Room Acoustics and Body Counts... - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 12 Old 02-17-2017, 09:27 AM - Thread Starter
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Room Acoustics and Body Counts...

If we tune our theater with only ourselves sitting in it does adding more viewers significantly change the room's audio dynamics? For instance my theater will have 7 seats and I am wondering if that has an impact when all seats are occupied vs. only 1 or 2 occupants?
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post #2 of 12 Old 02-17-2017, 09:39 AM
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That's a great question actually! I've often wondered this myself. I would assume there is some impact, but it must be minimal. I've asked myself why we don't run things like audysey with people sitting in the chairs.

Ok pros! We need an explanation!
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post #3 of 12 Old 02-17-2017, 09:49 AM - Thread Starter
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Just wondering because I've seen people go the the nth degree getting their room dialed in and I'd hate to have all that work compromised just because the rest of the family selfishly wants to watch a movie with me...
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post #4 of 12 Old 02-17-2017, 10:16 AM
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I've often wondered if reading information on this place is like having an ailment in your side and you google what might be wrong with you. Once you are done reading Web MD, and a host of other medical sites, you think you need an appendix removed, kidney's replaced, you have a blockage in your intestines and may need surgery to stitch up your multiple hernias.

I really do want to get as much out of my sound system as reasonably possible, and will be incorporating as much as I care to off of the suggestions here, but I think I'm past the stage of being too nit picky with smaller items like this. To those that want to go that far, you have my utmost respect.


*and total disclaimer: seeing your thread title after reading that you wanted 4 - 18's in your theater, I thought this was going to be about how many lives were lost in home theaters due to overpowering them with low frequencies.
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Last edited by arcticbowman; 02-17-2017 at 10:19 AM. Reason: disclaimer
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post #5 of 12 Old 02-17-2017, 10:22 AM
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Death by subwoofer! Not a bad way to go!

Related question, does a bald guy make a good diffuser? If so, should I seat them on the sides or the back row?
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post #6 of 12 Old 02-17-2017, 10:24 AM
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Short answer: Yes, people do cause an acoustic change, but not significantly. Stadiums do try to account for this. The large number of bodies will absorb midbass/bass energy. (at work or I'd site sources, maybe if someone reminds me later I'll find the info again).

I'd say realistically don't worry about it. Tune the acoustics for what you expect to be most common (you and wife or something). If you have seven people over most of them won't notice or care if it doesn't sound 100% optimum and I doubt it would cause a large enough difference to be a concern.
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post #7 of 12 Old 02-17-2017, 10:25 AM
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Quote:
Originally Posted by drunkpenguin View Post
Death by subwoofer! Not a bad way to go!

Related question, does a bald guy make a good diffuser? If so, should I seat them on the sides or the back row?
They'd make a terrible diffuser. One single pattern is just a (hopefully) controlled reflection. You'd want to put them on the back row and reflect the energy up into 2D diffusers on the ceiling. Next question.
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post #8 of 12 Old 02-17-2017, 10:36 AM
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Quote:
Originally Posted by brazensol View Post
If we tune our theater with only ourselves sitting in it does adding more viewers significantly change the room's audio dynamics? For instance my theater will have 7 seats and I am wondering if that has an impact when all seats are occupied vs. only 1 or 2 occupants?
Quote:
Originally Posted by drunkpenguin View Post
That's a great question actually! I've often wondered this myself. I would assume there is some impact, but it must be minimal. I've asked myself why we don't run things like audysey with people sitting in the chairs.

Ok pros! We need an explanation!
If you are waiting for a pro, you will need to keep waiting. But, this issue has been extensively discussed on the Audyssey thread in years past, with several pros weighing in. The consensus was that the way our bodies, and clothing, reflect sound waves is not significantly different from the way that the chairs themselves reflect sound waves. So, for purposes of an Audyssey calibration, there would be little to zero practical difference.

If I remember correctly, someone even tested that theory with REW, to determine whether he could see a meaningful difference in the frequency response (every calibration would have at least minuscule differences). He couldn't see one.

Regards,
Mike
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post #9 of 12 Old 02-17-2017, 01:03 PM
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Mushroommunk makes a good point, that bodies have reasonably similar characteristics to the furniture in a typical home theater. I have experience with large venues like stadiums, auditoriums, convention centers halls, etc., and in those cases, there is most definitely a difference. But those venues tend to have rather hard and reflective surfaces, including the seating. I would also venture to guess that 10000+ people in a large venue make up a larger percentage of the surface area in the environment than a small number of people in a home theater.
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post #10 of 12 Old 02-17-2017, 01:49 PM - Thread Starter
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Quote:
Originally Posted by drunkpenguin View Post
Death by subwoofer! Not a bad way to go!

Related question, does a bald guy make a good diffuser? If so, should I seat them on the sides or the back row?
Hey! I resemble that statement.
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post #11 of 12 Old 02-17-2017, 06:14 PM
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Hey! I resemble that statement.
Maybe we could knit you a hair piece out of rock wool. Not only would look good, but would be functional too!

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post #12 of 12 Old 02-17-2017, 09:46 PM
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Quote:
Originally Posted by brazensol View Post
If we tune our theater with only ourselves sitting in it does adding more viewers significantly change the room's audio dynamics? For instance my theater will have 7 seats and I am wondering if that has an impact when all seats are occupied vs. only 1 or 2 occupants?
Our bodies have very little impact since our bodies have very little depth. Our bodies are roughly 50-65% water depending how much adipose tissue we have. More precisely, our bodies salinity content roughly matches that of sea water. Sea water is much more absorptive for sound energy than fresh water, and is also more effective in the absorption of high frequencies rather than low. In fact, at 250 Hz, the absorption in sea water to a depth of 1000 meters is only 0.005 dB. So, you can see where problematic frequencies are for a small room, it means nothing that bodies are in there for low frequencies. It may affect high frequencies more, but with them bouncing around the room a bit depending on surfaces, and the fact the direct sound reaches your ears before interference, it will still make little difference in the end. Enjoy however many people you want in the room!
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