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 Post subject: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 10:05 am 
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Joined: Tue Nov 10, 2015 1:27 pm
Posts: 3
Location: Lorraine, QC, CA
Hello guys,

I need your help regarding some crossovers upgrade/rebuilding. I have a decent pair of B&W DM7 MK2 and I want to replace the capacitors on the crossovers. They sound a lil bit dull and I beleive the old caps on those crossovers might be responsible. Now, I know how do solder/desolder, but I never changed capacitors before so I,m a bit confused when its time to get the right ones.

Now i'v removed the crossovers and I can already see that the big caps (1000uf) are leaking...

here's the infos marked on the caps :

1000uf 100 vdc (big ones)

11 mfd 50 vnp +- 10%

40 v100 uf (m) ceo4w

40v 47vf sml

I also dowloaded the circuit diagram from B&W

If some of you guys could find the time to help me pick up the right replacement parts it would be greatly appreciated. Any advices, any suggestion are welcome. What type of caps should I buy?

thanks in advance


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 11:26 am 
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Joined: Sat Jul 04, 2009 6:08 pm
Posts: 18449
Location: Montreal, QC, CA
heimrick wrote:
Hello guys,

I need your help regarding some crossovers upgrade/rebuilding. I have a decent pair of B&W DM7 MK2 and I want to replace the capacitors on the crossovers. They sound a lil bit dull and I beleive the old caps on those crossovers might be responsible. Now, I know how do solder/desolder, but I never changed capacitors before so I,m a bit confused when its time to get the right ones.

Now i'v removed the crossovers and I can already see that the big caps (1000uf) are leaking...

here's the infos marked on the caps :

1000uf 100 vdc (big ones)

11 mfd 50 vnp +- 10%

40 v100 uf (m) ceo4w

40v 47vf sml

I also dowloaded the circuit diagram from B&W

If some of you guys could find the time to help me pick up the right replacement parts it would be greatly appreciated. Any advices, any suggestion are welcome. What type of caps should I buy?

thanks in advance

1000uF sounds like a huge value for a crossover. Could you please post a picture of the crossovers?


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 12:10 pm 
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Joined: Tue Nov 10, 2015 1:27 pm
Posts: 3
Location: Lorraine, QC, CA
Here's a picture


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 12:22 pm 
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Joined: Tue Jun 14, 2016 8:33 am
Posts: 1051
Location: Kingston, ON, CA
1000uf, 100v, non polarized. ('reversible' as it says on the cap body)

Gonna be tough to find anything like that. You'll probably have to stack up a few in parallel. (3X in this case)

https://solen.ca/products/capacitors/no ... 5a100k337/

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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 1:37 pm 
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Joined: Tue Nov 10, 2015 1:27 pm
Posts: 3
Location: Lorraine, QC, CA
How do you stack capacitors in parrallells?


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 3:28 pm 
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Posts: 451
Location: New Westminster, BC, CA
This is one way. Those, in the centre, are 30 uF poly caps, to give you an idea of the difference in size to NPE's.


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 5:16 pm 
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Joined: Fri Oct 21, 2005 7:02 am
Posts: 166
Location: Cornwall, ON, CA
The 100 mf 16 volt and the 4.7 mf 16 volt are in the protection circuit, no need to change. The others except the 1000mf look like film caps mylar or pp, these don't usually go bad especially in a speaker. That 1000mf is used in alot of b&w speakers from the 70's, pretty sure they were used as a king of infrasonic filter. I had them in a b&w dm6 and in a pair of inifinity speakers too.


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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 5:45 pm 
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Joined: Mon Mar 31, 2008 9:17 am
Posts: 13719
Location: Toronto, ON, CA
You may find some useful info at this forum:

http://audiokarma.org/forums/index.php? ... ir.540507/

I ran the original DM7 for years and loved them to bits before I discovered planar dipoles. They rock big time with a hefty amp like a Threshold Stasis or equivalent. Great with classical and jazz, too. If they had a weak spot it was mid-range Doppler distortion caused by heavy bass excursion, a side effects of the small midwoofer and low tuned passive rad. Only noticeable on deep bass heavy records, though. They were eager to hit the bottom notes, and I was happy when they did. :D

