Impulse and Pioneer MCACC sample delay question - Home Theater Forum and Systems - HomeTheaterShack.com
 
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post #1 of 7 Old 03-04-14, 06:59 PM Thread Starter
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Impulse and Pioneer MCACC sample delay question

I have Question for the experts.

During Pioneer's MCACC AVR tuning, after the full auto, you can select Manual Mode and within that category select EQ Professional. One of the options is to select a sample delay for the readings that system will take during the process. Pioneer suggests and provides reverb graphs and a criteria for interpreting them to arrive at an optimal sample delay for a more accurate test result.

The sample delay choices are in ranges of milliseconds as follows:
0-20
10-30
20-40
30-50
40-60
50-70
60-80


Here's the question. Examine the impulse chart below. Could it be used to accurately determine an optimal sample delay?

I'm thinking as soon as possible but at a low impulse intensity. Anything before the small spike at ~11 would be too active and the spike just past 40 may cause issues. So as I read it the best SD range would have to be 20-40 or anything at or greater than 50-70.

Thoughts?
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Impulse and Pioneer MCACC sample delay question-right-speaker-impulse.jpg  


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Last edited by GCG; 03-05-14 at 08:20 AM.
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post #2 of 7 Old 03-05-14, 08:54 AM Thread Starter
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Re: Impulse and Pioneer MCACC sample delay question

Is this just a dumb question that displays my lack of knowledge or is it that nobody has an answer?

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post #3 of 7 Old 03-05-14, 12:04 PM
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Re: Impulse and Pioneer MCACC sample delay question

Few of us have investigated MCACC. At least I know nothing about it. The brief description you cite is obtuse. It's not a normal method or process that is recognizable. It may be a reference to a window function, but that does not help in understanding what they are doing with it. Possibly their description is obtuse on purpose?

You will probably have more luck with a site or thread that specifically deals with the this subject.
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post #4 of 7 Old 03-05-14, 03:24 PM
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Re: Impulse and Pioneer MCACC sample delay question

You might want to read up on the Haas Effect / Precedence Effect to better understand some of the underlining applied principal behind this feature ( from MCACC's bag of magic tricks ).

I'm pretty skeptical that staring at an IR will help you ( or anyone else ) select the best ( portion of the impulse, to then add it back into the original signal ) to optimize this effect .

Room size ( & by extension the rooms RT60 times ) will give a bit more guidance ( ie; shorter times for bigger rooms / & vice versa ,to some extent ) .


Last edited by EarlK; 03-08-14 at 04:36 PM.
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post #5 of 7 Old 03-05-14, 07:58 PM Thread Starter
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Re: Impulse and Pioneer MCACC sample delay question

Thanks for the link. I'll look into it.

My reasoning for the use is to determine when the first reflection would be seen and bracket that with the chatter produced by the speaker's immediate environment (in my case a shelf where the speaker sits). If the space between these is relatively quiet it might be a good candidate for the sample delay setting for the MCACC process. For this chart (and all others would need to be evaluated for a valid choice) the spike at 11ms is most likely the near wall ~5-6ft. from the speaker and the one at 40ms should then be the opposite wall. (Room size 24x18) By my logic (right or wrong) the clutter prior to the 11ms spike would rule out 0-20 or 10-30. The quiet period between 11ms and 40ms allows the choice of 20-40ms as the earliest sample delay range to be set.

However the reading you have provided may make the subject mute.

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post #6 of 7 Old 03-08-14, 03:41 PM
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Re: Impulse and Pioneer MCACC sample delay question

Quote:
EarlK wrote: View Post
You might want to read up on the Haas Effect / Precedence Effect to better understand some of the underlining applied principal behind this feature ( from MCACC's bag of magic tricks ).

<<<<<SNIP>>>>

My apologies GCG, my link ( upon further research ) wasn't relevant to what MCACC does ( when it Auto-EQ's ) .

For the record, the Auto-EQ function ( as implemented in MCACC ), uses as it's starting point ( default response ) , a curve retrieved from a very time specific snap-shot ( or window ) of the main IR .

This default window ( set at 80-160ms ) , is already quite far down into the decay path ( of the "main" impulse ) .

While quite interesting, it's not the usual approach taken & I can see why some MCACC users complain about it returning overly "bright" results .

That said, I would chose ( the manual override option ) & use the 0-20ms window as the basis for Auto-EQing ( see below for my reasoning ).

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Impulse and Pioneer MCACC sample delay question-auto-eq-curves.png  


Last edited by EarlK; 03-08-14 at 05:36 PM.
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post #7 of 7 Old 04-18-14, 08:25 PM
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Re: Impulse and Pioneer MCACC sample delay question

Interesting.

I found that using all six memories, running MCACC exactly the same with the only change being the MS capture time, then running REW sweeps provided tons of information.

For me, and my room, the best response I got was using the 30-50 ms capture time. Followed by the 20-40 and 40-60 slots.

I have the REW file if anyone wants to see and/or analyze it.
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