Here are a few closeups of tweeter "A" (classic 1970's ESS AMT tweeter). I haven't pulled the damaged diaphragms out yet.
Front side closeup:
Rear side closup:
Missing putty closeup. I need to find out what type of putty is needed so that I can replace the diaphragm properly. I have extra diaphragms that I can insert that I got from @LifeOfBrian .
I'm not generally an open back guy, and I tried using the ESS in a monopole configuration but the magic was gone so that's why it ended up open in my build. As a matter of fact there are several domes that I would choose before it in a monopole configuration.
Here are the OmniMic HD distortion plots comparing tweeter "A" and tweeter "B" (classic 1970's ESS AMT tweeters). These plots were taken at a distance of 1/2 meter (19.5") on axis with the tweeter. SPL was approx 96dB for tweeter "A", which translates to 90dB at 1 meter. SPL was approx 98dB for tweeter "B", which translates to 92dB at 1 meter. The amplifier volume level and mic position were the same for both measurements. As you can see, distortion is much lower for tweeter "B", even at a 2dB higher playback level!
I pulled the damaged diaphragm out of the tweeter that I am calling "A" (classic 1970's ESS AMT). Below is a side-by-side comparison with two other diaphragms. The left most is the damaged "A" one. As you can see, It is badly melted. In the middle is a used original style diaphragm from the 1970's. On the right is a newer style replacement diaphragm. I think I will start out by inserting the used original style diaphragm (1970's) and see how this vintage one measures. Then I will try the new style diaphragm. The new style diaphragm measures 3.5 ohms DC resistance (Re) whereas the original style diaphragms, from the 1970's, all measure 5.2 ohms. Don't know if that DC resistance difference will cause a problem. As long as I can get a good SPL and distortion match, I should be OK.
"The new style diaphragm measures 3.5 ohms DC resistance (Re) whereas the original style diaphragms all measure 5.2 ohms. Don't know if that DC resistance difference will cause a problem."
I don't envy you doing a left/right specific crossover.
@rjj45 said:
Did you ever find out what kind of putty is used to seal the diaphragms?
No. There are several threads on Audiokarma and diyaudio talking about swapping these diaphragms, but noone ever seems to mention the type of putty used. So I am on my own on this one. I've decided to try a "no residue" type mounting putty that is designed to hang things temporarily on walls. They are safe for plastics and wood and do not leave marks. Don't want to use something like mortite caulking compound or plumbers putty. I know that mortite caulking compound has oils in it which could migrate up onto the diaphragm over time. Not sure about plumber's putty, but its probably a good idea to stay away from that as well. The gorilla mounting putty looks like a good choice. Heading out to the hardware store to see if I can find some.
So Van Halen Eruption, at max, was the likely demise of ESS "A". RIP
@4thtry said:
I pulled the diaphragm out on the defective tweeter. Below is a side-by-side comparison with two other diaphragms. The left most is the defective "A" one. It is badly melted. In the middle is a used original style diaphragm. On the right is a newer style replacement diaphragm. I think I will start out by inserting the used original style diaphragm and see how that one measures. If that one looks wonky as well, then I will try the new style diaphragm. The new style diaphragm measures 3.5 ohms DC resistance (Re) whereas the original style diaphragms all measure 5.2 ohms. Don't know if that DC resistance difference will cause a problem. As long as I can get a good SPL and distortion match, I should be OK.
@ugly_woofer said:
Why not just call ESS and ask what putty to use?
Thanks, Nick. The web site lists Simply Speakers as an authorized dealer for replacement parts, so I submitted an email question and am waiting for a reply.
I don't realy have experience with AMTs yet. Please someone tell me this is nothing to worry about because I'm on the edge of being rather annoyed.
I'm no expert, but based on my limited experience with this driver and diaphragm, those impedance curves look perfectly normal to me. The newer diaphragm used on these is spec'd at 3.7 ohms DCR. That matches your curves almost perfectly. The small bumps are probably normal. The older diaphragms (from the 1970's) that I am testing are 5.2 ohms DCR with a couple small bumps like this as well. I don't see a problem here.
