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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

Showing 10 responses by dylanthecat

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
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
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
dylanthecat
11 posts
 
Hi Ian,

I have ordered those other foams as a spare. Thanks for the link.

Have you changed your drivers over to eliminate the crossover?
Have you changed the speakers overs to eliminate the amp outputs?

Does it sound like metal hitting a dense hardwood block? I have heard of dry joints causing noises like this in bass drivers.

Best regards, Martin
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
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
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
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