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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

Showing 3 responses by tobes

tobes's avatar
tobes
436 posts
 
I've found treating first reflection 'zones' to be very beneficial in my 6 x 4.3 x 2.7m (L/W/H) room.

Many other things come into play of course. Optimum speaker positioning for best sound balance is fundamental and should be determined before adding treatment IMO - the latter should not be used as a bandaid for lazy positioning/toe-in etc. 

I used experimentation to determine what sounded best to my ears, propping up panels with stacks of books or whatever else I had handy so I could move/orientate panels and then listen.
I found too much absorption on the side reflection points over-damped the sound. I opted for Vicoustic Wavewood diffuser/absorbers in that area, which sounded much more balanced than my thick DIY absorber panels.
Treating the ceiling reflection 'zone' between the speakers and listening position with eight 600x600mm diffuser panels provided one of the most profound improvements in clarity and image focus/stability.
https://systems.audiogon.com/systems/2229#&gid=1&pid=1
tobes's avatar
tobes
436 posts
 
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.
tobes's avatar
tobes
436 posts
 
Yes, reflections can 'enhance' the sound - though unchecked they will play havoc with precise imaging/scaling and the individuality of recordings.
Some can't get enough of reflections - Amar Bose built a company on speakers leveraging enveloping reflected sound. Not for everyone though. 

I've certainly enjoyed previous systems in rooms without any acoustic treatment, though wouldn't go back to that now.
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