My B&W 801 Restoration project.

801f

The "F" denotes the upgraded tweeter and midrange head which was made from Fibre-crete. It looks identical but was an upgrade for the original 801. which had the manual reset overload protection ( two buttons and a light on the front cloth panel and was powered by a pp9 battery)

Then I have the originals, regular wood midrange heads and the original cloth tweeter. I've got to get back to work on these puppies.

Now this is the kind of vintage speaker I would put time into. There is always room for improvement and after you make a good original pair I would replace the tweeters with something modern like a ring tweeter and make a hot rod pair with what you have left. The cap in series with the woofer interests me and I will call Tom Nousaine this afternoon to discuss.

OK Tom says the capacitor article was by Dave Clark and Earl Geddies and it indeed was to extend (not boost) the bass response by lowering the resonant frequency. He did not have details so I will now have to call Dave to get more. (not home right now). I would experiment with the cap in/out to see what it sounds like.

It did in fact provide some boost. Look up the article.

I'm back. I've got one speaker finished, and it sounds pretty good. I replaced all the electrolytics with slightly lower value, but much higher voltage Bennic electrolytics and strapped them with low value, usually 3.3 uF, mylars from Carli to get the values correct and improve the sound. I unplugged the protection board, removed and jumpered the relay, removed the diode from one of the crossover boards and voila, it sounds pretty awesome! The only protection now is a 5 amp fuse in line with the whole speaker, and I'm thinking of jumpering that too (EDIT, I did). I also replaced the under-rated 5 watt resistors with new 15 watters and elevated them off the board for better cooling (and fire protection!).

It seems I'm not done yet, there is a third crossover board in the midrange module, and it has fried resistors and and one electrolytic. The ones I chose to mod are very early series 80,s from 1979

As God as my witness, I am going to make these puppies sing! They don't now. Very analytical but no fun. I will leave the flat "environmental" position alone and tweek the HF + position. Maybe the magnet in the tweet has lost power, but there is no real detail stock even with the environmental controls bipassed. EDIT: Maybe "detail = coloration or "zip"?.

Worthy project. You will not regret the effort. Somebody musta been crankin those puppies to fry those resistors like that. Is that the same cab with the fried tweeter?

You're a lucky man to have them on your hands.

Looks like they played quite hard in the day though.

Good luck with the restore!

Nice work! I'm sure you'll get them all sorted out.

There was an issue with early ferro fluid turning into something like black burnt oil and almost a solid after extended over temp ... I wonder if this was an issue with early B&Ws?

There are comments here about ferro fluid and tweeters with reduced output:
http://www.roger-russell.com/driverst.htm#d095

He measured little if any rise in impedance probably because the voice coil was frozen in the burnt ferro fluid, however early FF was usually very thick causing even a properly working tweeter to have only a very small impedance peak. No peak at all is a good sign of a frozen VC. It would be good to know the characteristics when they were new, or at least properly working.

StarMover said:

Worthy project. You will not regret the effort. Somebody musta been crankin those puppies to fry those resistors like that. Is that the same cab with the fried tweeter?

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Yes. Like I said, I have two pair, one pair is real rosewood, the other some fake wood formica, so I'm going with the rosewood cabs (center pair in the picture in the first post) and the older version crossovers that have (had) the separate battery powered protection. I haven't dug into the second pair yet, but they have the later passive protection circuit integrated with the crossover, completely different stuffing material, and real binding posts instead of the silly banana plug recepticals, (see photo) on the rosewood pair. I might have to put some real binding posts on as my final mod. Three out of the four tweeters were blown. The functional one actually sounds excellent now, just not as bright as my ADSs or JBLs, but incredibly realistic, especially on vocals. I brightened up the plus position on the tweeter ("B" on the HF "environmental" control) about a db and left the rest of the settings alone, but now flat sounds good too so I might change the + tweeter position back to stock just for originality sake. For the record, the pair I'm restoring are series 80, serial nos. 589 and 590. BTW Pete, there is no evidence of ferro fluid in the tweeter gaps, and no mention of it in the extremely detailed owner's manual.

Original Owner

I have been the proud owner of the 801's for close to 32 years. They're still in perfect condition. Let me tell you some of the mods I've made over the years.
Almost 30-years ago I updated to the so-called 'concrete heads'.
By-passed the fuse to improve the dampening factor.
Removed the castors and replaced them with spikes, composed of 4-hardwood (alder) blocks with a counter-sunk and apoxied nut on the back- side and a washer and a couple of nuts on the bottom-side and a sharpened thread-all passing through all of this. All this was glued and screwed into the bottom of the speaker in line with the holes from the castors. Now the speakers are slightly angled upward.
I treated all the contacts, including the molex connectors and the contacts on the switches on the backs of the heads with Stabilant 22A.
Over the years the protection circuit was never activated so, therefore, I felt that it wasn't necessary. I unplugged the middle connector on the top board (LF and HF).
To improve the conductivity of the contacts in the relay, I connected the brown wire (input speaker positive) to the red wire going from the top board (M4 pin4) to the bottom board (MF) with a jumper wire. In essence, this made the poor connection in the relay a moot point. This was the easiest way to by-pass the relay without removing it from the board.
All these modifications, especially by-passing all the protection devices, made significant improvements in the sound.
In the past, the 801's have been said to have 'boomy' bass. Not so any longer especially with the spikes anchored on a concrete floor. All the capacitors and resistors, etc. are original and in perfect condition and the speakers sound great, but my queston is, "Could the sound be improved by replacing some of the capacitors, particularly those in the path of the high frequencies, with polypropylene (or better) in place of the polyester and electrolytic?"
P.S. I have enjoyed reading your posts.

