Bi-amping

Hi CT,

Just looked at the Stereophile measurements. I have to say, those were among the best B&W made, at least based on that!

https://www.stereophile.com/content/bw-matrix-801-series-2-loudspeaker-measurements

I would disagree, but just a little, about them with tubes. While the impedance barely drops below 6 Ohms, the rise to over 20 Ohms at about 2 kHz (text says 15, chart says more) could cause a little trouble. I would be tempted to add an impedance correction circuit to see how it behaves.

Best,

E

Sorry for adding more. 

What's interesting also is the impedance rise in the treble, along with a drop in response in the top octave. This is a speaker which might actually cry out for a tube amplifier to bring out the most output in that top octave.

This combination is not uncommon, especially for speakers of the era. 

A solid state amplifier would ignore the impedance rise, and present the top octaves as JA measured. 


Best,

E

Erik
the links you are showing are for the Series 2 801. The 801 that the OP is using, and that I used previously is the Series 3.

There were changes with the Series 3 - away from the Studio requirements and toward the Audiophile; so much so that the Sound Anchor stands for the Series 2 won't even fit on the S3.

S3 used a different crossover than s2 - less component count.
Better isolated mid and hf boards.
Bass inductors with an iron dust core .
Rotating midrange – tweeter head assembly was permanently connected. (from 3 to 4 pin delivering separate ground signals to midrange and tweeter)
Magnetic fluid cooling of the tweeter (like the 800 matrix) - the reason the apoc protection eliminated (circuits needed for this were also removed)

Here is the impedance graph for the 801 S3 sent to me by B&W England years ago. All markings are theirs.

801 Matrix S3

Cheers Chris

Some of the info above is not accurate. Anyway, I’m not sure it would be worth it and this is coming from someone who’s bi and tri-amped for 40 years. Your B&Ws are a relatively easy-to-drive load averaging around 6 ohms with a complementary manageable phase angle and you’ve got a great amp with plenty of power with somewhere around 300 watts RMS at that impedance. You have adequate power.

First, to go active line-level bi-amping, you must be able to bypass your passive speaker crossover components or the whole effort doesn’t work. Finding a good active XO and bi-amping is going to be expensive. Even if you can, to dial it in properly and match signal levels, you must use measurements - dozens of them. You can’t do it by ear unless you can hear .5dB changes. You should use the same amp which you are considering-good. The whole thing’s very fiddly, time consuming, and frustrating to get it right. Done improperly, it’ll sound totally worse.

Don’t take my word for it, check out what Jim Smith (Get Better Sound) has to say about it. I learned this the hard way because I did it wrong for more than a decade. My system never sounded right. To see what it takes to do it, check out my system comments from 2012 to 2015 and read the trials and tribulations, then go spend your money on something more fun and effective.

Luvrockin Maybe you’re still thinking about it?

Here’s an excerpt from Nelson Pass in the Intro of the Pass Labs XVR-1 product manual. It’s the bible (literally at 20+ pages) on active crossovers basics, theory, and how to set them up. Have at it.

" Some audio products are designed so that you plug them in and you don’t have to fool around with them for a year before the system is greatly improved….".

http://www.passlabs.com/sites/default/files/XVR1_om.pdf