Six Klipschorns in a Round Room???

[HornEd]

I am committed to building a 6.1 Klipschorn Home Theater with a custom subterranean fully-horn loaded subwoofer. The theater will be free standing in a forest glen. It was my intent to build the room to ideal proportions for multi-channel sound. However, all of the approaches to ideal rooms seem to be for a rectangle. I'm looking for a recipe for building a listening room in a circle.

The last time I tried it was with the 8 Legend Theater which was built in a 30' circular yurt... and the results were better than I expected. So good that I am thinking of mounting the six Klipschorns in a circle with false walls extending through the walls.. What do you think of a 36' circular mini-concert hall? What should the dimensions be? -HornED

[MrMcGoo]

HornED,

Have you considered an ellipse. It would have two focci, and might (???) help distribute the sound more evenly and be a bit closer to the expected shape of a theater. An oval is also a possible shape.

The ellipse would allow the precise location of sound absorption materials. I assume that you intend to build false corners for the bass lenses needed.

Bill

[Q-Man]

The circle idea is good, because it will place all the speakers an equal distance from the sweet spot. This is ideal. 36 feet is most likely the min. size, because it puts you about 18' from the screen or RPTV. You don't want to be closer then that if you can avoid it. I also find it a nice distance to be away from klipschorns. This is all from the top of my head right now. I have to give the idea a little thought.

The sub idea is a good one. I've seen one or two of them on some web sites.

[Q-Man]

This is crude, but do you remember this idea?

[j-malotky]

Ed

I like the circle or Oval idea. With wider side walls you should have a very wide sweet spot.

Did you consider angling the walls vertically as well? I built a room 12 years ago where I slightly angled the rear of the side side walls, and rear walls down towards the carpeting. That does a real good job eliminating bounce back.

JM

[jdm56]

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On 3/25/2004 9:31:21 PM HornEd wrote:

I am committed to building a 6.1 Klipschorn Home Theater with a custom subterranean fully-horn loaded subwoofer. The theater will be free standing in a forest glen. -HornED

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I think you need to be commited to a round room - a round, RUBBER room that could absorb your brainwaves as your mind goes into hypersonic oscillation. Obviously, you've become unstable!

[Q-Man]

I went to bed, but I couldn't fall a sleep thinking about your round room. I'm now wondering if a round room would suffer from the same problems as a square room? Now that I said that maybe I can fall a sleep.

[nicholtl]

Hmm, this is interesting. I too would think that a perfectly circular room would make for the ideal sweet spot. However, I remember a lecture on this exact same subject by Tom Holman during film sound class. He said this is not ideal, and it was even considered for actual movie theaters once, but because the roundness of the walls would in effect cause extreme wave refractions and reverberation, causing echoes from every which way. I am assuming he meant if the room didn't have acoustical treatment.

[jdm56]

From my farm days, I recall how that inside a cylindrical steel grainary, you could never tell what direction any sound was coming from. Front, behind, above or below, it all sounded the same.

[Colin]

I have heard two modest bookshelf loudspeakers sound wonderful in a two story geodesic dome home: they cast a large and wide image with very little effort. Cheskey Records has recordings for a circle of six loudspeakers. Since you need two angled walls for your classic Klipsch corner Khorns, you should consider a pentagon structure instead of a circle yurt; maybe a geodesic dome? That has flat walls with corners to put the big ole horns into.

[Colin]

something like this?

www.royaldevice.com/ custom2.htm

[Colin]

Future Music Blender : Space

The FMB is a collaborative musical instrument, with visitors creating and playing sounds at different stations. The architects at Propeller Z drew inspiration from the curves inside classic musical instruments, like guitars and pianos.

home.comcast.net/~bleppie/ blepco/fmb/space.html

[Colin]

I cant find the link, but there is a guy in Europe who built large concrete horns into the wall of his house, like the soundstage of a theater, expect he is the only one in the audience, has huge horn array, but cant Google him...

[Klipschfoot]

Though the room is not round, the setup is. Check it out at wendycarlos.com. There are also some good thoughts about sound setups on other pages. Check out his/her studio with four cornwalls suspended from the ceiling!

[DrWho]

I would think a round anything room would introduce so many acoustical problems that it would just give you a bunch of headaches...if you're really serious about this, give artto down in the architectural forum a buzz.

