PDA

View Full Version : B&W DM4



Tweedle-Dee
14-06-2011, 21:10
I recently acquired two pairs of these - one pair very rough, but working well - the other pair partly dismantled (nice cabinets though). The mid/bass units have the white surrounds and in the removed ones the cone has become unstuck at the outer edges (repairable?).

My main question has to with the Celestion and Coles tweeter/supertweeters. I have been amazed by the HF response of these 40 year old speakers. Based on having a spare set of each of these, I was wondering if this pairing could be used in an Open Baffle application with high sensitivity mid and bass units? Can anyone help with the specs of the Coles 4001 and Celestion HF1300 (this is right isn't it?). My feeling is that the sensitivities may not be enough, but could I add extra units?

Cheers,
TD

DSJR
15-06-2011, 19:47
See if you can find anything from the Yahoo Spendor group.

There were slightly different versions of the HF1300/Coles setup made, mainly impedance differences, but this may have an effect on sensitivity. The Spendor versions were higher impedance ones with larger rear magnets IIRC. The standard version wasn't quite the same magnet-wise as I recall.

The high efficiency Celestion Ditton 25 used twin HF1300's to get the treble sensitivity up. The catastrophic effect on dispersion was not a joy to hear, the treble sounding smeared in the Ditton 25 implementation - not an issue back then, but Ditton 44's were much better and the 66's were shedloads better ;)

The HF1300 has a very narrow bandwidth by modern standards, nasty resonance at 3.5KHz which needs a steep roll-in at 4KHz or so and a peak at 14KHz followed by a nosedive into oblivion, hence the Coles, coming in out of phase at 10 - 12KHz to smooth the 14KHz region and extending the EHF smoothly thereafter. Seems a right bodge but it worked well then and still sounds clear now IMO.

Don't despair of modern tweeters though. The ring-radiators made by Scan/Peerless? these days are very good if extremely expensive. Check Falcon Acoustics out on their re-vamped website. These modern tweeters are scrupulously clean, clear as a bell and have wide bandwidth, better for simple crossovers.

spendorman
15-06-2011, 20:06
DM4's, very nice, I have several pairs.

If you want the most sensitive Celestion HF1300, look for some out of a pair of B&W DM3's. They have a bigger magnet than the version used in the DM4/Spendor BC1. The DM3 ones are actually Celestion HF1400. Magnet is a bit deeper than DM4/BC1 version.

Tweedle-Dee
13-10-2011, 20:13
Thanks for this Dave,

Just to show my ignorance, can I ask a stupid question that's been bugging me; would 2 drivers/tweeters covering the same frequencies produce cancellation waves etc and strange effects? I did 'study' Physics at school, but that is a loose term as I learned very little and remember even less! If the cancellation effects are indeed an issue, I'm also interested in how 2.5 way speakers work where LF drivers are close to each other?

BTW, I've moved on a bit with my plans and have 15 Ohm Decca Kelly ribbons and Bakers (Alnico; anyone know much about these drivers?) mid/bass units now to try out that came from a pair of classic Mordaunt speakers together with associated crossovers.

Cheers,
D.

See if you can find anything from the Yahoo Spendor group.

There were slightly different versions of the HF1300/Coles setup made, mainly impedance differences, but this may have an effect on sensitivity. The Spendor versions were higher impedance ones with larger rear magnets IIRC. The standard version wasn't quite the same magnet-wise as I recall.

The high efficiency Celestion Ditton 25 used twin HF1300's to get the treble sensitivity up. The catastrophic effect on dispersion was not a joy to hear, the treble sounding smeared in the Ditton 25 implementation - not an issue back then, but Ditton 44's were much better and the 66's were shedloads better ;)

The HF1300 has a very narrow bandwidth by modern standards, nasty resonance at 3.5KHz which needs a steep roll-in at 4KHz or so and a peak at 14KHz followed by a nosedive into oblivion, hence the Coles, coming in out of phase at 10 - 12KHz to smooth the 14KHz region and extending the EHF smoothly thereafter. Seems a right bodge but it worked well then and still sounds clear now IMO.

Don't despair of modern tweeters though. The ring-radiators made by Scan/Peerless? these days are very good if extremely expensive. Check Falcon Acoustics out on their re-vamped website. These modern tweeters are scrupulously clean, clear as a bell and have wide bandwidth, better for simple crossovers.

DSJR
14-10-2011, 08:11
This is all gleaned info, so second hand at least, but I believe that Celestion doubled up the Hf1300's in the Ditton 25 to increase sensitivity and beggared up the dispersion and treble detailing in the process. Perhaps vertical inline may work if you sit a few metres away from them..

Do please be aware that the HF1300 is a very narrow-band tweeter by todays standards, a massive resonance at 3.5kHz or so (usually hidden in the crossover slope), another peak at 14kHz followed by sudden death above - the reason why the Coles was used out of phase with it (in the Spendors) to flatten the response and take the range out further. I love my BC2's dearly, but I am trying to be real here.

spendorman
14-10-2011, 09:08
Decades ago I used Celestion HF1300's with Elac 8" units in a Hi Fi news design "Paraline". The Paraline was very efficient and the HF1300's worked fine. My home made 2 x 1W amplifier was sufficient to produce enough (nice) noise to make my father ask me to turn it down.