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Q I’m wondering if my center speaker is damaged. When I watch movies with 5.1 soundtracks, voices sometimes sound strange, as if the actor is speaking with a lisp. I seem to hear it most with movies streamed from Netflix, and occasionally on cable movie channels like HBO. Do you know of any test DVDs or other material I can use to evaluate my system and speaker set up? —Craig A. Childress / Lake Charles, LA

A You can find a few calibration DVDs with audio tests for $10 or less at Amazon.com, including Disney Wow: World of Wonder and Digital Video Essentials. If you own a Blu-ray player, you can find Blu-ray versions, along with the AIX Audio Calibration Blu-ray for $24.99 at oppodigital.com. Each of these discs provides test tones to ID speaker assignments in a multichannel system, plus phase tests to confirm that the positive and negative terminals on each speaker are wired correctly. In addition, many THX-certified DVDs and Blu-rays include a THX Optimizer supplement with similar content that allows you to perform the same tests.

I should add that while the above discs can verify that your center speaker is both active and in phase with the left/right channels, the test suites they provide aren’t comprehensive enough to confirm that it’s in perfect working order. Short of sending the speaker out for repair, your best bet will be to watch a DVD with a dialogue-heavy soundtrack. If voices coming out of the center channel sound muffled or distorted, the problem is likely to be with the speaker and not with your streaming and cable TV services. I’d also recommend temporarily swapping the left and center speakers. If the problem moves, the speaker is defective. If the problem stays in the center location, the speakers are probably fine and there are other issues.