Hi All
So i just acquired these wonderful tweeters which i have been wanting to use and test for a while now.
I want to use them with some goodmans axiom 301 drivers in a horn enclosure.
What i want to do is give the tweeters a good check over, one of the bodies of the tweeter is cracked, so i would like to take them apart and have the horns repainted.
So my questions are.
How do i test the transformer and check the tweeters are ok i.e using a multimeter and what to look out for.
Can i safely take apart the housing for the tweeter without damaging the ribbon and get the body repainted?
Also what crossover would i need for these?
Thans in advance!
So i just acquired these wonderful tweeters which i have been wanting to use and test for a while now.
I want to use them with some goodmans axiom 301 drivers in a horn enclosure.
What i want to do is give the tweeters a good check over, one of the bodies of the tweeter is cracked, so i would like to take them apart and have the horns repainted.
So my questions are.
How do i test the transformer and check the tweeters are ok i.e using a multimeter and what to look out for.
Can i safely take apart the housing for the tweeter without damaging the ribbon and get the body repainted?
Also what crossover would i need for these?
Thans in advance!
Hi vishalk!
These appear to be the original Decca London Ribbon tweeters with the metal horn.
Here's some information to be getting on with, including instructions on ribbon repair (scroll to end of link).
Ribbon Tweeter Horn Loudspeaker: Decca London/Stanley Kelly - Efficiency, Size, Filter and Frequency Response.
These appear to be the original Decca London Ribbon tweeters with the metal horn.
Here's some information to be getting on with, including instructions on ribbon repair (scroll to end of link).
Ribbon Tweeter Horn Loudspeaker: Decca London/Stanley Kelly - Efficiency, Size, Filter and Frequency Response.
Attachments
The attached frequency response curve suggests a crossover frequency of 3 - 4kHz may be applicable.
Decca London Ribbon Tweeter - Frequency Characteristic and Polar Diagram.
Decca London Ribbon Tweeter - Frequency Characteristic and Polar Diagram.
Attachments
The ribbon itself, when disconnected from the transformer, has a very low resistance of about 0.7Ω. The DC resistances of the transformer primary and secondary windings will be low and you should simply check that they are not open circuit.
P.S. Are your tweeters 8 or 16Ω versions?
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Excellent Galu!
I'll measure both with a multimeter, I want to hook them up to an amplifer and use REW to measure them. What value capacitor should I use in series to do this? I've got a few spare capacitors in my tool box.
I'll measure both with a multimeter, I want to hook them up to an amplifer and use REW to measure them. What value capacitor should I use in series to do this? I've got a few spare capacitors in my tool box.
If 8Ω use around 4.7uF, if 16Ω use around 2.2uF.
The impedance of the transformer primary (i.e. the impedance presented to the amplifier) is either 8 or 16Ω - is the figure stated on the label?
I would advise not to disassemble horn and the ribbon driver or screwing the driver off of the horn. The ribbon is very, very fragile. You cannot replace it, no spare ribbons available, repair attempts resulted in having very different frequency and distortion response in the best cases.
Even if you manage to disassemble them without damaging them, reassembling them with a different fit and seal (it was kind of a paper if I recall correctly) will change the linearity, distortion and sound impression.
Don't meddle with the cracked case either, even if it sounds like a crude redneck fix, if it's on a surface (and not on a corner or near a screw hole) just tape the crack shut with duct tape, that's airtight (enough), dampens resonances and you can remove it without any trace to keep the potential resale price up. They are very rare.
Ribbon Tweeter Horn Loudspeaker: Decca London/Stanley Kelly - Efficiency, Size, Filter and Frequency Response.
YouTube
Even if you manage to disassemble them without damaging them, reassembling them with a different fit and seal (it was kind of a paper if I recall correctly) will change the linearity, distortion and sound impression.
Don't meddle with the cracked case either, even if it sounds like a crude redneck fix, if it's on a surface (and not on a corner or near a screw hole) just tape the crack shut with duct tape, that's airtight (enough), dampens resonances and you can remove it without any trace to keep the potential resale price up. They are very rare.
Ribbon Tweeter Horn Loudspeaker: Decca London/Stanley Kelly - Efficiency, Size, Filter and Frequency Response.
YouTube
I'm with ICG and wouldn't want to break what's not needing fixed! 🙂
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The Decca London is one of my favorite tweeters of all time. I owned 2 pair and sold quite a few more.
At one point we got our hands on a Decca prototype, 8” + tweeter XO at 1kHz. Once we finished with these they were very good.
Commonly XO is 1.6 KHz. The tweeter has an essentially flat impedance so XO u=is fairly easy.
The tweeter can be dissssembled into horn, ribbon, and ribbon holder/transformer.. This is part of the repair process, it is fairly straightforward. I got new ribbons from a fellow in the UK who ended up with the original tooling
The ribbon is extremely fragile.
The horn itself needs damping (we coated it in DuctSeal).
dave
At one point we got our hands on a Decca prototype, 8” + tweeter XO at 1kHz. Once we finished with these they were very good.
Commonly XO is 1.6 KHz. The tweeter has an essentially flat impedance so XO u=is fairly easy.
The tweeter can be dissssembled into horn, ribbon, and ribbon holder/transformer.. This is part of the repair process, it is fairly straightforward. I got new ribbons from a fellow in the UK who ended up with the original tooling
The ribbon is extremely fragile.
The horn itself needs damping (we coated it in DuctSeal).
dave
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Thanks Dave always helpful when you reply. Thanks for the crossover design aswell. Do you have info on the gentleman you got the spare ribbons from?
You obviously duct seal the outside of the horn body? Are you also saying that I could probably safely remove the horn from the tweeter? Or just best to leave it?
You obviously duct seal the outside of the horn body? Are you also saying that I could probably safely remove the horn from the tweeter? Or just best to leave it?
I knew you were going to ask. It was something like a decade & a half ago, i’ll have to see if remnants can be found in my email or if google can help
dave
