SOME DETAILS ON THE MUSIC ROOM

 

OK. The details of this room which has been referred to as the Chamber of Horrors. The origin of that name goes back about 15 years or so when a friend who didn't understand my obsession with loudspeakers saw it for the first time. It was, at that time, just a closed in 2 car garage with a carpet. Originally 20 by 20 feet, the wall which replaced an opening garage door was built 1.5 feet thick. That was a compromise from the ideal which would have made the internal dimensions 20 by 14 by 8.5 feet; however, the thought of losing all that space and being that close to the loudspeakers didn't appeal to me. At that time, I never thought of placing the speakers on the 14 ft. wall. Why? I'll tell ya. I dunno. Never thought of using the internal 6 ft. as storage either. Fifteen years later, 1991, when I finished the room walls with gypsum board, that thought still never occurred to me. Now that's it's finished, there's no way I'm gonna get into a project of that magnitude.

The original dimensions of 20x14 stemmed from calculations, all done manually as I didn't have a computer in 1976, which determined eigentons, or standing wave patterns in a closed area. The room response at low frequencies below 300 Hz would have been relatively flat as there were no even number multiples of any two dimensions in the room. The best compromise considering maximizing the room size came out to 17.5 feet for one dimension. This does, however, give a close 2:1 ratio with the ceiling height but I was confident that the anomalies at the low frequencies could be smoothed by use of an equalizer. Well, as it turned out, a 10 band EQ couldn't do it. Then came 3 parametrics. Still couldn't do it. Even tried a high Q notch filter in the preamp tape input/output loop. The notch was close to 40 dB down at the fundamental resonance in the room, about 64 Hz. and the bandwidth of the notch was less that 10 Hz. wide at the -3 dB points. I didn't care about the room peak at 32 Hz, as that would be a bennie and also thought that if I eliminated the fundamental, the lower and upper harmonics would be reduced also. WRONG. At the first harmonic, 128 Hz, the notch filter had no effect. So, Neil Diamond sounded like he was singing in a drum. So, I skuttled the notch filter and the equalizers. It was suggested I rotate the room, or at least the contents, which I did, to it's current configuration. Lo and behold, the 64 Hz. resonance vanished. Well, it was there but not audible due to my different seating position. However, now I had a null in the 50-60 Hz. region. No, I didn't reconnect the EQs. Just moved the sofa a few feet. Removing the rear wall would completely solve that problem by eliminating the rear reflecting surface and opening the music room into the living room but that was a bigger project that moving the right wall in a few feet and gaining closet space. See, the rear wall is block as well as its being a supporting wall.

By this time, mid 90's, I was a seasoned computer nut. A friend had acquired a program that calculated eigentons merely by inserting room dimensions and a few other tidbits of info. By dragging the speakers or the listener around the screen the response was calculated in seconds. It also allowed for 1 or 2 sound sources. My ingenious friend, Jerry, used one low frequency sound source and found a woofer location that virtually eliminated the response irregularities. Unfortunately, the point source was to have the woofers in one corner, facing down from the ceiling. That let out the corner horns, but the reflexes were considered. However, at close to 300 pounds each, it seemed a formidable task. They'd also have to be insulated from the 160 degree attic temperatures in Arizona during the summer. Placing the 2 reflexes in either corner was a very good compromise but not aesthetically appealing. Soooooo, I got very creative and wired the reflexes in MONO off one channel and did the same with the horns on the other and padded the horns down about 10-12 dB. It worked. The horrible peaks were diminished to a very acceptable level, unless one is into response curves. However, the response curves of most rooms that sound good are anything but flat.

The moral of this story: If you have to have 2 woofers reproducing below 125 Hz., you might consider wiring them together in mono. However, this can introduce other problems. Low frequencies are essentially non directional below about 40-50 Hz, but the mid bass region isn't as such. This isn't a serious problem when listening to music but surround sound is something else altogether especially with respect to the front speakers. As I mentioned earlier or on aother page, I'm not "into" surround sound so I'm willing to make the compromise. Besides, the reproduction of sound under any, other than the original performance, is a series of compromises. I'll sound off, heehee, on that one later.

Well, if ya got this far, you may have a few things upon which you agree, disagree, want clarification upon or whatever. SO, in the event of that being true, I have provided this handy dandy, new and improved low calorie, poly unsaturated, fast acting, pleasant tasting?, quick responding green and purple email link for your convenience.

 

 

 

GREEN and PURPLE.......Email Link

 

 

 

Main Loudspeaker Page

My Special Mr. Klipsch page

Briggs' Wharfedale Three Way System

More On Loudspeakers

A Few Other Systems

My Room - aka: Chamber of Horrors

Corner Horns - Photos taken during construction

Phonograph Stylus SEM Photos

 

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