Do diffusion products affect room measurement or only produce subjectiv spaciousness?

[caesar]

Do diffusion products affect room measurements in any way? If so, how?

Or is only about increasing subjective spaciousness?

 

[DonH50]

Frequencies diffused will not contribute the same at the measuring point, same as for your ears. If you use diffusors to break up some reflections, the measurements will show reduced energy at those frequencies. If you add diffusors to provide additional reflected energy at the listening position, a measurement mic will register the increased energy. Impulse response will be similarly affected, along with decay/reverb measurements and so forth. In short the effects are measurable, and will show up in time and frequency domain plots if you care to make them.

Same is true for absorptive products, natch.

As always, taking the right measurements and interpreting them correctly can be a challenge.

I use measurements to help confirm optimal placement of room treatment.

FWIWFM - Don

 

[JonFo]

^^^ +1 Don is correct

I've been measuring and testing room treatments for large dipole electrostats for over a decade, much of it documented in these two threads ( Part 1 & Part 2 ) over at the MartinLogan Owners club that are full of measurements and other pics of room treatments and their results.

Just to provide one simple example of how a room treatment effect is clearly visible in a measurement, here is an impulse response of a speaker placed close to wall, then treating said wall with broad-band absorption:



It totally kills that nasty spike and cleans up some of the comb filtering (visible in the Bode plot in the threads I linked to).

 

[Ethan Winer]

Do diffusion products affect room measurements in any way? If so, how? Or is only about increasing subjective spaciousness?

You already got knowledgeable answers and I can add a bit more. Most important, understand that every change that is heard can be measured. Now, I'm not talking about changes that are imagined, which also happens! But any change that is consistently heard will show up in a relevant measurement.

How diffusion changes the perceived and measured sound depends on where it is in the room, and where it is in relation to your speakers, and to you (or the measuring microphone). The most common place for diffusion is the rear wall behind the listener.

--Ethan

 

[caesar]

Gentlemen, thanks for the replies. How do the diffusion measurements jive with the absorption measurements? Are they of different units? How can they be connected to holistic view of the room?

 

[JackD201]

Hi Ceasar. One thing to remember is that there is a place for both. Diffusions reasons for being is to create spectrally even coverage throughout the listening area. It is the homeowner's call whether this is important to him or not. Solo listeners require little more than a single sweet spot. In this instance diffusion/even coverage throughout is not a must and mainly absorption will go a long way.

If a person that likes to do different things and move around the room a lot, if a person likes to entertain, then diffusion becomes very helpful.

It also must be pointed out that diffusion products also have absorption coefficients and that these coefficients must be a part of the acousticians calculations toward the complete solution package.