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30 Years of Manufacturing Electrostatic Loudspeakers

Get back your Hörgenuß

 

 

  • Repair, Refurbishment  and modifications,
    finishing and refining
    of the great  B&W Bowers & Wilkins DM70....

    ....we master these matters

    The B&W DM 70’s are a musically cohesive masterpiece. The Gramophone

     

  • And they are worth any effort to keep them running at its best. And to our opinion it is also an optical masterpiece, which deserves to be conserved as a fine piece of modern design.

 

  • The B+W DM 70 was my first hi-fi loudspeaker. I bought and imported it second hand from a London hi-fi dealer in 1974. From that time on I was immediately convinced 1.) of the ESL electrostatic loudspeaker in common,  2.) of the Bowers & Wilkins DM70 especially and last but not least 3.) of the ESL hybrids principle of sound reproduction.

 

  • Since that time I learned a lot about the special advantages and the special problems of the B&W DM70. Finally I knew all parts by heart and I was able to make my work on these loudspeakers with closed eyes. All in all I can look back on  having a 33 years experience with that special type of electrostatic loudspeaker model.

 

? DM-70 wanted ?

Every once and a while we do have some speakers for sale.
Naturally fully refurbished by us, means like new or even better.

Like this beautiful pair  below  for example.

If you are searching for a special finish or OEM version of the B&W DM70, like e.g. the  special DM-70 SONY version or a white model,
give us a call and we will make a reservation for the next available item

 

 

!Simply lift off the ESL panels and send your jewels in and, if you send the electronics unit as well,

!Please do not follow the safety advice
like a DM70 possessor did on the photo below!
!!There are very much easier ways to
disconnect the unit from mains
supply  !!

 

Testimonial
September 2008, James F., Ashford, Kent, UK

"Reiner, I managed to have a good night listening last night,
wow, really very impressed I wish I had got you to do the
work a long time ago. The only problem now is that I have
to go through my complete music collection as I need to hear
everything again.
They really do sound incredible,
the levels, the detail,
the depth, and sound stage are just awesome.
I was impressed before with
the speakers and never wanted to change them, now there is
nothing that will make me sell them.
I cannot say thanks enough Reiner for your work. I am even
leaving work on time which makes my wife happy.
James"

 

The above mentioned refurbished B&W DM70 has been refurbished by using the Shackman PP foil instead of PET with very new Shackman VLC coating. Furthermore  new internal cabling and copperless HV contacts have been used.

.

Testimonial
October 2008, Peter K., Germany
Nun funktioniert alles wieder! Klingen wunderbar.
Die Investition hat sich für mich wirklich gelohnt!

Sehr
gute Arbeit! Von mir aus nochmals herzlichen Dank.


 


The very sensitive HVconnection

 


A panel under the stretching jig


A panel to be refurbished as well as the one below

Using double sided sticky tape, the result after some decades.
Believe it or not - it was still playing... without "light show".
Probably there are thousands of the  DM70 in this condition
running world  wide. Wonders could be given to their possessors' ears.

 

 

!Let us keep these jewels alive!

!Simply lift off the ESL panels and send them in!

 

Spare foam surrounds

We also fix and repair broken foam surrounds of the DM70. As the chassis has an irregular diameter the spare foam is very difficult to get. We do  do have the right ones.

We also repair destroyed/burnt  Bowers& Wilkins DM70 bass driver voice coils.

And we have complete spare drivers which fully fit the original ones in physical size - but  electrically and  acoustically even better.
Please ask for a quote for these extraordinary  spare bass drivers. It is a former 1st  class British driver manufacturer, producing for the greatest ones and for B&W as  well.

 


DM70 Bass driver with "cloth" surround after servicing


Exactly fitting spare "foam" surrounds


B&W DM70 Original  DW13/70/BX bass driver


B&W DM70 Bass driver of "Continental" version before refoaming.
Pay attention to the chassis' curvature fitting the curved front panel.
The manufacturers switched from corrugated paper to Polypropylene

 

 

 

Modifications on the B+W DM70? Why that??

There are not that much weak points in the Bowers and Wilkins DM70s 
which are crying for immediate change.
 No "usual" modifications would promise any improvement in a good 
working DM-70.
Except perhaps some better interior speaker cable from the Input
unit to the crossover.
But in case that the bass has been damaged and replaced by a
non original one, there may occur level discontinuities between bass driver and
ESL MHT panel.
A tweak to that would be a level attenuator for the MHT panel 
and/or/or an
adjustable bias voltage in the very small range of about 100V to 200V.
That may allow an output variation of +/- 1,25dB

 

 

The royal road to approach a brand new, and even better than original,  B&W DM70 ESL Tweeter Unit

What  we really and very simply modify are three imminent weak points
of the B+Ws technical production solutions (other ESL brands as well).
1. The coating material and its resulting long time surface resistivity
2.The adhesive type (no "punctual" heat curing) and its mechanical attachment.
3. The physical contact area of HV voltage bias supply to the diaphragm.

These three reromanus modifications, or better actualizations with respect to former technological knowledge,  are true permanent assurances for an actual  longevity of the DM70 electrostatic panels.

 

 

The "Know-How-To"

Conclusion: Trust in our experience. You will be satisfied.

Repair of B&W Bowers & Wilkins DM70....

....we master these matters

 

!!Get a DIY repair kit somewhere and try your luck ...
or simply give the panels  to our jig!

Prefixing before stretching process

 

Panel stretching with "Linear technology" devices.

 

Stretching process.
The panel under the foil tent,  ready to be lifted.

The panel lifting device and the foil seen from below  towards the foil sky above


Masking for coating procedure

 

Have a look at th jig working, and at "Doc" Reiner E. Römer as well

http://youtu.be/Skx9CH_L9Rs

 

Simply lift off the DM70 ESL tweeter panels and send them in to our stretching jig

 

Prices depend on overall status of the panels. No costs for checking. Best lasting results guarantied. It will pay.

 

 

Some Version History of the B&W DM70


At least 2 different crossover Low pass versions


With two different response curves. Top >1972, bottom 1970-1972

 


3 different Panel HV shortcut protection versions


4 different EHT power units versions. other connectors and sockets, more and more fuses

 


This is serial No. mid 100 in our workshops for refurbishment . The very earliest version of the DM70, enclosure still in mint shape, like brand new from factory, excellent B&W craftsmanship

 

The original "1. Edition" 1970 manual with a remarkable essay of  Mr. Bowers on ESL loudspeakers can be downloaded here. (Courtesy J. Fox, U.K.)

The 1974 edition of the Bowers and Wilkins DM70 user manual can be downloaded here.

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