Bose 901 Modifications

[karlos879]

I realise this is mostly a DIY forum, but I am wondering if anyone out there has modified a pair of Bose 901's?

I have a pair of series VI's, and although they do sound good, they are now 15 years old and I think might be a little softer than when I got them, and instead of buying a new pair of speakers, I am looking to see if I can give back to them what they might have lost, or more!

There is a modification guide book out there somewhere, but I think it just recommends replacing the drivers with other, better quality drivers.
That's a bit disappointing after buying them and now having to spend more money to update them to what they should have been in the first place, but anyway...

I think the guide recommends replacing the later series drivers with earlier series drivers because they have heavy-duty voice coils and a longer excursion and cloth surrounds unlike the later series that have helical voice coils, short excursion and foam surrounds. At least I think that's the way it goes...

In case I cant get hold of any early series drivers, anyone out there have any serious recomendations on what sort of full range drivers I should use ?
I'm not opposed to spending some dollars, I just want a driver that will tighten the bass response and improve the overall frequency response.....the better quality, the better.

Thanks,
Karl.

[Cal Weldon]

Here's a spot to find some drivers. Check near the bottom of the page.

http://simplyspeakers.com/bosespeakerrepair.htm

Another place.
http://www.oaktreeent.com/Bose_Speaker_Parts.htm

Don't try and use another driver. The EQ unit for the series V and VI is meant for specific drivers. Using earlier series will throw that off. Also, the early drivers are 8 ohm, the latter are 1 ohm.

[Cal Weldon]

Also, you're likely to get some flack for considering putting money into them. They are not well made, have poor quality drivers and rely heavily on the EQ to balance things. There are much better ways to spend your money.

[Nelson Pass]

And of course there are worse.

[chrisb]

well, there's 18 drivers in a single pair of 901's , and while I'm inclined to blithely ignore a lot of the math involved in designing loudspeakers (at least, to allow others to crunch the numbers), one piece that's unavoidable is the cost of any type of repair to surrounds, etc.




as for Cal's second post on the subject, that could open a whole 'nother can of hurt, so let's not go there

no, can't help it

one could certainly build something quite spectacular for far less than the cost of surround repairs x 18 pieces, and the thought of replacing the drivers with something theoretically better than the stock driver, but not specifically tailored for this system, makes absolutely no sense at all - if for no other reason that the EQ would likely need redesign as well.

A couple of decades ago one of my brothers in law built a clone kit of the 901, which apparently had "the right drivers", as well as EQ available. He elected to save the money on the latter, and use just the 3 band EQ on his Marantz (Superscope) pre-amp.

A pair of small advents or Boston A70s and NAD 7020 receiver would eat this system for breakfast - thank God playing his system was never a focal point of any of our family visits.

[GM]

Originally posted by karlos879

I think the guide recommends replacing the later series drivers with earlier series drivers because they have heavy-duty voice coils and a longer excursion and cloth surrounds unlike the later series that have helical voice coils, short excursion and foam surrounds.

If you're willing to spend the $$$, then this is what I'd do. I spent several years being around an early (1970-72, not sure what year) pair with the premium cabs/chrome stands and there's really no comparison performance wise to the later ones I auditioned in a ~optimized set-up at Best Buy? many years later. The drivers in these looked more like a construction paper toy mock-up compared to the robust, studio mini-monitor duty units of the originals.

Sorry, never measured its specs and considering its electronic EQ I don't have a clue what might be a suitable replacement.

GM

[scott wurcer]

Originally posted by chrisb

A couple of decades ago one of my brothers in law built a clone kit of the 901, which apparently had "the right drivers", as well as EQ available. He elected to save the money on the latter, and use just the 3 band EQ on his Marantz (Superscope) pre-amp.

IIRC CTS got in a lot of trouble for selling QC rejects with BOSE still printed on the cones.

[chrisb]

Originally posted by scott wurcer


IIRC CTS got in a lot of trouble for selling QC rejects with BOSE still printed on the cones.

I thought it was either them or was Misco in business around that time?

Anyway, as I recall, the early 901 drivers looked rather similar to those in original EPI microtower - one of the funnest speakers of that era for sure, and now that I think about it, the first "serious" FR driver that I'd heard (mantle radios don't count, and the cheapie little Norescos had some kinda tweeters)

[Nelson Pass]

Personally I think some Bose type drivers in eq'd phased arrays
with open baffles would be a hoot.

Something like a "Sweet 60"

per side....

[Cal Weldon]

Not to take away from the subject but...

One of things that never seems to get mentioned about Bose is how he and his team(s) managed to get the most from the materials. It's great that injection moulding is cheap once you've looked after the tooling but the one that really gets me is the triangle pincushion flange. He saved 9 screws per box. Multiply that by goodness knows how many 901's and you get a near astronomical number of screws saved.

IMHO once you reach a certain age, making sure you have a few screws for later on is not a bad thing. Three cheers for the Doctor.