Matrix 801 series 2 with(out)? extern filter

[JürgenW]

Yesterday I bought two of these speakers. Part of the speakers is an external filter that especially should be used in small rooms. (See e.g. a review of Stereophile in 1987.)
My room is small: 3 m in the direction of the boxes (but it is high: 3,6m and rather long: 8m).
I find that the boxes sound rather beter without the filter than with it. With the filter the sound is too much laid back, like behind a curtain.

Has anyone experience with this box and can an explanation for this effect? And if he has a similar (or just not) impression.

Probably I haven't done anything right. I have connected the extern filter in the loop of monitor out and in, so that I can switch between with and without this filter, like the manual by B&W states.

Perhaps I should add that I use a Quad 606 as power amplifier and a Audionet MAP V2 as pre-amplifier.

Thanks, Jürgen

[aarsoe]

Hi Jürgen

First - nice setup. have the 801 and the 606 my self and it is hard to believe that the small 606 can do such a wonderfull job with the big 801's.
Now back to your question. No - bass alignment filter is exactly the opposite of what you describe. It is a filter that extends the deep end of the 801 so that it can be used better in larger rooms.
So the recommendation would be to not use it.
I have the filter my self, and can say that with my 802's (now my rear speakers) it worked well - but with the 801 I did not like it.
However please note what you should do to use it is place it between your pre and power amp. The tape loop can be used, but the other way is better..

Now seeing that your model is the series II, I dont know if you have applied the "van allen fix" to the cross over - if not you should do it. If you dont have the description, then let me know and I will send it to you.
If you havent done the modification, and if you decide to do it, then you should also considder moving the cross over out of the speakers into an external box. The sonic benefits are very clear..

[JürgenW]

Hi aarsoe,

Thank you for the answer, it really helps.

I don't have the 'van allen fix' - nor do I know what it is supposed to do.
So if you would send me the description I would appreciate it.
(If you have it digitally, just send me a pm.)

[I have the Quad 606 al quite a few years and I sometimes think I should buy another used one as back up.]

Thanks, Jürgen

[aarsoe]

Jürgen

I will send it to you. If you get a second 606 you could also try to bi-amp the 801's :)
Not a night and day difference, but it will give you something..

[aarsoe]

Correction - its not called Van Allen - but Van Alstine..

For people not knowing what this fix is about I have included some of the description her..


Upgrade Plans for B&W 801 Matrix Loudspeaker Crossover
(Revised 8/19/91)
Preliminary Comments
We wrote to Stereophile in December of 1989 informing them (and you) of a design oversight in the
crossover layout of the B&W Matrix 801 speaker. They published our letter and provided copies of our
plans to those who were interested. Later, we investigated the speaker further and detailed the findings of
our circuit analysis in several 1990 Audio Basics issues, providing significant refinements to the crossover
upgrade. An enthusiastic letter to the editor was published in Stereophile the next year from a
person who had upgraded his speakers per our plans, He noted that we had told him about further improvements,
but unfortunately these upgrades were never spelled out in detail (except in Audio Basics).
Now B&W has taken note of our improvements themselves and has put all of our upgrades into production
in the “25th Anniversary Limited Edition” of the 801 and into the 801 Series III loudspeaker. Thus
many 801 Matrix owners may be wondering how they can go about upgrading their existing speakers to
equal the much better performing Limited Edition or Series III models.
We felt that since all a B&W owner needs to do is execute our original simple and very low cost upgrade
to their existing speakers to have essentially the same performance as the new model, we should rewrite
and simplify the upgrade plan to make it easier to follow so more people will actually do it. One note -
the new model does have a ferro-fluid damped tweeter. Our judgement is that the electronic damping our
crossover revision provides does about 95% of the work so that the replacement of the tweeter itself will
be much further out on the cost-benefit ratio curve.
We urge 801 Matrix owners to make these changes. Its easy to do, you will no longer need speaker
stands or an electronic bass filter at all, you don’t need to bi-wire, and you will make a better musical
improvement than buying a new power amplifier. (If you want that too, check with us first!)

