Axiom Home Page Forums General Discussion Home Theater Brwsaw's Room Plan

Initial images.

Explanations to follow.

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!

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.

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.

Whew. I get tired just reading all of this interesting stuff. Way too complicated for me.

Time for a nap, ha!

TAM

Let the fun begin....

Thanks.

Might be tight, the legs for the self supporting screen may interfere with the subs location.
Door swings out.

Took a chance on the door. 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.

The way too far into the room...would that be 65 inches?

No, 4'2" to front of speaker. Changed to inches for you. 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.

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.

That's the beauty of having a wall of screen. I can save a setting for games (say 120 inches for sims) or 80 inches for SD content.
The legs that support it may be an issue moving forward. I may need to shorten the pieces on the floor and weigh it down instead of using the back wall cross brace to keep it from falling forward and square to the room.

Trevor, did you assume the subs were behind the screen or is this the reccomendation for this room?

And....
Where would you place a third sub?

FWIW, the screen calculator says a 143" diagonal (16:9) image will fit on the current screen.
Too big but the kids love it.

Sounds like you have a good plan. Are you planning some sort of removable masking for the different screen sizes?

Ha! 145" would be awesome, but awkward, at that distance.

Short answer- I would place the 3rd sub center of the back wall as a default.

I knew you had an AT screen, so hiding as much stuff behind there as possible was my intention.

The studies at Harman have confirmed 2 opposing subs give the smoothest and most tactile LFE response for a group of listeners. What I found opposing subs lack in my own tests is a natural bass presentation. It always feels like the bass is coming from under you like an earthquake. I like the bass to couple to the images in the soundstage. A stand up double bass should not feel like split between the main loudspeakers and a nebulous place from below. I stole the word nebulous from Grimani. Like it.

My opinion anyway.

Believe it or not there little need for masking, the room is very dark.
The only thing you see is the image being projected.

Ok, ok....
Maybe it's not that black but I don't notice the remainder of the screen.
I'll take an up to date pict after I reinstall everything.

That wouldn't work in my room. It sure simplifies things though.

Game on! I'm excited you are going ahead with the plan it seems . Please provide any feedback you can so my methods can be tailored accordingly for future plans. I am planning an inwall setup for a high end home on the side too. In the prelim stages. Love this stuff.

Trevor can you confirm an exact dimension from the listener to the back wall, sorry to be a pain.

Thanks

96" no pain.

Thanks

Any updates? Good or bad news?

Working on it as I write this...

Slow going...
Managed a few hours but only set up the front 3 and the subs.
They are exactly as drawn with exception to the co-located 3rd sub, an executive decision, and the subs being a foot of the back wall.
This should help with the ground loop hum I was getting, fingers crossed.

I did lower the towers down to the floor, they were raised about 12 inches.

Will probably keep the rear seats, the two lazy boys were already positioned with the ears 8' from the back wall. I booted out the 4 kid seats a while ago. Will still sit 4 with unobstructed views.

More another day...I came up just in time to watch my two oldest run for the bathroom, both leaving a trail of flu as they ran. Lots of fun...

Awesome job so far!

The front soundstage is the most important aspect. It looks perfect!

I had trouble lining everything up this time. Not sure why.
The legs for the screen should just fit between the subs. Just.
Catch is the gap I had/wanted on the one side will be gone. The screen will be roughly centred. No harm, it will be back where it was before I started only 3 inches further into the room.
The real issue will be setting up the subs with no access and no screen movement freedom.
I won't be able to tuck the legs under the 2x4 mounted at the bottom of the wall and it looks like I'll need to add an additional one in front of the centre tower joining both legs to keep them square to each other. It didn't matter before, I had a foot of swing/wiggle room without the subs behind the screen. It will be tight. I can move the uprights the legs are attached to but would like to avoid the extra bit of hassle, at least for now.
Will try running the receiver at +10 with the the subs at their lowest power levels, just out of curiosity, and go from there.
I need/want to drop the screen down closer to the floor so the lowest woofer can fire forward un-ubstructed.
I'll be restretching the screen this time too. It'll be nice to have a taught screen again.

Since the gain is a physical setting and preout settings are software, it might be best for setup flexibility to set subs higher and preout +/-0 to start.

Craig probably has a quick and dirty way to set sub gain levels. I measure with full band pink noise and set them 5-8db hotter than the mains. It is probably easiest to set each subs' gain one at a time since they arent matching (treat the co-located subs as one sub and set together) then set the global sub level in bass management. With both front wall sub positions on vs only one there should be a ~3db increase if all pans out at the mlp. You will just have to turn the global setting in the AVR down a bit to your preference.

Its fun if there's no hurry and beer is involved.

It's all in good fun...
It didn't work. At +10 on the receiver and with the power turned all the way down on the subs the bass is roughly equivalent to 2 towers. I turned the subs off after and listened while I grinded away.
I still have lots to do. I relocated 1 side and rear surround last night. I swapped the side and rear speakers too but didn't like the look. I swapped them back. In my last home the room was wider, the towers on stands worked well as surrounds. Here the walkway is along the side rather than across the room, it makes for a tight walkway in a room frequented by monkeys with no ears.
I might get down there tonight, later tonight.
The rooms half empty so I'll need to reserve my SQ thoughts for another day.

All speakers are in place and the screen has been lowered.
The image is 90" diagonal and 18 inches off the floor, pretty low. Once the seats are back in I might need to raise it back up.

If you keep your second row you may have to raise it up a bit. At 18" off the floor your eyes should be at just under the midpoint of the screen while seated in the first row.

Do you like the smaller screen size? Might take a movie to get used to.

We're hoping to get some time down there this weekend....
The screen size isn't as bad as I thought it would be, a bit of a shock to the system, but not bad. I'm already happy with it. I did move it up to 22 inches off the floor, my big toe was on screen while reclined with legs crossed.
I do want to increase it to 115" just to compare, I'd say the 90" is perfect from my chair for games though. Just want to see 115" from the back row.
It sounds great, I needed to lower the volume on the receiver again.
I ended up with more room between the rows, not sure how that happened...
As it is now the main seats (ears) are 8' from the back wall while reclined.
The Martian tonight, fingers crossed.

Great stuff. I have questions but they can wait till you've tweaked your levels if needed and lived with the setup for a bit. Sounds like you are happy. That makes me happy.

So now its been a while how did the design help you? Was it close to where you ended up leaving your speakers? Any general feedback on the accuracy of the plans would be great. Basically I want to know if they were worthwhile for you in the end or a crap shoot.

Having dimensions provided was nice.
Most of the room is currently as you drew it.
The rear surrounds are slightly further apart.

I am about to swap out the leather seating for fabric covered ones.
I'm also going to be adding my QS4's back into my system but they'll be on the side walls about 2' from the back wall.
I'll be moving one sub behind my seat again (under my second row again), I miss the tactile sensation it added.

I havent spent a lot of time in there this spring and summer but the leaves are turning color so movie season is near.

I just did a screen upgrade after doing the atmos upgrade, from 106 to 120 and did a hdmi upgrade from 1.4 to 2.0 becuse of the PJ upgrade (coming in next 2 or 3 weeks) the PJ has lens zoom memory and faux 4k with HDR can't wait...

I'm still working on screen size. I'm considering sitting in the back row and the images seems small from there. It might mean raising the Front soundstage again but to date this was the most impressive. Raised and firing straight forward.
The kids like the screen to be bigger so I'm sure I can find a middle ground.
The rooms pretty much put back together just need to recalibrate after swapping speakers, moving the rear surrounds to the sidewall/corners and placing a sub under the second row.
Might even have it done today.