I would never claim to be an expert on room acoustics, but I have found the topic very interesting and have been reading up a lot about all the cool high tech studios and all the tricks they used regarding room acoustics...they have always used straight walls. However, they never use rectangle rooms.

If I remember right, I think the "golden angle" is around 135 (this is the angle that the side walls would meet at if they connected). I think it might depend on the speakers, but i think this is the angle where the sound travels down the side and doesn't reflect out at you. and if possible, you want the rear wall to be non-existent. but since in reality that's impossible, you end up building a fancy wall in the back to seem like it's not there (also making it angle backwards so that it'd reflect into the cieling). also, you'll want the cieling to move up as it goes further back as well. basically, the whole room opens up as it goes back, and with the correct angles, you end up with an extremely flat room response with very little echo and no room nodes. i've got a book somewhere that talks all about this...

but then you throw khorns into the mix and you're stuck with having to have the correct corners and walls...you might try a large room (kinda like q-man suggested), but i would try to avoid all the sharp corners...if nothing else, make the room a bit larger and round out all those edges. it's just that sharp corners sound unnatural...if you've ever been to any of the fancy opera houses or the symphonies or whatever, you'll always find all the edges rounded out.

and lastly, bigger is better when it comes to the room...and you're gonna need a huge room anyway if you're planning on building that huge subwoofer.

[HornEd]

Wow, a lot of good input... particularly the "rubber room" concept since it brings up a whole area of membrane absorbers to dampen secondary low bass reflections. And, Q-man, (my hero) I hope you got some sleep... and yes, I do remember that sketch you sent me... it is what led me to try a circular room with minimally reflective walls.

My 30' yurt has a steep conical ceiling with a large (5') Plexiglas dome that raises to provide hot air venting in summer. Acoustically the worst seat in the house is under the middle of that dome. Since the supportive timbers are essentially 2"x3 studs on 18 centers, the amount of reflective surface that faces the room is minimal. The bottom 6 of wall is reinforced by a latticework that does little to impede bass waves. The skin of the building is a hybrid that is essentially a flexible membrane that is a sandwich of two membranes with an insulation layer in the center. Thus, this building provides a somewhat ideal acoustic benefit for those inside but would cause neighbor issues if I didnt own the neighborhood!

And even that has its downsides. There were about forty of us in the theater listening to the loudest depth charge part of Das Boot when someone pulled a main switch to create an electrical black out to a portion of our mini-grid causing an immediate cessation to the rumble going through the forest including some RVers camped over a hundred yards away! Since then, I have built some reflective and absorbent surfaces behind the front array and the dual SVS Ultra subwoofer tower and have had happy campers inside and outside the NuDome Theater (Eight Legend Theater to Klipschers) ever since!

So, as to the silo effect (a fun one that I remember from my youth on my grandfathers farm), the yurt dissipates sound by being largely non-reflective while a silo, would tend to reflect in a diffuse way kind of like WDST on steroids! Not a pleasant thought for a properly mixed DVD that has carefully calculated ambience apportioned over appropriate channels.

Virtually all approaches to acoustically ideal rooms that I have found are based upon rectangular boxes with no in-depth theoretical approaches to round or oval listening spaces. Dr. Floyd E. Toole muses about odd shapes (such as the one advanced in this thread by Q-man) but he holds little hope for an ideal coming out of non-parallel complexities. His thoughts can be researched in his illustrated talk that can be found at http://www.infinitysystems.com/homeaudio/technology/whitepapers/inf-rooms_3.pdf

Another issue of room design is the fact that sounds with shorter wavelengths tend to benefit from a certain amount of reflection but longer wave lengths are impaired by reflections that cancel out or reinforce axial waves (the first order of standing waves). Thus, the ideal room would have to have different characteristics for long, medium, and short sound pressure level waves. For example, bottom scraping subwoofers need an anechoic room but the lost mids and highs would make it a definite bad idea as a listening room. The lower you go, the more mass and space have to be allotted to bass traps in fact, Tooles calculations indicate that building an acoustically correct low-bass environment would add 20% to the dimensions of a room in every direction!

