B&W DM2A refurb's

[spendorman]

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.

The resistance of 23 Ohms is correct for the 4001G, even says so on the Coles site. I reckon that the actual impedance of the 4001G is in excess of 23 Ohms.

The 16 Ohm impedance rating is probably because the Coles (originally STC) may have been used on early Hi Fi speaker systems of 16 Ohm nominal impedance.

http://www.coleselectroacoustics.com.../super-tweeter

[spendorman]

Just measured the resistance of a Coles 4001G, get 23 Ohms, also measured it's inductance, result 0.2mH.

Inductive reactance in Ohms is XL = 2PiƒL. Using L= 0.2mH and frequency = 13Khz, we get a calculation of XL = 16 Ohms, if I am correct. Someone please check!

[Pharos]

Yes.

[spendorman]

Yes.

Thank you. Seaford, nice place, not been there for about 30 years!

[Barry]

So Coles quote the inductive reactance as an impedance? Impedance should include the resistance.

As far as I am concerned the modulus of the impedance |Z| = sqrt(R² + X²). Thus sqrt(23² + 16²) = 28 Ohm.

But I digress, as it not helping VanDeGraff

[spendorman]

So Coles quote the inductive reactance as an impedance? Impedance should include the resistance.

As far as I am concerned the modulus of the impedance |Z| = sqrt(R² + X²). Thus sqrt(23² + 16²) = 28 Ohm.

But I digress, as it not helping VanDeGraff

Spot on, I did not do the impedance calculation for fear of confusing, self included!

Still, I think we have got there explaining the so called 16 Ohm rating.

Next, is Emmett going to buy some nice new Coles 4001G?

[Barry]

Spot on, I did not do the impedance calculation for fear of confusing, self included!

Still, I think we have got there explaining the so called 16 Ohm rating.

Next, is Emmett going to buy some nice new Coles 4001G?

No problem - it was just me being a bit pedantic (caused by working 30 years in electronics research).

[spendorman]

As discussed previously, we basically worked for the same company, I was only there for a bit less than 20 years, before that still in electronics / engineering.

In fact my BAE Systems (Marconi) Pension Newsletter just came through my letterbox!

[Emmett123]

Spot on, I did not do the impedance calculation for fear of confusing, self included!

Still, I think we have got there explaining the so called 16 Ohm rating.

Next, is Emmett going to buy some nice new Coles 4001G?

Yip, got some from Falcon yesterday. Popped out the old ones to have a look, a simple enough procedure to solder them in. Though I noticed that old ones do not have a + or - terminal rather the wires are soldered to a flat panel on the back?

Started too to rub down the cabinets. White spirit, wire wool and a light sanding. A bit bashed on a few corners but not enough to be annoying. Debating whether to introduce some teak wood stain . Otherwise some Danish oil, or a varnish.

[spendorman]

Not quite sure what you mean in your first paragraph. Unless you mean the terminal strip.

The bashed corners can be carefully repaired using Brummer Stopping Wood Filler in the correct colour, I'm assuming that your cabinets are teak veneered, most are. I would not stain, just oil or a satin varnish.