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?


@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.

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.

Which I agree with, but is subtly, different than what I am arguing about. :)

I don't think the laser line matters so much as having the area in general treated.