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New to me 901's. What is up with the eq?

Drum

Drum

Active Member
Was doing some charity work a couple of years ago for a service organization, and noticed some 901's in the basement. I bugged them off and on about buying them, but nobody seemed to know who could give me permission to buy them. Finally got it worked out today and picked them up. They were just going to give them to me, but I offered $50 - it is a service organization after all. They actually asked if I was sure I wanted to give that much. Not sure if they are series I or II, but have the wood veneer on the front. Should be a fun little project to get going. All 18 speakers are in good shape.

My question is. What is the deal with the eq? I have never seen one like it. Is it homemade, or modified?
 

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Listening to one of them right now - switching balance between 901 and EPI M202. I wanted to be able to compare easily to a known speaker. I must say they are terrible without the eq - as expected. They are much better with the eq, but still not very good. The song playing right now has some violins that just are not there on the Bose, but the EPI's play them beautifully. Strangely, the cymbals seem to be there. I suspect with this much discrepancy there is an issue with the eq. As it may be as much as 50 years old, it probably needs some new caps. I will replace those before I judging them. I must say I was expecting them to be more power hungry, but they seem about the same as my 4 ohm EPI M202's.

Still a little stumped on the eq. It seems similar to the Series II eq, but the rockers are narrower, the light is different and the knob is also different. It does look fairly normal inside though. No bose logo anywhere.

Anybody know where to get some good grill cloth for these - something close to OEM?
 
Your EQ appears externally to be a walnut vinyl veneered Series II unit. Absolutely necessary for the speakers and absolutely shouldn't be use on regular speakers. There is twice the bass and treble boost compared to max bass and treble control positions on amps. Too much for some woofers and tweeters, needed to make those Bose midrange sized drivers do bass and treble, properly.

EQ seems to be this one: https://retrovoltage.com/2013/09/03/bose-901-series-ii-equalizer-96399-repaired/

enjoy your project.
 
Placement and the equalizer is everything with these speakers. I believe on the inter webs can give you proper placement techniques per the manuals and here on AK
 
Blue Shadow said:
Your EQ appears externally to be a walnut vinyl veneered Series II unit. Absolutely necessary for the speakers and absolutely shouldn't be use on regular speakers. There is twice the bass and treble boost compared to max bass and treble control positions on amps. Too much for some woofers and tweeters, needed to make those Bose midrange sized drivers do bass and treble, properly.

EQ seems to be this one: https://retrovoltage.com/2013/09/03/bose-901-series-ii-equalizer-96399-repaired/

enjoy your project.
Click to expand...

Thanks. That is pretty much what I thought about the eq. - just strange that it had different knobs and rockers.

Don't worry I only have the eq set up for the left speaker right now. The right side skips the eq and goes right to the power amp.
 
Just noticed another thing about these. There don't seem to be any screws holding in the drivers. Looks like silicone only - no sign of a screw in the 4 holes for each driver. Is this how they did it, or were these worked on at some point?
 
That EQ looks home made, but at a glance it looks like the circuit board is correct - very strange.
 
I'm not 100% sure that's an original Bose driver. All the pics I could find of the earlier 901 series show a pincushion shape frame, not round. And, yes, they should be screwed in, not glued.
 
Drum said:
Just noticed another thing about these. There don't seem to be any screws holding in the drivers. Looks like silicone only - no sign of a screw in the 4 holes for each driver. Is this how they did it, or were these worked on at some point?
Click to expand...
No. Screws and seals were used.

Cheers,

David
 
Pete B said:
That EQ looks home made, but at a glance it looks like the circuit board is correct - very strange.
Click to expand...
Agreed about the circuit board, which was removed from its cabinet. Rocker switches are not original but will work since they're SPST style.

On the cabinets, turn them over and examine the bottom for a Bose label. There should one for each cabinet labeled Part 1 and Part 2.

I'm sure the EQ could be made to work but put a bag over that vinyl EQ cabinet - that's pretty darn ugly.

Cheers,

David
 
Now I am wondering if they are even 901's. If not, somebody went to a lot of trouble to copy them almost exactly. Not a single thing anywhere that says Bose now that I am looking. Maybe they are some kind of knock off. Maybe I shouldn't have paid anything for them.

Crazy thing is they are starting to sound better as they have been playing all evening. Maybe caps are reforming a little.

Guess I'll have to pull a driver and see what it is.
 
I agree that they are home made - and not a bad effort, either. If I'm remembering correctly, CTS offered those 4.5" drivers in pincushion (used by Bose) and round frames. When I had my 901s back in the mid-1970s I purchased a number of each style and made extension speakers that could use the 901 eq to boost the extremes.

I'd use them for what they are and have fun. Considering that they are using the Bose eq guts and the equivalent drivers, they should not sound far off from the original.

I would have paid them $50 for them without blinking an eye.

By the way, there are multiple suppliers for vintage-style grill cloth. Just be selective in what you buy. Some of the cloth intended for guitar amps is woven so thick that it dramatically attenuates the high frequencies. This is what I used on my recent project, and it seems to be near transparent: (absolutely no affiliation with the seller)

https://www.ebay.com/itm/36-x24-Tan...930274?hash=item3607abbfe2:g:OocAAOSwQTVV~ixa

GeeDeeEmm
 
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