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Hi,I know there are internal crossover network jumpers inside the B&W 801 matrix S2 speakers. The jumpers for the positive between LF and HF were for sure removed, as I can bi-amp the speakers w/o any issue. Because the phase of my preamp is inverted, I need to invert the speaker cables on both speakers. However when I do this, my amps are shutdown due to protection. I suspect there are also internal jumpers on the negative terminals from LF to HF. Because the speakers are super heavy and the crossover networks are at the bottom of the speakers. It is difficult to open the speakers to check. Could someone please confirm there are also internal jumpers on the negative terminals?
Thanks
Edits: 11/14/24Follow Ups:
You have 2 internal jumpers positive and negative
I honestly don't know why someone would only remove one of the two jumpers if they did only remove the positive jumper, and left the negative this would definitely cause your amps to go into protection mode. Your going to have to open them up and look at the crossover.
If you love the speakers, you could consider upgrading the crossovers. Your stock 801 s2 crossover uses some electrolytic capacitors and these types of capacitors have a lifespan 10 years is old for these types of capacitors so your 30-year-old speakers should have the old caps replaced.
I remember northcreek audio did crossover upgrades for 801 s2 they cost around $2000.00 maybe you could find a used pair on eBay. Also Van Alstine offered a crossover upgrade for 801 s2 you can email Frank @avahifi.com he will give you schematics for his crossover upgrade for free you just have to build them or find someone in your area to build them for you. And right now on eBay you can buy upgraded made to order crossovers for the 801 s2 I remember people in forums that upgraded 801 s2 and said it was well worth it.
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The electrolytic capacitors are C13, C14, C16 and C17. They are in the protection circuit, not in the music path. So they shouldn't affect the sound.
Edits: 11/18/24
Audiophiles removed those protection circuits so did B&W on the 801 S3 the S3 has no protection circuit. And the electrolytic capacitors do not have to be in the signal path to degrade the sound. The capacitors that are in parallel or not in the signal path greatly affect the sound and you have multiple electrolytic capacitors in parallel in your 801's crossover.
Here is why that is so important you won't see a tolerance under 5% +/- on an electrolytic cap so an 8uf capacitor with a 5% +/- tolerance could be from 7.6uf to 8.4uf. But over time electrolytics lose capacitance and gain resistance or ESR equivalent series resistance.
An electrolytic capacitor can lose 20% of its capacitance over time so your 25-year-old capacitors need to be replaced. So, if an 8uf capacitor lost 20% of its capacitance it would be a 6.4uf that is huge. So your woofer crosses over at 380 HZ losing 20% of capacitance on the Parallel capacitors could be as much as a couple hundred hertz difference so your actual crossover point could be as high as 580 Hertz. And the ESR equivalent series resistance key word resistance increases so what happens when we increase resistance, we lose volume so not only are the electrolytic capacitors faded capacitance changing your frequency response they are slightly lowering the driver's volume.
So, you have the schematic that is great now you can make better crossovers. Higher quality caps and resistors and you could even use inductors that are a lower AWG for example an 18 AWG 5MH inductor has 0.50 OHM resistance a 14 AWG 5MH inductor has 0.09 OHM resistance. The less resistance on your woofer the better bass response. The more resistance the less dampening factor your amplifier has, and dampening factor is your amp's ability to control the speakers cone especially around the crossover point that is why you see really high-end speakers always using large gauge inductors
Do yourself a favor and change those electrolytics get some good, metalized film capacitors with a modern tolerance of 2% it does not cost much can be done in an afternoon and you won't regret it.
It is important to understand what those caps not in the signal path do they are controlling the frequency response. On a woofer an inductor in series is a first order crossover 6db per octave slope add a cap in parallel after the inductor you now have a 2nd order crossover 12db per octave slope these components are removing high frequencies. The larger value inductor & capacitor the more high frequencies removed the lower the values the less high frequency removed so if your capacitor has lost 15 to 20 percent capacitance it is now removing less high frequency which means your woofer is now playing well past it's 380 HZ that B&W intended.
Also B&W used some cheap components in their crossovers. Like the electrolytic capacitors are bennic very cheap i think they have a huge tolerance range like 10% or 12% =/- that's bad they should have used Mundorf and instead. And shock!! they are not using polypropylene capacitors in the signal path they used polyester capacitors, and they suck for crossovers. Polypropylene has a lower dielectric loss than polyester and that is way better for high frequencies they use cheap sand cast wire wound resistors they should have used non inductive wire wound like Mills so I am sure all the inductors are probably 18 or 20 AWG. This is why so many people upgraded these crossovers back in the day I can only imagine how bad those bennic caps measure after 25 years.
The attached spreadsheet conveys, with some careful study, differences between 801-S2 and 801-S3 crossovers. It also has, in the right most Column, proposed changes to an S2. Note: Elimination of the parallel notch filter (which is in series with the woofer coil) is, per Van Alstine, et al, useful when NOT using the B&W Bass Alignment Filter.
I gave Leo loves music Fank Van Alstine's contact information in my first post on this thread. Frank gives away the schematic and parts list he uses for the B&W S2 for free. B&W even uses one of franks fixes on the crossover in the S2 on their S3 model.
So, it is pretty safe to say franks improvements are well worth it. After all, if B&W uses his corrections on the S2 in their S3 that says a lot about Franks ability's.
My B&W 801s sound wonderful already (with my DIY bass alignment filter). I have no intention to further improve them.I have a Plinius SA-102 and a Proac response two. I will hook them up some day when I catch my breath. Ideally a new speakers for the Plinius.
Thanks for the help.
Edits: 01/12/25
Yes, this blue box does the magic. Top secret.
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This is from the manual. Looks like there are jumpers on the negative terminals also.
This picture is very clear.
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