Quick, tell me what frequencies in this graph are room modes, and which are boundary issues?
The mere question indicates you don’t know what you are looking at. Hint: look at the measurement again. It says right there.
Oh really now. You mean this graph? I know exactly what it is showing. Do you? There are clear room modes in the response. There are clear boundary effects in the response (and not low frequency reinforcement which can be corrected). Do you know which is which? Can room correction fix this? No. Can acoustic panels fix this? Absolutely.
The graph below shows that the total number who preferred absorption or diffusion exceeded the number who preferred reflective. The only other conclusion is those that preferred reflective used a higher volume. After adaptation (3rd trial) the diffuse group referenced to a lower volume and worked faster than the other two groups.
Here is the thing, though, referencing this paper was a bit of a intentional trap. The only condition in that paper that applies to your side wall situation well is the baseline. The relative path distance of your first reflection off the side wall (at least on left) is probably at best 2 msec (and looks like less) and those speakers have wide dispersion. I do commend you on using different left/right toe-in to balance the sides, made possible by a speaker with good dispersion.
The majority of the Brad thesis looks at a much different scenario, where "first" reflections are 4 and 8 msec, not to mention large reflections from both left and right speaker from the safe reflecting surface. Those times are more indicative of speakers far from a side wall and also would never occur in a home environment. The primarily lateral reflections would also not be a case for a home environment and would behave differently upon interaction with torso/head/pinna. This is the problem when trying to apply the result of experiments with drastically different conditions. The results of the experiments indicate the potential for preference in a more reflective environment when the first reflections are larger in time, but given the primarily lateral reflections, even that conclusion is suspect. You know, science.
I know you are a fan of Toole. Most of us are. Review specifically what he said,
Chapter 6 shows that in normal rooms the first lateral reflections in rectangular rooms of normal listening and control room dimensions are above the threshold of audibility. They can be heard, but are below the threshold at which the precedence effect breaks down, so there is still a single localized image. They fall into a region where there are varying amounts of "image shift" - the image is either perceived to move slightly or to be stretched slightly in the direction of the reflection. I, and others, spent hours in anechoic chamber simulations of direct and reflected sounds and can confidently state that the effects, while audible in direct A vs. B comparisons, are rather subtle. Was it ever unpleasant? No, the apparent size and/or location of the sound image was just slightly changed. The effect was smaller than tilting the head a small distance left or right of precise stereo center. The dramatic change happened when the precedence effect broke down and two images were perceived – that was a problem. The strength and spectrum of any reflection depends on the strength and spectrum of the sound radiated in that specific direction by the loudspeaker, and by the frequency-dependent acoustical performance of the reflecting surface
I could quote more and reference his book, but in summary, nothing is perfect, use what you want (at first lateral reflection). That use what you want is critical, as not all listeners, or even audiophiles listen with the same goals and may not even listen with the same goals all the time. In a music space targeted at casual listening or for the more casual listeners in the household, a space with more side wall reflections has a high likelihood of being preferred. For those who are into critical listening, muting the sidewall reflections can sharpen perceived imaging leading to a higher preference. Are you a casual or critical listener Amir?
In terms of throwing out those "professionals", I would have to throw you out as well for your insistence on only your way when your luminaries don’t even say what you claim.
What is unfortunate is I agree with you far more often than not, but you like so many here let your ego get the better of you and you let that drive a need to be right to the point that you make poor use of the available science, drawing conclusions that are beyond what the science is able to reliably claim.
Toole (with others) did do testing on reflections, but even those had limited scope, and they were done in anechoic conditions which may have either amplified the effect or muted it. I personally would lean towards the former, but I can only lean, not state, as the data is not there.
One thing is clear, there are not volumes of research on this very specific topic of acoustic panels of diverse properties with the diverse speakers, or even on speakers with good dispersion properties, in listening rooms of diverse proportions. There is some research, sometimes somewhat related, the rare bit closely related and some that is only loosely related.
See the title? "Estimated in-room response" which we formally call PIR (Predicted In-Room Response). This can even be used to predict listener preference although the formula can misfire.
- This is the steady state response
- This is a spatially average response, not the response at a particular spot, in a particular room, with a particular set of speakers, placed in a particular spot, and with the listener at a particular spot.
Bottom line, don't go slapping mattresses all of your everyday room. It is not necessary and will uglify your room and likely not have the effect you think it will have.
Bottom line few are recommending that. As well, carpets only treat the floor and are narrow in absorption no matter how thick
