I had my ML Aeon i panels rebuilt by Russ Knotts in 2020. Initially the frequency response was acceptable (blue line below) but now there is a big dip below 5KHz. The woofer crossover is 450Hz so you can see that the left hump in the red line is basically all from the woofer, and the panel itself has little volume below 5KHz. Ignore the overall level difference in my chart because they were measured at different levels, but you can see below 400Hz and above 5KHz the speaker is basically same as my 2020 measurement, but the panel is not making any volume below 5KHz now.
Any idea what would cause that? Is it likely to be the panel or electronics? Both speakers measure nearly identically both in 2020 and now.
Any idea what would cause that? Is it likely to be the panel or electronics? Both speakers measure nearly identically both in 2020 and now.
The fact that both speakers measure the same makes it unlikely it's something in a speaker.
Looks more like a change in the xover frequency etc to me, like a mistake of factor 10 in a xover component.
Same mike? Same mike cal file?
Try another setup, different positions, see if it persists.
The idea is to be absolutely sure it is the speaker before tearing into it.
Jan
Looks more like a change in the xover frequency etc to me, like a mistake of factor 10 in a xover component.
Same mike? Same mike cal file?
Try another setup, different positions, see if it persists.
The idea is to be absolutely sure it is the speaker before tearing into it.
Jan
Most likely it comes from the tweeter (NAC), it's polarity has switched! Or more likely the ESL polarity, depends on how tweeter is wired internally (the manual doesn't tell)
https://www.martinlogan.com/en/product/aeoni
NAC (natural ambience compensation) reveals larger-thanlife sound by eliminating dispersion problems inherent to small electrostatic transducers. By expanding off-axis highfrequency dispersion, Aeon i assures listeners of a perfect performance no matter where they’re seated or standing. A true audiophile solution, the NAC is parallel to the signal path and features an on/off switch to adjust for listener preference.
https://www.martinlogan.com/en/product/aeoni
| High Frequency Transducer | 37" (94cm) Generation 2 CLS™ electrostatic transducer; 1"(2.5cm) soft dome NAC™ (Natural Ambience Compensation) tweeter |
NAC (natural ambience compensation) reveals larger-thanlife sound by eliminating dispersion problems inherent to small electrostatic transducers. By expanding off-axis highfrequency dispersion, Aeon i assures listeners of a perfect performance no matter where they’re seated or standing. A true audiophile solution, the NAC is parallel to the signal path and features an on/off switch to adjust for listener preference.
Last edited:
You are absolutely right! I disabled the NAC tweeter and it measured like this:
The NAC is a tiny tweeter mounted behind the speaker and pointing backwards so I didn't think it would affect measurements so much.
So it looks like the rebuilt panels didn't last long before losing most of its volume again. Russ rebuilds them by cleaning and re-applying a coating instead of completely replacing the diaphragm. Guess it didn't last long, at least for me.
Looks like it's time for new panels. At least I know that's the problem now and not anything internal. Thank you!
Can you test it with ESL wires in "wrong" polarity and NAC on. Still spl difference might be too big...
I have zero experience with ML speakers, they are very rare here in Finland. But a friend has Acoustats, even more rare beasts!
I have zero experience with ML speakers, they are very rare here in Finland. But a friend has Acoustats, even more rare beasts!
There's no chance the polarity is wrong. It's just the panels, they lose volume when they degrade. It's "normal", I just didn't know why there was a rise at higher frequencies and I know now.
Try breathing on the membrame near the connection point of the bias supply. The moisture in you breath will improve the conductiviy of the coating. If the volume temporary and locally increases you know the coating is bad.
Not saying this is accurate, but maybe your friend used a conductive coating that degraded over time, which is bad.
The membrane coating and its resistance is the most important part in the construction of electrostatics.