B&W DM2A refurb's

[walpurgis]

I believe the soft dome was a Heyco/ Peerless, no ferrofluid in those either.

Could be. It's a hell of a long time since I saw any .

[spendorman]

Heyco/ Peerless tweeter used as supertweeter in early DM2

dm2 by A60man, on Flickr

[Barry]

The capacitors look to be made by TCC and are generally quite reliable.

I have a pair of DM2As, with the Coles and Celestion tweeters, and the HF level switch on the back. I picked them up a few years ago for £50, and are used in my second system (largely used with my TV).

They have been variously powered with a Quad 303, Quad 520 and a Mini-T digital amplifier; the latter of which works very well with the speakers.

[Emmett123]

They may well be OK. They come in very high up the frequency range and emit little that most of us would hear. They handle only a small amount of the overall signal power and generally don't fail.

Given that it might not be possible to hear the super-tweeter even if they were working, would them not working make a difference to the overall operation of the speakers?

[Pharos]

Unlikely.

[Batty]

I was just going on what the insurance guy said.

[sailor]

Hi Emmett,

The tweeter for the extreme highs will definitely make a difference. Perhaps remove them and connect them to your amplifier with a cap in series with either leg. If they work when you do this but not in box then the XO is faulty or the voice coil is open circuit. Post 31 has a link to the crossover which shows C10 is 1.5uf. Snip it out and use it for the job. Turn volume up very slowly. Best if you download a clip of white noise for testing both tweets.

Your speakers are from the mid 70's which means they are about 45 years old!

Just rebuild the crossovers. The caps might still measure to spec but discard the lot. Not everything in audio has advanced that much but modern caps most definitely have. Replace with film caps and certainly no electrolytics. I notice the inductors are all jammed close up to each other and incorrectly orientated. This means they are all talking to each other and smearing fine detail.

Were it mine I would salvage the inductors and configure them correctly on a much bigger board, at the same time spacing them as far apart from each other as possible, similar to the requirements for Covid 19

Try and assemble the XO boards using the leads of all components to connect point to point avoiding adding little scraps of wire or PCB traces.

The story below I copied and pasted from another reply which I feel is pertinent to your predicament.

"Hi Keith, rebuilding the XO with good parts will minimize the damage components do to the signal. My previous recommendations stand. This will provide a cleaner and more detailed signal which will give you the clarity in the top end and also improve bass and midrange. This may seem a little hard to comprehend when the main target of this rebuild is to improve the tweeter's response.

What is at play here is that the upper harmonics of voices and instruments, from the drummers bass drum, side tom, snare drum and other instruments going upwards, is reproduced by the tweeter. The transient performance is crucial for life-like sound, this stems from our senses being tuned for survival in the wild. The sharp snap of dry twig alerts you to danger and gives its location.

The transient or leading edge of the waveform is handled by the tweeter so when you provide it with a cleaner signal your ability to recognise and locate their position is enhanced, hence better imaging and staging.

I mentioned using Mills resistors. Use the 12W and not the 5W. Remember you are looking to maximise the transient snap and the bigger resistor will cause less thermal compression, and that's good. This is an excellent choice, noticeably better than that grainy thing used in your XO and used by many so-called high end designs. For a more precise response, and is what I like using, and feel may suit your speaker better is the Powertron, a Vishay foil. rated 3W or 30W when mounted on a heat sink"

This link takes you to a very informative in depth look at caps from cheap to stratospheric. http://www.humblehomemadehifi.com/Cap.html

I am situated on the same damp rock in the North Atlantic as you, just a little further south in Abbeyfeale. If you need a little help you can load up your beauties and drive down when this silliness is over. My room has acoustic treatment and am able to measure the response.

I include pics of one of my builds for OB speakers
1st: original XO supplied with speaker
2nd: the planning stage
3rd: close of of my new favourite resistor
4th: XO hooked up

[Emmett123]

Hi Emmett,

The tweeter for the extreme highs will definitely make a difference. Perhaps remove them and connect them to your amplifier with a cap in series with either leg. If they work when you do this but not in box then the XO is faulty or the voice coil is open circuit. Post 31 has a link to the crossover which shows C10 is 1.5uf. Snip it out and use it for the job. Turn volume up very slowly. Best if you download a clip of white noise for testing both tweets.

Your speakers are from the mid 70's which means they are about 45 years old!

Just rebuild the crossovers. The caps might still measure to spec but discard the lot. Not everything in audio has advanced that much but modern caps most definitely have. Replace with film caps and certainly no electrolytics. I notice the inductors are all jammed close up to each other and incorrectly orientated. This means they are all talking to each other and smearing fine detail.

Were it mine I would salvage the inductors and configure them correctly on a much bigger board, at the same time spacing them as far apart from each other as possible, similar to the requirements for Covid 19

Try and assemble the XO boards using the leads of all components to connect point to point avoiding adding little scraps of wire or PCB traces.

The story below I copied and pasted from another reply which I feel is pertinent to your predicament.

"Hi Keith, rebuilding the XO with good parts will minimize the damage components do to the signal. My previous recommendations stand. This will provide a cleaner and more detailed signal which will give you the clarity in the top end and also improve bass and midrange. This may seem a little hard to comprehend when the main target of this rebuild is to improve the tweeter's response.

What is at play here is that the upper harmonics of voices and instruments, from the drummers bass drum, side tom, snare drum and other instruments going upwards, is reproduced by the tweeter. The transient performance is crucial for life-like sound, this stems from our senses being tuned for survival in the wild. The sharp snap of dry twig alerts you to danger and gives its location.

The transient or leading edge of the waveform is handled by the tweeter so when you provide it with a cleaner signal your ability to recognise and locate their position is enhanced, hence better imaging and staging.

I mentioned using Mills resistors. Use the 12W and not the 5W. Remember you are looking to maximise the transient snap and the bigger resistor will cause less thermal compression, and that's good. This is an excellent choice, noticeably better than that grainy thing used in your XO and used by many so-called high end designs. For a more precise response, and is what I like using, and feel may suit your speaker better is the Powertron, a Vishay foil. rated 3W or 30W when mounted on a heat sink"

This link takes you to a very informative in depth look at caps from cheap to stratospheric. http://www.humblehomemadehifi.com/Cap.html

I am situated on the same damp rock in the North Atlantic as you, just a little further south in Abbeyfeale. If you need a little help you can load up your beauties and drive down when this silliness is over. My room has acoustic treatment and am able to measure the response.

I include pics of one of my builds for OB speakers
1st: original XO supplied with speaker
2nd: the planning stage
3rd: close of of my new favourite resistor
4th: XO hooked up

Hi Charles,

Thanks for this. Certainly a lot to get my head around. I have never dabbled in electronics beyond soldering in some new caps on a set of Dovedale 3. But constructing a new crossover would be a nice wee project to attempt in the coming weeks of CoVid restrictions. I think the biggest challenge to me would be getting the order/pattern/ circuit right.But if I'm slow and careful hopefully I can get it right.

[Emmett123]

I opened the speakers today, just to have a look and check on all the connections were in place, no broken solders. Appears to be sound in this regard.

[walpurgis]

Bear in mind that in revamping the crossovers, you may spend as much or more on components as the speakers are worth. And that there is no guarantee that you will like the end result.

I still think a good first move would be to use some contact cleaner on the rotary switch, the results may surprise you.