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Multi-Way Conventional loudspeakers with crossovers

B&W DM14 from 1980 - hot pics -
B&W DM14 from 1980 - hot pics -
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Old 29th March 2021, 08:20 PM   #1
diyiggy is offline diyiggy
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Default B&W DM14 from 1980 - hot pics -

Hi,

Found that B&W DM14 on the side of the road. This sealed 2.5 ways made from chipboard two 18 cm polypro like cone and a 2.5 cm tweeter sounds a little boxy but I find the high mid and treble to be very nice. Quite heavy box assembled September 1980.

Shouted some pics of the drivers and the internal for Diyaudio archives:

1" (2.5cm) tweeter : TW26, 8 ohms soft dome, seems hand coated and is a little bright for a fabric dome. The dome is very soft at finger push but recover its shape back.

7.3" (18.5 cm) mid-bass x 2 : DW150/14 (14 ohms?) from the half of the surround it's a 5.76" (14.5 cm) polypro cone. back of the cone has a sort of wave a little like plastic coated paper but front cone suggest it's a full plastic cone. Not sure what the dust cover is : hard coated paper ? Surrounds are butylene, very light and thin... Speeder is weak, aging or born like that ? Qm should exhibit a high number. My ears are saying it has a good high mid and mid but not so a good bass. Perhaps the load, the drift value of the caps changing the crossover characteristics ? I can't say.

Not studied the filter yet. Lytic caps are PYE brand cap (the red 560 uF & 5 uF), some MKT or Mica (the browns) and mkp (10 uF) There is a little resistors network probably to supply the red led of the loudspeaker in the low left edge as it's not an active speaker and just mono wired.

Veneering varnish reacts to the methylated spirit. Enclosure has two U pieces of dense foam to line the walls and the top/ back. Full of stuffing, synthetic wool. Enclosure is 57 cm x 25,5 cm x 28 cm (deep)

Any thoughts or documents/links about this loudspeaker and/or drivers please ?
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Last edited by diyiggy; 29th March 2021 at 08:53 PM.
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Old 29th March 2021, 08:38 PM   #2
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hummm have a little problem to upload the pics....
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Old 29th March 2021, 08:40 PM   #3
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then
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Old 29th March 2021, 08:42 PM   #4
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Old 29th March 2021, 08:45 PM   #5
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Old 29th March 2021, 09:47 PM   #6
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Box is 28.32 liters (1 cubic/F)
Cones are Bextrene material.
DM14 shematic filter attached.
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Old 30th March 2021, 04:51 AM   #7
Shaun is offline Shaun  South Africa
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What a score! These are well-loved speakers. My brother-in-law owns a pair and refuses to part with them. These usually come with integrated stands; I see yours doesn't have them. They are quite enjoyable speakers and I agree with your impression of their sound characteristic.
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Old 30th March 2021, 05:15 AM   #8
meanman1964 is offline meanman1964  Belgium
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I also have a pair of DM14 speakers and they have the richt amount of bass .
What amplifier your using ?
Please lift them about 25 a 30 CM from the ground .
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Old 30th March 2021, 08:57 AM   #9
system7 is offline system7  United Kingdom
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Amazing what you find in the Street! Probably after a house clearance by people ignorant or uncaring about what they discard.

I can help with the crossover. Top section. Simple third order tweeter with a slightly rare 0.22uF snubber network (aka KEF Acoustic Butterworth) designed to fix the Fs resonance of a soft dome cloth tweeter. A 8.2R / 0.68uF zobel network to tame the harsh top end.

Middle section. A 2.5 way (Heavy 6dB bass bafflestep) bass network still in use to this day by people like Zaph. Bextrene is considered a bit passe and unrevealing these days, but worked. The late great Jeff Bagby approved this circuit too.

Disregard the bottom section electronic protection circuit. A luxury incorporating BC107A low power transistor and BC177A medium power transistor, all powered off the bass input by 1N4004 power diodes and kept powered by the 100uF capacitor.
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Last edited by system7; 30th March 2021 at 09:03 AM.
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Old 30th March 2021, 04:06 PM   #10
diyiggy is offline diyiggy
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Thanks guys, indeed nice surprise, too bad two or three edge were wasted when the owner put it in the trash ! But nothing terrible.

I personally found it's not lacking of bass but just it's a boomy one, typically barrel sound (empty of wine or whiskey). But go figure, the amp tested is a Pioneer SA506 from the same years I found one week ago at the same place (town recycling wastes where I'm locked down in the countryside... so far of my better toys to test it.

Weird it's lack of bass for my ears, maybe the Qm is not playing its role - but most of the time that's the electrical damping that rolls back the cone?-, while the upper mid section after the roll off of the 500 uF cap is sounding astonishingly good ! Maybe they should have putted a paper cone in the bass but I can understand the reason why 2.5 wys use similar drivers most of the time.

Steeve, I knew you will like the story, it's not my first, but this one is worthing the refurbishing. Thanks for the crossover analyze


Shaun, I wish it were an ESL63 , For you and meanma1964, I found the owner manual if not having it.


look also what I found in the cabinet, the cabinet supplier was abroad... Sydney, strange ! (this cabinet where never opened before I did)
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Attached Files
File Type: pdf ENG_FT00065_DM14_manual.pdf (994.1 KB, 2 views)
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Last edited by diyiggy; 30th March 2021 at 04:33 PM.
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