Aug 1, 1998 12:00 PM, Bob Heil
Little can compare to the feeling and excitement generated by attending alive event-albeit a music concert, boxing match or baseball game. Theexperience is sensational. When discussing a home theatre system, it isagreed that a similar feeling (or part of that live experience) can berecaptured by projecting the video image onto a large screen andreproducing the audio through a multi-channel Dolby sound system. Byassembling the right equipment and installing it in the correct space, onecan have an impressive home theatre system, even at a reasonable price.Many consumers have been misled by dealers whose motto seems to be, "themore you spend, the better it looks or sounds." How terribly wrong. Ego hasdone a lot to ruin many potentially wonderful media rooms. And so we haveto trundle through the pile of rumors, rubbish and myths to create anaffordable home theatre system.
The first step is to choose the best space. Room dimensions are crucial forgood sound reproduction. It is always better to have a rectangular roomwith an approximate height, width and length ratio of 1.0 to 1.6 to 2.5.Because most homes have an 8 foot (2.4 m) ceiling, an appropriate mediaroom would be 13 feet (4 m) wide by 20 feet (6.1 m) long, and if this isnew construction, the walls should not be parallel. They should be slantedby several degrees to help reduce the standing waves.
Sound does not simply emit from the front wall to the back wall and stop.It reflects 90degrees off the back wall and hits the floor, ceiling andside walls simultaneously, thereby creating all kinds of reflective soundpatterns. Because sound travels at 1,120 feet (341 m) per second, this cancertainly create some pretty mean phase cancellation, all of which resultsin slight echoes and hollow-sounding audio. The solution is simple. Kickthe top of the wall in about three or four inches (76 or 102 mm). Curve theceiling a bit. Ever notice a high-dollar recording studio? None of thewalls are ever parallel. They were not built like that for purely modernvisual appeal; they are designed deliberately to help reduce the standingwaves, and it is so simple to do. A good interior designer can take thatand get really creative with matching swirls and curves in the carpets,furniture and wall coverings.
A quick point about wall coverings. The best wall coverings for a greatsounding media room come from covering the virgin wall board with cotton,which, in turn, is then covered with satin or similar material. Thispractice creates a great look and virtually eliminates reflective soundpatterns, all for very little money.
Front or rear projectionUpon defining the space, the major equipment decision will be the type andsize of the video image. The easiest (and usually least expensive) will bea rear-projection television. There seems to be a glut on the market todayof the 40 to 60 inch (1,016 mm to 1,524 mm) varieties with several latecomers out to 70 and 80 inches (1,778 mm to 2,032 mm). The caveat here,however, is that many of these do not exhibit the most pristine videoimages. As I said earlier, bigger and more expensive does not always equateto the best. There are some exquisite rear project TV items lately, but youare going to have to hunt for the specialty custom and industrial dealersthat carry the likes of Hitachi's new SBX and such reference monitors asthe Pioneer ELITE. These are excellent rear-projection display devices, andthey would serve as an adequate centerpiece around which to design andbuild your room.
The alternative is a front-projection unit. In the past decades, thethree-gun analog projectors from Ampro, Runco, Zenith and Sony were quitewell accepted; however there have been a number of terrific breakthroughscoming from Sharp, Ampro and others giving us LCD (liquid crystal display)projectors that are more than capable of filling the role. They arelighter, need little service (no lens convergence) and are relativelyinexpensive (starting below $3,000). All can rise to the task of producingbeautiful video images on screen sizes up to 15 feet (4.6 m).
An interesting approach to the design of the room is to place the projectorbehind the screen. The throw distance of usually about 12 feet (3.7 m) isstill needed, but using a special membrane-type screen that can beprojected through (instead of a front projection screen upon which imagesare projected) can allow the projector to be moved out of sight. A greatexample of this is shown in the August 1997 issue of S&VC on page 16.Mounting a projector behind the screen can give the designer tremendouslatitude, help cut down on ambient light refractions and provide astunning, bright image on the screen with all focus on the picture and notthe projector blaring its beam of light across the room.
Keep in mind that any of the front projection systems are not usable inhigh ambient light, so if you have lots of windows in the media room, somemethod of motorized drapes or blinds will be needed to darken the room ifused during the daylight hours. If this will be a multi-purpose room ratherthan a dedicated media or home theatre room, it would be advisable to lookin to the 50 or 60 inch (1,270 mm or 1,524 mm) Elite rear projecttelevision monitor or similar product instead of a projector and screen.
Loudspeaker placementIn this case, we actually are dealing with firm science. No questions aboutthat, but so many of the systems seen today just seem to forget that,Worse, many even attempt to defy it, and, of course, it shows in the poorquality of many home-theatre systems, regardless of their expense.Loudspeaker placement is crucial to the faithful reproduction of the dialogsound, the music and the special effects. Even the sharpest video imagewill not alleviate poorly planned loudspeaker placement, especially if theaudience is incapable of understanding the dialogue.
