Repairing Sonance In-Ceiling Surrounds ~ Blown 3.5" Mid-Bass Driver 02Dec25-11Dec25

Debugging... I heard a buzz from one of my in-ceiling surround speakers in the Blodgett Fam Rm; I needed to fix it. They are Sonance 3-way speakers and actually sounded pretty nice, but they're 20 years old. I took pics and wrote the company's tech support but they neither have direct footprint replacements or a sufficient archive on the drivers they used or specs of the crossovers used... grrr. I pulled down the speakers and tested them; the blown driver is an 85mm mid-bass on the left channel.

Assessing... I removed the failing driver. It was 'no joy' attempting to glue the surround foam cracks back together, and the surround was old and decaying anyway. I measured its impedance @6.5Ω and the dimensions of the driver, hole pattern, and "cabinet."

Investigating... Realizing I was going to need to replace the driver I dove on Madisound and Parts Express for a suitable replacement. I didn't want to change the crossover or the other drivers in the 3 ways so needed something pretty close to the original, especially as to impedance. Of course nothing was a dovetail fit, especially as to dimensions, but I found a couple of possible replacements after building a comparator spreadsheet.

Selecting... I was hoping the MA Pluvia 7.2 HD would work as it's the same 4" driver as I used in the front L/R mains and the center channel, in the custom builds already installed in the Blodgett Fam Rm... but it is just too big for the in-ceiling "cabinet." The Dayton RS100 was about half price of the Fostex FF105wk, despite the latter's lauded performance, and it was likely a less problematic physical adaptation to the "cabinet." I bought a couple of the Dayton Audio drivers; reviews were strong enough. I did a prophylactic replacement of the same driver in the right side surround as it'd likely fail equivalently at some point and this'll give the set the same timbre.

Installing... The install with "cabinet" modifications went OK. The driver's came with gaskets and while the hole patterns don't match (known), I just secured the 6 screws directly through the plastic "cabinet" and backed the screws with speed nuts. It's all very secure and buttoned-up despite the dimensional differences. I reinstalled the speakers into their ceiling locations.

Listening... There's a noticeably better low end from the new surrounds now; the new mid-bass/full range drivers are 1" larger than the originals. And they are cleaner too. The key of course is that the repaired surrounds no longer buzz from being blown. The surrounds sound great and smooth in the new system, though they are not too vital for music. The sound on 5.1 (derived or discrete) soundtracks, with the custom front NanoOnken mains with the Onken-like center channel, backed by the SVS sealed subwoofer, is excellent. We watch plenty of games, shows, and movies on the Blodgett Fam Rm system and the kit is very strong and dialed in now after a number of fairly recent upgrades.

Measuring... I will do some measurements when I retrieve the mic from Summit.