Free IACC Tool

[RayDunzl]

Do you know your interaural coherence coefficients?

Find out now.

http://www.audiovero.de/en/downloads.php

JBL LSR 308

MartinLogan reQuest and Cheezewoofers

(no DRC applied on either one above)

---

With some DRC applied:

JBL (about the same, no change)

ML (a little positive change)

---

It was this Archimago post

https://archimago.blogspot.com/2015/11/measurements-digital-room-correction.html

"As you can see with my sofa moved aside and no coffee table in front of the speakers, I'm getting 69% which looking around at others' results seems reasonable for a domestic sound room without a large amount of room treatments. 80's would be awesome and I'm amazed at Mitch's achievement of 90's - great! For the purpose of the room correction, the data from the first 10ms would be most important."

... that made me curious.

He's referring to this, posted by @mitchco:

https://www.computeraudiophile.com/...me-Alignment-Driver-Linearization-Walkthrough

"Please note that an average setup results in an IACC around 75% based on Uli’s experience. Higher IACC values, like what I have obtained (88.5% and 87%), does require very careful setup and consideration to room design, as I have outlined in the system under test section."

 

[RayDunzl]

Gee, my lousy little room and crappy* 18 year old speakers did good!

*Certified to be of the least preferable type in a 4-way speaker shootout among all tested listener types.

 

[March Audio]

My old Usher BE718 no correction

95% does seem exceptional, well done.

The one bit its missing is the clicky microphone alignment tool thats found in the full Acourate package, which I would have thought would be essential.

 

[Blumlein 88]

Gee, my lousy little room and crappy* 18 year old speakers did good!

*Certified to be of the least preferable type in a 4-way speaker shootout among all tested listener types.

Are you going to use that last statement as a signature Ray? Would be a good one.

 

[RayDunzl]

Are you going to use that last statement as a signature Ray?

I'd probably get banned.

 

[RayDunzl]

I wonder what the unit/method of calculation is for IACC.

95.6% = 0.2dB (deviation from 100%)

---

A (perhaps specialized) example:

Page 991 - http://chrgasa.org/wp-content/uploads/2015/12/Hidaka_IACC_1995-part-1.pdf

... and so on.

 

[Blumlein 88]

I'd probably get banned.

Are you kidding, Frank hasn't gotten banned exactly. I think you would be okay with that for a sig.

I wondered about that IACC too if the percentage was really percentage of some other calculation. I haven't download the software yet, but couldn't you fake it out doing a loopback with tracks you varied by level to see which way it is getting the percentage.

 

[RayDunzl]

My untrained eye estimates it is not a trivial calculation.

 

[RayDunzl]

couldn't you fake it out

I could muck up the EQ on one side with my crappy* DEQ2496.

That oughta piss it off.

 

[Blumlein 88]

Yes I had found in another location that same mathematical expression in a paper about 3D object oriented sound.

 

[RayDunzl]

Hmm.

It doesn't seem to care much about volume mismatch or delay on one channel.

Right -10dB and delayed 5ms:

 

[RayDunzl]

I unbalanced the EQ at the miniDSP - turned off the IIR portion (lower frequencies and broad ranges) on the right side:

 

[Blumlein 88]

Hmm.

It doesn't seem to care much about volume mismatch or delay on one channel.

Right -10dB and delayed 5ms:

View attachment 7830

Well that is surprising.

 

[RayDunzl]

Ceiling fan doesn't change much:

 

[RayDunzl]

Ok, finally.

Signal from left, unmolested.

Signal from right - took a 2 sq ft piece of thin plywood and variably reflected some of the sweep on the right, maybe blocking the direct during part of the motion:

 

[RayDunzl]

External noise (me talking during right channel) upsets it some:

 

[RayDunzl]

Only the worst of those were lower than the best of the unmolested JBL readings.

I guess that's going to end my contribution to circulus autem confusione for this evening.

 

[Cosmik]

Is this because large transducers (panels) are highly directional i.e. beaming at higher frequencies?

 

[dallasjustice]

IACC as an absolute number using this tool probably isn't very meaningful.

But IACC is a great tool for positioning speakers assuming you can control the room bass in whatever speaker position you choose.

 

[RayDunzl]

Is this because large transducers (panels) are highly directional i.e. beaming at higher frequencies?

I think it's a factor in the higher unmolested readings above.

I seem to measure a 10dB or more relative SPL difference between direct and reflected between the ML panels and the JBLs.

Possibly due to being immune to the highest and assumedly beamiest frequencies, I barely notice a difference in casual off-axis listening, after the boom of both is DRC'd away. I now use the panels only for special occasions, the JBLs being the daily drivers. Like right now.

In the sweet spot, when consciously listening "in stereo", the JBLs give a diffused wide image, the panels a narrower (more distant perspective?), more distinct, and more stable, image (IMHO), easily distinguished eyes closed (blind), with the panels being preferred by a large margin.

I still haven't listened to them (JBL) nearfield and away from the sidewalls where that effect might be less noticeable. They are high and immediately outboard of the panels with no corrective control of first reflection.