A force canceling subwoofer for implementing DBA's ( and Trinnov variant) around the periphery of a videowall based on the Purifi PTT10.0X04-NAB-01.

[kemmler3D]

I have "force cancelling" subwoofers that I designed myself.

View attachment 388718

The force cancelling effect does not work. Music with a lot of bass can make these subwoofers go walking. I am not sure what I did wrong!

Hmm, interesting... I guess if the drivers vary significantly due to manufacturing tolerances they won't get the same excursion per voltage, and so the force doesn't cancel after all? (seems unlikely)

Also, the force only cancels along one axis, but if they are mounted asymmetrically or the drivers exert other forces on the housing, I guess it could move.

Somewhat related:

It occurred to me that 3D printing a small-ish sealed enclosure and filling the walls with concrete might actually be a reasonable approach for a dual-opposed sub. You can make the interior space spheroid to avoid any kind of panel resonance, make the outside look fancy like a KC62, etc. Whatever CAD can provide.

But it still doesn't seem like a slam dunk in terms of bang-for-buck against (say) a low-tier SVS, after drivers and amps.

Anyone know of 500w plate amps and reasonable drivers to go into a budget implementation of one of these?

I think the material to build the housing for one might cost as little as $30-40, building it *should* be pretty easy, and the finish should end up pretty nice.

But I am not sure if it's really worthwhile...

 

[CINERAMAX]

All I can say is that the second in command at Trinnov which is the waveforming expert said that force cancelling prevents rattling of the walls krix showed this with a dual opposed facing each other venting through a slot, the founder of Speakercraft and part owner of Origin said sheetrock rattles the most in the 80-100hz when a subwoofer is wall mounted.

 

[Impossible]

Force cancelling prevents the speaker rattling in the wall which reduces wall rattle but the energy/sound propagating out can always be transferred to the walls. If you have 2 guns back to back and shoot at the same time, the guns won't move going back to newton's law of equal and opposite force but the bullets are doing their own thing.
Maybe he meant reduces rattling.

Found this not read it yet.

US10631096B1 - Force cancelling transducer - Google Patents

A transducer assembly having a frame; a dual diaphragm and voice coil assembly suspended from the frame, the dual diaphragm and voice coil assembly having a first diaphragm and a first voice coil attached thereto and a second diaphragm and a second voice coil attached thereto, wherein the first...

patents.google.com

 

[Impossible]

Have you considered the new ascendo the 28 sub. Maybe 4 of them 2/3 in the front, 2 in the back. Recent results of people implementing waveforming in a none optimised way have still shown great results.

Depth of 30cm (10 inch) and can come in custom depth of 20.5cm (8 inch). This gives much more room to isolate the sub to reduce transfer of energy from the enclosure to the wall.
Maybe 2 layers of dynamat to surround the sub followed by one layer of foam sound absorption.

This would be less then the purifi ptt10 depth. Less excursion required so will help with rattle and also much better group delay I suspect then a 10" sub woofer.

Its also less risky then making your own and less time consuming.

I also think the kef in-walls are not force cancelling and may need to be crossed over higher.

 

[CINERAMAX]

Oh I considered it alright, what a great invention, but not appropriate for this Project.

Marke Seaton was pretty convincing that his low profile 21" 7 of the would work in this room in a cylindrical waveforming application, you can't beat the price for the performance there.

In the meantime, I have been advancing the development of high-performance videowalls. The Frankenwall integrates the latest Samsung The Wall LED driver chips with Sony Crystal LED MIP Flip chips, binned to achieve otherwise unattainable perfect uniformity in a flip-chip LED screen. Additionally, the extra layer of glossy filtering has been removed to eliminate reflections, resulting in a charcoal matte surface that delivers pure, flawless pixels.

 

[Impossible]

So just to confirm, your not going in wall with the subs now?

If you have any spare purifi ptt10's let me know.

 

[CINERAMAX]

So just to confirm, your not going in wall with the subs now?

If you have any spare purifi ptt10's let me know.

I asked the owner about the 4 units for you.

 

[Impossible]

Thank you

 

[Flaesh]

for a 12" depth

and 12" width

 

[charlielaub]

and 12" width
View attachment 394711

OP didn't respond to my post, so maybe he did not understand the resonance effect... A 15dB peak at 200Hz would not be a great feature of your new $20k subwoofer installation... It's important to stress that even if you use a lowpass filter this may not completely eliminate the peak because it is mechanical in nature (arises from air moving within the cavity) and not electrical (not from the driver, crossover, or amplifier). A relatively narrow peak like this will give rise to ringing of the time domain response.

 

[Impossible]

OP didn't respond to my post, so maybe he did not understand the resonance effect... A 15dB peak at 200Hz would not be a great feature of your new $20k subwoofer installation... It's important to stress that even if you use a lowpass filter this may not completely eliminate the peak because it is mechanical in nature (arises from air moving within the cavity) and not electrical (not from the driver, crossover, or amplifier). A relatively narrow peak like this will give rise to ringing of the time domain response.

Thanks sensei, I learnt something. This explanation was very helpful.