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-   -   What are these pads for? (http://www.diyaudio.com/forums/full-range/188348-what-these-pads.html)

Rullknufs 3rd May 2011 05:15 PM

What are these pads for?
 
http://piclair.com/data/u3xkv.jpg

I found this B&W DM1 (according to the seller) on a swedish market-site.
I see there are like foam pads on the largest driver, what are these for?

planet10 3rd May 2011 05:21 PM

The oval driver is essentially a FR (brand escapes me at the moment). On the other side of the cone from the inner dark part is an aluminum subcone. I expect the pads are to restict or control its top-end.

dave

Rullknufs 3rd May 2011 05:23 PM

Interesting. So it acts like an LP-filter?
Why is there an aluminium subcone? Shouldn't the mms of that driver be pretty high?

planet10 3rd May 2011 06:15 PM

Quote:

Originally Posted by Rullknufs (Post 2560232)
Interesting. So it acts like an LP-filter?

I would guess

Quote:

Why is there an aluminium subcone?
Similar in function to a whizzer cone.

dave

Rullknufs 3rd May 2011 06:59 PM

Quote:

Originally Posted by planet10 (Post 2560283)
I would guess



Similar in function to a whizzer cone.

dave

Ah, cool :)

AstroSonic 3rd May 2011 08:01 PM

I think the elliptical cone driver is an EMI - a very fine driver. The foam pads are probably placed so as to damp cone breakup modes. As mentioned earlier, this is a full range driver, quite usable all by itself.

The dark (1 1/4 inch) dome driver is a Celestion HF1300, commonly used on as a mid-tweeter on top of the line British loudspeakers in the day.

The small (3/4 inch) dome is probably a Coles 4001G super tweeter.

These two domes were also used in the Spendor BC-1, one of the top British designs in its day.

Most of these designs had fairly complex crossovers, and were pretty inefficient (78-84 db/w/m).

Regards,

Bob

Rullknufs 3rd May 2011 08:07 PM

Interesting. Was this a good speaker back in the days or was it just rubbish?
It's being sold at the moment paired with a Fisher CA-77 amplifier (what about this, rubbish too?) for 1200SEK which is around $195. Not thinking of buying it but vintage hi-fi is interesting :)

planet10 3rd May 2011 08:14 PM

[QUOTE=AstroSonic;2560374]I think the elliptical cone driver is an EMI - a very fine driver. [QUOTE]

Yes, that is it.

Quote:

These two domes were also used in the Spendor BC-1, one of the top British designs in its day.
And i a zillion other British commercial & diy speakers. Sometimes a Celstion HF2000 was subbed in for the Coles.

Coles 4001 - Loudspeakers & Drive Units

dave

AstroSonic 3rd May 2011 10:14 PM

"paired with a Fisher CA-77 amplifier "

The Fisher CA-77 is best forgotten (unless you are into solid state grunge). :-(

The B&W DM-1's are collectable vintage if in near mint condition. The cab looks a little rough, and the associated CA-77 'could' have been run into severe clipping which might have blown one or more domes. Neither of them (the Coles or Celestion) had much power handling capacity. If the price is right, they could be worth purchasing just to get a pair of the EMI full range drivers.

Bob


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