Re-foaming Bose 901's

**BCbud** · 04-07-2008, 09:29 AM

Good day!

I have a set of 901's that I am going to re-foam. My question is there are 2 or 3 companies that sell them and I was wondering if some one could recomend one?

Thanks

**BCbud** · 04-08-2008, 05:48 PM

Good day! I whent with Simply Speakers out of florida. I will let everyone know how it turns out.

**Luvin Da Blues** · 04-08-2008, 06:06 PM

Ya, do keep us informed. If you can take some pics to post.

LDB

**JohnMichael** · 04-08-2008, 06:10 PM

Please do let us know. Members continue to ask this question and your input will help the next person needing to refoam. Also let us know how they sound when you are finished with this project. I have a soft spot for 901's but do not tell the flamers.

**Rush2112** · 04-08-2008, 06:26 PM

I am also looking foreward to your updates.

Will this be your first attempt or something you've done before with other speakers?

**BCbud** · 04-08-2008, 06:32 PM

Glad to see some interest. I had planed on doing lots of pics and posting them with commets. As far as to how they sound, this is my 2nd set. I bought my first set that were already rebuilt with EQ and stands for $300 and the cabs are mint. Thy are series III the first Acoustic Matrix box.It took me a while to find a good spot in my living room to get a good sound out of them but once I found that spot, well I bought the 2nd set. I use too have a kick ass system in my 20's, 2-15" woofers, 2-2" mids and 2-3/4" tweeters per side wirered in parralel to give me a 4 ohm load whitch alloud my power amp to put out 470 watts a side.Now that I have a small house I whent with the 901's, bought a yamaha p2201 power amp off ebay for $280 and puled my SAE MKXXX pre amp out and a Panasonic DVD player. Works great for my needs.

**BCbud** · 04-08-2008, 06:36 PM

Rush2112

You must have posted while I was trying to type oul my last reply. I posted to you other post and know that you have a pair of 901's need the same thing. This will be my first try at this and as I said, I will post pics and comments to help out others like yourself.

**bfalls** · 04-09-2008, 05:26 AM

Back in the 70's the Bose 901 were all the rage. It sounded like a good concept being able to hear stereo anywhere in the room. I've seen many a coffee house with a pair or two hanging from the ceiling. Then I started to read and listen more seriously and their design make no sense.

Why have 8 - 4" drivers facing away from the "sweet spot" bouncing sound off rear and side walls and one 4" driver facing forward? The negative effect on imaging is undeniable. I can't imagine the effect of two pairs in a room or HT with 5 or 7 901s. It seems to undo what the sound engineer took time and effort create. If elevator/mall music, or vintage gear is your passion, more power to you. I think you'd do better purchasing a pair of vintage Advents or AR3s. I'd be interested in hearing the cost for your renovation. I've seriously heard new Bose 4" drivers are manufactured in China and can be had for $1.50/ea. You may want to investigate and save some money. I've also seen them on Overstock.com.

**BCbud** · 04-14-2008, 04:46 PM

bfalls, the sweet spot is what I dont like with other speakers. The 901's dont have a drastic sweet spot so I dont have to be stuck in one chair to get the best sound. I plan on mounting the 2nd set directly above the ones I have on the Bose stands. This will keep all the drivers on the same virtical axis and hopefully will not cause a mayhem of reflection.

**BCbud** · 04-14-2008, 05:03 PM

Good day!

I just got my vintage Bose 901 add that I bought off ebay and thuoght I would try to post some scans of it so I can learn how to post pictures.

**BCbud** · 04-14-2008, 05:36 PM

First try didnt work, pictures where too big. I hope my camara has a low enough resolution to allow me to post more pictures of the rebuild.

**BCbud** · 04-21-2008, 06:01 PM

Good day!

I have not received my foam repair kit yet but decided to try and get the front grill off one of the speakers. This is not too hard to do once you find the info on how to do it ( took me half a day to find the info ) The grills are fastend with 8 small staples seen in one of the pics. You take a dinner knife and pry the grill from the top center and work it to one side or the other and the corner staple will come out of the box or out of the grill. It dosnt matter as you do not see anything from the front of thr grill. Once one corner becomes free, you work your way around the edges with your hands and finaly the center. The staples are placed in each corner, left and right side midway from top to bottom and 2 in the center. One above and one below the driver. I removed the 3 fasteners and lifted the driver out. The wires are quite short and are a solid core type of wire. I was a little surprised to see the light guage of the wire. I may try to upgrade to a heaver guage. The wires are attached to the driver by being wraped aroend 2 pins that are on the driver and no solder is used. I have read that soldering is recomended but must be done with care as the driver basket is plastic and can melt if too mutch heat is used or you take too long trying to solder.Also solder the wires to the speaker terminales. I have marked on the back of the driver what color wire was on whitch pin, the top of the driver as it was mounted and the box it was in. I plan on putting them back in the same holes they came out of.

**BCbud** · 04-21-2008, 06:02 PM

One more pic.

**BCbud** · 05-04-2008, 08:29 PM

Good day!
I have started the repair. I took some pics of the 2nd front grill removal. It was more stuborn than the first. I had to use a heavy duty putty knife in the end and I did break the wood.

**BCbud** · 05-04-2008, 08:40 PM

Once I got the 2nd grill off I removed all the drivers and marked on the back of them whitch box they came out of, what hole in that box and what color wires where conected to each post so I can put them back the same way they were when I started.

**BCbud** · 05-04-2008, 08:48 PM

I was suprised to see the drivers in box 2 had 4 different production drivers in the lower 4.Not only the dates stamped on the back are different but the metal backing plates are octigon in shape insted of round. Also one driver had one wire not conected to the pin.

**bfalls** · 05-05-2008, 08:42 AM

Are the replacement surrounds foam or rubber? It doesn't make sense to me to go through all the trouble to replace the surrounds with an inferior material. Do any of the surround replacements kits use rubber instead of foam?

**BCbud** · 05-05-2008, 11:04 PM

For my speakers there are fabric surrounds available. From my reserch, I have decided to us foam and here is why. Using optional surrounds can affect how the driver was made to work.The foam that was made 30 years ago had a life span of 10 to 15 years.The foam made today has a life span of 25 to 30 years. If I am still around in 25 years and still have the speakers, I think I will have received good service for my time invested in the project that I am having fun doing!

**hermanv** · 05-05-2008, 11:26 PM

I certainly admire enthusiasm, it keeps our hobby vibrant. Not to mention admiring the initiative to tackle a project such as this.

If I understand correctly the Bose 901's were originally designed to fix the dreaded "hole in the middle" of early stereo recordings by dispersing audio energy. Todays speakers are mostly designed to focus acoustic energy (imaging). Most modern speakers can be placed in such a way as to disperse music if that's the goal.

The basic Bose 901 design is 40 years old, it's my guess there's been progress since then.

**BCbud** · 05-12-2008, 05:29 PM

So now it is time to prep the drivers for the new foam rings.

**BCbud** · 05-12-2008, 05:34 PM

First I remove the old foam from the basket. I am usind a putty knife with the corners rounded off. Doing this it is easy to remove all the foam from th basket.

**BCbud** · 05-12-2008, 05:48 PM

Now I puy the black putty knife behind the cone to give it some suport and using the rounded edge of the yallow putty knife, carefuly remove the bulk of the foam off the cone.

**BCbud** · 05-12-2008, 05:50 PM

2nd picture

**BCbud** · 05-12-2008, 06:03 PM

Now i soften the remaining foam and glue with Methyl Hydrate and use the same process to remove the rest. I tryed Isopropyl Alcohol and Lacquer Thinner but found the Hydrate worked the best.