I went back and edited several of my earlier posts in this thread to make it clear that I am measuring a very old set of classic ESS AMT tweeters from the early 1970's. Not a new set of ESS AMT's like many others are testing. The diaphragms in these old units are very old (50 years+). I also have a set of newer diaphragms, but they have been sitting on @LifeOfBrian 's shelf for many years. They look like the newer ones and have a lower DCR of about 3.5 ohms, but I do not know exactly how many years old they are. Sorry for the confusion.
I understood yours are older versions. When searching around online I thought I had seen plots that look pretty identical to the blue line. With the typical 800hz resonance. The green line.. not so much. I just don't want to be dealing with a fat wad of distortion around or higher than I read these can typically be crossed at. If that is probably not the case, then that is good to hear.
The wobbles you see are about an eighth of an ohm variance, and are likely nothing to worry about. AMT/planar drivers are known for their flat impedance, so self resonance is not really so easily excited.
Measure HD and see for yourself, but I think they should be fine even at 1k. The rolloff will already be drooping to -6dB for a LR summation, and this means that the bump will already be rolled off a bit. If it looks funny to you, tweak the resistor in the coil leg of the highpass and it will take a hike.
@Nicholas_23 said:
So Van Halen Eruption, at max, was the likely demise of ESS "A". RIP
"Ran when parked"
Interesting to see the progression of sophistication in diaphragm design. I initially thought the mesh was some sort of grill. Now I'm thinking it is likely fiberglass that is glued to the tips of the pleats to lock them in place preventing resonaces traveling across the whole thing.. since the pleated geometry is rather spring like. I bet the 3 "snot" lines on the middle one was a more crude attempt at the same idea.
Comments
Here are a few closeups of tweeter "A" (classic 1970's ESS AMT tweeter). I haven't pulled the damaged diaphragms out yet.
Front side closeup:
Rear side closup:
Missing putty closeup. I need to find out what type of putty is needed so that I can replace the diaphragm properly. I have extra diaphragms that I can insert that I got from @LifeOfBrian .
I'm not generally an open back guy, and I tried using the ESS in a monopole configuration but the magic was gone so that's why it ended up open in my build. As a matter of fact there are several domes that I would choose before it in a monopole configuration.
Bill, that looks like it's toast...
InDIYana Event Website
I agree with Wolf. AMT diaphragms are like accordion pleats and should have uniform ridges. Yours looks like its been melted.
Ron
I liked the sound of the Heils in Nick's project. Open and realistic presence. Not sure if I would like them castrated with a rear enclosure.
Here are the OmniMic HD distortion plots comparing tweeter "A" and tweeter "B" (classic 1970's ESS AMT tweeters). These plots were taken at a distance of 1/2 meter (19.5") on axis with the tweeter. SPL was approx 96dB for tweeter "A", which translates to 90dB at 1 meter. SPL was approx 98dB for tweeter "B", which translates to 92dB at 1 meter. The amplifier volume level and mic position were the same for both measurements. As you can see, distortion is much lower for tweeter "B", even at a 2dB higher playback level!
Tweeter B (the good one):
Tweeter A (with wonky looking diaphragm):
I received my pair today, if I can I'll measure them.
I pulled the damaged diaphragm out of the tweeter that I am calling "A" (classic 1970's ESS AMT). Below is a side-by-side comparison with two other diaphragms. The left most is the damaged "A" one. As you can see, It is badly melted. In the middle is a used original style diaphragm from the 1970's. On the right is a newer style replacement diaphragm. I think I will start out by inserting the used original style diaphragm (1970's) and see how this vintage one measures. Then I will try the new style diaphragm. The new style diaphragm measures 3.5 ohms DC resistance (Re) whereas the original style diaphragms, from the 1970's, all measure 5.2 ohms. Don't know if that DC resistance difference will cause a problem. As long as I can get a good SPL and distortion match, I should be OK.
