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This is the second revision of the room. Later revisions look similar, but differ acoustically. I know some of you have already read a previous post of mine describing the construction of room, but for sake of convenience, I'm re-posting here:
I built an entire room around my Klipschorns in the early 80’s & the room has undergone a number of revisions. You & other readers might benefit from what I did & what I learned from my mistakes. The room has been published in several audio magazines over the years.
First things first. Ideally…….you need a room with the proper proportions to achieve uniform distribution of eigentons (low frequency room modes). The ratio is 1: 1.26: 1.59 (called the “Golden Mean”) (see Klipsch Dope From Hope newsletter Vol9, No1 Feb 1968). It doesn’t have to be exact. And rooms outside of these proportions have been known to sound good. Use the long wall for the “stage”. It makes a dramatic difference & you may even find that you don’t have to “turn-it-up” as loud.
Another “trick” you can use is the Half-Room Principal (Room Dimensions for Optimum Listening and the Half Room Principal, IRE Transactions on Audio, Vol AU-6, No1 Jan-Feb 1958, pp 14-15). For instance, my room is 27’ wide. A 42Hz note has a wavelength of aprox. 27’. So based on the longest dimension of the room, the room will accurately convey the full wavelength of a 42 Hz tone. But based on the Half Room Principal, you can expect a reasonably flat room response down to 21Hz (21Hz=54’ wavelength. 54’/2 (one-half of the wavelength)=27’.
If you take this one step further & use the diagonal dimension (which you can do with K-horns because of their corner placement & 45 degree angle toe in) it works even better. My room has a diagonal dimension of 32’ which ½is one-half of 64’. 64’ puts you at about 17-18Hz. My system has measured down only 9Db below 20Hz with no electronic EQ. Not bad for folded horn-loaded speaker of this size. And in fact, that puts the K-horns at about 95Db/watt below 20Hz. Much better efficiency than any of the “sub-woofers” or so-called “flat” “audiophile” speakers out there.
A dimension you want to avoid is 19’ (or multiples & fractions) thereof as it is the wavelength of 60Hz (electrical hum).
A quiet room is a good room. Avoid exterior windows if you can. In my room, I isolated all plumbing (sump & ejector pump plumbing too) from the frame of the house. The plumbing is also insulated. Same thing with any forced air vents. If you can isolate the room’s ceiling & walls from the structure of the house, do so. I didn’t have the luxury of doing that. Remember that wall mass & no air leaks has more than anything else to do with blocking sound.
In my room, I applied silicon beading to the interior of the outside wall studs. Standard R-19 wall insulation between studs. Over the studs I placed 1/2 inch Celotex http://www.us.bpb-na.com/products.html rigid insulation board. Sealed the joints with silicon beading. Silicon beading over the Celotex where the studs are located. Created a 1” air space by putting 1x2 lath over the studs/Celotex. Repeated this process again. Then applied 5/8” sheet rock (Gypsum wall board). Since my room is only partially below ground, the upper wall exposed to the outside received an additional layer of Celotex with a 2” air space between it & the wall. Similar treatment was done for the ceiling. Ilbruck (maker of Sonex acoustical products http://www.mhtc.net/~lowey ) now makes a product called ProSpec Barriers which I would recommend using between the layers of the wall & ceiling.
I also heavily reinforced the corners for the Klipschorns, from the corner, to 8’ out from the corner. I used a staggered 6-12” stud spacing, both horizontally & vertically to eliminate any wall resonances. I then made 4 “plates” out of 2x12” wood, fit into the studding & secured them & the wall, tightly against the foundation. I made a corner fitting out of 2x12 to fit securely & air tight (use foam weather striping) in the corner for the tail board of the Klipschorns to be secured onto. The corner board is secured to through the wall to the foundation with 10, 1/4 inch lag screws. The tailboard of the K-horns are secured with 8, 1/4 inch lag screws to the corner plate. The K-horns are sealed air tight into the corner with weather stripping foam.
In regards to electric, have everything on its own circuit. I’m not sure that 20 amps is enough nowadays. Obviously this depends on what kind & how much equipment you have. Tape decks for instance can draw a lot of current because of the motors in them. Make sure you use an isolated ground for that circuit, isolated from the rest of the electric in you home. Ground the system at only one point, preferably from a regulated power supply that everything else is plugged into. Float all the rest of the ground connections on your equipment using a 2-prong adapter so that the ground(s) “seeks their own level” & does not produce any ground-loop hum. If you are using light dimmers, make sure they are the kind that have RF filtering. No fluorescent lighting.
Now for acoustics. The Klipschorns do not like “dead” areas around them, so forget that “dead-end/live-end” room stuff. It doesn’t work with K-horns. I use large polycylindrical surfaces made from 1/4 inch tempered Masonite (a wood-based fiber hardboard) (cheap) bowed to 12” on larger ones (4’x8’), 6-9 inches on smaller ones. These can be painted to match room décor. Behind the cylinders I mount Sonex acoustical foam on 3-6” standoffs on the Celotex behind the Masonite so the Sonex can capture sound more effectively from all directions & angles. This produces a room with very well distributed/dispersed middle & high frequencies. The larger polycylindrical surfaces help to damp bass resonances & break up standing waves. The principal here is to allow the room to be relatively “live” at low volume levels. But as the sound levels increase, more & more reflected sound gets trapped behind the cylindrical Masonite panels & gets totally absorbed by the Sonex & Celotex behind it so the room does not acoustically overload due to increased reverberation time at higher volume levels. A simple thing such as clapping your hands can be very useful in locating “hot spots” or ping in various areas of the room which will require sound absorption or dispersion. Likewise you don’t want any dead spots either. These Masonite panels can create quite a dramatic appearance, so be creative & experiment. Keep in mind that the bow in the Masonite panels will tend to “push the walls of the room in” making the room seem somewhat smaller. This can be overcome by the use of lighting to highlight the depth & curve of the panels.
The carpet flooring you see in this picture is composed of large sections of rug remnants. This allowed me to experiment with their affect on the room's acoustics. Later it was decided that very heavy weight carpeting & padding wall to wall would be best.