Quote:From what I learned, know, and even heard Steve mention is that absorption is the #1 thing to set up and then diffusers. Absorption helps with frequency control and diffusers are for imaging. Diffusers I don't think will do much for controlling frequencies.
The last part of this paragraph about diffusers improving frequency response is an often misunderstood point.
If you think about how absorbers work, you'll see that diffusers also help with frequency. I'll clarify by using subs to illustrate a point, because it's painfully apparent at that frequency, what our issue is (reflections).
Let's look at it this way - why do we have bass traps? Well, it's not because the the bass is too loud and we want to make it quieter, no. It's because as the bass bounces between the walls you get hot-spots where a positive wave meets another positive wave, and we get dead-spots where a positive wave hits a negative wave and they cancel each other out. So we place traps to try and tame those reflections so they are less damaging to the original wave. If you were outside, playing your subwoofer in an open field, you would truly hear the bass as it is because there are no reflections adding and subtracting to the source wave from the driver.
So why wouldn't this also apply to the rest of the frequency spectrum?
It absolutely does, which is why we use *broadband* traps at reflection points to deaden the reflection and allow our clever ears/brain to hear the source more accurately. We are deadening those reflections, so they don't muck with the original wave coming from the drivers. When we have strong reflections mixing with the original source, we get comb filtering...which is basically like the hot-spots and dead-spots that are so apparent in the subwoofer frequency. Except at higher frequencies it would look like sharp peaks (and valleys) in an otherwise flat response making the response look like a comb if you saw it on a scope.
So how does this comb filtering effect what we hear? Well, lets take a saxophone for example; it has a particular sound which is rich in harmonic overtones, and that gives it its particular timbre or "voice". If you have comb filtering you are shifting or changing those harmonic overtones and your sax loses it's timbre...it's flat and less believable. When it's right, it's "realistic and engaging".
So, circling back to diffusers - how do diffusers help with frequency response? Well, technically exactly the same way absorbers are, but in a less subtractive way; basically it's breaking up that direct-reflection and turning it into many smaller reflections in many different directions so it's less damaging to the direct wave. The difference is absorbers are sucking energy out of the reflections, and diffusers are keeping (most) of the energy in the room and just redirecting those reflections.
Diffusers also have the advantage of being able to add a bit of a time delay (bouncing around in those wells before exiting) to your reflected sound which at least makes your room seem bigger, if not completely making the walls disappear! That's something absorbers simply can't do. Diffusers really make the music more engaging.
TL;DR ;D
Both absorbers and diffusers help with frequency response by dealing with reflections that damage the original sound wave.
IMHO - if I were starting fresh, I would start with absorbers to treat problems, then bring in diffusers to bring life back into the room and assist (with time delay) in making the walls disappear. *Both* help with frequency response.
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