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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
dylanthecat
11 posts
 
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.
dylanthecat
11 posts
 
Hi, I should have clarified that mine are the Continentals.
I note the previous comment about suspended wooden floors, I will place them on some marble slabs.
I am located only a few miles from both the Stenying and Worthing factories though they offer little support to the very early models of which I have a number including DM3, DM4, D5 etc.
Best regards, M
iscm OP
40 posts
 
I suspect that the energiser units needs some caps replacing.
dylanthecat:
After speaking to One Thing Audio, they suggested that it is normally the diodes in the energiser units that go.
They will, of course, do this work for you if you need.
The capacitors are NOT electrolytic in the DM70’s, so they are usually OK and One Thing said that the resistors are normally OK.
Apparently the diodes available at the time were not of a high enough rating, so tend to fail over time.

The bass drivers have green felt DIY surrounds that are not helping
It seems that the brother of the person who did mine had been active with your bass units!
I managed to get hold of a pair of 13 inch Leak Sandwich bass units in 8 ohm versions (most are 15 ohm).
These seem a good match in the DM70 cabinets, but will require four new mounting holes.
Wembley Speakers tell me that they should be able to redo my surrounds on my original speakers.
If you have the Continentals where the bass units have the curved front this may be your only option. (Some Continentals have a curved adaptor plate for the bass unit)

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.
Regarding power, that I think is personal.
I have an Art Audio Quintet which when in triode mode only gives me 15 watts, but seem to control the bass units well. Of course I can not get thrash volumes, but it still seems to go to realistic volumes with classical and most progressive.
When I tried my 70 watt Unico mosfet amp, I found that it offered very little extra headroom and no better bass damping, so I have stuck with my Art Audio.


dylanthecat
11 posts
 
Thank you ISCM,
I have the adapter plate with the EMI bass driver. I have ordered a pair of foams from the Netherlands that were the closest match I could find. Hopefully they will arrive today. Fingers crossed there.
I do have a pair of the Richard Allen high end audio bass drivers that I could try as a back-up.
I have two very good local chaps with huge B&W experience to look at the electronics. They will both have first hand experience here.
I need a new grill to the rear of one panel. Any suggestions for a source will be welcomed.
I brought these as spares not working only to find they just needed a few minor tweaks. I paid very little for them so are very happy with the purchase to date. Best regards, Martin
iscm OP
40 posts
 
Hi Martin
I have the adapter plate with the EMI bass driver. I have ordered a pair of foams from the Netherlands that were the closest match I could find.
I do hope that the foams are the correct size, as most are for 12 inch and not 13 inch speakers.
The foams for 12 inch speakers were used for mine and caused problems.
When I get the chance I will get the correct surrounds fitted to my original bass units.

This is a repeat of the link from ct0517
http://bwgroupsupport.com/manuals/bw-service#ID_DMSeries
You should see that the energiser boxes contain the Energisers for the HT, the High Frequency Crossover and the associated transformer.
The Low Frequency part of the crossover is separated on the bottom of the cabinet.

I did wonder if it would be worthwhile making the speakers bi-wireable, as it would be quite easy to do.

Ian
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