My B&W 801 Restoration project.

[audiomagnate]

This is a continuation of my recent, "Why Did I Buy These" thread.

Anyway, I'm a few days into my restoration of a pair of B&W 801 Series 80s. I bought 2 pairs of 801s, hoping I could at least get one nice functioning pair.
It turns out I have one pair of 801 Series 80s, but the second pair turned out to be first gen bass cabs with 802 Series 80 mid/tweet modules.

First the bad news: One woofer is rubbing slightly and the 180 degree rotation didn't fix it. One of the 802 tweeters is completely fried, (see photo).

Now the good news: One of the tweeters is fine, and the other two are not fried, the voice coils look fine, but the voice coil wire has broken from fatigue where it attaches to the little jumper wires. I don't have the skill to fix those, but maybe I can find someone who does, (hint hint). I've done this repair on Kef and ADS tweets, but this is like microsurgery.

The only missing parts are the long bolts that attach the mid/tweet cabs to the bass cabs. I have the bolts for the smaller 802 modules, but they are too short for the larger 801 modules. I suppose I can have a metal fabrication shop extend the shorter bolts.

So I have three good woofers, four good mids and one good tweet but two more that might be brought back to life. B&W doesn't stock parts for these anymore and there's nothing on the internet, so if I can't fix one of these tweets I'm screwed.

I've got one speaker working and it sounds great and looks really cool. One of the crossover boards has a smoked wirewound resistor and the cabinets need a little work. The grilles (three per speaker) need a little work, but that's simple enough.

 

[KenP]

I first listened to these speakers in 1981 and was really impressed with them, at the time I couldn't afford the $2500 asking price but bought some dm14's for around $1000. keep posting and let us know what happens..

 

[Pete B]

Do you have any specs on the tweeters?

How do they mount in that small head?

I wonder if something like this could be adapted as
a last resort:
http://www.madisoundspeakerstore.co...stige-27tffnc/g-h1396-1-textile-dome-tweeter/

 

[audiomagnate]

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!

 

[audiomagnate]

Do you have any specs on the tweeters?

How do they mount in that small head?

I wonder if something like this could be adapted as
a last resort:
http://www.madisoundspeakerstore.co...stige-27tffnc/g-h1396-1-textile-dome-tweeter/

Thanks, but I'm pretty sure I can get the broken tweet fixed. I want to keep them as stock as possible while getting rid of the infamous protection stuff.

I've played around with a lot of speakers, but it's just goofy how much they spent on thinks like grill cloth frames, mounting hardware, cabinet construction, etc. Bean counters did NOT have a role in the design of these speakers.

 

[Pete B]

Sure it would be best to get the originals working if possible.

Do you have a schematic for the crossover? I'd like to see it.

Do you want to keep the caps electrolytics as original or do
you prefer films?

Bennics are good quality electrolytics:
http://madisound.com/manufacturers/bennic/bennic-caps-electro.php

Daytons would do for films and they are a fairly good price.
Axons from Zalytron are sometimes a bit cheaper.
There are 1% Dayton films if you care about matching.
And 3% Erse films from Meniscus:
http://meniscusaudio.com/capacitors-pulsex-polypropylene-c-101_104.html

 

[audiomagnate]

More pics.

 

[audiomagnate]

Sure it would be best to get the originals working if possible.

Do you have a schematic for the crossover? I'd like to see it.

Here's a link to where the service manual lives. The model number is 801F.

http://www.bwgroup-support.com/techmanuals.html

 

[audiomagnate]

Schematic. (LOW TECH UPLOAD) I don't understand the 1000uf cap in series with the woofer. It doesn't exist anywhere that I can find it. A capacitive coupled speaker.

 

[marne]

Audiomagnate, congrats to the project . I would have bouhght the bunch too.
Mine have these 1000µf caps, afaik these are a kind of subsonic protection.

From time to time tweeters appear on eBay. The last pair was new and pretty expensive, around 400$ if i remember right. Used ones maybe around a hundred.
I believe that mdf is heavier than pure wood, which adds more damping.:scratch2:
My 802 have environmental controls.

Please keep us up to date :thmbsp:

 

[leesonic]

Hi there,

What always amazes me is how some people treat their audio equipment. There are tons and tons of cheap speakers out there you can buy if you want to have a party. Why use a pair of expensive B&Ws for that? I have a pair of DCM KX10s, and last night I was comparing them to a pair of Advent Legacy 2s I just re-foamed. The Advents sounded a lot more accurate, but the DCMs are way more efficient, and produce more bass, albeit not as accurate. I know which pair I'd use for a party.

If you want big resistors, check out the ones over at Erse Audio. When I did my JBL L100 restoration I used parts mostly from Erse Audio. I made a spreadsheet up with prices from Parts Express, Erse, and Madisound, and Erse were the cheapest on a lot of things. I still ended up ordering from Parts Express, as Erse didn't stock any electrolytics smaller than 12uF at that time. I stayed away from "boutique" capacitors, as the crossovers were already costing me enough money as it was. I'm pleased with the results I got from using the components I did.

