S&V Q&A — May 2006

Faulty Formula

Q. The salesman at my local electronics store gave me an interesting formula for determining which screen size works in a given situation. He said to take the distance you sit from your set, multiply it by itself, and then divide by two. In my case, I'm 8 feet away, so I get 32. Turns out I was actually considering a new 32-inch LCD panel! Is there a valid mathematical basis for this formula, or would Sound & Vision simply toss it off as marketing magic? Eric C. Palik Lyndhurst, OH

A. Al Griffin says: I'd actually reject it wholesale as bad advice. The general rule of thumb for choosing an HDTV is to multiply the diagonal screen size of the set you're considering by 2. The result is the minimum distance you should be sitting from the set. Pulling out my calculator, I'd say you should be getting at least a 42-inch model, and a 50-inch screen isn't out of the question. Also, the extra resolution provided by new 1080p HDTVs means that you can sit even closer to the screen without seeing pixels. But why take my word for it? Head to the store, position yourself about 8 feet in front of some 50- and 60-inch models, and decide what feels right.

The Small and Large of It

Q. I understand the idea of "large" vs. "small" speaker settings in a receiver's bass-management menu, but I'm not sure why it needs to be done. Most speakers have an internal crossover network, so aren't the speakers' frequencies already limited? If that's the case, why not run them full range and spare yourself the extra confusion when setting things up? Steve Manning Suffolk, VA

A. Ian G. Masters says: The Small and Large speaker settings in a receiver's setup menu tell the receiver whether the speaker is equipped to handle low-frequency signals, or whether the lowest bass should instead be sent to the receiver's subwoofer output. That has mostly to do with the speaker's woofer size rather than its crossover, which is probably intended only to split the signal between the separate low- and high-frequency drivers, and not necessarily to limit low-frequency information coming into the speaker. It's true that a small speaker simply won't generate sound at the lowest frequencies, but that doesn't mean the speaker can handle a low-frequency input signal without negative effect. Not only will you be wasting amplifier power, but it might cause distortion or speaker overload. In addition, on some receivers or processors, setting the speakers to Large may tell the surround decoder that there's no subwoofer in the system and disable the sub output.