B&W DM2A refurb's

[spendorman]

I have a late (UL10) set of those too.

Strangely, I have not come across these, I remember the UL6. The UL10 seem very interesting, look like that have a good selection of units, should sound very good.

[walpurgis]

Strangely, I have not come across these

You won't. The thermally shaped poly bass cones would start flattening out and the cone surround adhesive failed.

[Emmett123]

I hope it does not put Emmett on a long unnecessary road of actions.

Just for example in the DM2a one can accurately measure the resistance on the Coles whilst still in circuit. It is a good start to checking the unit, however there is a chance (smallish) that the coil measures around 23 Ohms and the unit does not work. For example if the coil has separated from the diaphragm former.

In an ideal world we would space the inductors differently. I am aware of these things having worked the major part of my working life as an electronic engineer. Admittedly, I don't know everything.

Hi,

Multimeter arrived and I tested the Coles (out of circuit). It read at 3.2 ohm for one and 2.9ohm for the other. Is this significant when the tweeters are rated at either 8ohm or 16ohm?

Tried it again with the cords connected back in to the crossover and it measure the same.

[spendorman]

Hi,

Multimeter arrived and I tested the Coles (out of circuit). It read at 3.2 ohm for one and 2.9ohm for the other. Is this significant when the tweeters are rated at either 8ohm or 16ohm?

Tried it again with the cords connected back in to the crossover and it measure the same.

If that is a correct reading(s), your Coles are fried, not the end of the world, but unfortunate.

Try measuring something else to check the meter, like the Celestion HF1300, they should measure something around 11-13 Ohms.

[VanDerGraaf]

I'm rather late on this great thread but yes it does sound like the Coles are goners. At least new replacements don't break the bank from Falcon.

I am fairly sure that the ones in my DM2a are dead too. Despite what people say I think if you are young enough you really do notice their absence- I don't have the data in front of me but the crossover point isn't astronomically high- 13kHz?

We hear this as a lack of air and what I always refer to as a lack of "crystalline" sound. I certainly have noticed something different, and I can't hear them anymore when I put my ear next to them- which I can on my similarly-Coles-equipped Mordaunt Short MS400.

[Macca]

I'm rather late on this great thread but yes it does sound like the Coles are goners. At least new replacements don't break the bank from Falcon.

I am fairly sure that the ones in my DM2a are dead too. Despite what people say I think if you are young enough you really do notice their absence- I don't have the data in front of me but the crossover point isn't astronomically high- 13kHz?

We hear this as a lack of air and what I always refer to as a lack of "crystalline" sound. I certainly have noticed something different, and I can't hear them anymore when I put my ear next to them- which I can on my similarly-Coles-equipped Mordaunt Short MS400.

The supertweeter comes in at 14Khz according to the internet. Sounds about right. Most of us should still just about be able to hear it make a contribution.

[Emmett123]

If that is a correct reading(s), your Coles are fried, not the end of the world, but unfortunate.

Try measuring something else to check the meter, like the Celestion HF1300, they should measure something around 11-13 Ohms.

Thanks for the tip. Just tried them too. Reading at 11.9 and 12.4. So they seem good. To replace the Coles, I take it that the 16 ohm Coles 4001 G are the ones to go for, as opposed to the 8 ohm "K" variety?

[walpurgis]

You can't just change a tweeter to a different spec or model without altering the crossover to suit. Better to stick with original types unless you're feeling adventurous .

[spendorman]

Thanks for the tip. Just tried them too. Reading at 11.9 and 12.4. So they seem good. To replace the Coles, I take it that the 16 ohm Coles 4001 G are the ones to go for, as opposed to the 8 ohm "K" variety?

You are correct. If the new Coles 4001G tweeters are too expensive, I have a reasonably good bodge.

[Barry]

Re the Coles 4001G units, I don't understand how the resistance (~ 23 Ohm) can be greater than the impedance (~ 15 Ohm).

But having sold some 4001Ks a few years ago, I did measure the DC resistance and it was around 23 Ohm, with accceptable and expected unit-to-unit variation.