bose 901 driver surround repair replacement

[Cal Weldon]

The kits are available and if you replace surrounds for a living, the 18 drivers will be no problem. My concern when considering the undertaking is how will the first driver compare with the last if you're a hobbiest.

[TICUL38]

This project went the back shelf....but still very "mind" active.
Back in november took many test readings with different cone weighings using 1 to 5 size 3/0 split shots (fishing sinkers)..concluding that weight mods for the 901-2 drivers would not be that beneficial towards designing a compact TL speaker. Also the same weight mods towards recycling these into sealed boxes gave results like:
With 4 lead sinkers (0.72 grams/sinker):
Fs 55 hz (no mods = 78)
Qm 2.76 (2.46)
Qe 0.58 (0.44)
Qt 0.476 (0.372)
Re 7 ohms
Vas 7.9L
L 0.24mH
Best F3 is 89 hz in 4.1L box with heavy fill, no leaks and Qtc 0.7
Without mods best F3 was 166 hz with Vb at 1.8 L (heavy fill, no leaks)
The 901-2 as designed by BOSE simulates as follows using Unibox (freeware):
Vb 20L, heavy fill, no leaks, 9 drivers (3 paralleled series of 3)
F3 164 hz
Fb 154 hz
Qtc 0.661
Max power input 465 watts SPL at 1W/1M 101 dB / 118 dB at 50 Watts
Driver ratings worked out at:
each driver at 30 Watts...music rating =270 Watts / 125 dB at 1 kz/ 116 dB at 100 hz / 90 db at 20 hz.
each at 5.5 Watts for continuous sinewave = 50 watts

All simulations done without the electronic signal booster.

Here are the output graphs using Unibox (excellent software)

[TICUL38]

Attempts with *.gif attachments not successful.....any suggestions?

[901Fixer]

Has anyone ever found a frequency response graph of any series 901? This has always been a heated discussion point as Bose would never provide one. I have searched some but only found one somebody did outside in a garden so not exactly optimal. I'm curious to know what range they do cover well and where they roll off.

[TICUL38]

901.Fixer

There is a summary of a frequency response test published in Stereo Review (70's). Testing was performed by the "Hirsch-Houck Laboratories.

I made a 576 kbts pdf copy of the article which I am mailing you...tried to place here but weighs more than the 102.4 Kbts limit imposed here.

Louis

[901Fixer]

Thank you Sir.

My current project uses a pair of 901/VI as though they are just wide mid range speakers supplemented with a 15" Selenium ProAudio woofer and Linaeum di-pole ribbon tweeter.

I see you email. I'll check it now so I have a better idea of where the crossover points are gonna be.

[art64]

Originally Posted by twistedsymphony

this is an old thread but I wanted to bump it to say thanks!

I personally don't care for the 901s... but my father has always loved them, he talked about getting a set all the time and eventually bought a new pair several years ago... he recently lost his job and had to sell almost everything he owns to stay afloat including his 901s.

a member of my car club was cleaning out his garage and had an old set of series IV 901s up for sale for $20. I though it would be a great fathers day gift if I bought them and fixed them up a bit.

Of course upon pulling off the tweed grills the speaker foam was all rotted way.

I was searching for whole replacement drivers when good 'ol diyaudio came up with this thread... I never knew they made repair kits for the foam surrounds

I'm sure the $$ could be better spent building a nicer pair of speakers, but the 901s have some kind of sentimental value for my father so I figured it was worth it.

After fixing the drivers I'll probably sand down and paint the enclosures black and then work out some better looking grill material to replace the 70s tweed.

The speakers did come with the equalizer and it is much needed. If my memory serves you can use the speakers without the equalizer, Bose even sells them separate from the equalizer but they "require" that the equalizer be used at all times with the speakers. They sound like tin-can speakers with out it... but they do have a very warm and inviting (albeit horribly inaccurate) sound when the equalizer is in use.

I still have them since I bought them in 1985 at an AAFES store overseas. Have not used them much over the years except nowadays after I did some mod on them. I removed the restrictive cloth on the back and then turned them backwards. It's still a direct reflecting speaker cause the sound still bounces to the sidewalls. I had to add some bass (low and mid) reinforcement to the system using an old Crate 2 x 15 bass guitar cabinet. The bass is driven by a portable Sony AM/FM/Casette/CD player combo which happens to have a bass boost feature. The bass is sure loud and can be felt. The Sony probably only has 25watts/ ch or less. I'm also using Gemini Active Crossover to filter out the high frequencies from going into the bass cab. Sounds incredible. Sounds BIG. Not just loud but BIG. 901 array is doing a good job filling up the room. Highly recommend mounting the 901's up high on the wall, closer to the ceiling with the front or V point pointing slightly down.


The only drawback with this set up is that the room looks like a club now with those big speakers. I'm also using heavy gauge speaker wires for all speakers. Hope your Dad enjoys them. My dad did not have a chance to hear mine. His time ran out.

[Espina]

I like what you've done with these. Do they have a sheer/metal grill? I can't tell from the photo/my monitor. I picked up a pair for 50 bucks a few months back. I wanted something that played loud and could hang from the ceiling in my work out room. I tried them in a listening room when I first got them home. They sounded quite a bit less than OK. The amp I had hooked them up too was likely too small. I'm sure part of the problem is age, although the EQ had just been refurbished by the factory a few years back. They were set up per the manual. In the workout room with a 60watt 20 year old integrated amp and the EQ, hanging high and playing loud rock while I work out they ARE PERFECT! I'd have to say they have motivated me to workout more often. They beat the heck out of using mini monitors or headphones. I bought a second pair as I'm planning on stacking them and hooking them up to a serious pro use power (500 - 100watt) amp for the occassional party. I may even hook them up to my alarm system.