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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
 
This is where I get my wool filling:
https://www.worldofwool.co.uk/collections/british-wool-filling?sort_by=best-selling
I would say that 4Kg is enough for the two speakers.

It was put into these:
https://www.amazon.co.uk/gp/product/B01I95ER9M/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
and
https://www.amazon.co.uk/gp/product/B01HT2K1E6/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I used a total of four laundry bags per speaker to contain the wool and stop it going into the bass units.
It also helps stop the wool from settling.

normaleila
1 posts
 

Hi. I'm not really qualified to be here because I don't know much about the technical side. Just want to say that my late father in law designed the case for the DM70 and I think it's beautiful. We have a pair of speakers, a central unit that I think is unique and the original Sugden amp that was used for the original demonstrations. The whole system will have to go to auction because we've downsized. Any ideas on the best place to auction it? I'd post a photo but I can't see that it's possible here.
iscm OP
40 posts
 
May I ask how much you may want and where in the country you are located?

I would love to see a picture of the central unit.

You could upload photos to Google photos and insert a link (I think)
iscm OP
40 posts
 
Update:

I finally put in refurbished energiser units into my DM70’s.
I fact I was lucky enough to buy a spare pare of DM70’s for £200 that needed new foams for the bass.
The energiser units from these ’new’ speakers have now had all their diodes replaced and I am now using them in my original DM70’s.
This has made a massive difference to my treble.
I then tried the treble units from my ’new’ speakers and found that the treble was even better and now matches the level of the bass unit.

My advice to anyone is, GET THOSE DIODES REPLACED.

I have ordered the foam surrounds:
https://www.ebay.co.uk/itm/Bowers-Wilkins-DM-70-hochwertiges-Sicken-Set-speaker-foam-surrounds-315/183148017101?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Soon I will put these surrounds on the bass units from my latest pair of DM70’s and install them in my original speakers.

UPDATE TO FOLLOW

Ian
ct0517's avatar
ct0517
2,041 posts
 
Assuming the DM70 ESL panels themselves are good.
Another reason for the lack of ESL Panel output could be related to the 3- 800m ohm resistors in the EHT power supply, whose values may have drifted much higher and are preventing the panel from being charged properly.
Carbon resistors values have a tendency to drift higher over time and those are Carbon resistors - in the Panels power supply.

A megaohmeter is required to test them. They can be bought for cheap at Amazon.

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