Matching Front and Surround Speakers
I respectfully disagree with those who say it's not important to match the surrounds with the front speakers. All speakers have a certain tonal character, and speakers from a given manufacturer tend to have a similar character, while speakers from different manufacturers often have noticeably different tonal characteristics. If you combine front speakers from one company with surrounds from another company, chances are that, when a sound pans from front to back or vice versasay, when an airplane flies across the room as depicted aboveits tonal quality will change and potentially distract you, taking you "out of the movie."
This mismatch of tonal character is not always noticeableyou might get lucky and have no such problem with fronts from one company and surrounds from another. But for those who are buying a surround system, or adding surrounds to existing fronts, I recommend staying with one manufacturer to minimize the potential for tonal variations. Ideally, get surrounds from the same product line as the fronts, which further reduces the odds that the tonal character will be different between the front and back.
Some THX-certified A/V receivers have a feature called Timbre Matching, which is designed to address a related problem. Because of the shape of the outer ear, or pinna, the timbre of a sound changes depending on whether it comes from the front or the side. THX Timbre Matching strives to mitigate this effect and create a consistent timbre throughout the surround soundfield. This might also help integrate the tonal qualities of fronts and surrounds from different manufacturers, though I haven't tried it myself.
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