Dual Center-Channel Speaker Setup
Q: I wish to place center-channel speakers above and below my projection screen. I know the distance from the two speakers to the seating position at ear level will not be the same, and I would like to know how to calibrate or compensate for this difference. I have a 5.1 surround setup with an Oppo BDP-105 Blu-ray player, a six-channel amp, and a powered sub. I am patient enough to do the onscreen setup from the Oppo, but I’m at a loss over the dual center speaker issue. Dale Kay / via e-mail
A: Here’s my advice for a dual center-channel speaker setup: Don’t do it. Why not? There are a number of good reasons. You’ve already mentioned the first: The distance from the two speakers to the seating position (or seating positions, if more than one person will be watching) won’t be equivalent. Because of this, there will be a difference in arrival time of sounds emanating from the two speakers—something that’s likely to add a “smeared” quality to dialogue. Most A/V receivers and processors can time-delay signals on a per-channel basis to compensate for speaker location (the Distance setup item), but I don’t know of any off-the-shelf electronics that will compensate for two separate center-speaker outputs. And your system as you describe it (Oppo player’s multichannel analog outputs connected to a six-channel amp) won’t offer a useful alternative since the speaker-distance compensation control in the Oppo’s setup menu is only available for its lone center-channel output.
Another reason why two center channels is a bad idea is that the same mono signal coming from different locations will create a lobing effect that alters the frequency response of each speaker’s output. Some frequencies will see a dip; others will end up being reinforced. So do yourself a favor and forget this whole dual center speaker madness. The primary function of the center channel is to lock dialogue, and primary action, to the screen. Any variation that reduces the center speaker’s accuracy and stability is a step backwards.