Home theater automatic speaker calibration dos and don’ts

Auto speaker calibration is supposed to ease home theater setup hassles, but getting it right requires some homework.

By Steve Guttenberg 

Source: c/net

Just about every home theater receiver comes with an automatic speaker setup and calibration system: Denon, Marantz, and Onkyo feature Audyssey; Pioneer has MCACC (multichannel acoustic calibration); Sony’s is called DCAC (digital cinema auto calibration); and Yamaha’s proprietary system goes by the name YPAO (Yamaha Parametric Room Acoustic Optimizer). The systems handle the basics like determining the sizes of all the speakers, setting speaker and subwoofer volume levels and the speaker-subwoofer crossover point, measuring the distances from the speakers to the listener, and checking that all of the speaker cables are correctly hooked up. Some autosetup systems also employ equalization to balance the frequency response of all the speakers, and they try to minimize room acoustic problems.

To accomplish these goals, the systems send test tones through all of the speakers and the subwoofer, and they all use a microphone to capture the sounds of the speakers. Autosetup is a great idea, but there’s no guarantee you’ll have a perfectly adjusted home theater sound after the test tones have run through all of their beeps, whooshes, and thumps. The volume levels of the speakers may not be perfectly adjusted, the speaker-to-listener distances may be inaccurate, and the subwoofer volume may be too loud or too low. In the worst cases, the autosetup sounds worse than doing no setup at all.

These malfunctions can be caused by a number of things: your room may not be quiet enough, microphone placement can have an effect, or your subwoofer’s built-in volume control may be set too low or too high. I’d recommend checking that all of the speakers are wired “in-phase,” meaning red/+ and black/- connections are consistent at the speaker and receiver ends. Some autosetup systems check the wiring, but try to get it right in the first place.

Confirm that (+) red connections and (-) black connections are correct at the speaker and receiver ends of the cables. Steve Guttenberg

I recently met with Chris Kyriakakis, Audyssey’s CTO and founder, to talk about new developments at Audyssey, and while I had his ear, I brought up my concerns about autosetup problems. He followed up with a list of tips that generally apply to most autosetup systems. There’s a lot of useful information about Audyssey setup on the company’s Web site.

Kyriakakis advises that if you have a subwoofer, all of your speaker-size settings should be “small.” Audyssey works best that way, and there’s a practical advantage to small settings: they redirect the speakers’ bass to the subwoofer, so the receiver’s amplifiers don’t have to reproduce low frequencies.

Continuing with subs, Kyriakakis recommends using the sub’s direct input (aka, LFE input). That input bypasses the filters in the subwoofer and allows the bass management system in the receiver to operate properly. If there is no direct input, then the lowpass filter knob on the subwoofer should be set to the highest frequency it allows. Set the subwoofer volume control to its midpoint. If there is a Phase control, it should be set to 0 degrees.

We next covered calibration microphone placement; note that the delays (speaker-to-mic distances) and volume levels are calculated only from the first mic position, so it’s important that you start in the exact center of the listening area, at the same distance from the left and right front speakers.

If the subwoofer settings aren’t correct, autosetup won’t work properly. Steve Guttenberg

The mic should always be placed at a seated listener’s ear height and facing the ceiling; it’s calibrated to work best that way. The ideal way to position the mic is to place it on a camera tripod. Start in the center position and then move 2 feet to the left of it and then 2 feet to the right. Continuing through the next mic positions move 2 feet forward and take three more measurements in parallel with the first three. If you have Audyssey MultEQ XT, take the seventh and eighth measurements about 1 foot to either side of the center point and slightly forward of it (or behind it, if the couch is not up against the wall).

Kyriakakis does not recommend taking mic measurements from every seat, and if there are seats off to the side, they should be avoided. The idea is to capture information in the central listening area, and try to avoid placing the mic within a foot of the back wall. The bass buildup that happens there would result in too little bass.

I’ll be using Kyriakakis’ tips in my next Audyssey-equipped receiver review.

So maybe automatic setup isn’t so auto after all; getting it right takes a lot of work. Or do what I do at home: stick with stereo home theaters . No setup skills (other than proper speaker placement) are required, there are no setup menus to navigate, and HT 2.0 is nearly impossible to get wrong.

I almost forgot to mention it, but Audyssey just announced a new setup system, MultEQ XT32, that uses higher-resolution digital-signal processing algorithms for even better sound quality.

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