B&W DM70's - top end lacking
ct0517: Have you ever had you treble panels repaired? If so, where did you go and what was the difference? I know about One Thing, but they are quite expensive and I have heard that their place is a tip. There is also a German man, but I have had mixed reports about him and he is VERY expensive plus there is international post. My ideal would be somewhere that I could drive to easily from Somerset. Friends who had Quad ELS units serviced have said that the sound comes 'alive' with the repaired speakers. I may look at the energiser units as well, as I am sure that small fluctuations in mains voltage should not make so much difference to the sound. Perhaps I am being hypercritical as I know that higher end equipment can show up other issues and that all equipment tends to sound at its best late at night. I have ordered some ribbon super tweeters and it will be interesting how they work. |
Hi iscm I acquired my DM70 ESL already refurbished. here is a link that shows a pic of the woofer as well as an experiment with the Quad ESL. The experiment did not go well as the B&W crossover Woofer to ESL Panel is 400hz. https://photos.app.goo.gl/jB2ocyZ1sMjUI86X2 It is using silver wiring. If there are periods when they sound great, and other times when not so, that tells me the ESL panel may be ok and I suspect the ESL power supply / capacitors. So I would be tempted from your posts to have the capacitors / power supply checked out and recapped. I am pretty sure the DM70 are using electrolytic capacitors versus the polypropylene film capacitors of the 800 matrix series. The manual recommends that they not be closer than 8 feet apart. Owners manuals can be found here. http://bwgroupsupport.com/manuals/bw-archive#ID_DMSeries Service manuals can be found here. http://bwgroupsupport.com/manuals/bw-service#ID_DMSeries |
ct0517: The service manual is a great hep. I had no idea that it could be accessed and as it is from 1970 there is a good chance that it is correct for my early versions of the DM70’s. One thing that I notice straight away is that I have a missing pin A to one of my HF units. This is the Ground connection which is also connected to the centre tap of the audio transformer. This may explain why I do not get an even treble across the whole panel. I could either get hold of a new plug or remove one of the redundant pins from the other speaker, as only 4 pins are used out of the seven. First I will try to get a spare if at all possible. The pin may have fallen out when I first transported the speakers. The seller was not keen for me to remove the HF panels, but I was not happy to transport them in one piece. After the above I will check the electrolytic capacitors and the resistors. I am working my way through the wiring replacing with Chord Odyssey as I go. This is the cable that I use for the speakers and I use Chord for the rest of the system interconnects. When you bought your speakers did the seller say anything about their restoration. Thanks again |
I just noticed a slight buzz in the right speaker. When I checked, I could see that some of the filling was pushing very slightly against the cone. I corrected this and now the sound it much cleaner. These speakers rely on being totally filled, so it is hard to stop this happening. In future I may try a different type of filling around the area of the bass unit to prevent this kind of ingress happening again. I have also raised the speakers by two inches using two 2 * 3 between the speaker and the stand. This has also made the bass much better (less volume and better definition). Later I could turn the wood to make the extra lift 3 inches. |
