February 29, 2008 by Bryant Moore
Q. 5.1 or 7.1 or 7.2? Yikes, I thought 5 speakers and a subwoofer were already a lot in my living room. My local retailer is trying to convince me to purchase a system with 4 rear speakers and 2 subwoofers. Do I really need these? What will I gain? - Tommy, St. Louis, MO
A. A 5.1 system might be completely adequate – especially in a family room-based surround system. The idea for the additional rear channels is to provide a more immersive listening experience with more realistic surround effects. What you may (or may not) gain from moving from a 5.x system to a 7.x system depends on many factors including room size, room dimensions, furniture placement and seating location(s), and honestly, your own performance expectations for the room. There is also overall budget to consider and whether or not you are planning on distributing music throughout other areas of the home. If you plan on doing the latter, you can usually use those 6th and 7th amplifier channels in the receiver/processor to send audio to other areas of your home. This added feature and flexibility might be of more value to you then the more realistic surround effects.
A discussion on multiple vs. single subwoofers would involve many other factors than could be adequately addressed in this forum. Suffice to say, and without employing sophisticated, read: expensive, room optimization equipment and software, start with one subwoofer and experiment on the bass response you get through your seating area. Locations where the bass response seems to disappear are called “nulls.” These locations are the point at which the low-frequency sound waves subwoofers produce run in to each other, canceling themselves out. This is the same science used in noise-canceling headphones, by the way. These null areas can be mitigated/moved/reduced by moving the subwoofer around to different locations in the room. Moving the subwoofer even just a few inches can make a world of difference. The point at which you want to leave the subwoofer is the location that provides the best overall bass response at your main listening location. If you simply cannot minimize these null areas with one subwoofer then you might consider adding a second (or even a third) subwoofer. Let your room, budget and personal performance expectations dictate how far you go.
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A classically-trained musician and former network administrator, Bryant Moore has turned a lifelong passion for music and A/V equipment into a thriving business with Charlotte, NC based Moore Audio Design. He has over a decade of experience in designing and implementing home electronics systems.
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