Where can I find schematics for speaker crossovers?

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Those of us who have dug around for speaker details with the Google search engine know where to find stuff. :D

KEF stuff can be found here:
Technical Details of KEF Crossovers

You have KEF Concertos, DN12 SP1004 crossover updated by Falcon Acoustics who are pretty good. You might also find new crossover components at Wilmslow Audio:
KEF Concerto B139B B110A T27A network DN12 SP1004
Concerto Upgrade Crossovers

See those old Non-polar electrolytic capacitors dry out with age and degrade. :mad:

I presume you aren't terribly interested in B&W designs, but I dug up some stuff at The Art of Sound Forum - Powered by vBulletin. You have to join to see the scans in "The Knowledge." B&W themselves publish good documentation too.

The below KEF Concerto stuff should look familiar. Hope it helps. :cool:

Edit: You are on it, Don! LOL


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All B&W speaker service manuals are available from B&W.com. <snip>
Thanks for that. Sadly the information for the DM2 is pretty sketchy. There is an impedance graph (which looks pretty "all over the place" to my untutored eyes) but it isn't great quality and it isn't really possible to read it. Thanks anyhow.

Some time ago I did try contacting B&W with an enquiry about replacing the sound dampening material inside the DM2s (there are three different varieties) but they said that there was nobody there any longer who knew anything about them.

Thanks for the Kef stuff system7 & Don. I am aware of the Falcon Acoustics crossovers and they do look good, particularly the 5aB.

Anyhow, thanks to all for the various replies - I will try to make better use of Google in future
If I have an old cabinet with old and worn-out drivers, I usually measure the bass cutout and volume and wonder if I can fit modern drivers. :D

Maybe something like the Troels Gravesen Classic three way could be done in a biggish box:
3-Way Classic

I suspect the SEAS CA18RNX might be too small, but George Krilov has some nice designs:
DIY loudspeaker "OPTIMA" - YouTube

See, diyaudio has only your imagination as it's limit! :cool:


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Following the link to "B&W Group North America Service & Support - Owner's Manuals & Drawings" shows that the DM2 was available from 1973 to 1984 and cost $300; the DM2/II was available from 1978 to 1981 and cost $525 - why?

So far as I can tell, the obvious differences between the two was that the /II used the Coles 4001 in place of the B&W supertweeter and had some adjustment options on the crossover - other than that they seem identical except that the former is most improbably described as a "Bookshelf" speaker whereas the latter is a "Floorstanding" speaker. I don't know what was different about the DM2A other than the shape of the port.

I have now realised that much of the foregoing is utter tosh - the DM2/II seems to be a completely different beast. There seem to have been three different versions of the DM2; what I have described above are the first two versions (I have a pair of each), the port on the third one had rounded edges.
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I do remember being rather impressed with the B&W DM-2A speakers. Very nice smooth bextrene bass performers that have a considerable fan-base even to this day. :D

An externally hosted image should be here but it was not working when we last tested it.

This is the earlier DM2:

An externally hosted image should be here but it was not working when we last tested it.

Uploaded with ImageShack.us

I'd think the crossover and 1/8 wavelength transmission line bass loading evolved a bit. But only the supertweeter is really different by the look of it.

I'd incline to renew capacitors with 50V NP electrolytics and resolder some connectors with old leaded solder which you can still buy for personal use at Maplins. Otherwise, where are we going on this? :)

Oh, FWIW, IIRC that's a B&W 8" bextrene bass and a Celestion HF1300 tweeter. And, IMO, bextrene was best not used above about 2.5kHz, which is possibly part of why these were good speakers.
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I was working for B&W in 1979 and the only DM2 that I can remember is the one that system7 has posted photos of.

Please don't ask me any technical questions. I was only a part time 17 year old and my job was to take the hundreds of cabinets off a big lorry and pair them up. In those days every speaker was uniquely matched to its pair, I would stand in a large room with hundreds of cabinets and stands and match the random delivery together.

In that era we also had the DM4 which I had, a delightful 3 way - I'll loosely call it a bookshelf but it was realy a standmounter.

The DM7 - a real beauty even today.

There was also a DM6 - a sort of halfway house up to the monstorous 801.

The 801's. The daleks.

There was also the DM1 but you don't hear much about them these days.

After I left the company we started to see speaker series. Today for example we have the DM6XX which covers everything from tiny bookshelf speakers to great big floor mounted speakers. I wonder if that was the case with the DM2. B&W might have found a sucessful menu and built a series of speakers around that idea. Please correct me if I am wrong.

I've always stayed loyal to B&W. I started with the DM4 and eventually upgraded to the DM14. A few years ago I adopted a pair of DM603s2's which after the passing away of my brother-in-law have now been replaced by DM683's.

If I wasn't busy saving for a house I would jump at a pair of 802D's.
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Here's the crossover schematic for the B&W DM2 version II speaker.

Hope it helps.
Thanks for that, I will use it to try and understand the different crossover in my DM2s and to renew the capacitors which I should be able to find on the Falcon Acoustics site.

There is an even earlier version of the DM2s than the images you have posted. It used some unidentifiable Super-tweeter (not the Coles 4001) and the Mid/High unit and the Super-tweeter were place side-by-side. The crossover didn't have the adjustment control that appeared on the later version. I have no idea whether the crossovers were identical apart from the control - I will eventually work that out.

This LINK shows my early version of the B&W DM2 with the Mid/High frequency HF1300 & the unidentified Super-tweeter side-by side below the DW200 bass unit.
This LINK shows the second version, with a Coles 4001 and all three speaker units in line vertically.
This LINK shows the first (white, lamb's wool?) and last (grey) layers of wadding.
This LINK shows the first and intermediate (carpet underlay like) layers of wadding.
This LINK shows the last, coarse and stiff layer of wadding which sadly is now turning to powder.

The cabinets on the later versions I own are VERY beaten about. Rather than trying to refurbish the cabinets, I may try to make an exact (but undamaged) copy. I don't understand the three different types of wadding used or know what I could use to replace the final section nearest the port opening. B&W can't offer me any help.

I have read somewhere that the B&W DM200 bass unit has characteristics very similar to the 8" bextrene coned Kef B1039 but have no idea whether or not that is true?
What can I use to replace this deteriorating wadding?

I have just realised that the link showing the last, coarse and stiff layer of acoustic wadding on my B&W DM2s was wrong - this is the correct LINK. The material looks and feels rather like a loofah

Unfortunately, as a result of the age of the speakers this wadding is now deteriorating and turning to a fine powder as can be seen to the right of the photo (the base of the port). This tends to spill out of the front of the port.

Does anyone know what I might use to replace it?
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