Bowers & Wilkins DM 70

[Combwork]

Hi. Has anyone heard a pair of these? They're a hybrid design with a conventional 12" (?) bass driver below a curved array of treble electrostatic units. I missed a pair (computer froze) but bought a couple of Quad ESL 57's from the same seller. The Quads sound very nice; I'm running them with a NAD 3020B, but I'm curious about how the DM70's would have sounded, and whether the are a more comfortable load to most amplifiers than the Quads are.

 

[Nat]

If my memory serves, I think they were the speaker that put B&W on the map. They certainly would produce more and deeper bass than the Quads, but I think you got the better deal. The Quads are one of the great speakers of all time, and some of their qualities have yet to really be bettered -- the transparency of the middle frequencies in particular. I doubt that the B&W would approach it in the midrange or in overall coherence -- its notoriously hard to match a dynamic woofer with electrostatics.
Its worth noting that you had to ask about the B&W -- if it were generally considered better than the Quad, it would probably be better known than it is, even though it wasn't in production all that long. And I suspect that the Quads will hold their value better.
You could do much much worse than the NAD as an amp for the Quads, but if you can afford better amplification, you'd hear a difference. The NAD is/was an outstanding entry level amp, but it can't do complete justice to the Quads. And NADs are a little on the hairy edge in terms of component reliability, and it would be a pity to blow it up into the Quads.
But congratulations on a nice system.

 

[Brian]

The DM-70s were a great speaker and one of the better hybrid esl speaker systems. When in production there were few dealers and the speakers were expensive. Like the JansZen Z824HP the total production was very low. They show up for sale once is great while and turn over quickly in the esl community. In that community they are fairly well known and respected.

 

[Nat]

I'm glad to have the better informed opinion -- I knew they were fine speakers, and I hope that by suggesting they advanced B&W's reputation, that I made that clear. But I still would rather have the Quads -- I've had a couple of hybrids -- long ago, AR 2s with Radio Shack Electrostats and then about ten years ago the Janszen with the 12 inch woofer and four electrostatic panels. I liked both, but they didn't have the revelatory nature of the Quads. In both cases, the transparency of the upper end made you notice the liimitations of the lower end, in a way that a dynamice tweeter doesn't. Obviously the B&W is a much superior speaker, but I can't see how it could avoid this discontinuity.
Besides, he has the Quads, so I was trying to cheer him up.

 

[Brian]

Nat, there are tremendous challenges in getting a dynamic driver to mate well in a hydrid electrostatic system. I have never found a hybrid that was seamless though M-L has gotten it better than most. I have had many sets of JansZens and some were pretty good and some pretty bad. I prefer a full range ESL and given an oppurtunity at either would probably take the DM70s only as they are very scarce. The Quads (any of the esl models), KLH Nines, and M-L CLS and CLS IIs all have the magic. I am actually a believer in a reverse hybrid with an esl low end and mid range and allow a dynamic tweeter. Once you hear a esl that goes into the bass region, the dynamic woofer thereafter is just not where it is at. Sadly, no one ever made such a system. I still have a pair of JansZen HP412HP that have the 12" woofer and 4 panels with a bi-ampable crossover. They do better as an addon tweeter array for my Bozaks than as a standalone speaker system though I do like them better than say my Advents. At best though the Quad is at the near top of the pecking order of speakers and the DM70s at least several steps down.

 

[kfa888]

I am actually a believer in a reverse hybrid with an esl low end and mid range and allow a dynamic tweeter.