Bellair said:

OK Tom says the capacitor article was by Dave Clark and Earl Geddies and it indeed was to extend (not boost) the bass response by lowering the resonant frequency. He did not have details so I will now have to call Dave to get more. (not home right now). I would experiment with the cap in/out to see what it sounds like.

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I just came across the article that I was referring to, it is "A Passively Assisted Woofer System" by Tom Nousaine Speaker Builder 2/89. He does call the alignment a CG3 type and references the Clark and Geddes SAE Technical Paper #860123 from 1986. Tom goes through a lot of effort adding mass to the drivers that he chose to get a lower Fs and there is the cap (1900 uF) to get the proper response however he did not document the before and after response very well. I simulated such a system and the bass extension comes from the added mass with slight boost coming from the cap as a result of resonating with the driver's reactive input impedance. The original Clark and Geddes article is probably a better paper to provide an understanding of this alignment.

Binding Posts

I recommend replacing the binding post with the Dayton Audio BPA-38G HD.
With a little bit of tapering at the input and with careful alignment, they will easily fit.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=091-1245

I have attached a circuit diagram of the crossover in case you don't have one. I have more schematics but this is the main one. I could not post it because the file is larger than is permitted to upload, but I can upload sections at a time.

I would be interested in knowing the actual value of the functioning capacitors in relation to the spec values. I'm considering replacing my electrolytic caps. The speakers sound fine but I don't know if, over the years, the caps have somewhat deteriorated and my ears have just been adjusting and, to check mine, I would have to unglue and unsodder them. At that point, I would just replace them but I'm worried that the ESR of the new caps might vary substantially from the original specs.
Sa

audiomagnate said:

Well, it looks like I'm I'm going to need to replace a total of ten caps and two resistors. The 6 ohm resistor in series with the midrange is cooked in both speakers. The original design called for two 12 ohms in parallel. Any suggestions on what I should use to replace those big red caps? Values are 85uf/70 volt, 35uf/50v, 26uf/70v, 20uf/70v, and 63uf/70v.

Here's my plan:

1.Eliminate the protection circuitry, including bypassing the relay.
2.Recapping the electrolytics.
3.Replacing the cooked 6 ohm resistors with double 12 ohms, per the original design.
4. Repairing the opened up tweeter.
5.Cleaning up the cabinets. (Light sanding, revarnishing)
6. Replacing the foam rubber on the top of the bass cabinet.
7. Replacing the grill cloth.
8.Selling off the spare parts to finance above.
9. Making subs out of the two leftover bass cabs.
10. Kicking back to some vintage Beatles, on my Abby Road specials!

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Thanks to gdwrench's magical ability to bring dead tweeters back to life, I was able to fire up my 801s Series 80s last night and I am EXTREMELY pleased. Here's what I've done so far:

1. Replaced all electrolytic caps with new electrolytic + film combos.
2. Replaced and upgraded the power rating of all resistors.
3. Removed APOC speaker protection circuit. Relay is removed and bypassed.
4. Replaced input terminals.
5. Bypassed environmental controls.
6. Soldered all speaker and crossover connections (replacing push on connectors).
7. Removed fuse from circuit.

They sound really, really good. Voices are just spot on with no coloration, and imaging is scary good. Bass can be a bit overblown, but I plan on getting some stands to cure that.

Nice work, I enjoy reading about your progress here and how they sound!

What sort and how much damping material is used in the bass sections?

Pete B said:

Nice work, I enjoy reading about your progress here and how they sound!

What sort and how much damping material is used in the bass sections?

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The bass cabs are stuffed to the brim with what I think is good old English rock wool. The mid heads are also stuffed with rock wool, but it's green in color, not purple like in the bass cabs. What I call "rock wool" is on the right in the photo. It's like loose fiberglass, but it's not fiberglass and doesn't make you itch. In a pair of 801s there is a HUGE amount of this stuff, enough to fill a 50 gallon trash bag!

All Poly Caps

This is what my new re-capped boards look like. There is a significant improvement!:tresbon:
Sa

Sa_M said:

This is what my new re-capped boards look like. There is a significant improvement!:tresbon:
Sa

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I was going to suggest that you recap your crossovers. Thirty plus years is a long time for an electrolytic. They look excellent. I got mine off the ground last night; just on to some cinder blocks, but it made a huge difference. Bass is much tighter now. It looks horrible so it's not a permanent solution.