Boston Acoustics T930 Woofer Mismatch?

[HotRodStereo]

So I grabbed up some BA towers on marketplace the other day for $30, i have a couple pairs of a70s that i have really been enjoying and recognized the grills in the blurry photos, figured i would do some "speaker speculation". They seemed to be in pretty good condition from the quick check in the walmart parking lot, but of course once i got them home the woofer beneath the grill i didnt open up was totally blown out.

Serves me right, I know.

But no problem, surrounds are pretty easy to come by and within the scope of my abilities. I wanted to ohm out the coils just to make sure though, so i popped the bad one out and it ohmed at 4.1, as did the good woofer. Great.

BUT. The screws were different. Hmmm not a good sign.

Upon closer inspection, a couple of other things were different at well, the back of the good speaker has "Boston" stamped on it which from what my extensive googling last night revealed, appears to be original for the 1989 models. The blown speaker does not.

The good speaker aslo has different terminals, and the proper date code speaker, the other does not.

So it seems pretty evident that the woofer has been replaced, but the plot thickens. As i was searching for replacements ( i like my speakers stock) on the bay (none up right now) I saw a couple of speakers that resembled mine, namely the VR975s (terminals) woofers. The metal frame is almost exact, and there are enough similarities for me to belive its pretty nearly an exact replacement, but also enough differences to make me sure it didnt come this way from the factory.

I'd like to get these running, my question is first and foremost, does anyone have some BA 10" woofers out of a T930 tower? Get in touch. Have money, will pay it.

Alternatively am i making a mountain out of a molehill? are these the same speakers, or maybe even a factory replacement? I don't mess with drivers much, so I am way out of my depth here. I would rather not refoam the wrong speaker and have my balance be off, on the other hand i would rather not replace a driver that doesnt need replaced. And/or may be difficult to find.

Pics for reference -


The cone material on this driver is also extremely subtly different from the other.

The good woofer

The bad woofer

Bad woofer below, good woofer above. I DID NOT BREAK THE TERMINAL ON THE GOOD ONE.
It was dangling by a thread when i opened it up, reinforcing the theory that something has been fiddled with on these. When I pulled the wire off it gave way despite my best efforts not to let that happen.

 

[sam562]

The blown one looks like a factory replacement. The baskets are basically identical and that flange fits perfectly so you can be confident that they are both made by BA. I bet the specs are identical as well.

For many years BA used to sell replacement woofers for people who owned their speakers long enough to have rotted foam surrounds. People would just switch out the entire speaker and bin the old ones. It's a shame to think of all of those perfectly good (other than the replaceable surrounds) BA woofers hitting the trash bin but that's exactly what many BA owners used to do. I've read that there were subtle differences in the BA supplied replacements compared to the originals.

You could possibly get the blown one re-coned, or you just be patient for a BA 10" woofer to become available on the bay. Check facebook marketplace, craigslist, hifishark as well. Sometimes you'll even stumble across someone selling an orphaned single speaker you can canibalize for parts.

Be sure to buy proper "filleted" profile surrounds for your BA speakers. AK member looneytune2001 ( rick cobb i think) sells them but I've gotten them from simply speakers and midwest speakers as well

 

[HotRodStereo]

The blown one looks like a factory replacement. The baskets are basically identical and that flange fits perfectly so you can be confident that they are both made by BA. I bet the specs are identical as well.

For many years BA used to sell replacement woofers for people who owned their speakers long enough to have rotted foam surrounds. People would just switch out the entire speaker and bin the old ones. It's a shame to think of all of those perfectly good (other than the replaceable surrounds) BA woofers hitting the trash bin but that's exactly what many BA owners used to do. I've read that there were subtle differences in the BA supplied replacements compared to the originals.

You could possibly get the blown one re-coned, or you just be patient for a BA 10" woofer to become available on the bay. Check facebook marketplace, craigslist, hifishark as well. Sometimes you'll even stumble across someone selling an orphaned single speaker you can canibalize for parts.

Be sure to buy proper "filleted" profile surrounds for your BA speakers. AK member looneytune2001 ( rick cobb i think) sells them but I've gotten them from simply speakers and midwest speakers as well

Great info, exactly what i was looking for. These speakers pre-date me, so this community is fantastic for information like this.

Pardon my ignorance but truly drivers are not something i usually mess with, its just that my BA addiction is strong at the moment. The hooked up the driver still produces sound, albeit less so than the other one with the intact surround, it makes a crackle but I have been lead to believe that could simply be a misaligned cone since it looks like someone put a fist into it. It ohms out identically, are there any other ways i can tell if the problem speaker is salvageable? What would tell me that a re-cone was in order?

 

[sam562]

Looking at your pictures, neither one of those surrounds is intact - they are both hopelessly in need of replacement.

If the speaker makes any sound then it's probably not blown and definitely worth buying a surround kit and re-foaming them both.

You can gently re-shape the dented center dust caps with a vacuum cleaner hose using your finger (or something -see YouTube) as a suction adjustment.

The BA woofers from this era are have much tighter clearances (less play) than the older paper ones so figuring out how you are going to align them while the glue sets up is important.

I re-foamed some t830's (with the woofers installed) by laying the speakers on their backs, centering and gluing the inner lip of the surround first and letting that set up to where it was not movable anymore. Then I used the 30hz CD (you can find a YouTube vid of this now) and glued the outer lip and used my fingers to push the cones (actually I pushed the glued outer lip of the surround inward or outward) around until it no longer was audibly rubbing. I then just sort of babysat the speakers for a few minutes (maybe it was longer?) until I was satisfied that the glue was stiff enough that I could turn off the CD and just let it dry. I think I eventually came back a time or two two to play the 30hz again to make sure they didn't move while I was gone.

 

[HotRodStereo]

Looking at your pictures, neither one of those surrounds is intact - they are both hopelessly in need of replacement.

I should have defined this better in the photos, both of those are photos of the same woofer, the flash just made it look a bit odd so i included two photos. The other woofer is pristine!

If the speaker makes any sound then it's probably not blown and definitely worth buying a surround kit and re-foaming them both.

Thats what i was hoping for! It seems like its worth a shot and i have another set of A70s that need a refoam anyway, both will get ordered tonight.

You can gently re-shape the dented center dust caps with a vacuum cleaner hose using your finger (or something -see YouTube) as a suction adjustment.

The BA woofers from this era are have much tighter clearances (less play) than the older paper ones so figuring out how you are going to align them while the glue sets up is important.

I think i am going to get the full kits that include shims for centering the cones from SimplySpeakers, when i have done it before that seems to work pretty well?