Hope this helps,

Lee.

 

[Pete B]

Thanks for the link to the schematic.

I actually studied the 801 that was the subject of the B&W
paper in the AES on computer aided design of crossover
networks:
http://www.aes.org/e-lib/browse.cfm?elib=2822

http://www.aes.org/e-lib/browse.cfm?elib=3830

I think that was also the same one that Van Alstine
had mods for. He noted crosstalk between the midrange and
woofer inductors in the crossover. This was in his Audio Basics
89/12, 90/01, 90/02:
http://www.avahifi.com/index.php?option=com_content&view=article&id=85&Itemid=181

Is the 801F vented? It might be the Series II that I'm thinking
of but the crossover looks very similar.

 

[audiomagnate]

Thanks for the link to the schematic.

I actually studied the 801 that was the subject of the B&W
paper in the AES on computer aided design of crossover
networks. I think that was also the same one that Van Alstine
had mods for. He noted crosstalk between the midrange and
woofer inductors in the crossover. This was in his Audio Basics
89/12, 90/01, 90/02:
http://www.avahifi.com/index.php?option=com_content&view=article&id=85&Itemid=181

Is the 801F vented? It might be the Series II that I'm thinking
of but the crossover looks very similar.

The 801F (F for Fibercrete) is not vented, nor is the series 80. The series 2 vented to get the sensitivity up. Those fried 6 ohm resistors in series with the mids say it all. More power was being turned into heat than making sound. BTW, the fried MR resistors are not wirewounds, my mistake. They didn't seem too worried about a perfect seal - no gaskets, lots of opportunities for leaks - so I would call them infinite baffle. This was a speaker that was in a constant state of evolution. That service manual is a hoot! The voice coils on the woof and mids are exposed, but they didn't even use netting to keep the enormous amount of stuffing out of the way. I understand IMFs and ADSs, but these things are downright wacky. It's like the designer was "playing it by ear." Literally.

The woofer and midrange inducters couldn't be interacting, they're almost three feet apart! There's a dedicated midrange board on the bottom, and a tweet/woof board hanging from the top of the bass cab.

 

[audiomagnate]

Audiomagnate, congrats to the project . I would have bouhght the bunch too.
Mine have these 1000µf caps, afaik these are a kind of subsonic protection.

From time to time tweeters appear on eBay. The last pair was new and pretty expensive, around 400$ if i remember right. Used ones maybe around a hundred.
I believe that mdf is heavier than pure wood, which adds more damping.:scratch2:
My 802 have environmental controls.

Please keep us up to date :thmbsp:

What's the voltage rating and size of those 1000ufs?

 

[audiomagnate]

"A design technique is described whereby the component values of a passive loudspeaker crossover network are selected by a digital computer such that the value of some specified function is minimized. The functional chosen for the purpose of illustration represents the difference between some desired sound-pressure amplitude-frequency response and the calculated sound-pressure amplitude-frequency response of one component system of a multiple-driver loudspeaker system. Minimization of this functional is carried out using a numerical optimization technique implemented on a PDP-11 computer. To ensure that an accurate prediction of the frequency response of the system and the network combined is used in the optimization procedure, the calculation of the functional takes into account the measured sound-pressure-frequency response and the input terminal impedance of the component loudspeaker system. As a result of including these factors in the design procedure, the traditional requirement for trial-and-error adjustment of the values of the actual crossover components is shown to be eliminated. Because the functional is evaluated numerically at a number of discrete frequencies, the desired frequency response may be specified by any function of frequency. The technique is illustrated with several design examples."


I'm old enough to remember 1970's computers. Did they have a Wang?

 

[Pete B]

PDP-11 is from Digital (when the name was Digital Equipment), one of the most popular 16 bit minis. I've designed Unibus hardware for them.

 

[Pete B]

Schematic. (LOW TECH UPLOAD) I don't understand the 1000uf cap in series with the woofer. It doesn't exist anywhere that I can find it. A capacitive coupled speaker.

There is a sealed bass alignment where boost (about 1 or 2 dB) is provided by a series cap as unintuitive as this might be. It was described in Speaker Builder (might have been Audio Amateur) by Tom Nousaine if I remember correctly. It requires a high Qms driver IIRC. Otherwise, it is a subsonic filter, but I would not use it since you want a cap with very low ESR. I'd simply use a line level subsonic filter.

 

[Pete B]

The woofer and midrange inducters couldn't be interacting, they're almost three feet apart! There's a dedicated midrange board on the bottom, and a tweet/woof board hanging from the top of the bass cab.

He was working on the vented version where they probably combined the boards for cost reduction.

 

[audiomagnate]

There was method in his madness.

 

[thymanst]

I picked up a pair of 801s2's for 300 and they needed refurbing also - the crossovers had a couple of bad capacitors and I had to replace the two tweeters - I also had to get new long bolts to attach the heads - they had he correct bolts at home depot-I had to get washers to help attach at top. They work great now and sound fantastic