B&W Matrix 800: Bi-amping thoughts?

Ferro fluid is probably best off being changed.  I did mine a few years ago after 35 years.  It made an audible improvement.  It’s not a bad task, and there are helpful vids online.

The amps do not need to have matching power output if  you do a horizontal configuration with one amp on the bottom and one amp on top, as it sounds like you’re planning to do.  It’s very common in the type of setup to use a more powerful amp for the woofers.  I’m using 100 wpc on the woofers, and only 17 wpc on the midbass/tweeters.  You will likely need a method to match the gain so that they play at the same volume, unless the amps just miraculously happen to have the same gain.  There are a few ways to match the output. 

Every situation is a bit different, so no two bi-amp setups are alike.  Don’t worry if you do somethingn different than other bi-amp setups you see, because you’re starting from a differnent place with a different rig than anyone else. 

In my case, relieving the smallish tube amps from woofer duty really made the midbass/treble clearer and more dynamic.  The solid state amp also has better dynamics and control over the woofers, so that improved too.  Also in my case, I added an active low pass crossover for the bass amp @ 63hz, which gave me a separate gain control for that amp, but I also bypassed the low pass passive crossver from the woofers.  (For you that could be a significant mod from the stock crossovers because of how elaborate they are, but I’ve read of people doing it, so some info is out there for you).  Along with the active low pass, I also installed an inline high pass for the tube amps, but my speakers had only a natural acoustic rolloff for high pass and no passive crossover mods were necessary.  (different situations.) 

It’s fun to do, and there’s definitely some potential benefit.  A lot in some cases.  I approached my bi-amping in phases as I went a long starting with a vertical configuration (monoblocks).  Then added the solid state amp later (horizontal), so it’s hybrid vertical/horizontal. It’s also tube/solid state hybrid, and active/passive hybrid.  

Wow lots of people to respond to! I appreciate your inputs. 

@knotscott Ah right, I’ve read that article. In fact I bookmarked it for the tweeter manufacturer in case I need to replace the OEM components. As they will have been silent for almost 30 years by the time I set them up, I’m desparately hoping the ferro fluid in the tweeters is still viable. And thank you for the info on the cross over points.

Never having bi-amped anything before, don’t the amplifiers need to be of similar wattages? I’d thought about using the Defy7 for up top and the ML-335 for the woofers but would be concerned with the greater output from the ML-335 that it would over power the Defy7’s output.

@68pete It’s been a couple of years since I took the system down and packed it for transport. And as I was limited on time, I didn’t make a good inventory of things like cables of which there was a dizzying array. I swear he kept every set of cables he ever bought.

When I do unpack it all, it’s going to be like an audiophile’s Christmas for me! 

Happy listening.

PS: I don't what anyone says. I think they're beautiful!

I own a pair of the Matrix 800, and find the stronger the amp the better the sound.The ML 335 is nice amp for its age. It did the bass very well on mine. what cables and jumpers are you using?

Keep us posted on your journey

@musicfan2349 It was initially Meta AI. 

"what are the crossover points on the B&W Matrix 800 speakers

The B&W Matrix 800 speakers have separate crossovers housed in the three separate cabinets. Each woofer enclosure has a low-pass crossover dedicated to the driver inside, and the central cabinet houses the mid/high crossover boards. The crossover points are approximately at ¹:

• Low-Frequency Crossover (Woofer to Midrange): around 300 Hz, where the woofer’s output transitions to the midrange units.

• Midrange to Tweeter Crossover: approximately 3 kHz, where the midrange units’ output transitions to the tweeter.

It’s worth noting that some users have modified their B&W Matrix 800 speakers to use active crossovers, allowing for bi-amping. One option for this modification is the KBX crossover designed by Dan D’Agostino, which includes custom crossover points and a bass alignment filter ² ³."

I found that Aurel Hifi as well as hifiwiki.com called them "transitional ranges" of 300hz and 3,000hz.

https://auralhifi.com/products/vintage-bowers-wilkins-matrix-800-rosewood-speakers-installed-new-satori-beryllium-tweeters-refinished-cabinets-na-matrix

https://hifi-wiki.com/index.php/B%26W_Matrix_800

I also saw another AI blurb on Google that stated 380hz and 3,000hz that referenced DIYAudio.com and Stereophile. 

@knotscott You said: "From what I can find, the woofer crosses over to the midbass at around 300hz".

Would you direct me to where you found that please? Thank you.

Happy listening.

And, I was surprised to find that when the monoblocks were in play, even lower volumes sounded more filled out.

sorry for the double posts, but I'm kind of a slow thinker.

Bill

I can only speak about my own experience.  My N801s are 91db.  The recommended power range is 50 to 1000 watts.  Using my 300 watt amp, volume levels would go high (SPL) but the bass just didn't keep up.  I think a high power high current amp is what will bring those woofers to life.  However, YMMV.

Bill

From what I can find, the woofer crosses over to the midbass at around 300hz, which is smack in the middle of both male and female vocals, which will make it more critical to blend well between two amps. 

If done well, it could help improve the clarity of the midbass/tweeter amps by relieving it of low bass duties, but will require a woofer amp with not only ample power and the ability to handle large woofer excursions, it’ll also need to have good lower midrange sonics to get it blend well.  You’ll likely want the ability to blend the gain of the two amps to match.  

Please keep us posted on your progress.  

@wbs Hi Bill,

I don't disagree with the "more power is better" approach most times. However at 93db sensitivity they are fairly easy to drive. Even being set up with 100wpc running in full range, they did push out some impressive SPL.

I also have pop's Mark Levinson ML335 (which needs to be serviced) He used it for a brief period and I considered using that with its 500wpc into 4ohms muscle. However the Defy7 is simply magic in the mid and upper frequencies. I can only imagine what it might be if I could liberate it from having to drive those woofers and instead assign that duty to a robust SS amp of sufficient caliber. 

Consider this: Bi-amping the 800s the way I'm considering would also double the power.

Happy listening.

I forgot to add that those are wonderful speakers.  You are a lucky person.

Bill

I agree with the similar caliber, but you would want more power if you want the bass to really do what it can.  Those speakers are rated to 800 watts power handling capability and while you don't need 800 watts, you will want more than 100 watts, especially if you enjoy listening at higher volumes.

I kind of assume your pop didn't listen to hard driving music much using only the Defy7.

When I bought my N801s I thought that my 300 watt Mcintosh would get me by but it only took about 10 minutes of listening to realize that the speakers sounded kind of starved in the low frequencies.

I ended up biamping with 130 watts on the highs and 1k watts on the woofers.  This is probably overkill but at the time I wasn't sure how much I really needed and I didn't want to disappoint myself a second time.

The monoblocks really opened up the low end and I have never regretted the purchase.

If I were you I would look for at least 400 watts or more for your low end, and really the more the better if you like to thrash.

Bill