How do you handle the surrounds with 2 seating rows? - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 08-18-11, 10:06 AM
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SAC

Join Date: Dec 2009
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Re: How do you handle the surrounds with 2 seating rows?

Theaters deal with problems associated with large acoustical spaces, whose acoustical rules differ from those of small acoustical spaces.

One of the most significant differences that define and distinguish the two spaces from one another is reverberation. Meaning, in one space it exists and is an issue, and in the other space it does NOT exist to any significant degree!

In a small acoustical space, you do NOT have a significant reverberant space. So, to make this issue simple for you, FORGET RTxx calculations in a small acoustical space!

A small space does NOT have a significant statistically diffuse well mixed reverberant field.
Instead a small acoustical space is dominated by room modes below the Schroeder frequency (a region whereby the wavelengths are larger than the room dimensions) and specular reflections that can be resolved into both direction, gain and arrival time - exactly the opposite of a reverberant sound field where said energy cannot be resolved into direction, as by definition, in a statistically diffuse reverberant soundfield the energy is arriving equally from all directions simultaneously! And all such RT calculations are predicated upon this definition.

(Also, to go just a bit more into this important subject, the only reverberant sound field that will exist in a small acoustical space will be at frequencies that are far to high in frequency for us to care about - meaning that the wavelengths are so short with such low energy content that they can be stopped by almost any object in the space. And a reverberant sound field is NOT like most imagine it to be! Most think of it as if it the electronic FX that we have all grown up with labeled "reverb" on an amplifier! This is NOT how reverberant soundfields behave! A reverberant soundfield in a large acoustical space manifests itself as the residual noise floor that may increase sufficiently such that it may destructively mask low level direct signals! Thus i hope this gives one a Quick idea of its difference.

For more information on this, PLEASE refer to Sound System Engineering by Davis and Davis (2nd ed.) or Davis and Patronis (3rd. ed.) and review the chapters o Large Room Acoustics and Small Room Acoustics. This distinction is critical to understand, as far too many fall into the trap of using the larger more general rules that apply ti Large Acoustical Spaces to Small Acoustical Spaces. And to make it really simple, in a small acoustical space, forget RT calculations (as they are a derived calculation) and focus instead on the ETC response and on frequency specific resonances viewable via wither the waterfall of cumulative spectral decay.
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Old 08-19-11, 07:20 AM
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OJ

Join Date: Oct 2006
Location: Toronto, Ontario
Posts: 1,966
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Re: How do you handle the surrounds with 2 seating rows?

Duly noted. That must be one of the biggest illusions of the whole home theatre culture... most of us at some point get it into our heads that the goal is to recreate the atmosphere and methods of a large movie theatre (whether knowingly or not). As it turns out, trying to miniaturize a commercial theatre and put it in your house doesn't really work, and some of the concepts and implementations of a commercial theatre will actually detract from the overall result when employed at home.

Sigh. Oh well, hopefully this is the kind of knowledge that can make our theatres just a little bit better and a little bit more special in the end.

- OJ -
DIY Ported Original Tempest Sub (offline)
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Old 08-25-11, 05:33 PM
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Join Date: Aug 2011
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Um ok I have a similar problem, my room will be 22.4x12.2x8.0' (LxWH) so if I decide 5.1 with 2 rows what's the best placement?
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Old 09-07-11, 07:09 AM
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OJ

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Re: How do you handle the surrounds with 2 seating rows?

mozez, I think that with 5.1 you may be best just using one pair of surrounds, at least according to the discussion here so far. In a way, its actually easier with 5.1 because you can put the surrounds behind the back row, and still have them coming from the right direction in the front row. But it really depends on a few things. Room layout? Where do you have room to place them? ...Personal Preference? Do you like the surrounds to be behind or beside you? It kind of depends what you like and what you have available for placement. And speaker type as well, if you use bipole/dipole speakers you will probably want them positioned differently than monopole. If you have directional tweeters or mounts that allow you to aim the whole speaker, you may gain some additional flexibility in placement.

- OJ -
DIY Ported Original Tempest Sub (offline)
DIY SDX10 Sub
DIY Dipolar rear surround
DIY XLR to RCA cables (offline)
DIY 1 to 4 RCA splitter
Owen Bartley is offline
Old 09-08-11, 03:02 PM
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Todd Anderson

Join Date: Jul 2009
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Re: How do you handle the surrounds with 2 seating rows?

Have you thought about using bipole/dipole speakers for your side surrounds and then directional speakers for your rear surrounds?

Anyhow, just my 2 cents!
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