Q: We’ve heard that there are certain frequencies that the human ear can’t hear, and thus it doesn’t matter if all the various “highs and lows” are represented. What’s your expert opinion?
A: This becomes a trick question… almost. On the one hand, if the frequency range is not audible to you, it does beg the question about whether or not reproducing that frequency is a priority. On the other hand, the job of a speaker is to accurately reproduce the audio signal provided to it. If certain frequencies cannot be reproduced, the speaker is not accurate. If the speaker is not accurate you have to ask why? And why are you spending money on something that does not meet the basic established criteria for sound reproduction? The generally acceptable audible range for humans is from 20Hz to 20kHz. While I admit that very few people can hear 20kHz, it is not an excuse for a speaker manufacturer to cut corners. Do note, though, that certain speakers are designed specifically to not reproduce low bass and, in general, the manufacturers identify those speakers as requiring a low frequency speaker (aka a subwoofer).
Q: Is it true that you can’t mix and match speakers if you want good sound?
A: By and large, this is true specifically for the front three channels. I would go so far as to suggest all of the surround or ambience speakers should also be matched. In an ideal situation, the front main speakers would be identical to the surround speakers. But from my perspective there is generally so much going on (identical speakers mounted differently are no longer “matched”) that taking the pragmatic approach of using equivalent-quality surround speakers is perfectly acceptable and can provide stunning results.
Q: Is there really a difference in sound quality between a 5.1 and 7.1 surround sound system?
A: The use of two additional surround speakers has a dependency on the size and design of the room. Where the addition of surround channels comes into play is with sound panning around the room. These additional channels eliminate holes in the sound field or in the accurate recreation of the ambiance of the recording venue (i.e. a concert hall). When a sound starts at the front of the room, disappears and then reappears somewhere behind or beside you, that distraction will pull you out of the film and back into the room. Clearly, there is a loss of realism to the mix when a 7.1 soundtrack is played back in a 5.1 environment.
Q: How much better are high-res soundtracks than plain old Dolby Digital or DTS soundtracks: Is there a huge difference as marketed?
A: I hesitate to put a factor on this, be it five times, ten times or 100 times. A very good Dolby Digital or DTS soundtrack will sound better than a poorly-mastered high-resolution soundtrack. To the vast majority of listeners, it is likely they will not discern any difference between high-resolution and DD/DTS perceptually encoded material. However, once you do point out the differences to a listener, they will hear those differences every time. It’s rather like showing someone dot crawl on a CRT. They’ll hate you for it because all they’ll see in the future is dot crawl.