Bose 901 driver question

[stan461]

My thanks to Soundminded for his informative response to my origianal 901 thread. Extremely helpful.

I did hook up my 901 speakers and quickly found out one channel didn't work at all. To be honest, I'm glad.

I found someone who replaces all the caps, had the job done and that was the problem.

I promised myself to this project right so only an hour or 2 of listening. They are quite different than any other speaker that I have owned. More on that after I take care of other things.

Next was the foam surround inspection. Pressing lightly withn 5 fingers in and out when I discovered that a few

of the drivers were pushed out. I figured that they got stuck in the out postion and the surround hardened.

But when I took the driver out I found a rag like material stuffed behind the surround.

All the ones that worked smoothly had nothing behind the foam.

So once again I call upon your expertise.

What is this? To my knowledge the guy I bought these from purchased them new and didn't seem like the type to go tinkering like this. So is it a Bose thing?

A picture is indeed worth a thousand words.

[Carlspeak]

That doesn't look like a Bose driver to me.

[tysontom]

I agree with Carl: that driver looks alien to the 901. I don't even believe it fit the hole properly from the looks of it, but I can't really tell. Do you have an image of the front of the driver? What series 901 is this? If it had foam rot, it had to be a Series III-to-VI. The first two versions were sealed-enclosure versions with treated-cloth surrounds, which dry out but don't deteriorate. The early first versions used Motite to seal the drivers, but later ones went to gaskets.

Just a guess, but I suspect that someone crammed the cloth behind the driver to try to "dampen" its sound somewhat with the bad surround. It seems like a "Jack Leg" thing to do, but some people will sometimes do anything.

--Tom Tyson

[stan461]

From what I have read, this appears to be the original series.

It seems to me that for some reason the factory drivers were discarded. The stuffing is an attempt to make the sound as close as possible to stock. None of the surrounds look bad. This could be a hack job by someone who attempted a restoration.

My next logical step is to find out more on these drivers.

Then pull the stuffing out of the drivers and insect the surrounds. This stuffing can't be from the factory.

If no info on these drivers then Email Bose.

If that comes up empty then purchase Bose drivers from Ebay or buy another set with original drivers and beat up boxes.

What would you do?

P.S. - drivers fit perfectly. The center to center distance between holes that are 180 degrees apart is 4 11/16 inches.

[tysontom]

From what I have read, this appears to be the original series.

It seems to me that for some reason the factory drivers were discarded. The stuffing is an attempt to make the sound as close as possible to stock. None of the surrounds look bad. This could be a hack job by someone who attempted a restoration.

My next logical step is to find out more on these drivers.

Then pull the stuffing out of the drivers and insect the surrounds. This stuffing can't be from the factory.

If no info on these drivers then Email Bose.

If that comes up empty then purchase Bose drivers from Ebay or buy another set with original drivers and beat up boxes.

What would you do?

P.S. - drivers fit perfectly. The center to center distance between holes that are 180 degrees apart is 4 11/16 inches.

Stan, can you take another picture or two of the speaker showing all of the drivers on the rear panel. The model you have is definitely the first series (sometimes referred to as "Series One," but there was never that nomenclature), but I can't tell exactly what's going on from the images you sent. The cabinet appears to have been painted black or something. Those drivers are not stock items, but a retrofit of some description, and the sealant looks like an overdose of silicone rubber. Also, reduce the size of your images if you can to about half the size you are using.

My recommendation to you would be to get some replacement drivers off eBay that will fit your model. The treated-cloth surround drivers are the correct ones.

Attached Image: Series II Bose (CTS-built) driver. This is approximately what the drivers for your speaker should look like.

--Tom Tyson

[stan461]

It is painted glossy black. Maybe the person who did the "restoration" felt it made a better reflective surface or something. Who knows! Not me. That's for sure. It never dawned on me to remove the grills.

At any rate I must move on from here. My inclination is to watch Craigslist for another local pair. This time I'll insist the grills come off! As far as EBay is concered, I think buying just the drivers will be safer because from the pics and description I should be able to determine that they are Bose 901 drivers.

The other thing I would like to ask you guys is .....let's say a Bose 901 III or IV or V or even VI comes up for sale. Are they worth me purchasing or did things go down hill after the II series?

Once again, I must thank you for all the feedback/help that you continue to provide me with.

[tysontom]

It is painted glossy black. Maybe the person who did the "restoration" felt it made a better reflective surface or something. Who knows! Not me. That's for sure. It never dawned on me to remove the grills.

At any rate I must move on from here. My inclination is to watch Craigslist for another local pair. This time I'll insist the grills come off! As far as EBay is concered, I think buying just the drivers will be safer because from the pics and description I should be able to determine that they are Bose 901 drivers.

The other thing I would like to ask you guys is .....let's say a Bose 901 III or IV or V or even VI comes up for sale. Are they worth me purchasing or did things go down hill after the II series?

Once again, I must thank you for all the feedback/help that you continue to provide me with.

