FlexFusor or other behind planar speakers?

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brucew268

FlexFusor or other behind planar speakers?
« on: 16 Feb 2022, 01:14 pm »
I'm trying to determine the best options for a planar (dipole) speaker in my room. With a planar speaker set up about 3 feet in front of the wall and me 6.5' away the room feels a bit unnaturally pressurised, which does not happen with my box speakers.

My first thought was, being more directional, the speakers were causing reflection issues on the wall behind me. But then the dipole has a strong back wave coming off it so thought of diffusion behind the speaker.

  • I tried large round rattan baskets at reflection points behind me which helped just a little.
  • I tried VersiFusors maybe 20" behind the speakers which seemed to do what I wanted but I don't trust that the EPS would hold up so returned them while I make a decision. (Being in my main lounge means they have to be moved into place whenever I want to have a proper listening session -- daily.)
  • So FlexFusors may be the answer since they are VersiFusors with a light wooden frame and frabric around them.
  • Alpha seem more geared to being absorption with a scatter plate than proper diffusion.
  • PolyFusors are cylindrical (diffusion or scattering?) and absorption

Am I likely to get best results in this application by sticking with a QRD diffuser like the Flex or Q7D, or will something else likely do as well here? (Generally planar speakers are said to do better with 1D diffusion rather than 2D.)

Mike-48

Re: FlexFusor or other behind planar speakers?
« Reply #1 on: 16 Feb 2022, 07:08 pm »
My situation is similar but not the same as yours, as I'm using front-firing electrostatic-panel hybrid speakers (Janszen Valentina P8) about 32" from the front wall. Despite the absence of direct rear radiation from these speakers, when I started out with a bare front wall, I got a glaring impression on some material. That may be the same as what you called too much pressure.

I reduced glare by adding six Vicoustic skyline-type diffusers across the front wall -- six panels roughly 24" x 24" each. I also added two ASC half-rounds I had on hand from a previous room. Those treatments really helped reduce glare, so I left them in place for a couple of years.

Gradually, I replaced the skyline diffusers with GIK Alpha Pro 6A panels (with 1D scatter plates) in the same locations. The improvement in bass trapping has been noticeable and helpful. The scatter plates prevent a dead room, and perhaps they send less sound up to the ceiling. I don't find them inferior in this situation to the depth-based diffusion provided by the skyline diffusers, and as I said, the bass trapping is a nice addition. (My room tends to be bass-heavy.)

I expect that what's needed with dipoles will be a little different, but I hope my experience generates some ideas for you. Good luck with your setup!


brucew268

Re: FlexFusor or other behind planar speakers?
« Reply #2 on: 17 Feb 2022, 08:15 am »
Hi Mike,

I'm not sure I would call it glare. I think of glare as a glassy sound that makes details in that frequency region a little opaque. I'm not sure how to further describe this except as pressure, almost like the pressure of a standing wave except that I think of those as is in the bass region and I don't actually notice a particular frequency (unless it's one above my auditory range).

As I said, this doesn't happen when I play box speakers in the room.

That's why I assumed it might be the wave form coming off the back of the Magnepans possibly a phase issue between back and front waves. In any case, the 17 root QRD diffuser seemed to handle it (VersiFusor / FlexFusor). The PolyFusor and Alpha look a bit better in a room but I don't know if they would accomplish the same thing so thought to ask of the GIK folk or other acoustic engineers.

BTW: my room is nearly square, 14x13.5', but directly behind me is an 4.5' opening to another room of similar size.

Mike-48

Re: FlexFusor or other behind planar speakers?
« Reply #3 on: 17 Feb 2022, 05:36 pm »
I'm not sure I would call it glare. I think of glare as a glassy sound that makes details in that frequency region a little opaque. I'm not sure how to further describe this except as pressure, almost like the pressure of a standing wave except that I think of those as is in the bass region and I don't actually notice a particular frequency (unless it's one above my auditory range).

As I said, this doesn't happen when I play box speakers in the room.

That's why I assumed it might be the wave form coming off the back of the Magnepans possibly a phase issue between back and front waves. In any case, the 17 root QRD diffuser seemed to handle it (VersiFusor / FlexFusor). The PolyFusor and Alpha look a bit better in a room but I don't know if they would accomplish the same thing so thought to ask of the GIK folk or other acoustic engineers.
As what we mean by "glare" is so subjective, it's possible that we are describing the same thing. Or not. I surely would say it was a feeling of pressure, but in my case, it was at a certain frequency.
Flat panels tend to be directional and IME more prone to cause such things, as the reflections are more focused. When the setup is perfected, I do think panels can sound wonderful.

I hope you get the input you are looking for from the specialists. My experience has been as a user of acoustic treatments in several audio rooms and a constant tinkerer.

Happy listening!

brucew268

Re: FlexFusor or other behind planar speakers?
« Reply #4 on: 17 Feb 2022, 06:15 pm »
As what we mean by "glare" is so subjective, it's possible that we are describing the same thing. Or not. I surely would say it was a feeling of pressure, but in my case, it was at a certain frequency.
Flat panels tend to be directional and IME more prone to cause such things, as the reflections are more focused. When the setup is perfected, I do think panels can sound wonderful.

I hope you get the input you are looking for from the specialists. My experience has been as a user of acoustic treatments in several audio rooms and a constant tinkerer.

Happy listening!

Good thoughts, thank you. Nice room!

JWL.GIK

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Re: FlexFusor or other behind planar speakers?
« Reply #5 on: 18 Feb 2022, 07:29 pm »
For sure dealing with the rear wave of a dipole speaker is important, and there are different strategies to do so depending mostly on preference.

One is to use broadband absorption, as thick as possible. The bass trapping on the front wall always helps, but fully absorbing the mids/highs on the rear wave sort of defeats the purpose & sonic characteristics of dipole speakers so it's nto the most popular option, even though some prefer it.

You can also use diffusion, which is a much more natural sound through the mids and preserves some of the rear wave energy in the room. However, unless your diffusors are several feet thick they are limited in bandwidth, ie, diffusors are more of a midrange thing, commonly operating from 500Hz-1kHz ish up to maybe 4 or 5k for most devices small enough to ship.

As a result my preferred method is to use hybrid devices that give some diffusion and also bass trapping. Thick binary diffusors (like our Alpha panels) are a great and very flexible option that I love in this role. I also like poly diffusors (like our Evolution Polyfusors) that give both poly diffusion and some bass trapping.

Feel free to reach out to us directly for more specific guidance.

brucew268

Re: FlexFusor or other behind planar speakers?
« Reply #6 on: 20 Feb 2022, 10:02 pm »
Thank you for the input. Since I already have bass traps across the room corners behind the speakers, that doesn't seem to be the presenting need and I could just add diffusers in front of the bass traps.