How about a ESL Quad with a JansZen inspired tweeter array and the bottom end supported by a pair of KEF 139 "racetrack" woofers in a TL alignment. Would that work?

http://audiokarma.org/forums/showthread.php?t=88841&highlight=superquad

 

[Combwork]

I'm glad to have the better informed opinion -- I knew they were fine speakers, and I hope that by suggesting they advanced B&W's reputation, that I made that clear. But I still would rather have the Quads -- I've had a couple of hybrids -- long ago, AR 2s with Radio Shack Electrostats and then about ten years ago the Janszen with the 12 inch woofer and four electrostatic panels. I liked both, but they didn't have the revelatory nature of the Quads. In both cases, the transparency of the upper end made you notice the liimitations of the lower end, in a way that a dynamice tweeter doesn't. Obviously the B&W is a much superior speaker, but I can't see how it could avoid this discontinuity.
Besides, he has the Quads, so I was trying to cheer him up.[/QUOTE]

Thanks Nat, so I was trying to cheer him up Much appreciated. but I'm very happy with the Quads. I'd been to see them plus the DM 70s; they were only 20 miles away and on Ebay from the same seller. The DM 70s were in a garden shed with the Quads outside in the grass. No leads, no way of powering them up but cosmetically both pairs of speakers were very good. The Quads were a known item; lots of information about them out there so the idea was to take a chance that they would be basically sound, get the necessary leads plus a suitable amp and if they worked, sell them for enough to maybe fully pay for the DMs. I'd read about the Quads "lack of bass" plus them being a challenge for some power amplifiers so I didn't think of them as keepers. That was before I heard them...................... What can I say that's not already been said? Maybe one thing. On any practical level, they do not lack bass. They might not be window rattlers (for all I know they might be, but I'm not going to push them hard enough to find out) or produce the kind of subsonic pressure waves that are felt rather than heard, but for music (which is what Quad designed them for) they are incredible. They've a hard edge when the music calls for it and a soft sound when the music's soft. I wrote to Quad, gave them the serial numbers and they told me they were manufactured in 1962; same year I started secondary school. That's a little bit scary......................... Jim.

 

[Brian]

A rather interesting speaker though the KEFs would violate my spec for an electrostatic woofer. Hopefully you'll spend the time and energy to rebuild these as they are possibly the rarest of esl hybrid systems, with the KEFs, or full range ESLs without the KEFs. Most certainly they are the rarest of the Quad mods offered on a commercial basis if they in fact went into production and these are not salesman prototype samples that were sold off. I suspect they may be.

 

[Nat]

I should edit my previous post to make clear that the DM 70s were superior to the hybrids I have heard, not to the Quads, which would have gone against what I was trying to say. But since its already been quoted, I'll just make a note of what I meant.

 

[kfa888]

Most certainly they are the rarest of the Quad mods offered on a commercial basis if they in fact went into production and these are not salesman prototype samples that were sold off. I suspect they may be.

I was told by the guy I got them from that was the original owner that he bought them in some store in California. He was a very weird and elusive dude and kind scared me so I grabbed them and left.

A rather interesting speaker though the KEFs would violate my spec for an electrostatic woofer.

I know it is still not an "electrostat" but I wonder how a Magnapan Tympani bass panel would integrate with some of these systems?

If we want to talk about this further we should do so in the superquad thread as we have derailed this one far enough. :thmbsp:

 

[thedelihaus]

I was told by the guy I got them from that was the original owner that he bought them in some store in California. He was a very weird and elusive dude and kind scared me so I grabbed them and left. ...

Kelly, when have "weird and elusive dudes" scared you in the past?

 

[Combwork]

Very low frequency damaging to ESL 57?

I put this question a part of a post on the vintage solid state forum, but as it's specific to the ESL 57 I'd like to post it here. If conventional bass drivers get a very low frequency signal, such a from a warped record their cones can move an alarming amount quite slowly; maybe 2 or 3 times a second. It's not desirable, but a long as the travel is not excessive it doesn't seem to do any harm. Does the bass panel on an ESL 57 behave the same way; if so is it potentially more damaging than on a conventional speaker? Maybe these extra low frequencies are filtered out in its drive circuits, I just don't know......

Maybe I'm being overcautious, but I really don't want to risk damaging anything just because I didn't ask........................Jim.