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#416512 - 01/16/16 10:45 AM Brwsaw's Room Plan
Serenity_then Offline
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Registered: 03/28/14
Posts: 1565
Loc: PEI, Canada
Initial images.

Explanations to follow.





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#416513 - 01/16/16 12:17 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
Serenity_then Offline
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Registered: 03/28/14
Posts: 1565
Loc: PEI, Canada
This is Brwsaw's room. It was a bit tricky. The images above represent the "ideal" speaker layout considering listener location, reflections, modal response and 2ch\multichannel layout.

The room is a little narrow for a conventional setup, and just a little short to make 2 rows optimal. The dimensions of roughly 21x12x7 make for some challenges in avoiding axial room modes.

Width Modes are 43 86 129 172
Length modes are 24 48 73 97 122
Height modes are 73 147 220

The speaker\listener distance from the front wall was most important to consider, as there is a nasty coincident height\length mode at 73hz. Since the subs are front wall located, we do NOT want them to energize that frequency. The loudspeakers should cross over to the subs at 60hz. The subs are placed at 1/4 width to negate the width null at 43hz and integrate seamlessly with the main loudspeakers for 2ch use. The default seated position height of around 36-38" places the audience out of a height null problem in this room.

The room is narrow for a conventional equilateral setup. Doing so lands the listener close to the center of the room, or forces the loudspeakers way to close to corners, or way to far into the room. With a bit of juggling I gave up ideal width locations to maintain a good width to listener ratio. The proximity to the sidewall is of less concern than to the rear wall. First reflections can be treated if he perceives them as a problem. Preference for a wide soundstage was mentioned, and these will aid in the perception of source width, giving a little image specificity away.

The imaginary toe in convergence point is an estimated 3'behind the seated listener in the MLP. A folded piece of paper can be placed on top of the speaker on-center and looked down from behind like a scope. A piece of string can be taped to the ceiling at room center a few feet behind the listener and aimed at. I used a hockey stick resting against a pool table to do the same thing over Christmas setting up a room. Anything works so long as the sight line from each speaker can be matched up to that reference.

For 2 ch use the L\R first reflections meet the sidewall at just over 5 1/2' (3rd image). These are of a very similar length to the direct sound so should be reduced in amplitude somehow. The second drawing highlights zones I would recommend for treatment. Green is the first priority, orange second, red optional. The room is prone to sidewall flutter echoes and the front 2/3rds of the room should account for some flutter reduction method. This can be as simple as adding irregular shapes to both walls. But they might as well be broadband absorbers or midband diffusers. These can be DIY of course! wink

The use of a QRD diffuser on the front wall is highly recommended as well as on the sidewalls adjacent the listener (9' from front wall.) This will improve the apparent width of the center channel's presentation, in this case an M80 tower. Diffusing the lateral angles from the listener to the center channel is a very good idea. It will make the source seem more natural. This is also very beneficial for speech intelligibility. The second reflection point is of little concern in most rooms because of the increased path length and reduced amplitude (red on sidewall in drawing.) This area should be treated with diffusion or to mitigate flutter echo if needed to preserve room energy.

36" wide front corner bass traps are already deployed in the room, and it is probably a good idea to add a deep (6") trap in the center of the rear wall. A limp membrane trap or 1/4" plywood resonating panel can be built and tuned to maximize effectiveness. Plans for these online. The rear corners can be treated to reduce the "cue ball" effect from L/R channels. They will also aid in bass absorption.

The overall decay time of the room will be long and uneven if untreated. The sidewalls will dominate the reflection times and mid to high frequencies will linger. To test this out, a balloon pop at either the L\R channel locations is a good test. Listen for a pitched boing or a ringing sound at the tail of the decay. No pitch no worries. The seating will likely contribute to the perception of echo in the room. Plush seating and carpet may have already mitigated any audible issues.

That's all I can think of for now. Need to eat lunch. Feel free to pick it apart and ask questions. smile
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Trevor. Cold turkey. Thanks guys. Cheers.

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#416514 - 01/16/16 12:25 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
Serenity_then Offline
connoisseur

Registered: 03/28/14
Posts: 1565
Loc: PEI, Canada
Oh yeah, the recommended screen size is 90" diag at this distance. The bottom of the screen frame should be 18" off floor. There is a large DIY screen in place, so this can be modded if Brwsaw deems the plans worthy of a room redo. It's probably a good idea to zoom and size based on preference.

The 90" diag seating to screen ratio lands right about 1.35w or so. (mid theater) This is a 2.39 chart, so ignore the height weightings.



Edited by Serenity_Now (01/16/16 12:28 PM)
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Trevor. Cold turkey. Thanks guys. Cheers.

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#416515 - 01/16/16 12:27 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
exlabdriver Offline
connoisseur

Registered: 09/07/11
Posts: 1725
Whew. I get tired just reading all of this interesting stuff. Way too complicated for me.

Time for a nap, ha!

TAM

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#416530 - 01/16/16 07:44 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
brwsaw Offline
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Registered: 10/12/12
Posts: 1781
Loc: Canada
Let the fun begin....

Thanks.
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#416533 - 01/16/16 09:22 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
brwsaw Offline
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Registered: 10/12/12
Posts: 1781
Loc: Canada
Might be tight, the legs for the self supporting screen may interfere with the subs location.
Door swings out.


Edited by brwsaw (01/16/16 09:23 PM)
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#416537 - 01/16/16 10:12 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
Serenity_then Offline
connoisseur

Registered: 03/28/14
Posts: 1565
Loc: PEI, Canada
Took a chance on the door. laugh I quickly looked into your old thread. Your tile ceiling is a good news situation for decay times. The modal issues in the room should also be greatly reduced in severity. Good stuff.


Edited by Serenity_Now (01/16/16 10:23 PM)
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Trevor. Cold turkey. Thanks guys. Cheers.

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#416541 - 01/17/16 12:29 AM Re: Brwsaw's Room Plan [Re: Serenity_then]
brwsaw Offline
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Registered: 10/12/12
Posts: 1781
Loc: Canada
The way too far into the room...would that be 65 inches?
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#416542 - 01/17/16 06:10 AM Re: Brwsaw's Room Plan [Re: Serenity_then]
Serenity_then Offline
connoisseur

Registered: 03/28/14
Posts: 1565
Loc: PEI, Canada
No, 4'2" to front of speaker. Changed to inches for you. smile What I would suggest is placing just the towers and listening position first. If it doesn't fit your room use it may be a wash. But it should sound fantastic.

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Trevor. Cold turkey. Thanks guys. Cheers.

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#416545 - 01/17/16 02:01 PM Re: Brwsaw's Room Plan [Re: Serenity_then]
fredk Offline
axiomite

Registered: 12/06/07
Posts: 7786
Loc: Canada
Originally Posted By Serenity_Now
Oh yeah, the recommended screen size is 90" diag at this distance...

The THX recommended (optimum) size for that distance is 115".

Once you decide on the best speaker/seating location, I would watch a couple of movies at different screen sizes to get a feel for what you are comfortable with. It seems everyone is slightly different in what size they prefer, but Generally it fits close to what the THX recommendation is. You will know when it gets too big.
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