Front left and right speakers should be placed at ear level when seated. Nohigher. Anything less than six feet (1.8 m) between these two will not givea wide enough front spread while 10 (3 m) feet or greater loses the wholefront image. It has been proven that in the home systems with a 15 foot(4.6 m) wide by 20 foot (6.1m) long room, eight to 10 feet (2.4 m to 3 m)is a perfect spread from the fronts with the center channel being in thecenter either above or below the screen.
With either front or rear projection, it is best to dedicate one wall forthe screen and front line of loudspeakers. There are two schools ofthoughts about this wall. Some like to have just the screen andloudspeakers with no distraction from anything else while others like tosee the equipment racks on either side of the screen.
Moreover, the ideal subwoofer setup is to use two of them-one under theleft and one under the right front loudspeakers. The subwoofer must be selfpowered with a parametric crossover so you can change the parameters foreach room in which it operates. The frequency, the roll-off and the levelis a must for proper subwoofers. The big caveat with all subs is that if itdoes not have a built-in power amp (or dedicated amp just for that sub)walk away from it. Your client should have no place for toys in his newhome theatre.
If only we could devote this entire month's issue to this subject ofsurround loudspeakers and their proper placement, but even then, we wouldprobably still have things to learn. First off, surrounds do just that.They are intended to surround their audience with ambience. Normally, thisis evident through such effects as crickets wind blowing, but it they areintended only for effects. You will never (well maybe for a simple effectin somebody's movie script) hear a leading role's voice speaking throughone of these loudspeakers. You will not hear a flute in the right, guitarin the left front, dialog in the center and piano in the rear. An importantnote, so read closely. Ray Dolby's wonderful Pro Logic technology is notthe same as old QUAD system. It is truly a surround effect channel, and itis because of this that we must pay close attention to their placement.Science dictates procedure here.
The ideal is to use Tom Holman's idea of dipole speakers so that weactually receive surround information from the reflections off the screenand rear wall. NEVER anything coming into the room directly from thesurround loudspeakers. The best in-wall or simple on-the-wall (picture hungtype boxes) placement involves placing them on the side walls two to threefeet (610 mm to 914 mm) behind the listeners ears and no more. This createsa wonderful sound field with the front line of loudspeakers and enhancesany four-channel Pro Logic system. As you can see, all this enhancementrequires is just simple and correct loudspeaker placement.
One last item about surrounds. It has always been an industry perceptionthat because Mr. Dolby only gives us 100 Hz to 7,000 Hz in these effectrear channels, there is no low-end response. Well, if you really want toenhance any home-theatre system, place a dedicated powered subwoofer behindthe intended audience and connect it to these rear surround loudspeakers.You will be amazed at the results. There is plenty of low-end response backthere, enough that at the small expense ($450 to $600) for some wonderfulpowered subs makes it a must to spec for your room.
Equipment locationLast, but certainly the most important, is the equipment itself. The idealthing to do is mount the equipment into a 19 inch (483 mm) rack and shelfassembly. The entire unit can be placed right in the wall or in a properlysized "hole" of your custom entertainment center,. It is the 70-year-oldtechnology of the telephone industry that allows us to wire, test and alignall of the gear and then simply slide it into place without having to getout the dental mirror and lose your religion trying to get behind theequipment to plug something in. Ultimately, the location is your call, andit should be based upon your client's individual tastes and preferences. Ifhe likes to see the flashing LEDs, place the equipment at either side ofthe screen. Placing the equipment behind the intended seating area willmean that you should install some infrared repeaters so that the user canpoint the remote at the screen and then send that signal to the equipmentbehind him.
Connect and enjoyOf course, once all of the hammers are at rest, the paint and glue is drywe only have to connect the wire, which, presumably, was run to the correctlocations during construction. After that, it is up to your client to savorthe results of your labor. One small note about that wire. Another of theindustry rumors is the bigger the better. Time and time again, study afterstudy has been performed, and a Julian Hirsch review of 1994 said it best,"the effect of the huge wires is normally only a minute change in frequencyresponse." This is hardly a matter to be concerned about unless you or yourclient happen to be the type of person who agonizes about how many angelscan dance on the head of a pin. After several thousand audio systemsdesigned and installed, I am still using 16 gauge, not the small stuff butthe large lamp cord for runs under 50 feet (15.2 m) and in most of themedia rooms, 50 foot cable runs are seldom, if ever, reached.
Intelligent planning and equipment placement, not expensive electronicdevices, are critical to the creation of a high-quality media room. Eventhe most expensive loudspeakers and display devices will perform far shortof expectation if their installation is not given due consideration. Followthese simple procedures, and you will go a long way towards satisfying yourclient, especially if you produce a good home theatre room while alsolowering his expenses.