Does the first reflection point actually matter??

Brad,

The one issue missing from this discussion is your impression of acoustic treatment at first reflection points completely depends on how wide a dispersion speaker you actually use.

For the purposes of this argument, alone, I want to argue that first reflection points don't matter, ever.

Again, I don't mean that room treatment doesn't matter.  I just argue that the idea that the first reflection points are some sort of magical acupressure point for speakers seems wishful thinking to me.

What does matter, a lot, is the overall acoustic field. An even decay rate and proper balance of diffusion and absorption.  But if you take a dozen panels placed around evenly in a room, I don't think you could tell that the 1st reflection points do anything more special than the rest.

And I am also _not_ making the argument that speaker to room acoustic matching doesn't matter, it does a great deal.

Best,

E

Yeh Brad that is a very valid point!

Some horns are symmetrical some have more width than height. That gives narrower spread up and down. And will result in less issues with ceiling and floor first reflection points. That I have experienced.

Eric I would put it like this. As we KNOW that the FIRST bounce (reflection point IS the strongest/highest in dB. Then it more energy (dB) that we can transform to friction with absorbing panels. And 2nd, 3rd reflection, and so on is, each decreasing in energy for each reflection that is done.

So if we only have 2 or 4 panels and want to absorb as much reflections from the room boundaries. Where should we places those few panels to get the most absorption as possible with those few panels? Yes at the strongest one of course.

If we wanted to preserve the side reflections but we wanted to absorb the same amount of dB but only treated the 2nd, 3rd and so on reflection points then we need much more coverage than what just 2 or 4 panels could contribute with.

So we see that first reflection points is giving us most bang per square unit of panel/treatment.

(As for me I want in general listen on what is in the recording and not get the "color" and delay of room boundaries.
The "color" is defined by what material the room boundaries consist of. We know that dry walls and concrete walls reflect different amount of dB for each frequency (frequency response). So we can consider that in a concrete there inside that wall sits a mixing engineer that use litle more level on the bass faders on his console compared to the mixing engineer in the dry wall.
Sorry for that dumb analogy.) :D

As my ceiling is only 6'6" high in my listening area, and it's *not* acoustic tile. It's a fairly hard surface. Speakers are not too close but it's a low ceiling. I'm sure there's a critical 1st reflection point there. Some have helped me try to troubleshoot my space a bit (thanks, brownsfan!). The side reflection points are less an issue. I can imagine I should do something with the ceiling, but I don't want to go down a room treatment rabbit hole at the moment. (I'm not a skeptic or unwilling to spend if it's worth it, but it represents a genuine investment of time I don't have right now.)

@hilde45, my pleasure.  As for your ceilings, don't fix it if it ain't broken.  If you are getting good imaging and vocal articulation, and you are not being troubled by slap echo, count yourself lucky and focus on things that will make a difference.   We are much more sensitive to early reflections in the horizontal dimension than in the vertical dimension.

Your room is so atypical in its dimensions that general rules of thumb may not apply, as long as you stick with the long wall orientation.  In your room I would still worry about front and back walls first.  Treating those surfaces is likely to do more than even treating the corners in your room. 

I got into room acoustics because my system sounded lousy despite the fact that I had superb gear. Treating the room was the right approach in my room, but It may well not afford you that same level of improvement. Your room and system positioning eliminates some typical problems, but affords you less opportunity for further improvement on those problems that remain.   It really could be a non-productive rabbit hole for you.  Cheers!

@erik_squires wrote: " For the purposes of this argument, alone, I want to argue that first reflection points don’t matter, ever."

Early lateral reflections contribute to spaciousness and expand the "apparent source width", according to Floyd Toole.

When "presence" is lacking the earliest reflections are the most responsible, according to David Griesinger.

So apparently early sidewall reflections are neither entirely beneficial nor entirely detrimental. They do some things which are desirable, and some which are undesirable.

Earl Geddes is aware of both the benefits and the detriments of early reflections, and here is his thinking on the subject:

"The earlier and the greater in level the first room reflections are, the worse they are. This aspect of sound perception is controversial. Some believe that all reflections are good because they increase the listeners’ feeling of space – they increase the spaciousness of the sound. While it is certainly true that all reflections add to spaciousness, the very early ones (< 10 ms.) do so at the sake of imaging and coloration. There is no contention that reflections > 20 ms are positive and perceived as early reverberation and acoustic spaciousness within the space. In small rooms, the first reflections from an arbitrary source, mainly omni-directional, will never occur later than 10-20 ms (basically this is the definition of a small room), hence the first reflections in small rooms must be thought of as a serious problem that causes coloration and image blurring. These reflections must be considered in the design [of the loudspeakers] and should be also be considered in the room as well."

My own investigation (controlled blind testing, but nothing peer-reviewed) leads me to believe that early reflections are strongly involved in conveying a sense of the playback room’s boundaries being nearby. The weaker the early reflections, the less "small room signature" the playback room superimposes atop the recording venue’s acoustic signature, whether it be real or engineered or both.

I have been involved in several professional recording studio projects, in which the acoustician has designed angles into the sidewalls which geometrically preclude early sidewall reflections at the mix position. This is to facilitate clearly hearing the acoustic signature which is on the recording, without the mixing room’s signature being dominant.

So imo what happens (or doesn’t happen) at the first sidewall reflection points makes a difference. Whether or not this difference "matters", and if to so what extent, is, I suppose, a judgment call.

Erik again: "if you take a dozen panels placed around evenly in a room, I don’t think you could tell that the 1st reflection points do anything more special than the rest."

This would be true in a large room, but not in a small room. In a large room the reflections paths are much longer and there are so many reflections that the reverberant energy is effectively uniform throughout the room, such that WHERE you place acoustic treatment doesn’t matter - the net effect is the same. But in our small home listening rooms, we experience discrete reflections. And the earliest and loudest of those reflections are the ones which have the strongest effects, whether their effects be beneficial or detrimental or both.

Duke