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 loudspeakers with a matching subwoofer , 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.
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.
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.

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?
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!
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.
Most room furnishings that can help a room sound good is not marketed to audiophiles and sound engineers!
That is definitely music to my bank account!

Plans will be underway and I should able to post them here in 2-3 days.

The wall construction that I described was from the HT room in my former home. Those walls were, unavoidably, parallel. However, that formulation can be done at reasonable cost (depending on the materials chosen) and it sounds and looks great. It's even better visually for in-wall speakers. If you want to consider double duty for 2ch/HT use (main L/R on the floor, center/ back/sides/subs in-wall), I'd probably do it that way even if the walls weren't parallel. For a strictly 2 channel room with non-parallel walls, maybe it's overkill.

Ok, what do you think of this first plan? - The original Golden Trapagon appeared too big for me, so I have reduced the horizontal dimensions by 25%... but now, it appears too small, doesn't it? What do you think?

I suspect that you'd regret not enlarging that floorplan. If you start with a minimum width of +/-425 and go from there, you'll probably be closer to the mark. You can probably get away with less flare to the side walls (smaller maximum width) if that is helpful.

BTW, if that's record racking behind the speakers, I'd also suggest that you stagger the depth of the racks, pulling some sections closer to the listener than others. IME, this is a great wall treatment. Similarly, you may want to put some racks (or decorative pilasters) flanking the doorway on the wall behind the listener.

Finally, while the ceiling arrangement looks good, you can also get away with drop panels of varying depth if that proves easier/cheaper.

Good luck


PS If you haven't purchased the subwoofers yet, you may wish to consider this approach:

I'd give Duke (the manufacturer of this system) a call to discuss. He's a very good guy who participates here regularly.
I should add that Duke (Audio Kinesis) also sells this less expensive variation of his multi-subwoofer set-up.
Thanks, Martykl. 4 subwoofers is definitely something I am keen to consider later. Also, I am in Christchurch / New Zealand; transport is not negligible.

Here is a new version of my music room plan. This one is fullsized. The shelves at the back are for CD storage only

Looks pretty good to me.

I notice your speaker placement in the diagram almost half way into the room. That is very insightful! Some of the best setups I have heard have been set up that way. ITs something that most can never try or may not even be aware of. It works especially well with planars like Magnepan that I have heard. Jim Smith used to do this in his shop in Birmingham Alabama with the MAggies he sold. I bought a pair on the spot! Nver had the option of setting them up that way indefinitely though. I've attempted it as best I can in my larger narrow L shaped room where my OHMs reside about 1/4 to 1/3 of the way into the room with my listening mostly from the rear of the room from various locations (the OHMs are pseudo omni/ very wide range and retain high coherency regardless of listening position when set up well).
Looks awesome, much nicer than a crypt. Feng Shui principal is to have doors and windows visible from the sitting or sleeping position. Idea is that you should be able to see who is entering.

I once lived in a house with a glass wall on one side of the den. I had the couch along that side facing into the room. Any time someone walked up and knocked, or walked in, I wasn't expecting it. I changed the couch to the other wall, without even thinking about why, and the feel of the space became noticeably more comfortable.

I don't know if this is possible with the design or if you care... just thought I'd mention it.

Looks like a fun project. Good luck.

If you can manage to get that 375mm dimension up to 400ish mm or a bit over 400mm, I'd think that you'd be in very good shape. As to record/cd racking - the same suggestion would apply to either:

Stagger the depth of the racking in order to break up the long, flat surface.

Keep us posted on the project.

Feng Shui principal is to have doors and windows visible from the sitting or sleeping position. Idea is that you should be able to see who is entering.

Bjesien, yes, but that would mean that the sliding glass door and windows are on the narrow side of the house, and that wouldn't work well either.

In the current setup, I am planning to have a thick theater curtain blocking the sliding door in my back. I do like to see who's coming, though, and I may consider a security camera, or maybe some outside mirrors on the side windows for that purpose. Not sure how compatible that is with Feng Shui?