Stan,

That does look like a similar-type driver to the original 901 drivers, but certainly differenent, and someone retrofitted them in there and sealed them with silicone rubber. I am pretty sure that they would not work properly with the equalizer. And the fact that you have some bad drivers with cloth behind the drivers is all the more reason to start over. You could probably repair these, but getting the right drivers and then wiring them correctly might be an issue. You could always ask to send them back to Bose, but I think they will refuse and offer to sell you a pair of brand-new 901 VIs for half price (around $700 or so I think) as a customer-service gesture. That would be a great price for the new ones, as they are really quite good. Although I can't speak from extensive personal experience, I do believe that the new 901s are excellent speakers; and after the Series II, Bose went away from the sealed box to a vented design with a carefully optimized port system. The new ones have specially designed drivers built in-house, and technically the new 901 can move a lot more air at low frequencies than the original versions, are more efficient and the equalizer has been improved significantly as well. The problem with the new versions is the surrounds for the drivers: urethane foam, and the ones built in the 70s and 80s and probably into the 90s were susceptible to foam rot, so if you get a used pair, determine if the surrounds are in good condition. Probably any of the Model Vs and VIs would be fine, however. If you could find a good price on a pair of VI versions, that would probably be the best thing to do.

--Tom Tyson

[stan461]

Tom,

I called Bose and to my surprise they will give me the trade in. Bose policy doesn't seem to care that I bought them used, only that the serial numbers are there and I ship the speakers back to them.

Buying them new and spending almost $800 with tax will require me to look at this as a possible long-term situation.

My major concern, the distance between the speakers will be 10 feet due to design constraints and WAF factors. Will the 901's span the center and not leave a hole?

I was also considering LaScalas because of my 10 foot placement situation. But LaScalas are a much larger committment both in dollars, size and wife convincing.

So now begins a week or so of intense research and thinking.

One more thing, what finish would you recommend? I read the veneer is cheap on the VI series. Maybe the black would look the richest?

Thanks again,

Stan

[JKent]

Tom,

I called Bose and to my surprise they will give me the trade in. Bose policy doesn't seem to care that I bought them used, only that the serial numbers are there and I ship the speakers back to them.

Buying them new and spending almost $800 with tax will require me to look at this as a possible long-term situation.

Sounds like a good deal and impressive customer service. Does that include the equalizer? I see some sellers (B&H for ex) sell the equalizer separately for $200. Or do you have the "Series I" EQ and if so will it work correctly with the new Series VI speakers?

Kent

[stan461]

Sounds like a good deal and impressive customer service. Does that include the equalizer? I see some sellers (B&H for ex) sell the equalizer separately for $200. Or do you have the "Series I" EQ and if so will it work correctly with the new Series VI speakers?

Kent

The Bose rep said that the list price was $1400. So the discounted price is for a complete set of speakers.

My understanding is that Series I equalizer should NOT be used with the series VI speakers.

The equalizer is an integral part of the 901 speaker system. Without the equalizer, it's not a 901 speaker system.

[tysontom]

Tom,

I called Bose and to my surprise they will give me the trade in. Bose policy doesn't seem to care that I bought them used, only that the serial numbers are there and I ship the speakers back to them.

Buying them new and spending almost $800 with tax will require me to look at this as a possible long-term situation.

My major concern, the distance between the speakers will be 10 feet due to design constraints and WAF factors. Will the 901's span the center and not leave a hole?

I was also considering LaScalas because of my 10 foot placement situation. But LaScalas are a much larger committment both in dollars, size and wife convincing.

So now begins a week or so of intense research and thinking.

One more thing, what finish would you recommend? I read the veneer is cheap on the VI series. Maybe the black would look the richest?

Thanks again,

Stan

Stan,

Sorry for the delay in answering you on this. The "hole-in-the-middle" problem with so many speakers doesn't exist, for all intents and purposes, with the 901 unless you have them very far apart. In other words, the dispersion off the back of the speakers is so broad that it will fill the wall with sound by reflection, and the distance is not a major issue. In fact, the manual says you can mount them between 4-12 feet apart, but they should be 18-36 inches off the floor or below the ceiling, and they should be from 18-48 inches out from either side wall. So your mounting conditions are probably pretty good. The La Scalas would be good, but quite frankly I think the 901s would easily out-perform them, and the spaciousness of the 901s would completely outclass the Klipsch speakers.

The $800 that you would be paying would include a pair of brand-new 901s with equalizer and the interconnecting cables. I believe this offer is made to anyone with older 901s, and it is certainly outstanding customer service. It is a complete system, but you have to furnish the power, etc. You might want to be sure that you have adequate amplifier power, but this newer series is much easier on amplifiers than the old original 901 and the Series II 901. A good 60-100 watts-per-channel would nevertheless be good to have with any 901 if you can do it, but the speakers will give satisfactory results with less power, of course, but at lower volume levels.

As for the cabinet finish, I believe that the 901 is available in two finishes, (1) Oiled Walnut real-wood veneer finish and (2) a satin-black finish. I have seen the walnut versions, and I think that finish is fine -- as good as anyone else's finish. It would require periodic (every two or three years or sooner) oiling with Watco Satin Oil or boiled-linseed oil or the like to keep it lustrous, but otherwise would not require upkeep. The black-painted finish would require a soft damp cloth for cleaning. Both are fine finishes, and it would just depend on how they would fit into your decor. Also, remember that you should have tables or surface to mount them up off the floor, and importantly, they need to be positioned 8-18 inches out away from the front, reflecting wall where they are placed. This last placement requirement is important.

The real beauty in the 901s is the simplicity of the design: no crossovers, no tiny tweeter wires to burn out, no phase problems and few spurious resonance problems. They can play very loudly and cleanly, something few other speakers can match. They have a spacious soundstage that practically no other speaker can match. But they are not for everyone. Set up properly, the speakers are hard to beat. Set up improperly, they sound like you-know-what.

--Tom Tyson