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
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.

dylanthecat
11 posts
 
Hi Ian,

What meter are you using? I do have a vintage frequency generator but not a meter.

I know that there are several apps available.

Many thanks, Martin
dylanthecat
11 posts
 
Hi Ian,
I have downloaded a few apps that were recommended on the internet. They appear to largely correlate with each other.
I am not seeing any obvious concerns. There is a very minor dip at 35Hz though it is very minor indeed. Nothing to cause concern or requiring remedy I would suggest. M
pepler
30 posts
 
Hello Gentlemen,
I too own a pair of DM-70s I am powering mine with mine with McIntosh MC30s.  The sound is amazing!  When I first heard them the bass seemed overbearing, but after some investigation I found the mounting nuts to be lose.  I tightened them and replaced the gasket on the back panel and all is well.  My bass units have been refoamed.
Cheers, Mike
iscm OP
40 posts
 
For checking the frequency response I have been using:
http://onlinetonegenerator.com/frequency-sweep-generator.html
and
http://onlinetonegenerator.com/
to generate all the frequencies that I need.
I only have a basic sound level meter (£15 from Amazon), but it seems to do the job that I require.

Today my wool 'filling' arrived.
I ordered 5Kg, which seems to be more than enough.
Next week I will take out the last of the fibreglass and keep adding wool until the bass frequency response is much flatter.
More to discover