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B&W DM70's - top end lacking

I have a pair of DM70’s.
They sound really good with vocal, blues and opera.
The bass is overblown with complex orchestral or progressive.

I am already replacing the bass units with Leak sandwich, as I found that the original units had not been repaired correctly.
They had some sort of home made surround made of thick paper with a 12 inch foam surround stuck on top.
The leaks seem to solve some of the bass issues.
I will get the bass units professionally repaired at some point.

Now to the treble units.
The mid and lower treble seems great, but things like symbols seem muted.
I was told that the electrostatic units had been repaired by One Thing, but now I am not so sure.

I am driving them with an Art Audio Quintet fed from a Conrad Johnson PV9a pre.
My CD is a Unison Unico and I am using a Focus One turntable just now.
Cables are from Chord. (Yes they do help a bit)

These are frustrating speakers, as when at their best, they sound so good.
First I need to know what to expect (especially from the treble).
Then I need to know how to fix any issues.

Sometimes they sound so so good and other times . . .
iscm
iscm OP
40 posts
 
I have the 57's set up with two Dynaudio BM12s Subs.
And how does it sound, as I have heard mixed reports about the results of subs with ELS57's?
iscm OP
40 posts
 
Looking at the B&W crossover it should be very easy to split the high/mid and bass to allow bi-wiring or bi- amping.

I could then get the best out of my 15/25 watt tube amp and use my Unico  for the bass. The Unison Unico has 70 watt from MOSFETs and should drive the bass easily.
My Conrad Johnson has two outputs to make this easy.
Level matching could be done using the volume on the Unico.

I should receive my super tweeter today, but think that I should still check out the power supply.
I would have thought that the resistors should be checked first.
B&W claimed that they used NO electrolytic capacitors, but how long do diodes last.
Perhaps the B&W claim only related to the crossover and anyway the paper in oil's may also need replacing.

Anyway, I will do what I can bit by bit.

The Leak Sandwich drivers have already improved the bass after I removed half the speaker stuffing.
I checked the original bass units and see that they both need replacement surrounds but one makes a metallic pinging noise which is not so good.

I will send them both to Wembley Speakers to have them checked out.

ct0517's avatar
ct0517
2,041 posts
 
Iscm
I have heard mixed reports about the results of subs with ELS57’s?

Yes. If your subs are across the room, near the main speakers, and one listens to different genres of music, high and low SPL levels, IMO, one needs to have remote DSP management. A remote control that allows you to control phase, crossover level and db levels from your listening position.
The Dynaudio brand version that I have looks like

this.

Once one has used a remote DSP you can’t go back to a Sub with controls only on the box.
I have detailed the Quad 57 and subs experience on my virtual system page and my Quad 57 review page. See my post here from the Quad 57 review.

https://forum.audiogon.com/discussions/review-quad-57/post?postid=1324755#1324755

The B&W DM70 ESL’s are probably the rarest known speakers I can think of in North America. I assume more common in Europe. Here is a speaker that cost more to make than what it sold for !
Unheard of today - B&W became a bean counter company (post - John Bowers era - RIP). They are definitely worth the time to restore.

iscm OP
40 posts
 
The B&W DM70 ESL’s are probably the rarest known speakers I can think of in North America. I assume more common in Europe. Here is a speaker that cost more to make than what it sold for !

I was told that only about 2500 set were made in total including the Sony versions which were basically the Continentals (SS7000 - same as DM70c - curved front).

One of my friends has a pair and I have been offered another at a fair price complete with spare bass units (the original units need new surrounds). They have Leak Sandwich 13" bass units in at present (like mine)

There is also a pair of Sony’s (SS7000) on eBay just now.
iscm OP
40 posts
 
I just took out the two power/ energiser units and was surprised to find that there were many voltage selections (250, 240, 230, 220, 115, 105) and that they were set to 250V.
When this was changed to 230V which is the nearest to my mains ay my current address, the treble units came to life and now produced output up to 14kHz. That is still not as it should be, so the next thing is to send the units to One Thing who repair these (Change all the diodes and whatever else may need doing).

If the sound is still not correct I will get the Panels repaired by One Thing, who say that they have made a jig for these.
I do wonder if the panels were last repaired with too thick a membrane and I do also know that if it is too thin there can be a bit of a gap between mid and bass. It may be for this reason that they always had a falling response above 16kHz.

Regarding the bass, I have now stuck a door mat to the rear panel of the main box (inside). This seems to have tamed a resonance in the upper bass, so now I will do the same with the other unit.

ct0517, I hope you are enjoying yours

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