B&W DM/2 Super Tweeter 8ohm or 16ohm?

[rizlablister]

Hi all,

I have just purchased a set of these huge B&W speakers, and have just replaced the super tweeters with brand new Coles Electroacoustic 16ohm tweeters.

Am I correct in using this impedance as I could not see any sticker or marking on the old one or should this speaker have a 8ohm super tweeter.

Also would it make any difference that I have used 16ohm instead of 8ohm, i.e. would I have to upgrade anything in the cross over section like caps or diodes.

Confused and worried that I'm not getting the full benefit from the speakers.

Am running Nad c350 amp 60w rating of min 4ohm.

Any help would be much appreciated to achieve maximum performance from these speakers.

Thanks

 

[ARguy]

Hi. Welcome to AK. Well, if I were you and living where you are I would contact B&W directly and talk with one of their service people and they should be able to give you all the helpful hints you should need. Personally I would have left them alone if they worked and replaced them with factory originals if they were dead. I own three different pairs of B&W speakers and enjoy them all just as they are. Nothing wrong with trying different things to see if you get improvements! Good luck!

 

[rizlablister]

Many thanks for the speedy reply and I hope to be able to offer some assistance to the members of the forum.

I replaced them due to one not working as the coil wire was fractured on one, so I replaced both with the CE 4001 Super Tweeter that was made for these speakers, and hasn't changed at all since it was first manufactured. but didn't count on there be two options.

The guys at Coles telephoned me yesterday and asked if I wanted 8ohm or 16 ohm so said 16ohm as I thought this to be correct but now have doubts.

Thanks again for your reply and look forward to offering assistance where I can.

 

[hifi_nut]

I have no idea whether the DM 2´s use an 8 ohm or a 16 ohm driver, however, having the double of the impedance, the 16 ohm version should require more power to attain the same output levell.

In short, if the speaker calls for an 8 ohm driver, you´ll probably find it lacking in the upper frequencies.

 

[Rolf Zetterberg]

Many,many moons ago I made a simple sketch of the Bowers & Wilkins DM1(the little one) crossover,but since it resembles the DM2,I upload it here.Maybe of some help to someone(lager simply means layers of wire).

 

[rizlablister]

Many thanks for the reply.

So it may seem, I should have brought the 8ohm instead of 16ohm.

I was expecting a pronounced difference in the sound and I haven't noticed it.

I was using these speakers before with one tweeter out and never even noticed, so expected some kind of change when I replaced both.

Maybe I need to look towards replacing any caps as these are around the 1974 vintage or am I just creating more work.

Any suggestions are always welcome.

Thanks to everybody who has taken time to reply.

Just wished I knew the impedance of this tweeter before, but something has come out all this.............................this forum.

Thanks Guys

Darren

 

[marantzbe]

I guess the tweeter are rated at 8ohms and the medium are rated at 16 ohms.
Problem there is no written information on the back of the tweeter.
For the medium there is a red sticker where the value is mentionned.

The DM2 are my favourite speakers, very nice combo with a Marantz PM5 or Marantz SC6-SM6.

 

[marantzbe]

Hi all,

I have just purchased a set of these huge B&W speakers, and have just replaced the super tweeters with brand new Coles Electroacoustic 16ohm tweeters.

Am I correct in using this impedance as I could not see any sticker or marking on the old one or should this speaker have a 8ohm super tweeter.

Also would it make any difference that I have used 16ohm instead of 8ohm, i.e. would I have to upgrade anything in the cross over section like caps or diodes.

Confused and worried that I'm not getting the full benefit from the speakers.

Am running Nad c350 amp 60w rating of min 4ohm.

Any help would be much appreciated to achieve maximum performance from these speakers.

Thanks

Could you be more specific about the DM2,,there are 3 different versions
2 of them were made in the early 70's and the third around 1977.
The 1st 2 are very similar (design), the later model is completely different

 

[rizlablister]

Thanks to all of you for all your assistance.

I will be testing the old tweeter today and will let you know what one it is.
This one was working as tested but couldn't hear it when it was connected in the DM/2.

Below is some relevant information of the tweeter that I obtained from Coles Electroacoustic.

If a super tweeter is barely audible if this is the case, seems a shame to spend money on something that makes very little difference.

I have uploaded some pictures of the monitor, old tweeters and with new in place.

Thanks again,
Darren.

