Force cancellation bass + OB top system

not to be too much of a pest but do you a cad file for the wo24 magnet mount?
What horn is that? qsc?
No can do re magnet mount. I think it was manually machined.

pairs of B&C DE250-8 & Eminence N151M 1" compression drivers along with a pair of B-52 PHRN-1014 10" x 14" 90x40 Horn

I also got a pair of SB Audience ROSSO-44CDN-PK which are clearly audibly superior to the other CDs above. A version with those in place of the BE domes will have to be tried.
 
Hi Dayne, yes, the project continues.

Mark listened to that setup after several days of my work on the setup with the Beryllium dome Satori + waveguide-modded Yamaha JA0801. He loves how they sound.

But Mark wants better reliability & longevity. So he asked me to find the best modern current equivalent of the JA0801, which can only be found used, mostly 25+ years old. The natural choice is Bliesma M74B-6. Around CA$2500 and a couple weeks later, a pair of these lauded transducers arrived in my studio. Integrating them into the system with active Flex 8 DSP was easy. The Bliesma has great manufacturing quality, better top & directivity, and likely a smoother low end, too. But subjectively, the improvement over the old Yamaha is relatively subtle.

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Once the config files were saved, the systems were broken down so the "enclosures" could be built. The plan was to paint the visible interior spaces of the bass bin black, skin it with 1/8" thick layer of BB plywood and add the top drivers in an extended baffle, the front of which would be 3/4" solid walnut.

That turned out to be extremely tedious and challenging. My woodworking skills are self-taught, and while I have many tools, my mastery with most is not complete. There have been lots of mornings when I identify & correct the mistakes made yesterday before I can move on to the next step. 😵 😕🤣
 
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Im sure they will sound fantastic but what is the the thinking/theory with the dipole, dipole, monopole, monopole construction? 🙂

If you go back through earlier posts, you'd see that a big challenge of this project is it's final destination: a 52x30' virtually undamped room with 20' ceiling. At high SPL, the reverb becomes overwhelming, especially at the higher frequencies. My lx521 inspired 4-way OB sounded fine there except for this aspect.

So...

The notion is that dipole effects are most significant at lower frequencies. The system is dipole to the crossover between the Satori 24TX & the Bliesma mid dome. It becomes cardioid in the transition between them, above which it's all monopole.

I am hoping the higher directivity of the domes reduces the harsh treble reverb of the fully OB system at high SPL. There'll be less of that higher frequency energy distributed in the room.

Even if my hypothesis proves erroneous, that's ok, it may be the impetus for the end users to add acoustic damping of some kind.

The mockup sounded fantastic in my fairly well damped studio, 19x22' with gently sloped ceiling. Much of the spatial quality of my lx521 clones was there, with a bit more in your face intensity, esp. in the mids & highs. It sounded very dynamic, with wide frequency bandwidth, utterly detailed but still natural.

The final speakers will differ significantly from the mockup in that the upper 3 drivers were nude or near so. The final speakers will have a baffle as wide as the bass part. I am hoping the added diffraction won't take away too much of the magic. The drivers have been offset, mirror L-R, to ameliorate the wide baffle.

We'll see how well the last couple Flex 8 configurations from the mockup work when the final system is put together. Hopefully it won't demand major rework on the crossover/PEQ.
 
That's really coming together! Literally!
Yeah, it's coming along fast now. Feels good. 😎

Was the jump from nearly nude to baffled driven by aesthetics, or other factors?
Entirely aesthetics. Mark, the end-user, loved the sound of the fully functioning mockup but could not accept any of the nude or near-nude upper driver configurations I came up with. Neither could his wife. 🤔 Customer's always right...?

What you see is the compromise: A Linkwitz Orion or Gainphile S19 type of look.

The top 3 drivers are aligned vertically to one side of the baffle (in a mirror image pair) to reduce effects of diffraction.

The Satori WO24TX will have at least as much open space behind it as the low-mid driver in the Orion. Not quite as open as nude but decently open.

The side edges of the walnut baffle will also be rounded with a big 1/4 round router bit.

I have 3 contenders for that job. My first choice is the yellow one which will cut a 1.25" elliptical shape 3/4" deep. The 2nd one isn't really usable -- the radius is 1.5" -- too deep for the 13/16" thick walnut. The 3rd one is tamest at 3/4".

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I'll probably use the 3/4" radius bit because it can be handled on a big 3hp handheld router. The others are too scary to use handheld.