"The new style diaphragm measures 3.5 ohms DC resistance (Re) whereas the original style diaphragms all measure 5.2 ohms. Don't know if that DC resistance difference will cause a problem."
I don't envy you doing a left/right specific crossover.
Curious as to how much difference there is between the old vs new diaphragm in regards to both measurable and 'hear-able' peculiarities.
Did you ever find out what kind of putty is used to seal the diaphragms?
No. There are several threads on Audiokarma and diyaudio talking about swapping these diaphragms, but noone ever seems to mention the type of putty used. So I am on my own on this one. I've decided to try a "no residue" type mounting putty that is designed to hang things temporarily on walls. They are safe for plastics and wood and do not leave marks. Don't want to use something like mortite caulking compound or plumbers putty. I know that mortite caulking compound has oils in it which could migrate up onto the diaphragm over time. Not sure about plumber's putty, but its probably a good idea to stay away from that as well. The gorilla mounting putty looks like a good choice. Heading out to the hardware store to see if I can find some.
Why not just call ESS and ask what putty to use?
open cell foam strips? . . .
Yikes! WTF? Those tweets were brand new? Or did I overlook something?
Looks like Blu Tack?
Mine arrived. Dang they heavy!
So Van Halen Eruption, at max, was the likely demise of ESS "A". RIP
These are a vintage pair from the early 1970's. Still going strong, but the pleats are getting a little tired.
12 lbs on my uncalibrated bathroom scales!
Thanks, Nick. The web site lists Simply Speakers as an authorized dealer for replacement parts, so I submitted an email question and am waiting for a reply.
hmm
I don't realy have experience with AMTs yet. Please someone tell me this is nothing to worry about because I'm on the edge of being rather annoyed.
I can run DATs tomorrow on mine , might be some swapping going on
One has been "tested" the other is still in its box
I'm no expert, but based on my limited experience with this driver and diaphragm, those impedance curves look perfectly normal to me. The newer diaphragm used on these is spec'd at 3.7 ohms DCR. That matches your curves almost perfectly. The small bumps are probably normal. The older diaphragms (from the 1970's) that I am testing are 5.2 ohms DCR with a couple small bumps like this as well. I don't see a problem here.
I went back and edited several of my earlier posts in this thread to make it clear that I am measuring a very old set of classic ESS AMT tweeters from the early 1970's. Not a new set of ESS AMT's like many others are testing. The diaphragms in these old units are very old (50 years+). I also have a set of newer diaphragms, but they have been sitting on @LifeOfBrian 's shelf for many years. They look like the newer ones and have a lower DCR of about 3.5 ohms, but I do not know exactly how many years old they are. Sorry for the confusion.
I understood yours are older versions. When searching around online I thought I had seen plots that look pretty identical to the blue line. With the typical 800hz resonance. The green line.. not so much. I just don't want to be dealing with a fat wad of distortion around or higher than I read these can typically be crossed at. If that is probably not the case, then that is good to hear.
The wobbles you see are about an eighth of an ohm variance, and are likely nothing to worry about. AMT/planar drivers are known for their flat impedance, so self resonance is not really so easily excited.
Measure HD and see for yourself, but I think they should be fine even at 1k. The rolloff will already be drooping to -6dB for a LR summation, and this means that the bump will already be rolled off a bit. If it looks funny to you, tweak the resistor in the coil leg of the highpass and it will take a hike.
InDIYana Event Website
This clay would probably work well. It's made for kids and doesn't dry out. I have a stick if you want it Bill.
https://amazon.com/gp/product/B011EG5KTO/?th=1
Ron
"Ran when parked"
Interesting to see the progression of sophistication in diaphragm design. I initially thought the mesh was some sort of grill. Now I'm thinking it is likely fiberglass that is glued to the tips of the pleats to lock them in place preventing resonaces traveling across the whole thing.. since the pleated geometry is rather spring like. I bet the 3 "snot" lines on the middle one was a more crude attempt at the same idea.
And edible 😁