CE 4001 Super Tweeter


Frequency Range 1.2KHz - 35KHz
Useable Frequency Response 8KHz - 35KHz
5KHz - 25KHz
+/-2dB
Nominal Impedance /K = 7 OHM
/G = 16 OHM
D.C. Resistance /K = 6 OHM
/G = 23 OHM
Max. Continuous Sine Handling 120W
System Programme Rating (Rec. Max): 120W
Sensitivity (dB for 1 Watt @ 1 Metre): /K 87dB 5K-
/G 85dB 15K

 

[marantzbe]

Those are the old ladies, I use to have the same, no tweeter or medium problems, I really love the sounds coming through those speakers
They are not easy to setup.
The 1st time I listened to them Iwas disappointed, in fact at this times, my main speakers were the DM4. DM2-DM4, same inspiration, same period, DM2 are bigger, so my logic was, how bigger, how better, and surprise less bass, medium were not present.
I begin to find another placement, ok improvement but no sufficient to reach the level of the DM4, I tried with the selectors at the back, and wow, everything was back and since then I enjoy every days those old ladies.

 

[rizlablister]

Quick update.....

Removed the super tweeters and soldered back in again as connection didn't look that good, now the sound is really dull and not as sharp and also amp volume needs to go up more as before and the other HF1300 tweeters which are 16ohm are working perfectly well, both speakers sound the same.

One possibility is that something may have damaged something when it was soldered, as I heard a discharge from the super tweeters when I was soldering. I will check this when I can get a meter. No power was connected to the speakers at this time.

Have put all the sound materials back as should be, as I thought that may be the cause of the problem but still no better.

When I first got them about two weeks ago all sounded perfect. Since new super tweeters went in all the problems have started.

Such joy

Picture of crossover attached

Any help on this appreciated

Thanks
Darren

 

[ColinR]

The B&W DM2 instructions clearly state that the supertweeter is a Coles 4001G, ergo 15 Ohm impedance.

If you're slow when soldering you can simultaneously solder on a lead in wire and desolder the voice coil wire due to the Cole's construction.

 

[rizlablister]

soldering was all good, with no fractures. I put the speakers through their paces without the super tweeters and tried without the tweeters, but all I achieve is a very dull muffled sound.

Since I put these 16ohms in nothing seems good, lack of base, vocals lost, you get the picture.

Any help please

Thanks
Darren

 

[ColinR]

The crossover uses polyester capacitors, as they aren't the Mullard Liquorice Allsort type, there should be no problems in that area.

So imho suspect parts are the connecting lead and the multiway connector (and the pcb block). Check visually for damage and for continuity with a multimeter.

Get some leads fitted with crocodile clips and check the wafer switch in the centre of the pcb.

Look at all soldered joints again.

Lack of bass is an odd observation, however putting any design through it's paces with drivers disconnected is not good for amplifier health.

The DM2s are bass shy in comparison to modern "in your face" designs.

 

[rizlablister]

Thanks for that Colin, so I did buy the correct tweeter being a 16ohm.

I wasn't able to find any information about the DM/2 all I could find was the series 2.

I will check all that you mentioned and hopefully have some good news or at least find out what the problem is. As said before sound was perfect just don't understand why it has suddenly lost it's clarity.

Thanks Colin off to Maplin to get a multimeter any recommendations as they have quite a range and difference in price.

Many thanks for your assistance.

Darren

 

[Radfordman]

I have the crossover circuit diagram somewhere. I am the friend of the guy on another forum that passed on info to you.

 

[voyager12]

Hey Rizlablister, did you sort out your DM2 speakers? Are they functioning properly? I seem to have a similar problem: a blown 16 Ohm super tweeter in my DM4 and having a 8 Ohm tweeter to replace it. So, actually the other way round.

 

[fredeb]

Please help with DM1 crossover

Many,many moons ago I made a simple sketch of the Bowers & Wilkins DM1(the little one) crossover,but since it resembles the DM2,I upload it here.Maybe of some help to someone(lager simply means layers of wire).

Hi Rolf - I have acquired a pair of B&W DM1 crossovers , a pair of Coles 4001's and a pair of Celestion HF1300's that were removed from a DM1 set . The one EMI driver was missing , so I have decided to build a new box using 2x Vifa P21W0-20-08's ( Mission Super 770 ) with above mentioned components .

In your DM1 cross-over sketch , are the drivers placed in ascending order ? ie. Woofer , Mid/HF Celestion HF1300 and then Coles 4001 ? The reason I ask , is because when I matched the colour wiring from the crossovers to the drive units ( the wires were clipped a couple of cm from the crossover units and drivers ) , it appears that the Coles 4001's were paralleled with the 15 ohm resistor . Now I am confused as to whether it is the Coles or the Celestions that gets connected in parallel with the 15 ohm resistor .

Help from anyone at all will be appreciated .

BTW - I have connected the 2 Vifa drivers in series , so as to get impedance of 16 ohm . When I calculate combined resistance in parallel , I get ~4.3 ohm in the instance where the Celestion is connected in parallel with the 15 ohm resistor , and ~4 ohm with the Coles connected in parallel with the 15 ohm resistor . That is without taking impedance of inductors into account . The B&W owners manual states the impedance of the DM1's to be ~8 ohm , which , by my calculations would have to make the impedance of the EMI driver 32 ohm ????