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?


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.  A speaker that narrows with frequency, say a horn, will send less info to the side walls as frequency increases.  A ribbon or any planar device will also do this but it can depend on what frequency the planar portion of the speaker is working in. 

So imagine a ribbon working at 3K and above.  You wont get as much energy at 3K and above on first reflection points as they get fairly narrow even at 3K and get even narrower as you get to 10K and above.  This is easily demonstrated by rotating the speaker until it almost faces the side walls, you'll hear bunch of splash as you get more energy on it.  Also the wall material matters- glass is very different frequency emphasis than wood.   There are many different types of absorbers- some work well at HF, and some work better at mids and some are built to be LF absorbers with membranes. 

SO there is no universal answer to this other than to say if you have a wide dispersion speaker, the first reflection point absorption is critical to improving image.   If you have a narrow dispersion speaker you may not hear much difference.  Also you need to buy real absorbers like GIK, or make them, I like the 4 inch thick ones, they absorb more for the same wall space.   


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.


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!