Ok, so I've gone over my defunct tweeter. I took it to a guy that sells B & W speakers here in SA, but he told me my two tweeters were different from each other (which is simply not true - they have absolutely identical geometry and they have the same label on the back, which even says that they were made on the same day.
Anyway... I separated both into voice-coil and magnet. I then swapped them over to try and single out the problem. The 100% functional one still worked, so I conclude that there is something wrong with the voice coil of the 'broken' one. I measured the impedences - the functional one measures at 5.8ohms and the broken one at 6.8 ohms..
This is very weird..
Anyone have any ideas? Basically the symptoms are that the defunct tweeter has a lower output (I'd say about half).
Anyway... I separated both into voice-coil and magnet. I then swapped them over to try and single out the problem. The 100% functional one still worked, so I conclude that there is something wrong with the voice coil of the 'broken' one. I measured the impedences - the functional one measures at 5.8ohms and the broken one at 6.8 ohms..
This is very weird..
Anyone have any ideas? Basically the symptoms are that the defunct tweeter has a lower output (I'd say about half).
Could it be that the coils are different depthwise and that one of them is only partly in the magnet gap. My guess is that that gap is very narrow and the coil winding height is small so small differences can screw things up.
Have you tried contacting B&W themselves. They are ever so helpful and love the DIY spirit in keeping their older speakers alive.
This is very true, have never found such a helpful company as B&W, they genuinely care about their customers (even when that custom was 3 decades ago!) and if can help, such as still having the information, they will.
Got a reply from B&W.
The guy suggests I try a 4ohm dome of similar size to the originals, and then attenuate it with a series resistor (starting at 1ohm).
Anyone have any recommendations for 4ohm 19mm dome tweeters of reasonable price (around $50 a pair) that work nicely for crossover at 5kHz? I wouldn't mind fabricating new mounting plates to get them to fit.
Thanks!
The guy suggests I try a 4ohm dome of similar size to the originals, and then attenuate it with a series resistor (starting at 1ohm).
Anyone have any recommendations for 4ohm 19mm dome tweeters of reasonable price (around $50 a pair) that work nicely for crossover at 5kHz? I wouldn't mind fabricating new mounting plates to get them to fit.
Thanks!
Here's a good resource with information about lots of tweeters.
If you could try a ring radiator, at that price range I'd suggest an XT25.
Zaph|Audio
If you could try a ring radiator, at that price range I'd suggest an XT25.
Zaph|Audio
I'd have a look at the Seas 19TFF, well below your price point (probably - I don't know about SA), quoted at 6.2 ohms but if that causes problems which I bet it wouldn't, try 4-8ohms in parallel. It's often used as a replacement for the superb Celestion HF2000 but is a considerable improvement even on that. Always thought it was a real bargain..
All the best
All the best
Great, thanks for the advice, and thanks for that link DrDyna!
Does anybody have any idea as to what I should be looking for regarding sensitivity?
Overall sensitivity of the cabs are 95db at 1m as of 7.8v pink noise.
Does anybody have any idea as to what I should be looking for regarding sensitivity?
Overall sensitivity of the cabs are 95db at 1m as of 7.8v pink noise.
Ok so in between uni I've had another look at this.
Measured series resistance of my voice coils - 5.8ohm and 6.8ohm. Inspected the lengths of the coils too (can't believe for the first time...). The 5.8ohm coil was about 0.7mm shorter than the 6.8ohm.
Also, did an informal headphone out test, the 5.8ohm is obviously louder than the 6.8ohm, so the 6.8ohms the problem. I had a thought about it, and realized I could probably shorten the coil myself. So I took everything apart, used a pen knife to break the glue holding the end wire down, gradually unwound the coil from the magnet side - continuously burning off the enamel and checking the resistance.
Got the 6.8ohm coil down to 5.8ohm - like the other one, and the top of the coils are now in the same position. It hasn't had a hugely noticeable impact.
