Does the first reflection point actually matter??

Hsw wrote:  " Is this discussion only limited to lateral reflections? It seems to me the floor is the largest first reflection. "

The floor bounce usually is the strongest early reflection, but perceptually is is not as detrimental as its magnitude seems to imply.

The floor bounce doesn't have a strong spatial effect, as it occurs in-line with the direct sound from each speaker.   

The floor bounce does result in a cancellation (comb filter) notch in the  frequency response at the listening position at the frequency were the reflection arrives 1/2 wavelength behind the direct sound.   

From a perceptual standpoint, the floor-bounce notch can be filled in by energy which arrives within a few milliseconds, such as by the ceiling bounce.  The ceiling bounce and the floor bounce will have different notch frequencies and will tend to perceptually fill in one another's bounces.   

The floor bounce notch is most audible when there are no soon-arriving reflections to fill it in. An example of this situation would be when talking with someone outdoors.  There will be a lower midrange frequency response notch from the bounce off the ground or pavement, with no other reflections arriving to fill it in.  Walk indoors to continue the conversation and the timbre of the person's voice noticeably warms up, and I think this is at least in part due to the floor bounce notch being filled in, perhaps largely by the ceiling bounce.   

The argument has also been made that our ears are so accustomed to the floor bounce notch and other naturally-occurring comb filter effects that we largely tend to ignore them.  That's NOT to say that there is no benefit from minimizing or removing them - only that they do not tend to cause colorations which draw attention to themselves.   

Imo there IS benefit from reducing the magnitude of the floor and ceiling bounce notches, or otherwise breaking them up.  But it is also my understanding is that they tend to be perceptually relatively benign in a home audio setting.   

Duke

hsw, I'm only going to answer for myself here.  My understanding is that humans are naturally more adept at localizing sources in the horizontal plane.  Our outer ears are mounted on the sides of our heads and aren't especially well designed to pick up vertical clues.  Presumably, our brains are similarly well suited for localization of sources in the horizontal plane.   What I can tell you is that in my room, which is 14 ft wide with 8 ft ceilings, effective "treatment" of the side wall 1st reflection point is orders of magnitude more important than "treating" the ceiling and floor 1st reflection points in providing a deep and wide image with good localization of instruments and voices.  My floor is not carpeted, and my ceiling is typical texture over drywall.   I'm not going to say that rugs and room furniture don't matter, just that in most rooms, treating the floor and ceiling don't matter nearly as much as treating the side walls with respect to imaging.  If you have a room that is atypically wide, or speakers that don't have wide dispersion, you may see something different.  Also, what you do with the floor and ceiling can certainly impact other aspects of room performance.  Floor to ceiling bounce can be a big contributor to slap echo, as example. 

@erik_squires, have you tried what Duke is suggesting on the sidewalls?  I stumbled onto this idea of redirecting the sidewall 1st reflections to the front of the room several years ago quite by accident.  Every attempt on my part to reproduce the benefit of redirecting by using absorbance has failed.  The image just collapses.  Had I not experienced just what this technique can do myself, I might be arguing as you are.  

Floors are a different thing, but we don't spot treat floors.  We treat the entire area in front of a speaker. I've never seen anyone put down a 2'x2' carpet exactly in the first reflection point, and this is kind of what i mean.

Audiophiles at some point were encouraged to use a flashlight and mirror to find first reflection points and center acoustic panels there. I call that particular practice bunk. 

We shouldn't spot treat surfaces.  We should treat the surface.  That is, putting 2'x2' panels in exactly the side, rear and even floor reflection points is practically useless. What does work is to treat the floor, side and rear.

Get a carpet to put in front of the speaker, treat the side walls and rear wall and wall behind the listener. Where the mirror points are won't matter.

Best,

E

Erik wrote: " We shouldn’t spot treat surfaces. We should treat the surface. That is, putting 2’x2’ panels in exactly the side, rear and even floor reflection points is practically useless. What does work is to treat the floor, side and rear. "

So if I understand correctly, you are saying that treating the relatively small area where a reflection occurs is "practically useless" - instead, we should treat the ENTIRE room surface - the entire wall, or the entire floor, and/or the entire ceiling.

Am I understanding you correctly?

And, just so we’re on the same page as much as possible, can you describe what you mean by "treat"?

Thanks!

Duke

So if I understand correctly, you are saying that treating the relatively small area where a reflection occurs is "practically useless"

Yes, in that I believe most audiophiles would be unable to tell if those treatments were at the reflection points or not, and that in many cases 4 panels of 2'x2', no matter how well placed, would be unable to effect an audible improvement.

And, just so we’re on the same page as much as possible, can you describe what you mean by "treat"?

By this I mean to alter the surfaces by increasing the absorption and decreasing the ability of those surfaces to throw a coherent reflection by both absorption and diffusion.



Best,

Erik