I just recently had to replace the passive radiators on my Shahinian Double Eagle subwoofers. They are part of my Diapason setup.
http://www.shahinianacoustics.com/ (hit the Diapason Ensemble link to see the subwoofers)
Each one is comprised of two 8" drivers, each in their own transmission line and each terminated in a passive radiator. I bought new passives from Shahinian because my old ones (which were 17 years old before one of them failed!) were an older design. The newer passives have a better piston response and have a more durable surround, so I figured it was worth buying the replacements instead of trying to fix the old urethane style surrounds.
The passives are held in place by a flexible adhesive (pretty much the equivalent of Amazing Goop) and then a pressure ring that surrounds the outer edge of the passive and is screwed into place. I removed the old passives, carefully dug out the old remnants of radiator and glue, sanded the flanges, and used new Goop (per instructions) to mount the new passives. I waited over 100 hours before even standing the Double Eagles back up to give no doubt as to the cure time for the Goop. Both of the subwoofers sound fine, buuuuuuut...
When I press lightly on either passive on my left sub I feel the sort of backpressure I expect (since I know what that's supposed to feel like). When I do the same to the right there is a noticeable difference in the backpressure; it's less. So here's all the stuff I tried to see if there is a real problem:
1) Ran low frequency test tones through both subs. All the passives visibly vibrate the same way when I do this, and both subs seem to sound the same.
2) Ran a candle flame around the face of each passive while running low freq test tones. A friend of mine suggested this, but he clearly had no idea what would happen. The vibration of the air made by the oscillation of the passives caused the flame to oscillate in harmony while in front of each passive. Maybe I shouldn't have been pushing them so hard for this test.
3) Look at the woofer cones while pressing the respective passive. When I did this it looked like all 4 woofers moved the same distance for the same kind of pressure being put on the radiator.
4) Press lightly on the woofer cone to see if the opposite happens. This seemed to work as well.
5) Play music! Did this, and things seem to sound okay.
Being the retentive nut that I am, however, I can't get past this concern about the pressure test not
feeling right. Is there a guaranteed to work way to tell if there is a leak? My fear is that I did install them properly (I'm almost positive I did), but that there's no way to tell for sure. I can't "uninstall" them; unfortunately the process for putting them on results in a seal that - if broken - would destroy the passive. And these things were not cheap! They're custom made for Shahinian somewhere in Norway.