Parts List
Two 1 ohm 5 watt resistors - one per speaker (any kind - they go in series with an inductor).
Eight large cable ties - four per speaker (3 for mounting inductor, one for rebundling input wires).
Four feet of 20 gauge insulated hookup wire.
Tools Needed
Phillips screwdriver
Solder pencil and good quality rosin core solder
Wire cutter/striper.
Needle nose pliers.
Instructions
1. Remove the head from one of your speakers and the top grill and foam pad.
2. Taking care to not damage the protruding top grill pegs, place (don’t tip) the speaker upside down
where you can access it with the tools, parts, and solder pencil.
3. Remove the bottom plate (8 Phillips screws).
4. Examine the crossover board and our pictorial diagram. Decide if our pictorial diagram is clear
enough to allow you to locate the necessary changes. If you are undecided, quit while you are
ahead and put the speaker back together and have your local friendly B&W dealer do the work (for
a price of course).
Page 2
5. If you are confident enough to press on then remove the six long Phillips screws holding the board
in place and cut the cable tie at the input wires to make enough slack in the wiring to lift and
access the bottom of the circuit board.
6. Locate and cut the two small green wires on the circuit board just behind the bi-wire jumper block.
This eliminates a crosstalk path between the woofer and mid/hi protect circuits and a possible
destruct path if the speaker is hi-amplified with the polarities of the amplifier reversed. Both
protection circuits will still work (this is desirable) but the LED will only light on mid/hi overloads.
B&W did this “improvement” a different way with the latest model - they did not install the
protection circuit parts on the PC card at all! We like our way better.
7. Cut the cable ties holding inductor L5 to the circuit board. On the foil side unsolder its leads to the
PC card and lift the leads clear of the board. Since this inductor is glued down with a soft “hotmelt”
adhesive, you may have to use a large screwdriver to gently pry it loose from the board.
Don’t damage the part - you will soon reuse it.
8. Install about one foot of hookup wire at each of the two PC card holes where L5 was previously
connected. Bend the leads over on the foil side and solder. The free ends will reconnect to the L5
leads later.
9. Locate the jumper wire near the lead end of L5’s location (going from near C1 to near C6).
Unsolder and remove this jumper wire and replace it with a 1 ohm 5 watt resistor as shown in our
diagram. Solder both leads.
10. Unsolder and lift one lead of C11 clear of the board. This takes the undesirable R2, C11, L8
“bump” to the upper base response out of circuit and lets you hear the deep bass without need for
the definition destroying external active filter.
11. Reinstall the circuit card with the six long Phillips screws.
12. Referring to our diagram, locate L5 on top of the bundle of output wires and cable tie it to the
bundle with three long ties, keeping the lead end pointing towards the circuit board.
13. Trim the free ends of the two one-foot wires to fit and connect and solder one to each of the L5
leads (making sure that bare ends cannot touch each other or short to other parts). This puts L5
back into circuit electrically, but removes it from the circuit magnetically.
14. This completes the project with one speaker. If you wish you can stuff a chunk of upholstery foam
rubber between L5 and the bottom plate when you reinstall the plate to keep the coil securely in
place with no chance for future rattles. Gently place the speaker right side up and reinstall the foam
pad (a little silicon spray is useful on the pegs to keep from popping the rubber mounting grommets
out of place), the top grill, and the head.
15. Now A-B this speaker (on mono source material with both speakers located close together) with
the “stock” speaker and tell me why you did not do this long ago when we first told you to in
Stereophile.
16. Repeat steps 1 through 14 with the other speaker then enjoy your “new” stereo system.
Finally, contemplate one thought for us please. If we have the necessary skill, powers of observation,
engineering expertise, and understanding of the music to find these problems that everyone else has
overlooked and then cure them so well that B&W puts all our improvements directly into production,
then what is the chance that we might build surprisingly musical amplifiers, preamplifiers, and CD
players too - ones that you might be happier with? Think about it please.
Thanks for your attention. You may freely copy and reprint this plan set with the only condition that
Audio by Van Alstine is credited as the originator of the information.

[delapoer]

Can anyone tell me where to find the diagram referenced in these instructions?

[JürgenW]

Delapoer,

If you send me a pm, I will send you one.

Jürgen