I'm not able to read carefully, so I may not be understanding correctly, but I think the issue is that Tim hasn't seen this problem before. :) I have, and I've gone through the modelling. This would be the third or fourth time I've seen this issue in total, and the fix is always "magic." :)
What no one believes until they see it is that the problem caused by the low ESR tends to not affect the section the caps are in, but the next one up. That makes it maddening to trouble shoot. People spend all their time and effort trying to fix the HP tweeter section, but the problem is caused by the mid or woofer section (whichever is next down). In a 3-way, these impedance issues can be compounded.
The issue isn't really whether you use polar or non-polar. It's the total ESR that is playing games with you. Tim is quite right that having 2 caps in series is going to double the ESR, so maybe that one could need an extra 2-4 Ohms.
With a little hacking of a couple of audio cables you can make your own cap measurement jig and use Room EQ Wizard. That will be pretty accurate and cheap.
Best,
E
What no one believes until they see it is that the problem caused by the low ESR tends to not affect the section the caps are in, but the next one up. That makes it maddening to trouble shoot. People spend all their time and effort trying to fix the HP tweeter section, but the problem is caused by the mid or woofer section (whichever is next down). In a 3-way, these impedance issues can be compounded.
The issue isn't really whether you use polar or non-polar. It's the total ESR that is playing games with you. Tim is quite right that having 2 caps in series is going to double the ESR, so maybe that one could need an extra 2-4 Ohms.
With a little hacking of a couple of audio cables you can make your own cap measurement jig and use Room EQ Wizard. That will be pretty accurate and cheap.
Best,
E