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 Post subject: Re: B&W DM7 MK2
PostPosted: Wed Jul 26, 2017 6:36 pm 
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Joined: Tue Jan 25, 2005 5:37 pm
Posts: 2405
Location: Toronto, ON, CA
I owned a pair of DM7 MKII and the best thing about these speakers was the high freq (tweeter) vertical dispersion. You would hear detailed sound drum cymbals imageing in a way that they sound several feet above the speaker cabinets. These were particular well internally braced speakers. My DM2A transmission line B&W have similar bracing with the mid baffle running down two thirds of the cabinet forcing air movement direction down and out of the large "moss" filled port. If the designer of Harbeth started learning about how he would have his speakers sound, he likely started with the B&W DM2A, DM4 more particularly and other speakers like Kef 104AB etc.. I also own a pair of 104AB which I still enjoy listening to as well.

The 7's can image very well and are in some ways one of the best of the B&W DM series in my opinion and I have owned them all including the DM17, DM 11 (rare). One of my other favs is the DM5.


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 Post subject: Re: B&W DM7 MK2
PostPosted: Mon Jul 31, 2017 7:02 am 
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Joined: Fri May 20, 2011 12:15 pm
Posts: 206
Location: toronto, ON, CA
Google is your friend 1000uF, 100V, non-polarized capacitor:

https://www.amazon.com/Parts-Express-10 ... B0002KR4BQ


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 Post subject: Re: B&W DM7 MK2
PostPosted: Mon Jul 31, 2017 12:07 pm 
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Posts: 13719
Location: Toronto, ON, CA
Bumpy wrote:
Google is your friend 1000uF, 100V, non-polarized capacitor:

https://www.amazon.com/Parts-Express-10 ... B0002KR4BQ


The ones in the link are 100uF.

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 Post subject: Re: B&W DM7 MK2
PostPosted: Tue Aug 01, 2017 5:06 am 
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Joined: Fri May 20, 2011 12:15 pm
Posts: 206
Location: toronto, ON, CA
Woops!


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 Post subject: Re: B&W DM7 MK2
PostPosted: Thu Aug 03, 2017 9:49 am 
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Joined: Sun Mar 03, 2013 5:03 am
Posts: 852
Location: Georgetown, ON, CA
Thanks to the OP for posting. I'll be paying particular attention to this thread, as I'd like to do the same to my old DM7 Mk2's.


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 Post subject: Re: B&W DM7 MK2
PostPosted: Sun Oct 15, 2017 6:03 am 
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Joined: Sun Mar 03, 2013 5:03 am
Posts: 852
Location: Georgetown, ON, CA
heimrick wrote:
Hello guys,

I need your help regarding some crossovers upgrade/rebuilding. I have a decent pair of B&W DM7 MK2 and I want to replace the capacitors on the crossovers. They sound a lil bit dull and I beleive the old caps on those crossovers might be responsible. Now, I know how do solder/desolder, but I never changed capacitors before so I,m a bit confused when its time to get the right ones.

Now i'v removed the crossovers and I can already see that the big caps (1000uf) are leaking...

here's the infos marked on the caps :

1000uf 100 vdc (big ones)

11 mfd 50 vnp +- 10%

40 v100 uf (m) ceo4w

40v 47vf sml

I also dowloaded the circuit diagram from B&W

If some of you guys could find the time to help me pick up the right replacement parts it would be greatly appreciated. Any advices, any suggestion are welcome. What type of caps should I buy?

thanks in advance

Any updates on the project?


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 Post subject: Re: B&W DM7 MK2
PostPosted: Sun Oct 15, 2017 6:43 am 
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Joined: Wed Jan 25, 2006 7:39 pm
Posts: 1673
Location: Toronto, ON, CA
ripblade wrote:
Bumpy wrote:
Google is your friend 1000uF, 100V, non-polarized capacitor:

https://www.amazon.com/Parts-Express-10 ... B0002KR4BQ


The ones in the link are 100uF.


Funny thing that there is a 1000uF (1000VDC 230VAC) film capacitor for sale, but it's huge and worth more than speakers... https://www.digikey.ca/products/en/capa ... 0uf%20100v

I'd just change to either 3 caps in parallel or with brand new high-grade electrolytic cap.


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