Ideal room shape for a 7.1 system

ZachBeale

Hello,

I'm in the process of laying out a floorplan for a home, and I plan to lay out the main living room to be a perfect listening venue for a 7.1 surround room. I'm open to any shape room, any kind of tilted walls needed, etc, to achieve the best possible room shape.

I've come across a few room audio analysis software packages out there, but I'm on a student budget, so they're really out of the picture.

I can only assume that the room would be seven-sided, with the woofer at the front end of the room. Here's an image to show what I was thinking:



I used Dolby's suggestions on speaker toe-in angles for the placement of the corners of the room, and put the sub down in that 'cave' in the front, to develop bass. The center channel will be just below the television, on an entertainment center shelf built above that cave.

rallyshark

Welcome to Club Polk! That's a very interesting design! I'm definitely not an expert, but it looks pretty good to me. The only thing I see or am not sure about would be the surround back speakers. Maybe they should be moved towards the center of the back a touch? From the diagram, it seems they may be a little too close the the surround left/rights. But what do I know

Hawkeye

I'd contact these folks before I built a room. If your going to that extreme, then pro help is highly recommended.

http://www.rivesaudio.com/

Gordon

ZachBeale

Thanks to both of you.

First of all, I'm not actually building this room...It's a design that's going into my student portfolo. I doubt I could afford a consultation with Rives.

Second, I took the angles for the rear speaker corners from dolby's site, but I'm right in the middle of their range, so they could go back a bit.

cheddar

Did they also recommend putting each speaker in a corner? All the dolby pictures I've seen have a rectangular shape. Are all those non right angle reflections supposed to improve the acoustics?

Also, what's the subwoofer cave supposed to achieve? If it's for a class project or something, you might want to research infinite baffle subwoofers and design the space custom for one. Might be something unique only your design has. Or even make the space a very large enclosure for a DIY subwoofer. I haven't done either myself, but there is lots of info on the web.

Please post the final design and what you learned if you can. Sounds like an interesting project. These threads usually deal with how to improve the faults of an already built room.

ZachBeale

My theory on the constantly-rectangular rooms you see everywhere was because...well...most rooms are rectangular. The site won't post a speaker setup for a room that's so strangely shaped that only .0000001% of homes would have it.

I understand it's best to put a subwoofer in a corner to strengthen the output of the woofer, so I took that to the extreme. It ended up in the cave at the front of the room. The second option would be to put it at the rear of the room, or mounted in an indentation in the floor, in the center of the room. I'm not sure which is the best option, but I haven't accounted for a fireplace.

My theory on the angled corners of the rest of the room was a bit of geometry...it's a system with seven speakers, so I designed seven corners. The front speakers are further from the listener than the rest for a few reasons: first, in an attempt to balance out the amount of sound emitted from the fronts and from the other channels, second, to provide for an ergonomic viewing angle, as well as creating a spacious room, third, since it's good to have your two front speakers relatively close together, they ended up further away, to avoid the effect you would get from projecting their sound into the width of the room. Instead, I project into the length.

Essentially, the room is based off of Dolby's rectangular room, but heptagonal in an attempt to distribute the sound of the seven speakers using the walls they sit between to spread the sound. I plan to mount fabric-covered foam panels on the walls between the speakers, to reduce reflectance from the speakers on the opposite side of the room.

And yes, It's going to end up in my application portfolio, however, it's mainly an exercise in design.

bevo

I'm actually thinking about doing what your project is. I'm going to build a house in the next few years and will devote the room above the garage to HT. I have asked many people what the best dimensions would be for a dedicated HT room. I don't care what shape it is, or how high the ceilings need to be. I just want to design my room around HT and not the other way around. Everyone keeps telling me that they need to know how big my room is, or come back after you have it built and then we can see what we have to work with.
No one can understand that I want to build the room around HT, and that if your room shape is the best I would use it. I really hope some people come up with some good ideas for you, because I can't seem to get anyone to help me out. I want the ideal room shape and size to seat up to 7 or 8 people with a 130-150 inch screen. I would be very, very interested in what you find out with your project you have going.

mmadden28

Check out this book: Sound Reproduction: Loudspeakers and Rooms.
.

Seems like it would have all the theory you need for this project.
I bought this book, but I haven't had a chance to go through it yet.

dorokusai

An elongated hexagon.

MANSKITO

From my understanding of it, the worst thing is a rectangle or any thing with parallel walls/floor celling. That is a VERY good design the only thing I would change is make the floor slanted to avoid parallels with the celling.

Also if your going to go that crazy with the design stereo subs is a MUST. Locating then next the front to speakers would probably be best(I'm not sure on stereo sub placement don't yet have the money).
Also I'm not sure if that sub cave will work well because it let the listeners know EXACTLY where the sub is located in the room and your theater will end up sounding like a HT and a sub rather then a seamless experience.

cnh

I realize that rectangles have reflections....and that Cinemas have speaker arrays. So why not use real theater configurations for HT since both spaces are usually rectangular?