I do have 4hp "shaper" type of router built into a Hammer B3 sliding table saw, and that can definitely handle the big bits, but the speaker box weighs 64 lbs, and is too unwieldy to slide on the less than ergonomic working position for the shaper. It was not possible to router the walnut board edge before the glue-up because I did not trust myself to cut the board to match the exact width of the speaker box.

The walnut boards are not perfectly flat, of course, bowing along the width as well as the length. Enough that there was a 3/8" gap between the walnut board at the top of the 50" height box. The board had to be pressed down hard -- with 18 clamps in total, and a whole lot of screws than will end up hidden.

If the bond looks/feels secure when the glue has dried at least 24 hrs, I'll router the edges in multiple increments. Maybe tomorrow pm.
 
Hello, clever project, could you tell how force cancellation works ?
If you're asking how well it works, it works very well.

In my lx521 clone, there's less vibration from the two 10" bass W-frame drivers than from the 8" mid in the upper baffle. Way less than in the V-frame bass box of the original lx521. I built a pair of them first & didn't like how much vibration was in the box, which is what led me to try the W frame. Way less vibration. This is my third W-frame OB bass build.
 
You've done a great work and i know that routing solid wood is a difficult job, i'm perhaps wrong but it looks like american walnut, isn't it ?
The SL orions woofers are firing in the opposite directions, so there is two opposite forces relied by a symmetrical rigid strucure, the two forces generate two equals moments in a opposite direction, there is a good canceling. The V frame structure moments of the two opposite directions forces are not located at the centrer of the structure because of its asymmetry.
The 8" vibrations can be avoided by the magnet mounting : https://www.linkwitzlab.com/orion-rev1.htm
 
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Thanks for your kind words.

It is indeed Am. walnut. 4 planks joined together. The glue-up came out OK so I spent routering a couple hours so far today. To make the outer perimeter clean/flush with the side of the enclosure. That was done slowly over multiple passes at the lowest 1k rpm. I'll tackle the roundover later today.

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The worse patch in the seam. It's maybe 1mm for a few inches. Should be able to hide it.

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I left a bit too much excess walnut on one side. Will use a straight edge guide bit on it first.

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The routering setup on the covered deck at the front of the workshop. I prefer working outside when sanding or routering because both create so much dust and debris even with the mutiple shop vacs and dust collection systems I run.

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Yeah, I know about the magnet mount for the 8". Used it on my Orions, works very well. And it's used here as well.
Pics of earlier versions of the steel/aluminum magnet mount below were posted before. This is the final version -- unless Mark wants to add holes to the sides.

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V-frame is not an option, imo, unless the "box" is overbuilt. And that's not worth it when W-frame works so well.

Downside of W-frame is that the cavity resonance gets uncomfortably low when the drivers are >10". In the test setup of the 12" drivers in the W-frame, that resonance fell to 190 Hz, from >300Hz in the 521 clones. I ended up using 120Hz/L8 (48 dB/oct) filter with the Flex 8 & that subjectively provided the best blend. No significant anomalies from the steep slope, afa several folks could hear over a couple test sessions.

OK, time to tackle the roundovers!
 
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After a few hours, routing on this box is 99% done. I might put a smaller round over on the bass opening... Or not. Lots of sanding, more black paint & oil finish still to go, not to mention wiring & connectors, but I can picture the drivers installed now. 😀

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Your router bit teeth will hit the wood fibers at 90° if you round over on the bass opening, it will require more sanding, is there any kind of chocolate odor when you route the walnut ?
You're right. It's not worth the effort, there's still so much to do.

I wanted to do it not for appearance but to keep the cavity from getting bigger, because the cavity resonance was already a low 190Hz, uncomfortably close to my desired 120 Hz XO. I'd already installed wedges in all 3 of the bass cavities to reduce their size & raise the cavity resonant frequency; I calculated the average depth of each cavity fell by ~1.5", which might have been enough for a 30Hz rise.

Haven't had a chance to check yet as the drivers won't be reinstalled until the enclosures are completely ready.

Chocolate?? If that was happening, I couldn't smell it anyway through the serious filters in the dust mask I use when sanding or routering.

I do have several producing walnut trees in my yard. 1500 walnuts one September. They smell nothing like chocolate. Interestingly, almost every part of the walnut tree is unhealthy for other edible plants that people grow.
 
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