Need Room Treatment Advice. Willing to pay! - Page 4

Hi Jim, as far as I know 1/6th octave is about the closest resemblance at mid and higher frequencies to our ear's ability to discern timbral colorations. The ear's loudness summing bandwidth is wider, more like the traditional 1/3rd octave. So even 1/12th smoothing is excessive

I dont think most ears can discern a <1db difference. Given the shown difference would be even less at 1/3rd octave (practically two lines on top of one another), I chose to show the 1/12th octave results. Had the difference been more than 1db, I would have shown 1/6th or 1/3rd.

The larger point is this:

1) A -10db at 24ms specular return (aimed right at the mic) doesnt make an audible difference in terms of FR.
2) The comb filtering caused by such a return may or may not be discernible (not to my ears)

Given the current direction of the thread, and the relevancy to the OP's question on how to treat his room, knowing what reflections are harmful and which are not seems relevant to me. It would be nice to know at what delay and magnitude (an ETC) Ethan's example was representative of. I kinda assume his were early reflections (<10ms) and possibly higher magnitude (-10db relative to the direct signal) than mine. Ethan?

Sounds like a good option, especially if mounted on the side walls flanking the seating area (I do not know where you planned to put them) and yes, do make sure to fill them so they do not resonate.

The depth relates with where the diffusion effect ceases at low frequencies. But the deeper the diffusor, the further one must be away from it to avoid undesirable side effects. I'm using 4.5" diffusors at a minimum of 40" from closest listener's ears with no problems.
That sounds more like an absorber to me, not a diffusor.

Yes.

To ensure identical settings I opened the same file again and exported the "with treatment" measurement from the same session, attached here.

--Ethan

It's not misleading, and it does affect what we hear. Hang on, I'll get to that. I agree that comb filtering that's different left and right is not as damaging as when the same response reaches both ears. If you run mono music through a recording studio flanger effect (comb filter) and play that through a loudspeaker, you will absolutely hear the severely affected response. But in a room the response is different left and right, so the nulls in one ear are not likely present in the other. However - and this is the big point - such a skewed response that changes drastically with small head movements harms imaging. As you move around slightly, the sound source locations change. This does not happen when early reflections are treated fully with absorption.

Yes, exactly. The measurements I posted were taken near field, which reduces the strength of the reflections. If the microphone had been farther back in the room, the response would be even more skewed.

Yes, what you (and some others) miss is how the changes in comb filter frequency versus position harms imaging, as explained above. I know anecdotes are not proof of anything, but here's a very short story anyway: When people visit me and hear my HT system playing stereo music, they're always surprised by the stable imaging and pinpoint phantom center. One time AlexO, a regular in the Stereophile forum, drove out from NYC to visit me. I have three front speakers, all active models with small power LEDs, and the middle speaker's light stays on while playing stereo. Alex was certain the middle speaker was playing as he listened, and he had to get up and walk right up to it before he believed me that it was not playing.

--Ethan

As we are talking about speakers and not headphones, both ears hear both speakers. The nulls from one speaker are somewhat "filled" by the sound from the other speaker, so both ears hear sound that is less severely combed.

Yes, of course, and I didn't mean to imply that one ear hears only one speaker. But the response at each ear is different, regardless of the loudspeaker sources. If you cover one ear it's easier to hear the comb filtering. Regardless, the main point is the comb filtering is not only a problem for frequency response, but also a cause of image-shifting.

--Ethan