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The ideal auditorium? Blank canvas

I am placing this under "Speakers", since it's all about building an auditorium that will become one with my speakers.

I have the opportunity to build a small auditorium in my garden (in Christchurch, New Zealand). This will be a house with one empty area for my audio and CD collection. It will be designed to be used only by myself, and maybe the occasional visitor.

My current music room is 4x3M, and I find that too small (acoustically). However, building an auditorium slightly smaller (max. 10m2) presents a huge advantage: there is no need for building consent and red tape...

I am using a pair of New Zealand built Image 414 http://www.imageloudspeakers.com/products/414.asp loudspeakers with a matching subwoofer http://www.imageloudspeakers.com/products/sub10.asp , powered by a Sony TA-FA3ES integrated amplifier - a combination that is very satisfying. I listen exclusively to classical; subwoofer helps a lot with organ, but is necessary in some other cases only.

The auditorium must be built with potential future uses in mind. It will have water connections for an eventual kitchen and bathroom. Whatever shape I give to it, it must be easily converted into accommodation / office later.

Since I have a blank canvas, what is your advice on:

- Ideal size, proportions (square? rectangular? other shape?)

- Ideal floor (carpet over concrete? over floating wooden floor?)

- Floor height? Should I plan a sitting area higher than the speakers?

- Ideal walls?

- Ideal height?

I suppose the ideal shape will be symmetrical.

Any advice would be appreciated. I plan to draw plans which I would publish here.
waryn
manitunc
795 posts
 
Try to keep each dimension in a range that is not a multiple of any other dimension. You could also use the Cardas Golden Ratio for your room dimensions. Use multiples of prime numbers, such as 1,2,3, 5, 7, 11, 13, 17, 19, 23, 29, 31 etc. That way you dont get any standing waves. Make the structure out of concrete or block, for mass and rigidity. Place absorbative material at the first reflection points from speaker to listening location. Sit at the height of your midrange speaker, unless its crossover is designed to raise or lower the soundstage, like many do. See PSB speakers. Elimiate corners if you can, by rounding or diagonal fillets.

If I was setting up a listening room, I would try to eliminate any reflections I could, so the main sound I hear is that which comes from the speakers. I want the recording to create ambience, not the room. I would also want to eliminate standing waves, or areas of reenforcement.
martykl
3,578 posts
 
I pretty much agree with all in Manitunc's post. I'd also add from my experience in building separate dedicated HT and audio rooms in my previous home :

Avoid parallel surfaces. Stadium seating and/or cascaded drop ceiling panels at various heights from the floor will do the trick in the height dimension and having the room width somewhat narrower behind the speakers than behind the listener will work in the length dimension. A gentle arc in the "front and back" walls will address the width dimension.

To maintain visual appeal, I created a wainscot with wood veneer to panel the first three feet of the side walls, the installed a strip of contrasting molding to form a "beltline" over the wainscoting. Above that, I lined the walls with acoustically absorbtive panels up to the ceiling and covered that with decorative (think speaker grill cloth) material. It looked great and was very effective for killing reflections above 150ish hz. (My speakers and subs were in-wall in the HT room and that helped in the true bass.)

Finally, in my 2 channel room, I had the happy accident of finding a 4' concrete caisson toward one end of the room. I had the contractor fir a wall around it and build a rack into the nook that was created. Four feet of concrete caisson turns out to be quite effective in isolating a turntable from airborne vibration. You will likely go a different way, but isolating the source components from the listening area is a good idea.

Good luck with the project and I'm sure you'll dig the results.

Marty
waryn OP
20 posts
 
I am thrilled with your replies. The Golden Trapagon seems like a good departure point! It will have to be slightly downsized. Now, I'll submit that nightmare to my builder!

Martykl, you write
I lined the walls with acoustically absorbtive panels up to the ceiling and covered that with decorative (think speaker grill cloth) material. It looked great and was very effective for killing reflections above 150ish hz.
but I assume your walls WERE parallel, and I should not plan to go to that extent inside my trapagon?
mapman's avatar
mapman
22,078 posts
 
Mani+ Marty have pretty much nailed it.

I'd only add listen first before adding treatments. They are easy to add and may or may not be needed.

Also I find any wall adornments/decorations, including even block style picture frames with an inch or so of depth to help break up large parallel surfaces usually only helps.

Then of course room furnishings applied in the end like chairs or sofas and other decorative items that lack hard reflective surfaces can be used to help dampen the room acoustically (similar to how internals of speaker enclosures are dampened with sound absorbent material) if needed to provide some final tweaks to whatever extent needed.

Also thin but dense carpet over the concrete foundation works best from what I have personally experienced over the years in many rooms and houses.

USe your imagination to find things you like and want in your room that serve a purpose and also might help with the sound. Most room furnishings that can help a room sound good is not marketed to audiophiles and sound engineers!

You are a lucky guy! Having/building a room that works good for audio is a huge advantage that can elude many music lovers!
bjesien
1,269 posts
 
Maybe you can pick up decent size mausoleum, or crypt. You can enjoy for a lifetime and ever after. Two birds with one stone!

Above ideas are good but if the room is important to you don't let code restrictions get in the way. Get the permits and do it right or you may have regrets later.
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