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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 did a basic test of the high frequency response and found that the cut off is around 10/ 11 kHz.
With a normal tweeter I can hear (just) to 16 kHz.

This may explain why symbols seem so recessed and why, depending on the music, things just don't sound quite right.

It could be the power supply to the panels or the panels themselves.
As my mains is just over 230V where I live, I could try setting the selector on the power supplies to 220V to see if the treble improves.

I suspect that it it is the panels themselves that need a refurb.
We will see
iscm OP
40 posts
 
an experiment with the Quad ESL. The experiment did not go well as the B&W crossover Woofer to ESL Panel is 400hz.
ct0517: With the Quads, I would have thought that around 200 Hz would be better.
I also have a pair of Dali Skyline 2000 and they have a great bass with the right amp and they are totally open baffle right up to their 40cm ribbon tweeter.
They get around the bass loss by using a super efficient 15 inch bass unit which is attenuated until it crosses over to the mid range.
Dali claimed a flat bass down to 38 Hz.

When driven correctly, they have been the nearest thing to Quads will balls that I ever heard, which is what made me think about using their open baffle method with electrostatics.
ct0517's avatar
ct0517
2,041 posts
 
ct0517: With the Quads, I would have thought that around 200 Hz would be better.

Hi iscm

A 200 hz setting is much too high for the Quads. the Quads are wonderful to 50 hz with the Music Reference RM10 which was designed for them.
they needed help below that for the bottom Octave only, and to help create fill /SPL in the room.

For the experiments I placed the DM70 as shown in the picture I linked,  and did not plug them in so only the woofer was active. The woofer plays to 400 hz as designed. This was way too high and the reason it did not work well. Did not mix well with the Quad ESL bass panels. 

In room 2 I have the 57's set up with two Dynaudio BM12s Subs. The subs come with their own Class A/B amp - 250 watts each - they are set to play 60 hz and down only. The RM10 is full out on the 57's.
The preamp used in that room has two direct outputs to allow for separate connections to the RM10 and the BM12s subs. 
So the subs are filling in 60 hz and down only.

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.

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