Top 10 Home Theater Mistakes and How to Fix Them
Sep 1, 2006 8:00 AM,
By Alan Lofft, Axiom Audio
Some days it’s hard to separate home theater help from home theater hype. However, the basic rules still apply for creating a home theater experience that your clients will remember.
1. Hiding speakers inside custom cabinetry.
Speakers already have their own enclosures (cabinets), and are carefully engineered to perform at their best in a freestanding location, unencumbered by special custom cabinets, nooks, custom shelving, or elaborately constructed cubbyholes behind special grilles. Extra cabinetry will degrade and change the neutral transparent tonal balance that Axiom speakers are known for. At the least, deep bass performance will be uneven or boomy and hollow sounding, and the midrange and treble tonal balance may become noticeably nasal or muddy and congested.
2. Using in-ceiling surround speakers.
Resist the urge to use in-ceiling surround speakers because you will not get the enveloping surround effects and precise directional cues originally conceived by movie directors and film sound designers. If in-ceiling speakers worked well for surround sound, commercial cinemas and THX Dolby theaters would use them—and they don’t. Dolby Digital and dts 5.1-channel movie soundtracks are mixed with the surround speakers on each side of the mixing theater about 2ft. or more above ear level, in order to imitate the enveloping sound field created by the surrounds on the side walls of movie theaters (plus a couple on the back wall behind you). Moreover, our hearing is much more sensitive to horizontal- and front-arriving sound cues, not to overhead sounds or sounds from the rear. It’s why our external ears are focused to the sides and forward. Look for quadpolar or multipolar surround speakers that use four drivers each to mimic the envelopment created by banks of surround speakers on a movie theater’s side walls.
3. Building square home theater rooms.
If you have a choice, irregular or rectangular room shapes are preferable. Avoid square rooms because deep bass sound waves really misbehave in square rooms. They produce “standing waves,” which result in areas of extreme bass emphasis and nulls (areas of no audible bass). Trying to fix the standing-wave problem after the fact is virtually impossible. Instead, select a rectangular shaped room with dimensions (length, width, and height) that are not evenly divisible by a common denominator. For example, don’t choose a room 24’x16’x8’; instead, lay out dimensions of 23’x13’x7’. That way, you’ll minimize standing waves.
4. Using Equalization Systems as an electronic ‘band-aid.’
Although the theory of auto-room equalization built into receivers as well as separate EQ units is a seductive one, the truth is that EQ cannot be used to compensate for bad rooms and poor speaker choices. EQ systems often correct one problem while creating others, and are, at best, an electronic band-aid. Accurate loudspeakers, careful placement that acknowledges the laws of physics, and professional measurement and installation will always cede the best results.
5. Blowing more than 50 percent of your client’s home theater budget on a big-screen TV.
Don’t blow a home theater budget on a super-expensive HD projector, screen, and furniture, while leaving too little for home theater speakers and amplification. In other words, match your high-definition visual image with a similarly high-quality soundscape from a fine home theater surround sound system—otherwise your client will only be disappointed at the jarring disconnect of combining a brilliant picture with lousy sound. Infatuated with the “coolness” factor of flat-panel plasma or LCD displays, too many people spend thousands on their TV display, only to find they haven’t left enough money to assemble a high-quality surround sound system. A $999 home-theater-in-a-box will sound pint-sized and out of scale with the impact of the big-screen high-quality video image. If you budget $3,000 or more for an HD front- or rear-projection system, then consider spending the same amount on a 5.1-channel home theater speaker setup in addition to an AV surround receiver or AV processor and amplifiers.
6. Trying to use one small subwoofer to fill a huge room.
If the room has typical dimensions— 20’x 14’x8’, about 2,100 cubic feet—one well-designed subwoofer with an internal amplifier equal in size to the full output of your receiver (full power for one channel + 1/8 power x the number of other channels) and a 10in. or 12in. driver should deliver solid deep bass extension and ample output for music and movie soundtracks. On the other hand, if the room is larger than usual (4,000 cubic feet to 8,000 cubic feet, or bigger) or has vaulted or cathedral ceiling, you should definitely consider running an extra subwoofer. Big rooms, especially the great rooms common in many suburban homes, really devour deep bass; so two subs will generate enough sound pressure to fill the place. They’ll also give you smoother distribution of extended bass over several different listening locations. My colleagues and friends who have large vaulted-ceiling rooms all run dual subs. Taste plays a role as well. If your clients like music or soundtracks really loud and deep, go for two subs. If they have a huge room and want really loud sound and deep bass, then look at physically larger subwoofers with bigger amplifiers, such as the Axiom EP500 or EP600.
