2. speakers
  3. 134439-109758

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 Ian,

I brought my DM70 through AoS as 'not working' for only £100.

I have had great difficulty getting hold of natural lambswool quilting. The material that I have used came from the thermal insulation that Completely Fresh previously used in their delivery boxes. It is perfect for my needs. Unfortunately they have changed the material now.

I removed 2 black bin bags full of glass fibre (I loath the stuff) from the cabs.

One of the problems when I first listened to them was that the damping was pushing up against the cone despite the cotton gauze.

I will upload some photos onto your AoS thread.

Martin
iscm OP
40 posts
 
Hi Martin

How many grams of wool are needed per cabinet?
I have found a source at £10 per kilo.

dylanthecat
11 posts
 
Hi Ian,

Rather than 'stuffing' I have used quilting in 25mm thick blankets therefore I have been able to apply to the inside faces and as gravity drop acoustic curtains directly behind the driver. As a mass/ volume I would estimate that I have now only 20-25% of the original.

These speakers are now sounding very good indeed. Speakers, as we all know, are highly subjective and personal. The DM70 are currently in a room with my Magneplanars and Apogees and are more than holding their own.

Best regards, Martin
dylanthecat
11 posts
 
Hi Ian,

The other foams have arrived. They are the correct size. I will probably change them over at some point in the near future.

Best regards, Martin
iscm OP
40 posts
 
I may have a go myself with new surrounds if I can sort out the ’pinging’ in one of the bass units.

Now I bought a sound level Meter and have been checking the frequency response.
There is quite a hump at 112Hz of about 8db.
Perhaps I could try adjusting the filling.
There is also a big drop at 60Hz.
Some more filling may help.

More to discover