Also, as I understand it there are actual mathematical proportions for a HT room that builders use to create the space? I assume the book mentioned above deals with all that.

cnh

ZachBeale

cnh;

Yes, there is a proportion that most designers use...but frankly it's rather arbitrary. They go by the golden ratio, with the length of the room being 1.6x the width, and the height being usually around ten feet, though that's also proportional. I'd also rather not design a movie theater, because honestly all the ones I've been in have horrible acoustics. They are most likely only rectangular because that's the cehapest method of construction. This also accounts for the massive amount of padding on the walls to reduce reflections.

MANSKITO;

I'm glad you like my design, that's fairly reassurring being the fact that I have no experience in audio-related construction. The sub cave might end up going, you've got a good point as to why. On top of that, it might end up actually making the bass boomier, and less tight. Dual subs wouldn't be a problem, I can factor them into my design. Honestly, with low frequenceies, it doesn't entirely matter where they come from...so perhaps locating them under the front speakers is a good idea. Also, it's not shown in this model, but the ceiling will also be slanted back from the front of the room. The rear of the room will have a higher ceiling height than the front. I'll also most likely pad the ceiling like I mentioned I would do with the walls, and offset the padding about 3' or so from the walls, just to reduce reflections.

mmadden28;

I might be going to B&N later today, I'll give that a look.

bevo;

That's been my problem all along, noone seems to actually lay out a room for audio, they lay out the audio for the room. My goal with this home project is to design individual room modules, with each module being absolutely perfect for it's purpose, regardless of shape, interior design, etc. It's really surprising that no one seems to have done this. I'll keep this thread updated with images as the room progresses, so keep watching.

mmadden28

Keeping in mind that your project is theoretical and your not actually going to implement, you probably do have to keep it realistic. I would imagine with Building codes, that there are limits to what one could realisticlly design and implement--Tilted walls and such would have to be non-load bearing, etc. Of course You could build a typical rectangle box room to comply with building codes, then lay in your angled walls inside it to get the effect you want. The again if it were a simple matter of angling and tilting walls, then I would imagine this practice would be more commonplace with any high end room designers who usually have very high budgets to work with, no?.


Of course, if I were doing this, I would look at a recording studio (or books on recording studio design)- they design the rooms for the audio - they don't usually try to make do with whatever building they get the cheapest lease on. And every one I've seen is loaded with sound absorbers and diffusers.

ZachBeale

mmadden28;

It's more of a design exercise than a ready-for-construction plan. Local building codes (In this case, Dare County, NC) wouldn't have a regulation on whether or not tilted walls can be bearing, that would be more regulated to what the structural engineer says can be done. Those walls won't be bearing anyway. As a matter of fact, they'll most likely be opaquable glass, with some kind of fabric accent similar to a curtain, to prevent reflectance. The rear walls, those behind and to the right and the left of the sofa will be cast-in-place concrete finished over with furring and gyp. This terminates about 3/4 the length of the long walls, where the glass starts. The concrete walls will be bearing, and will most likely let the ceiling cantilever over the main portion of the room.

I might take a look at a studio in our area...I have a friend that works at one.

ZachBeale

xcapri79;

Actually, it's a heptagon. I thought about an ellipse, but it would be much more difficult to integrate into the rest of the home than a room with flat walls. Even if you finished out the ellipse to be in a box, it would still take up an incredible amount of space compared to this.

I suppose an egg-on-its-side shape would be best....but the difficulty of integrating it into the rest of the house is an issue. Not to mention your floor needs to be flat.

ZachBeale

xcapri79;

Those are good points, however, to match with the location (oceanfront), it's not multi-story. If anything, it'll be a 1.5 story. Furthermore, an egg shape is incredibly difficult to design, much less lay out on paper. It would decimate the vocabulary of the home.

Is what I posted here first a close enough approximation to an egg? I can add an extra corner on the long wall more approximate the shape.

ZachBeale

xcapri79;

That's what you would assume, but it doesn't match the environment. A coastline is long and drawn out, as should the house be, in elevation at least. I enjoy a concept where the house looks natural in the environment...as if it belonged there.

I think my main argument against the egg is that it simply does not match with the vocabulary of the home.

Here's an example of the newest mass:



I've reduced the size of the cave, pulled back the top corners of the front walls, to angle them a bit more, and pulled back the top corners of the left and right (from the perspective of the sofa) corners to angle the long walls in some. The ceiling is also angled at about 4 degrees. I might bring the front walls inward some, to lessen the overall elongated appearance of the room.

ZachBeale

Bump, getting low on time to complete this.