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Rebuilding Bose 901 Series II - Foam or Cloth Edge?

kyledp

kyledp

Active Member
Hi All,

sorry if this has been covered before, but I didn’t see it in a search. I have a set of Bose 901 series II speakers and was thinking I’d refresh them. I see videos and kits available, but wanted your opinions.

I see foam kits available for the speaker edging
I see cloth kits available for the speaker edging

which should I use? Does it make a big difference? (No doubt it does)
 
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Oh, thank you RossW. I haven’t opened them up yet, so I’ll do that. I was just doing some preliminary. So did Bose ship both Cloth and Foam? And Cloth has better longevity? I can hear a little bass buzz at high volumes, I was thinking the speakers might need a refresh. I’ll open one up this evening...
 
Yes, these have cloth, so they are unlikely to need replacement. You'll have to try to figure out which driver(s) are causing the buzzing. Then we can start figuring out why. Typically buzzing is caused by something loose on the driver: the dust cap, the gasket, the surround or the spider, or possibly a torn cone. Check to make sure all are glued down properly. Torn cones can usually be repaired.

Occasionally it's also caused by something inside the cabinet, like a piece of wire, or the tinsel that connects the driver's terminals to the voice coil.

bose_901_ii_reduced4.jpg
 
Thanks guys, I started to unhook one of the speakers to begin taking it apart when I noticed all
The other 1/2 done projects I’m in the middle of, including rebuilding my turntable. So thanks for your feedback, I’m going to postpone this until I’ve crossed a few things off the list. The buzz only happens at high volumes, which I almost never get to do. I can live with it for a few more weeks. :-)
 
I have rebuilt several pairs of 901s and ONLY use CLOTH surrounds. Cloth is the best and I've never had any problems or customers that weren't 100% satisfied. Plus the cloth surrounds will last MUCH longer. I also ALWAYS use a paper shim for VC clearance. That's my 2 cents.
 
Use cloth surrounds on the CTS-built drivers (901 Series 1 and 2- four-mounting-hole frames). Although as mentioned- fortunately, these rarely need replacement.

Use foam on the Bose-built 901 drivers (all subsequent speakers- three-mounting-hole frames).

The cabinet tuning and EQ for each generation is set up around their specific drivers with their specific surround materials.

Fabric surrounds on later model Bose drivers, are only appropriate for those that had them originally (the Environmental speakers- such as the 151s, pro model 802s, and such). They're tuned to work with those surrounds.

Regards,
Gordon.
 
Thanks for sharing your experience with Bose 901. I'm in the process of defoaming a set of Bose 901 series V. They have been on my to do list for several years. I found an interesting comment from a person online concerning the re-gluing process. He had to use cups with small weights to ensure adhesion of the kit (form or cloth not specified) to the cone and a larger cup with heavier weight for the outer edge.
Did you have a problem with adhesion?
 
kyledp said:
Hi All,

sorry if this has been covered before, but I didn’t see it in a search. I have a set of Bose 901 series II speakers and was thinking I’d refresh them. I see videos and kits available, but wanted your opinions.

I see foam kits available for the speaker edging
I see cloth kits available for the speaker edging

which should I use? Does it make a big difference? (No doubt it does)
Click to expand...
I’ve restored five pairs of 901. I used foam. The modern foam is so much better than the older stuff. It will last for decades.
 
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