|
|||
|
As many Widescreen Review readers know, I have designed the first Optimum Performance Home®, now under construction at The Sea Ranch along the Pacific Ocean coastline of Northern Sonoma County, California. This home, while not yet completed, will be the “greenest” home in America. Regardless of “green” certification programs, the design surpasses the highest point rating of any certification program. CEDIA also has adopted the project as a national electronic lifestyle showcase home. I wrote a three-part article series in Widescreen Review on the design of the dedicated home theatre, which I refer to as an Optimum Performance Home Theatre, a shorter term for essentially the same approach as we took with our Holosonic® Spherical Surround™ Home Theatre Laboratory at the offices of Widescreen Review. Once completed, the new Optimum Performance Home Theatre will replace our so-called “Laboratory” and become the magazine’s premiere reference theatre. You can read about the design of this new theatre in Issues 118 (March 2007), 120 (May 2007), and 121 (June 2007). I recommend this as required reading if you are embarking on designing a dedicated home theatre with performance as the goal. Now, the architecture of the new Optimum Performance Home Theatre differs not in dimension or size but in the symmetry of the audio and visual system placed within the room. In the Laboratory we took the approach of offsetting the audio and video system in a non-symmetrical layout relative to the system’s relationship to the room’s width dimensions, but with the system otherwise perfectly symmetrical. During the design phase of the Optimum Performance Home Theatre, we explored the question of “Symmetrical vs. Non-symmetrical Layouts.” Norman Varney and Harry Alter, principals in A/V RoomService, Ltd. (AVRS) served once again as advisors on this question and the application of their high-performance acoustical panels. AVRS won another CEDIA Electronic Lifestyles Award for 2008, for Best Large Home Theatre Level V Gold Technical Design Award in the $340,000 to $465,000 category. (Visit avsroomservice.com) Below is a piece written by Norman on this subject that I recommend you read to gain a better understanding of the merits of a symmetrical room/system layout. Gary Reber Editor-In-Chief & Publisher Widescreen Review “Symmetrical vs. Non-symmetrical Layouts” Norman Varney “This may be more of a rant than a tip, so please forgive me in advance. I'll make it brief. “Audio has been a serious part of my life for more than 40 years. I've been attending AES conventions since the late 70's, the past 29 years of CES, and CEDIA from the first discussions. I've accumulated an office full of books and white papers on audio, performed thousands of audio tests, written numerous articles, and given and received countless seminars on the topic. Never has the notion of non-symmetry in audio layout been regarded as a good thing. However, I see it being done frequently these days. Open most any magazine about home theatre and you'll see pictures of layouts with no centered seat between the loudspeakers. Where is 'the money seat' that every audio set up should have? There can only be one designated location where all the loudspeakers can converge at the same space, at the same time, and at the same amplitude. To have two seats flank the 'sweet spot' is a disservice to the client. The spot where all the magic lives is unoccupied, and a large investment is not paying off to its potential. Sure, you can calibrate the system electronically to most any location, but it will still be severely skewed acoustically. Understand that the design hierarchy must be: set-up, calibration, acoustics, equipment. Even a stereo boom box can't be perceived as stereo unless your head is oriented correctly in front of it. “I have also seen more than one expensive, dedicated cinema where both the loudspeaker and listener positions are deliberately laid out off-center of the side walls!? This is very odd. Why would someone design such a layout? It turns out that the idea is to avoid the width axial room modes. Sounds like a great idea for about two seconds. Then you realize that even with a relatively small theatre width of 16 feet, the f1 axial mode cancellation is 35.3 Hz., which: a) is the fifth note up from the bottom of a piano, so except for keyboards, it is not likely that a soundtrack will play 35.3 Hz. long enough to cause much of a standing wave issue. b) the wave is 32 feet long. You may ask how far off-center will we have to move to be out of the canceled wave? You'd have to shift the seats about 3 feet just to gain about 5 dB. What about f2, which is a crest at 70 Hz. and f3, which is a trough at 105 Hz.? And what about the length and height axial modes? Modes are everywhere, and as you move out of one, you move into another. c) If we also move the loudspeakers, aren't we likely to exasperate the room modes? Yes. d) If we move ourselves and the loudspeakers closer to one side, aren't we likely to perceive a difference in low-frequency pressure? Yes, and also hear differences in timbre, spatial ques, imaging, etc., all due to the difference in distance between the listener and the left and right boundaries of the room. If we were to compare the same signal being fed to both L and R loudspeakers at the skewed listening position, they would be very different. And no, DSP ain't gonna fix it. “It is true that we want to avoid placing ourselves and loudspeakers in areas that will excite room modes. It is also true that in an enclosed space, we must make many compromises. The best choice for loudspeaker/listener position is to avoid the fundamental height and length modes and sacrifice the width. This has to do with human perception and the fact that, by design, we are much more sensitive to the horizontal plane than we are to the median or lateral planes. I'll gladly sacrifice a few rare low-frequency irregularities for constant linear mid- and high-frequency tonal balance and accurate soundstage and imaging any day. “Lastly, a rectangular room is predictable and easier to treat acoustically because of its symmetry. Irregularly shaped rooms are difficult to model and difficult to control acoustically. “Symmetry is always a good thing.” Internet Contacts: http://www.avroomservice.com
Tags:
- editor's couch -
|
|||
×
Access Widescreen Review on your iPad or iPhone.
Internet access is required, but PDFs of complete issues and individual articles can be saved to your device for reading offline.
Tap 
then "Add to Home Screen"
then "Add to Home Screen"