B&W DM70's - top end lacking

Iscm

from the manual.

Impedance
Nominally 8 ohms but rising throughout the mid frequencies to some 20 ohms, falling at 20 khz to 4 ohms.

The manual specifies the following for frequency response.
better than plus or minus 4db - 50 hz to 15khz
plus or minus 5db - 40hz - 20khz

This tells me they need really good setup or people will hear 50hz - 15khz (or less) with an average setup..

The manual also states the ESL panel has a removable pad to control the rear radiation pattern. Make them more dipole. This would be very important for a full midrange and keeping them a few feet at least from the front wall. You don't have a lot to work with - its a small panel. Everything helps. 

My feeling is if B&W kept producing them, the ESL panel would have grown in size - taller, as ESL Panels become more efficient with size. Interesting that the Quad 57 treble & bass panels are vertical. The DM70 mid/treble panel is horizontal. From what I remember the DM70’s have a bigger sweet spot over the 57’s when the 57’s are kept on the ground on their stock feet.

Mentioned earlier I was thinking of taking them out of the stored spot and setting them up. But this needs my son’s lifting help so maybe when he visits. The power supply finding is interesting. Will check the setting on mine before they do get turned on again. I have multiple dedicated lines in the house and live in the country so the demand is not high - Its a solid 121 volts. So the 115 setting it is, and it is low.

ct0517:
This is what I have on the DM70’s so far from different sources.
https://1drv.ms/f/s!AsdR4rYZVpE4sUzCKIvZoEG9f5Ag
Sorry, but there may be duplicates and it includes what I got using the link that you provided

I like this in particular, as there is a very long explanation about their development:
https://1drv.ms/b/s!AsdR4rYZVpE4sDU7GJjlvhBf1_2N
I note that a later equivalent for 1974 is much shorter and more simple.

This tells me they need really good setup or people will hear 50hz - 15khz (or less) with an average setup

My treble issues also show up when I use an amp that previously worked OK with these speakers, so it seems that there is some issue with my speakers.
I talked to One Thing Audio who suggested that I get the ’energiser’ units serviced as a first step.
They said that it is very common for the diodes to fail and that they would replace them all as a matter of course. If that does not work I will send in the panels for repair.

My feeling is if B&W kept producing them, the ESL panel would have grown in size - taller, as ESL Panels become more efficient with size.

I am not so sure, as making the panels taller would change the dispersion pattern.
Their horizontal dispersion is also quite good due to the curve used.
B&W did say, however, that a vertical arrangement was tried.

Hope this is of interest
Ian

I have owned two pairs of these.One pair sounded a bit dull but the other pair had lovely extended treble so it really depends on their condition.

One pair sounded a bit dull but the other pair had lovely extended treble so it really depends on their condition.

I think that either my energiser units need an overhaul of the panels need redoing.
First I will get the energiser units serviced and if I still have issues I will move on to getting the panels done.

I did not think that the electrostatic panels should sound dull.

Hi, new to the site.
I have just picked up a pair of DM70. The ESL sound very good but I suspect that the energiser units needs some caps replacing.
The bass drivers have green felt DIY surrounds that are not helping in that department. If anyone can help in the sourcing of replacement surrounds I would be grateful.
I currently have them hooked up to a pair of Williamson KT88 mono blocks. They are rated at 20wpc. I have been using these on my Maggies and Apogees to good affect. Do I need more power? I have a pair of NAD 214 that are 500+ when bridged.