Disgression 4: Raising the Roof of Your Listening Room

 

Raising the Roof of Your Listening Room

Telarc Height

At CEDIA 2001, was treated to a demonstration of an alternative 6-channel configuration: the inclusion of height channels.

The easiest of them, the Telarc height channel. In the Telarc configuration, you begin with the standard 5.0 speaker layout of Front L/R/C and Rear L/R. The subwoofer channel is reallocated to the height channel (Figure 10a). The height channel has two potential solutions. A single channel can be located directly above the center channel for a 6.0 solution.

Alternately, two channels can be utilized to present height information (Figure 10b). In this configuration, the two channels are placed at the sides of the listening position, well above the plane of the other speakers. In both cases, the information presented in the height channel is identical; the two speaker solution affords a more diffuse presentation of the height information. In Telarc’s multi-channel mixing room, dual height channels are employed using dipolar radiating planar magnetic loudspeakers (Figure 11, below). The speakers are wired in series, so a single channel of amplification can drive them.

MDG 2+2+2

Of course, there has to be more! And in fact there are two more configurations to cover. First is the 2+2+2 format, being brought out by MDG records in Germany. In this setup, the center and subwoofer channels are redirected for use as left and right height channels respectively. The height channels are placed literally above the main left and right speakers.

Chesky 6.0

We come now to Chesky’s 6.0 format, which includes front / side height channels which is similar to an earlier mentioned format that attempts to build a more spacious sensation when listening in this fashion. In the Chesky configuration, height channels are placed above and outside the main speakers at approximately 55 degrees.

MDG and Chesky’s six-channel system has two "front" speakers, two "high" speakers, and two "rear" speakers.

The front speakers, arranged as a standard toed-in two-channel system, give you the first direct wave-form of the sonic event, the most information.

In MDG systems, then mount an additional speaker pair directly above the two front stereo speakers. The distance between each of the upper speakers and the stereo speaker below it should be half that between the two front stereo speakers.

In Ckesky’s system the front side speakerts are somewhat off to the side, at 55°, but equidistant to the listening area, at the same height, or two to three feet higher than the front stereo speakers. These front side speakers recreate the proscenium reflections that dominate the ambience we hear in a concert hall.

The rear speakers are likewise equidistant from and aimed at the back of the listener’s head, and are similarly toed in and "ear-tuned" until everything clicks into place.

In Chesky systems, we also suggest that the rear speakers be placed 135° to 145°, but 110° to 5° will offer acceptable results. The best position is room-dependent. Rear speakers should be at the same height, or slightly higher than ther front stero speakers

Trust me, you’ll know it when you hear it. The listener gets an approximation of the direct sound, the ceiling and near side wall reflections, and rear wall reflections as they occurred in the original recording venue, whatever its size. The soundfield floats (adjustably, to taste) somewhat off the floor.

 

Since sound travels about 1100 feet per second (the only constant in audio), the differences between different sized home listening rooms will be a small percentage of, say, the distances involved in a symphony hall. Listening in a small room (ten by fifteen feet or less), compared to a medium room (fifteen by twenty feet), compared to a large room (thirty by fifteen feet or more) will introduce a difference of only five to ten, maybe fifteen milliseconds. Those are very small delays compared to those in a recording venue (symphony hall) that might be more than seventy feet across, and equally high (seventy milliseconds up and another seventy down), and perhaps two hundred feet long (similarly, two hundred milliseconds out and another two hundred back, about .4 of a second). Not to mention the natural acoustic decay that ranges from around one second (recital halls), to around two seconds (symphony halls) and sometimes three seconds or more (cathedrals, The Royal Albert Hall). So System 6.0, theoretically, could be set up in any adequately sized room, with modest gear, and it would be impressive. In a room as large as the Chesky studio (29’ x 15’ x 12’) and with immodest gear, it is mind-boggling.

The sound of 6.0

What does it sound like? Great! It sounds just great. It doesn’t sound like those old multi-channel set ups where the instruments entered the sound field like bits of shrapnel in an aerial dogfight, flying at us like B-17 tail assemblies that made us duck in 3-D movies. The Chesky 6.0 system sounds like a reasonable reproduction of the music in its original venue. The instruments are well placed in acoustic space, and you can hear the spaces between the instruments better than on really fine stereo. David at the control board took me through a recording of trumpet player John Faddis and his jazz group playing some standards. I listened to that in two channel (stereo) for a while before he added the two rear channels (quad); then, finally he added the high channels to make it six-channel (System 6.0). Next I heard David Johansen and the Harry Smiths. Then he played excerpts from a piano-cello duo’s chamber music recital, and finally excerpts from his own Oratorio with full orchestra and chorus. With each sequence from stereo, to quad, to System 6.0 the sound got deeper, the panorama got wider, instrument location got more precise, instruments rounded out, and there was a more convincing and more involving reproduction of ambiance. The music seemed to float in the air, in front, in back, above, and around the speakers (which curiously seemed to have no relationship to the sound). The speakers became pieces of furniture in the room as decor, certainly not the authors of this amazing sound field. I still felt like I was seated in the audience, first row front and center, but I wasn’t thrust among the instruments in the annoying way of the old quad playback systems.