Does the first reflection point actually matter??


Hello my friends,

So please read the whole post before commenting. The question is nuanced.

First, as you probably know I’m a huge fan of the well treated room, and a fan boy of GIK acoustics as a result, so what I am _not_ arguing is against proper room treatment. I remember many years ago, perhaps in Audio magazine (dating myself?) the concept of treating the first reflection points came up, and it seems really logical, and quickly adopted. Mirrors, flashlights and lasers and paying the neighbor’s kid (because we don’t have real friends) to come and hold them while marking the wall became common.

However!! In my experience, I have not actually been able to tell the difference between panels on and off that first reflection point. Of course, I can hear the difference between panels and not, but after all these years, I want to ask if any of you personally know that the first reflection point really matters more than other similar locations. Were we scammed? By knowing I mean, did you experiment? Did you find it the night and day difference that was uttered, or was it a subtle thing, and if those panels were moved 6" off, would you hear it?


Best,


Erik
erik_squires
"In a modest, average home listening environment, you can’t do much for the acoustics with just 4 panels, no matter how ideally placed they are."

why 4 panels? 2 for each side walls, one for behind the listening position, 1 for ceiling (but really a cloud needs to be at least 2-3 panel wide) and 1 for the floor= minimum of 5.
not sure who told you 4 (I guess some dont treat the floor)

the definition of FRZ is at least covering the 5 early reflection points. so only 4 panel is not reallya chieving a free-reflective zone (FRZ)

" Part II:
The overall decay rate of the energy in the room will probably so obscure the original and early reflected signals requiring a minimum critical mass of room treatment, or minimum sound field quality that must be achieved before those original 4 panels mean anything. Control the reverberation time first, and with 4 panels you are barely getting started."

this is quite confusing. early reflections are well established to be detrimental to SQ. secondary reflections (which you refer here as "sound field") have been well established to actually be desired for good sound. hence some studio room desing with trying to actually reflect the secondary reflections to the listening position.

" Part III:

"Once the overall sound field is treated, the _exact_ placement of the original 4 panels. becomes moot. You can move around the room and everything sounds good, no matter where you are, and no matter if the current reflection points (which change based on your position) are covered or not."

the definition of a early reflection must be located at one spot. its that one spot that determine the early reflection points. if you want to cover early reflections with multiple listening position that are far apart from each other, this is a almost impossible (unless you have every listening position on the same couch for example, there youd just have to have wider panels to englobe every different listening position) task as each different listening position will have its own different early reflection.

" Part IV:

"While the overall idea of our ears seeing / hearing mid-treble frequencies as light beams is attractive, it is my experience that even then we hear not photonically but statistically. Covering up that magic reflection point to 1 ideal seated location is a trivial if not imperceptible change. Treat early reflections statistically, not precisely. "

what a bunch of baloney. early reflection points are physics. its not magic, they are a fixed point related to the listening position.

about the behind the speakers panels. by definition, there’s no early reflections coming off behind the speakers (unless your speakers are toed in 45 degree). those "behind the speaker reflections" are called SBIR and its a entire different discussion.

just to add a bit, early reflections are those over the 300hz barrier. bass frequencies being omnidirectional are not related to early reflections. for bass, you need deep bass traps, as deep as possible.

sorry if yesterday ive acted a bit rude, in retrospect it was. sorry
What a bunch of baloney.
Wait a minute. Wait just a doggone minute. The man clearly said:
"it is my experience that even then we hear not photonically but statistically." You call that baloney? Word salad, I say!

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Another observation is that low bass is radiating omnidirectional so those low frequencies are radiated behind the speakers. I see great corner bass absorbers. But there is also thin foam that will not help against that the bass is reflecting from those surfaces. Instead those foam will only take hi frequency reflections and also contribute towards "over-damped" feeling. Maybe remove or replace with thicker absorbers. 

I found some mid/high absorption behind the speakers to be beneficial, the corrugated foam is there for that. As you say, it won't provide any absorption at low frequencies. It's a balancing act though, too much absorption definitely kills the sound. I've tried diffusers in place of the absorbers in that position, but I prefer the mix of both.

When my house was built I had some input into the room dimensions, which follow one of Sepmeyers ratios to avoid stacking of bass modes. This seems to have alleviated the need for heavy bass trapping, I certainly don't have any obvious bass drone or boom.
It probably also helps that my ATC speakers are blessedly free of bass bloat. Though quite extended, the active SCM100 maintains iron fist control of the bass for a taut linear sound. 

Is those cool white 3d diffusers the "styrofoam" or other material? 
They are Vicoustic DC2 styrofoam diffusers. Lightweight and easy to hang with removable 3M velcro tabs.  
The diffusers can be applied more liberally than absorbers before detrimental effects on balance - but everything has its limit, so best to add any treatment in steps rather than slathering it everywhere.
This has been an interesting thread. I’ve got a buddy who has gone completely opposite.

14x15’ room with 10’ ceilings, hardwood on concrete, drywall... listening sofa backed up to the rear wall... subs in both front corners... speakers pulled out 6’ from the front wall and positions to take advantage of reflections to create a sound presentation that can best be described as total immersion.

Ok, maybe imaging is not the best and some songs can be a little bright but overall the sound is very lifelike and enjoyable.