It is Dr. Tooles presumption that even a bad room can be made to be good if not excellent and that there is no such thing as a room that couldnt be made better and, therefore, there is no ideal listening room. At least not in any home he has lived in to date and if anyone has ever been ideally suited to build the ideal room, it is Dr. Toole. So, despite the high regard I have for Dr. Toole, somehow I think that with the inspiration and support of folks in the Klipsch Forum a better room can be built or at least we can have some fun in trying! Thanks for your support even if it got a little rubbery in one head case! HornEd

[HornEd]

Thanks Klipschfoot & Dr.Who for contributions while I was off writing the last post. The relatively newly established "European Standard" for multi-channel monopole speaker placement puts five speakers in a circle within a 20' x 24'rectangular room. Speakers are placed with the center main at 0° and the left main at -30°, the right main at +30°, the left surround at -110° and the right surround at +110°. One would presume that a sixth rear effects speaker would be placed at 180°.

Since I have achieved more success with the round yurt than I had expected, I have been doing some additional research in building a building that would reflect medium and higher frequencies for better ambience but let the bass and low bass into staged infinite baffles that would be comprised of a double wall that would be solid on the outside wall and easily permeable by low waves on the inside wall. There would be no mechanical connection between the inside wall and the outside wall... no electric, water or HVAC lines. Such lines would be buried underground and come up at the inside walls.

In fact, I am considering building the theater by digging a hole in this rocky mountain soil and finishing it with gunite when I do the even deeper subterranean sub. The shape of the roof (probably a done) would likely be cast in place using a technique similar to the way that was speculated as how the granary was built at Mission San Jose in San Antonio, Texas hundreds of years ago.

Currently, I also have four Klipsch Belles and a pair of vintage Cornwallis that could be pressed into service as Klipschorn friendly Front and Rear Effects. My purpose is to achieve a better sound tribute to the late Paul W. Klipsch in a multi-channel environment. And, so, while it may be more than a little over the top... hopefully there are a few Forum friends out there who will enjoy the read... if not the contribution of a post. -HornEd

PS: For those who think I started this thread for my own boastful gratification... you just don't realize that I know the Joy of striving for sound success... and will not wallow in the Misery of trying to avoid failure. I give myself the "Freedom to Fail"... and that allows me to use what resources I have to succeed.

Does having the Freedom to Fail work? Well, I believe if I didn't have the Freedom to Fail I wouldn't have the resources or the acumen to build this over-the-top theater. From what I have seen of innovators and entrepreneurs... you can always tell the pioneer by the arrows in his back. Since I have given up shooting down "mini-Klipsch-flaming-Indians"... I hope we can discuss the positive and negative aspects of this project like the adventure it should be. -HornEd

[artto]

There are some substantial problems with round, domed or oval/ellipse room configurations. The problem is also most likely to be related to the size.

Please try & follow me on this. Round type rooms basically form a concave surface. Concave surfaces tend to focus the sound to one point. This is exactly the opposite of what you want acoustically.

The radius of curvature determines the focal distance. The flatter the concave surface, the greater the distance at which the sound is concentrated. Concave surfaces might produce some awesome effects such as in whispering galleries (Chicagos Museum of Science & Industry has one) where you can hear a pin drop 100 feet away, but they should be avoided in listening rooms & small studios.

Note that I said small. In larger rooms, where the rooms dimensions are at least several times longer than the wavelength of the lowest frequencies to be produced this effect may not exhibit itself as much. Rooms such as theaters, or even planetariums (that have Laser shows with big sound systems) often have or are built around dome configurations. But these spaces are quite large & consequently have a large seating area to begin with.

Diffusion (preferably broadband) is what we are after for good sound & good sound distribution over a large® listening area, & this requires convex or geometrical plane surfaces and/or angles. Even geometrically progressive plane surfaces are inferior to convex cylindrical sections.

Once the space gets large enough concave surfaces are not as much of a problem, but they are, technically speaking, not a good approach and should be avoided.

[Frank Speaker]

When I was at college some friends lived in the Domes a village of 1970s vintage geodesic domes. There were some Freaky acoustics in those things. Sometimes I would be sitting close to a wall and could hear someone talking near a wall at the other side of the building better than the people right in front of me. In fact sometimes we used to sit at opposite sides of the building just to create the effect.

But consider the Century Theaters, one big dome theater. They must have those Freaky acoustics figured out to be beneficial.

[Colin]

list of dome companies, incluidng those that sell just the hardware:

http://www.ecobusinesslinks.com/dome_homes.htm

yes, you can hear everything said on the other side of the dome!