B&W Matrix 2 Upgrade Project

[as labs]

First time posting, hello!

My goal here is to track a diy project and get some feedback for this unusual speaker, the B&W Matrix 2, that I picked up on marketplace a couple years ago.
Some essentials:

• 8" poly midwoof + 1" poly dome
• sealed box (est. 32L) with a lot of internal bracing and foam damping material. expect to use with a sub for full extension.
• not sure exactly where the crossover was (if there was any overlap in the original design, for example), but the original low pass seems to be quite high ~3.5k Hz (see below)
• rated 87dB efficiency (not verified)

I paid very little money because the tweeters were not working (so I've never heard these speakers in their original, working form). The boxes are in good shape and my plan at the time was to gut them and reuse the nice enclosures for a totally new speaker, probably using the scanspeak 22w and 10f discovery drivers that I have had lying around. I enjoy vintage speaker "reimagining" projects... All this back story is to say that I'm not married to the original design.

original crossover for reference... "tested 1986," love it...
complete with funky protection circuit, all pass circuit, and a couple HUGE inductors and capacitors for impedance flattening...

here's my dilemma:

The 8" poly woofer (jazzed up with some sort of mineral compound) has some unusually linear midrange performance.

Measured on axis, 1m from the baffle, with and without the original crossover.
All measurements shown have 1/6 oct smoothing, no windowing. <200Hz is not to be trusted.

An 8" driver, linear to 6kHz, apparently was crossed over >3k! huh?? It also seems to be living quite happily in this enclosure (no surprise).

Would it be a shame to take this driver out of its happy home? I do imagine the 22w will do well, but then what will I do with the B&W original? [Obviously keep it on a shelf for a decade]

I'm thinking now that I have 3 options:

1. "Restore" to an interpretation of the original design (single tweeter, maybe a new crossover point). call it a day and get back to my job, wife, kid, terrible yard, etc...
2. Stick with my original plan and build into the box, potentially permanently altering past the point of restoration (scary, eek!)
3. OR... combine the two, using the SS 10f in the original tweeter location and add a new "B&W-esque" style tweeter on the top of the enclosure. I may at least try this out before going full gut.

I was impatient and got to fitting a new tweeter and making a quick crossover.

I landed at 2kHz LR4, so a bit lower than stock. This was the lowest I could get the Kartesian Twt28 to behave; the faceplate mounting holes just happened to fit precisely with the B&W enclosure, the dome+surround diameter too. Some foam for a gasket and my very temporary modeling clay filler were good enough to clean up a nasty dip ~8kHz, so the clay stays for now. And we're listening....

Sum in green, 30 deg off-axis in grey.

The 30deg off-axis response is better than I would have thought for the 8" woofer. I had assumed that 1600 would be falling off axis.
I suspect the diffraction peak at 1k is made worse by the close measurement range (limited time today). It is slightly better in my initial 1m measurements.

Let's see how the woofer is behaving off-axis, sans crossover... getting my ghetto-spin-o-rama going:

Wow! Seems that I'll have to adjust the low pass filter q as this is a very smooth midrange driver and is not losing much energy at 60 deg off axis at 2kHz and below.

ghetto-spinner for reference (it's a plant stand, and no, it's not great...)
testing crossover on the tool bag (pretty simple!)


Now I'm at an impasse... i was excited to use the 10f in a three way, but now subjective listening has been positive in the test configuration... maybe i need to get the other side going and see what they can do in stereo...


Here we have it....
Any thoughts are welcome, bring the opinions!

 

[zoink]

This is intriguing! I have a Matrix 1, which is, as far as I can tell, the same drivers in a smaller but similarly constructed enclosure. As is usual it is hard to find good modern measurements of these older speakers, so it is cool to see the graph for the midwoofer here. Given the stellar performance of the midwoofer's higher end, I'm tempted to say that this is one of those speakers where you could get excellent results in a two way configuration. Have you done the other speaker? And -- is there some kind of putty around the little tweeter waveguide? Mine don't have that.

 

[as labs]

This is intriguing! I have a Matrix 1, which is, as far as I can tell, the same drivers in a smaller but similarly constructed enclosure. As is usual it is hard to find good modern measurements of these older speakers, so it is cool to see the graph for the midwoofer here. Given the stellar performance of the midwoofer's higher end, I'm tempted to say that this is one of those speakers where you could get excellent results in a two way configuration. Have you done the other speaker? And -- is there some kind of putty around the little tweeter waveguide? Mine don't have that.

There is putty, yes, and it's just a stopgap fix to fill the gap that the rubber ring occupied. The sound >6k unusable until i added the putty- I will need to find some flathead bolts to hold the tweeter if I decide to return the ring thingy. boring details...

I have not done the other speaker, but continue working on the crossover. the tweeter actually preferred being crossed higher because of box diffraction and distortion, so I went with that.

I don't have an immediate use for them, so I still haven't decided if I will refurbish and sell or try to repurpose the boxes. After loads of listening i love the tuning of the box and the overall sound from the woofer, so I'm still torn. the original engineering is rather impressive in my opinion, it's too bad the original tweeters are both blown.

 

[zoink]

I wonder if it's possible to source original tweeters somehow. Though the original tweeters are pretty laid back, so if you drop some other tweeters in there with good results you might have a winner mod.

 

[souslamare]

This is very interesting! I’ve got Matrix 3 series 2’s in my main system, and hope to add some Matrix 2’s to my second system; the 2’s are going to need some work! A new crossover may be required (water damage), so a number of possibilities open up… I watch with great interest.

 

[sarumbear]

This is the first time I heard about Kartesian. Very interesting specifications throughout their range. Trust the French!

Thank you @as labs it’s nice to see a fellow acoustician in ASR

 

[sofrep811]

This is the reason for my Mission 772 rebuild. Figured might as well use the enclosures. Great job so far.

 

[SA Mark]

I bought a pair of these back in 1986 when I was very and loved them. Since then, life has pretty much quashed my music time so they sat for 30 years without being used. I recently tried to listen to them and one of them just doesn't want to play. I exchanged some resistors that looked burned to no avail.

The channel pushing that speaker my Sumo Andromeda also went out. I found a blown fuse in that which I changed and still no change. If you've ever heard the Andromeda, you know how great an Amp it is. I've contacted several companies who won't touch it without an unreasonable deposit.

The crossover on my Matrix 2 doesn't look the same as "as labs". Any ideas where to look on either/both now?