B&w Dm4 - Page 3

Eivind_E · 8th May 2012, 11:17 PM

Thanks for the tip, I have started thinking it must be the amp. Today I tried it again and it played sorta fine, but with unclear sound. So I'm going to give it a run with a tube amp, I'm just missing a couple of tubes

then I'll be all set.

Dazt · 28th May 2012, 11:17 PM

Hi I just found a pair of DM4 1973 speakers are they any good as I have no amp these are still in there boxes and never being open both boxes sealed any info on these will b great thanks

frperdurabo · 28th May 2012, 11:59 PM

Quote:

Originally Posted by Dazt

Hi I just found a pair of DM4 1973 speakers are they any good as I have no amp these are still in there boxes and never being open both boxes sealed any info on these will b great thanks

I never owned them, but a friend in the late 70s did - and I thought they were wonderful. The IMFs I own now have the same tweeter/super tweeter combo, and they're pleasant and musical. So, no longer state of the art, but definitely worth listening too, especially if free or cheap.

Eivind_E · 30th May 2012, 12:08 AM

Quote:

Originally Posted by system7

I'd be looking for a loose wire or shot tweeters myself. You need to use a multimeter to check them.

I hooked up my tube amps, but same result.
So I disconnected the smallest tweeter, the top one that has sort of a transparent plastic finish.
When I play them without that tweeter, the fizzy distorted sound is gone.
So clearly that is at fault for the trashy sound.

However, the remaining sound is a bit "hollow" and not very crisp.
Is this just normal, could the crossover capacitors be shot, or are the woofer and mid range gone stale or what could this be?

I was really hoping to make good use of these speakers, so any help is appreciated

system7 · 30th May 2012, 03:20 PM

I'd think the best way to trace the fault is to swap tweeters about and see which one the fault sticks to, if you follow, Eivind.

Surprisingly, the Coles 4001 supertweeter is still manufactured and available:
Drive Units

FWIW, if you run a speaker with a missing drive unit, you make the crossover very resonant because it has no damping, which will give the amp a very bad day at high volume.

Eivind_E · 30th May 2012, 03:55 PM

The supertweeters in both speakers exhibit the same fault, so need to be replaced.
I am just saying, while playing music without them, the speakers sound like "a football commentator stuck inside a small cardboard box" kinda numb and flatly hollow.

I am considering purchasing two new tweeters, but I guess the advice I am looking for is:
Will it be worth it, or will the speakers still not be up to the job afterwards?

system7 · 30th May 2012, 04:06 PM

What I would do is use a good multimeter on the crossover and measure some capacitor values, but I am guessing those capacitors are OK. Look for dry joints. Put a 1.5V battery over the tweeters to see if they make a satisfying crackle.

You'd have to unsolder the first capacitor in the supertweeter crossover to test them running on just bass and tweeter properly. They actually would probably work ok just on the Celestion HF1300 tweeters if you took out the last coil on the tweeter section, which probably just rolls them off so the supertweeter can take over.

The Ditton 15 by Celestion just used a bass and a HF1300. My flatmate used to have them.

But yes, worth fixing, I'd reckon.

Eivind_E · 31st May 2012, 10:12 PM

Ok cool, but I see the supertweeters are available as 8ohm or 16 ohm. Which ones is it that I need?

Mr. dB · 31st May 2012, 11:26 PM

Quote:

Originally Posted by Eivind_E

Ok cool, but I see the supertweeters are available as 8ohm or 16 ohm. Which ones is it that I need?

16

Eivind_E · 19th June 2012, 07:33 PM

Ok, well I have received the supertweeters from Falcon, and replaced them, but there's still an element of distortion somewhere, maybe the Celestion HF1300's are also faulty?

I read on Troelsgravesen.dk his review of the Spendor BC1, which uses the same woofer/mid/tweeter setup, and he rated it at 84db/1W/1M, and ohms ranging from 10-16 range.
Could it be that at 84db sensitivity, these things are just too heavy to power for my single ended KT88 amps? They are about 8-10 watts or so.
Or should I go looking for HF1300's?

30th May 2012, 03:20 PM	#25
system7 diyAudio Member Join Date: Aug 2008	I'd think the best way to trace the fault is to swap tweeters about and see which one the fault sticks to, if you follow, Eivind. Surprisingly, the Coles 4001 supertweeter is still manufactured and available: Drive Units FWIW, if you run a speaker with a missing drive unit, you make the crossover very resonant because it has no damping, which will give the amp a very bad day at high volume. __________________ Good Night, and Good Luck. Best regards from Steve in Portsmouth, UK.

30th May 2012, 04:06 PM	#27
system7 diyAudio Member Join Date: Aug 2008	What I would do is use a good multimeter on the crossover and measure some capacitor values, but I am guessing those capacitors are OK. Look for dry joints. Put a 1.5V battery over the tweeters to see if they make a satisfying crackle. You'd have to unsolder the first capacitor in the supertweeter crossover to test them running on just bass and tweeter properly. They actually would probably work ok just on the Celestion HF1300 tweeters if you took out the last coil on the tweeter section, which probably just rolls them off so the supertweeter can take over. The Ditton 15 by Celestion just used a bass and a HF1300. My flatmate used to have them. But yes, worth fixing, I'd reckon. __________________ Good Night, and Good Luck. Best regards from Steve in Portsmouth, UK.

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8th May 2012, 11:17 PM	#21
Eivind_E diyAudio Member Join Date: Feb 2008	Thanks for the tip, I have started thinking it must be the amp. Today I tried it again and it played sorta fine, but with unclear sound. So I'm going to give it a run with a tube amp, I'm just missing a couple of tubes then I'll be all set.

28th May 2012, 11:17 PM	#22
Dazt diyAudio Member Join Date: May 2012	Hi I just found a pair of DM4 1973 speakers are they any good as I have no amp these are still in there boxes and never being open both boxes sealed any info on these will b great thanks

30th May 2012, 03:55 PM	#26
Eivind_E diyAudio Member Join Date: Feb 2008	The supertweeters in both speakers exhibit the same fault, so need to be replaced. I am just saying, while playing music without them, the speakers sound like "a football commentator stuck inside a small cardboard box" kinda numb and flatly hollow. I am considering purchasing two new tweeters, but I guess the advice I am looking for is: Will it be worth it, or will the speakers still not be up to the job afterwards?

31st May 2012, 10:12 PM	#28
Eivind_E diyAudio Member Join Date: Feb 2008	Ok cool, but I see the supertweeters are available as 8ohm or 16 ohm. Which ones is it that I need?

19th June 2012, 07:33 PM	#30
Eivind_E diyAudio Member Join Date: Feb 2008	Ok, well I have received the supertweeters from Falcon, and replaced them, but there's still an element of distortion somewhere, maybe the Celestion HF1300's are also faulty? I read on Troelsgravesen.dk his review of the Spendor BC1, which uses the same woofer/mid/tweeter setup, and he rated it at 84db/1W/1M, and ohms ranging from 10-16 range. Could it be that at 84db sensitivity, these things are just too heavy to power for my single ended KT88 amps? They are about 8-10 watts or so. Or should I go looking for HF1300's?