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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
 
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
iscm OP
40 posts
 
I need a new grill to the rear of one panel. Any suggestions for a source will be welcomed.

One Thing should be able to help or advise here.
Mine are made of a slotted plastic.
iscm OP
40 posts
 
Just to make it clear, I am not pushing One Thing, but I know of no one else in the UK with DM70 expertise.
There is a chap in Germany, but he is expensive.

I did see the speaker surrounds being offered as a kit for £35,
https://www.ebay.co.uk/itm/B-W-DM-70-hochwertiges-Lautsprecher-Sicken-Set-speaker-foam-surround-315/183148017101?hash=item2aa478f5cd:g:3xEAAOSwlStauOhM 

but in my case I think I need a specialist, as one of my original bass units makes a pinging sound and needs a total strip down.
Hears hoping Wembley Speakers can do this.
dylanthecat
11 posts
 
Hi Ian,

I have reformed the bass drivers with the Dutch oversized 12" foams. Though tight, they are just large enough and a great sonic improvement over the felt DIY surrounds.

I have removed the cotton gauze and all the damping. This has been replaced with a medium density acoustic foam on the rear panel and top panel. Lambswool quilting has been applied to the sides and based. A synthetic matting acoustic curtain has been hung directly behind the bass driver and folder over the base quilting.

The speakers have been lifted onto layered marble plinths with isolating silicon feet between each of the three layers. I have slotted four heavy duty rubber mounts (designed for hydraulic car jacks) under the speakers frame with isolates the metal base from the marble.

Very happy with the results, the bass has been transformed. The speakers sound better across the frequencies.

The speakers were definitely over damped!

Martin
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