S&V Q&A - October 2006

Techs and Specs

Q. I have a technician coming to my house for regular maintenance on my Sony LCD rear-projection TV. Should I have him tweak any settings while he's here? I know in your Test Bench for TVs you frequently tweak the color temperature and grayscale tracking, so I was hoping you could give me some settings for the tech to work on. Ramon Aranda Union city, CA

A. Al Griffin says: The specs that TVs get tweaked to in the factory are rubber-stamped and documented by the company's engineers, so any maintenance visit you receive from a service technician will likely result in them checking that the settings meet those specs. (The tech may also get confused when you ask about grayscale adjustments, since that doesn't come under the category of regular TV maintenance.) To get your TV properly adjusted to the 6,500°K grayscale specification, a better bet is to contact a technician trained by the Imaging Science Foundation (visit imagingscience.com/isf-trained.cfm to find one in your area). You can also perform basic tweaks yourself by using one of the test DVDs out there, such as our own Home Theater Tune-Up DVD. By the way, I'm not sure what kind of service plan you signed up for, but most TVs don't require a "regular maintenance" visit.

What Watts?

Q. A few years ago, I bought a home theater receiver rated at 100 watts per channel into 6 ohms. The FTC standard for amplifiers now rates receivers at 8 ohms per channel. I'm considering upgrading and want to know how many watts I should look for so each speaker produces more volume. For comparison, how many watts would each channel of my 6-ohm receiver be producing if it were rated into 8 ohms? Joe Oberuc OGDEN, UT

A. Ian G. Masters says: Your existing 100-watt receiver would produce less power per channel into an 8-ohm load, but the differences are very small. It would probably put out about 70 watts for the same level of distortion, but this is only a couple of decibels down in volume, and the audible difference would be just barely noticeable at best.

But if your goal is simply to get your new system to play louder, these wattage numbers have little bearing. What determines perceived loudness is the average level of the signal, and that's likely to be only a very few watts at any given moment - often 10 watts or less. The power rating (that 100- or 70-watt number) says more about your amp's ability to handle momentary transients with minimal distortion. So if you want to play louder, simply turn up the level. You'll have a bit less "headroom" for those transient peaks, but you're unlikely to hear that. You could indeed buy a more powerful amplifier, but it would have to be twice as powerful to make a significant difference.

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