Now the only thing left: I had a look at the domes of the tweeters. The loud one seems to be a lot more stiff to the touch, and the 'broken' one much softer. The rigid one is also way shiny-er than the soft one, it looks as though its doped more or something? Either that or the broken one has lost its doping somehome. This is now the only discernible physical difference between the tweeters. The magnets are the same, as I tested both domes independently on each magnet.
So I'm going to give it one more shot before I take them in to the speaker wizard here in Cape Town or replace with some new production tweeters (for which I will most definitely have to get some mounting plates fabricated - mission).
My question is this: What kind of resin matrix is generally applied to polyester domes? I figure that I will have to try and paint on some kind of resin to get the dome's stiffness close to or on par with the working tweeter. That must work.. If it doesn't, then I'll be absolutely stumped 😕..
Hope someone has an idea!
Regards,
Jono
Measured series resistance of my voice coils - 5.8ohm and 6.8ohm. Inspected the lengths of the coils too (can't believe for the first time...). The 5.8ohm coil was about 0.7mm shorter than the 6.8ohm.
Also, did an informal headphone out test, the 5.8ohm is obviously louder than the 6.8ohm, so the 6.8ohms the problem. I had a thought about it, and realized I could probably shorten the coil myself. So I took everything apart, used a pen knife to break the glue holding the end wire down, gradually unwound the coil from the magnet side - continuously burning off the enamel and checking the resistance.
Got the 6.8ohm coil down to 5.8ohm - like the other one, and the top of the coils are now in the same position. It hasn't had a hugely noticeable impact.
Now the only thing left: I had a look at the domes of the tweeters. The loud one seems to be a lot more stiff to the touch, and the 'broken' one much softer. The rigid one is also way shiny-er than the soft one, it looks as though its doped more or something? Either that or the broken one has lost its doping somehome. This is now the only discernible physical difference between the tweeters. The magnets are the same, as I tested both domes independently on each magnet.
So I'm going to give it one more shot before I take them in to the speaker wizard here in Cape Town or replace with some new production tweeters (for which I will most definitely have to get some mounting plates fabricated - mission).
My question is this: What kind of resin matrix is generally applied to polyester domes? I figure that I will have to try and paint on some kind of resin to get the dome's stiffness close to or on par with the working tweeter. That must work.. If it doesn't, then I'll be absolutely stumped 😕..
Hope someone has an idea!
Regards,
Jono
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It might be fine to experiment with, but in the end the most solid recommendation would be to replace the tweeters imo.
Yep I'm not really expecting this to work.. But I guess its stuffed anyway so no sense in not having a go.. Does anyone have any other ideas? What do they normally uses as a matrix for forming polyester domes? I would imaging a poly resin of some sort?
Hi Shaun!
Some years indeed, but thanks for following up.
I managed to coat the softer dome with a very light coat of clear lacquer. Got it up to a very similar impedance to the louder tweeter. Seems to be working fine, although one side is still noticeably louder at close range, but from about 1m you can't really hear the difference.
I'm still super happy with them. They are in my lounge and playing as we speak being driven by an 80s Yammie. Super reliable room fillers even after nearly four decades. 🙂
Some years indeed, but thanks for following up.
I managed to coat the softer dome with a very light coat of clear lacquer. Got it up to a very similar impedance to the louder tweeter. Seems to be working fine, although one side is still noticeably louder at close range, but from about 1m you can't really hear the difference.
I'm still super happy with them. They are in my lounge and playing as we speak being driven by an 80s Yammie. Super reliable room fillers even after nearly four decades. 🙂
Good to know you got a workable solution.
I recently acquired a pair. Tweets and woofer had both been replaced with non-original drivers. The woofer isn't sounding too bad, so my priority is the tweeter. This I replaced with a Vifa NE19VTA-4. Sounds much better, but I think it will ultimately require a crossover tweak.
I found your thread while searching for info on the DM6es.
I recently acquired a pair. Tweets and woofer had both been replaced with non-original drivers. The woofer isn't sounding too bad, so my priority is the tweeter. This I replaced with a Vifa NE19VTA-4. Sounds much better, but I think it will ultimately require a crossover tweak.
I found your thread while searching for info on the DM6es.
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