical to the one in the service manual. There is no LF Contour control. I hope the fault is with a capacitor on the crossover circuit.

sreten · 14th December 2005, 03:56 PM

Hi,

your very lucky its not the driver,even if B&W had one,
it would be very expensive for a replacement.

Its certainly worth replacing all the reversible electrolytics
in both speakers, and if you don't use the contour controls
either soldering all contacts in position or bypassing the
switches alltogether.

/sreten.

jacques54 · 20th December 2005, 08:31 PM

Replacing the bipolar capacitors made quite a difference - bass is clearer and less 'boomy'. I noticed that the crossover printed circuit was tested on 10 Jan 1973 - almost 33 years old... I have done it for both circuits. Funny that the new capacitors take only one quarter of the volume of the old ones.

I was a bit amazed to find that the internal wiring is using rather thin wires - like 0.25 square mm - what is the use of special loudspeaker cable, gold-plated contacts etc.?

The cabinets themselves are extremely well built, with re-inforcing posts between the walls to prevent vibration. Once you are confident how to open these boxes, servicing them yourself is straightforward.

Thank you all for your feedback.

12th December 2005, 04:49 PM	#1
jacques54 diyAudio Member Join Date: Sep 2005	Repair/replace 30-year old B&W DM6 woofer? Hello all, My apologies if this issue has been covered extensively somewhere else, as in that case I haven't been able to find it back. The woofer of one of my old faithful Bowers & Wilkins DM6 (bought back in 1976 or was it 1977) is dead. The current B&W dealer tells me to forget about them, no parts are available anymore, there's much better stuff now etc. While there are definitely better speakers than this almost-30-year-old pair, I would consider to repair the faulty one. To what extent is it possible? My point of view would be that even a lesser-quality woofer might still be better than a dead one. Would any schematics be available? I may be relatively comfortable with electronics, but maybe less with furniture-like items like loudspeaker cabinets. Among other things, I seem to remember from earlier days that it was not safe to test unmounted speaker drivers... Any advice or pointers will be appreciated. Best regards, Jacques

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12th December 2005, 10:32 PM	#2
RobWells diyAudio Member Join Date: Aug 2002 Location: UK	Hi Jacques, You could ask these guys if they know of a replacement woofer: http://www.wilmslow-audio.co.uk/ They are quite knowledgable.. The other option is to measure the TS parameters of the remaining woofer, and search for a close match (then replace both to get a proper pair) Search for 'speaker workshop' If these are the speaker I think they are they're way too cool to scrap.. edit: They weren't the ones I was thinking of, but hey.. Cheers, Rob.

13th December 2005, 11:19 AM	#4
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, first point of call is : http://www.bwspeakers.com/downloadFi...DM6_manual.pdf The purist would change both bass units. You need 8 ohm units that model well into a 51 litre sealed box. The only critical parameter is getting the correct sensitivity. My calculations indicate 84dB/2.83V, for a bass unit in a 3-way this equates to 90dB/2.83V measured in half space (usual). The other issue is getting the form factor correct, you may be better off fitting an 8" unit with an adaptor, possibly converting the alignment to reflex or add an ABR on the back. /sreten.

13th December 2005, 02:52 PM	#5
Puggie diyAudio Member Join Date: Oct 2004	Have you contacted B&W directly for parts? They do have some suprising new old stock on the shelves when I last called about replacement drivers for our series 80 801s.

14th December 2005, 03:43 PM	#6
jacques54 diyAudio Member Join Date: Sep 2005	All, Thank you for the advice. Some investigation revealed that it must be either one of these DM6 switches or a crossover component. I placed the supposedly faulty driver in the other cabinet where it behaves as it should. It is 30 years old but still acceptable with the refurbished Quad 405 (new capacitors & op-amps). The circuitry isn't identical to the one in the service manual. There is no LF Contour control. I hope the fault is with a capacitor on the crossover circuit.

14th December 2005, 03:56 PM	#7
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi, your very lucky its not the driver,even if B&W had one, it would be very expensive for a replacement. Its certainly worth replacing all the reversible electrolytics in both speakers, and if you don't use the contour controls either soldering all contacts in position or bypassing the switches alltogether. /sreten.

20th December 2005, 08:31 PM	#8
jacques54 diyAudio Member Join Date: Sep 2005	Replacing the bipolar capacitors made quite a difference - bass is clearer and less 'boomy'. I noticed that the crossover printed circuit was tested on 10 Jan 1973 - almost 33 years old... I have done it for both circuits. Funny that the new capacitors take only one quarter of the volume of the old ones. I was a bit amazed to find that the internal wiring is using rather thin wires - like 0.25 square mm - what is the use of special loudspeaker cable, gold-plated contacts etc.? The cabinets themselves are extremely well built, with re-inforcing posts between the walls to prevent vibration. Once you are confident how to open these boxes, servicing them yourself is straightforward. Thank you all for your feedback.