Recapping B&W DM2's

[jhal]

I pulled the woofers out of my DM2 mark II's to make a parts list of caps. I am going to recap them to see if it helps tame the metallic-sounding high's it has developed. I first thought my amp was having problems, but it sounds fine through the headphone jacks and some other speakers. I definately think the crossover point for the tweeter has drifted lower than it should be. The woofers are stamped "NOV 22 1978, so they just turned 29. The caps in question are electrolytic and I would like to upgrade them. I need to find a source for these caps since Parts Express doesn't have all of the values I need which are, per speaker:

75uf 50v
80uf 25v
15uf 25v
30uf 50v
20uf 70v



I also want to upgrade the internal wiring used since it is about 22AWG. Can anyone make a recommendation or point me to a source to obtain these? Can I step up to polypropylene and retain the same characteristic or should I stick to new electrolytics and leave well enough alone? Thanks for any and all input, John.

 

[Urizen]

John,

You can "stack" caps by wiring two or more in parallel to achieve the desired value. For example, two 15mF caps wired in parallel will achieve a value of 30mF.

I use Dayton 1% for the tweeter and mid sections of crossovers and electrolytic caps for the bass section on my projects. You can spend more money for more exotic caps if you wish.

As far as wire goes, I would think a decent 18g zip would be fine. Again, you can spend more for more exotic cable.

Good luck with your re-cap!

Ken

 

[jhal]

I am downloading Digikey's catalog, they should definately have them.

 

[Dan ʕ•ᴥ•ʔ]

Avoid Solens. IMO, they tend to sound hard and edgy. Jantzen or even Dayton's would be preferable.

 

[Urizen]

Avoid Solens

Seconded.

 

[jhal]

Thanks, the crossover is mounted in the bottom of the cabinet and is a pain to get out- the stands need to be unbolted from the bottom to access the screws holding the xo board in place. I guess I need to do that to find out what each cap's role is in the circuit. I don't want to take these things apart twice if I can help it. A schematic would be nice.:yes: I wonder if B&W could supply me with one if I contacted them.:scratch2:

I forgot you could stack capacitors, been a while. I was thinking resistors, which is totally different. Anyway, PE has what I need. I will just use two 40uf caps to make 80uf uf of capacitance. Either way, it isn't cheap. Just over $114.00 for everything, using Dayton polypropylene. Seems well worth it though, since I only paid $240 for the speakers and they are mint.

 

[jhal]

I just thought about this while reading the recapping thread at the top of the list. Do you think I could have a problem with old dried out ferrofluid causing my tweeters to sound metallic and bright? I guess I need to find out if these are ferrofluid cooled.

 

[gearhound]

Those are huge values for crossover caps??

Steve

 

[jhal]

Those are huge values for crossover caps??

Steve

It's quite a crosseover. True 3rd order Butterworth design according to B&W. I pulled the woofer, as well as some of the foam dampening material. Thank goodness it isn't fiberglass. The midrange enclosure has animal hair, I kid you not. I will take some pics later on. I may go ahead and pull the crossover so I can study it. I stuck the camera in the cabinet as best I could to try and get some pics so you can get an idea of what it looks like. It takes up the whole bottom of the speaker cab.

 

[jhal]

Now that I have taken it apart almost enough to do a recap, I wish I had the damn parts. Anyway, here's some more pics. I stuck the camera inside and also got a shot of the midrange chamber (black hair!) as well as the drivers. Definately a well-built system, though it looks like they could have used better caps, or is that all they had in '78? I also notice that I forgot a cap, as it was hidden under the foam, so it is a good thing that I pulled it (the foam) out. It is 8uf @50vdc, for a total of 6 caps per system.

 

[Dan ʕ•ᴥ•ʔ]

I don't think cap quality was of much interest back then.

 

[hugoloureiro]

Hi there, old thread.. could you tell me how you took out the Crossover from the cabinet?

 

[QSilver]

the crossover is mounted in the bottom of the cabinet and is a pain to get out- the stands need to be unbolted from the bottom to access the screws holding the xo board in place.

Been looking for some information on these to get to know my own set a bit better. Thought I'd just highlight this if anyone needs the info again.

 

[sax6]

Verrrrry nice speakers ! Wish I.