I thought I'd upload some pictures of my ongoing Bose 901 Series IV restoration. I got these speakers with a bunch of other audio gear recently. The cabinets are in pretty good shape, apart from a huge piece broken off on the back that I'll have to fix.
But more on the cabinets later. Like a lot of these speakers, the surrounds on the drivers were all rotten, take a look.
I carefully removed all the drivers, writing on the back with a Sharpie the color wires that were connected to them, and I also labeled them to make sure I kept them in the same location as before.
I bought a surround kit from eBay and set to work. Here is a picture of what the driver should look like once the old surround has been removed.
The eBay kit I bought came with a test tone CD, and instructions on how to use this to correctly center the voice coils. Now I know some people have used this method and got good results. After I did four drivers this way, I played some bass heavy music and some other test tones through them. What I noticed was two of the drivers sounded alright at low to moderate volumes, but I could hear some rubbing at higher levels.
So I decided to do it the old fashioned way, and shim the voice coils. The eBay seller was very helpful and understanding, he sent me four additional surrounds and enough dust caps to do all 18 drivers FOR FREE!
I found some yogurt pots that were exactly the same size as the inner diameter of the surrounds. After applying the glue to the inside of the surrounds, I placed the yogurt pots on top, and used some sockets to weigh them down while they dried.
Moving on down the dairy food aisle, I found I could cut (and then tape back together) some cottage cheese pots to the exact dimensions of the outer part of the surrounds. I used a piece of the front cover of a glossy magazine and a piece of plain white paper to make up the shim. Then I applied the glue around the frame, put the cottage cheese pot over the surround, and then weighted them down with some cups. I used a piece of foam padding and cardboard to spread the load on the edge of the cottage cheese pots.
And here we have nine little drivers, all with new surrounds, just waiting to go back into their cabinets.
Lee.
But more on the cabinets later. Like a lot of these speakers, the surrounds on the drivers were all rotten, take a look.
I carefully removed all the drivers, writing on the back with a Sharpie the color wires that were connected to them, and I also labeled them to make sure I kept them in the same location as before.
I bought a surround kit from eBay and set to work. Here is a picture of what the driver should look like once the old surround has been removed.
The eBay kit I bought came with a test tone CD, and instructions on how to use this to correctly center the voice coils. Now I know some people have used this method and got good results. After I did four drivers this way, I played some bass heavy music and some other test tones through them. What I noticed was two of the drivers sounded alright at low to moderate volumes, but I could hear some rubbing at higher levels.
So I decided to do it the old fashioned way, and shim the voice coils. The eBay seller was very helpful and understanding, he sent me four additional surrounds and enough dust caps to do all 18 drivers FOR FREE!
I found some yogurt pots that were exactly the same size as the inner diameter of the surrounds. After applying the glue to the inside of the surrounds, I placed the yogurt pots on top, and used some sockets to weigh them down while they dried.
Moving on down the dairy food aisle, I found I could cut (and then tape back together) some cottage cheese pots to the exact dimensions of the outer part of the surrounds. I used a piece of the front cover of a glossy magazine and a piece of plain white paper to make up the shim. Then I applied the glue around the frame, put the cottage cheese pot over the surround, and then weighted them down with some cups. I used a piece of foam padding and cardboard to spread the load on the edge of the cottage cheese pots.
And here we have nine little drivers, all with new surrounds, just waiting to go back into their cabinets.
Lee.
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