7. Over-treating home theater rooms.
Don’t get carried away with the notion that you have to install special bass traps and sound-deadening materials in your new home theater room. Well-engineered loudspeakers designed for home listening have their tonal balance adjusted so they’ll sound smooth and natural when heard in living rooms that are typically furnished.
The formula for a fine-sounding room for your music or home theater is to have a reasonable mix of domestic furnishings that reflect and break up sounds as well as providing some absorption. A typical North American living room—with carpeted floor, fabric-upholstered furniture, drywall or plaster with some shelves, bookcases, and some fabric window treatments—usually results in a room that works well acoustically for both music and home theater. It’s easy to get obsessive about applying special treatments to a home theater with the misguided belief that this will bring huge gains in sound quality.
8. Differentiating between subs or speakers that are “good for home theater” and “great for music.”
A smooth, accurate, and transparent loudspeaker or subwoofer doesn’t distinguish between different types of sound. It does not know which electrical signals are reaching it from the amplifier, DVD player, CD player, or turntable, whether it’s the sound of a summer rain storm on a movie soundtrack, an explosion in a war picture, the dynamic musical shadings of a full orchestra, or the full-bore impact of a rock band. The final test of a transparent loudspeaker is always accuracy and musical realism—and that includes subwoofers. A neutral loudspeaker accurately reproduces the audio signals, no matter what the source, so a subwoofer capable of realistic reproduction of a jazz acoustic bass or pipe organ will do just as good a job with explosions and dinosaur footfalls. Likewise, the delicate timbre of male and female vocals and movie dialog, or even the sounds of a helicopter flying overhead, will be handled with equal aplomb by an accurate speaker.
9. Using pivoting tweeters to make up for poor speaker design.
The idea of using speakers with pivoting tweeters is deeply misguided. An excellent speaker has the dispersion patterns for its midrange/woofers and tweeters optimized so that listeners within a fairly broad angle and at different locations in the room will receive a balanced mix of bass, midrange, and treble sound. Moving a tweeter destroys the dispersion pattern of the speaker, producing “hot” areas of too much treble and too little midrange for some listeners and the reverse for other listeners. Pivoting tweeters are gimmicky and are no substitute for excellent acoustical design. A surround speaker with a fixed array of multi-directional drivers will do a better job of producing sound the way the director intended it to—not as a specific source of sound, but as part of an enveloping effect.
10. Using cube speakers to hide surround sound.
They may look cute and almost disappear into the room’s decor, but those tiny satellite speakers can’t move enough air. They’re OK at quiet background levels, but the little 2in. cones inside get rattled when things start to rock and roll. And a subwoofer will not fill in all the important upper bass and lower midrange sounds that the 2in. cubes can’t handle.
Any speaker with a claim to authentic high fidelity, even a fairly compact model, must divide the sound spectrum into at least two segments, the bass/midrange for the woofer, and the treble for the tweeter. The best speakers divide the spectrum into three parts—bass, midrange, and treble—and use multiple drivers for each part to achieve very clean, high-level, high-quality sound. Remember to scale the size of the speakers to the size of the space that needs to be filled. Advances in technology and design have made it very possible to combine unobtrusiveness with audiophile-grade sound: look for high-end in-wall speakers that have tuned enclosed cabinets, or customizable real-wood finishes that can be stained to match existing furniture, cabinetry, or trim.
Alan Lofft has been writing about hi-fi and video professionally for more than 20 years, ever since his first syndicated newspaper column, “Sound Advice”, began appearing weekly in The Toronto Star, Canada’s largest-circulation daily newspaper.