May 28, 2010
Got a pimple, spray some Windex on it. Got a sore throat, swish some vinegar and honey. Got a cold? Eat some chicken soup. Home remedies, some are good, others are a mixed bag at best. I spent years conjuring up home remedies or tricks for properly calibrating multiple subwoofer theater rooms.
In a perfectly rectangular room with the ability to place identical subs in the ideal locations around the room, this isn’t such a daunting task. This is especially true since you can use room mode calculators to help determine the best subwoofer locations before actually placing them in a real room. But what about real world scenarios of people that don’t have ideal rectangular rooms?
I suggest if at all possible to select a rectangular room for your theater room. This is a proven CEA/CEDIA recommendation for good reason. In rectangular rooms, bass reproduction is more predictable, making it virtually an exact science when choosing the ideal subwoofer locations and doing room analysis. This greatly minimizes trial and error, allowing for a more scientific and methodical approach. There are, of course, no free lunches - which means there are trade-offs for all listening spaces, even perfectly rectangular rooms.
Most of us don’t have dedicated rectangular shaped rooms for home theater but instead have multi-purpose recreational rooms that double as a theater room. Many of the suggestions and placement tips in this article assume a perfectly rectangular room but also serve as a starting point for any room. Regardless of room shape, these methodologies will work, at least in practice, for most room types.
In order to take advantage of the information in this article, you will need the following items:
-RTA or FFT analyzer with at least 1/12th octave resolution
-Patience and perseverance
The purpose of this article is to provide a method of achieving the smoothest bass response for all listening seats using proper placement, calibration and active equalization (when needed). The goal is met when measurably better performance is achieved by reducing excessive modal peaks and nodal dips across the entire bass spectrum (15 Hz to 200 Hz). Achieving +/-10dB or better for this frequency spectrum should be attainable for the primary listening area.
Step 1: Choose your Subs Wisely
Ideally you should use identical subwoofers for the best overall performance, but it is possible to mix and match subwoofer brands and types if you’re willing to do the extra work. If using mismatched subs, bear in mind that systems with different low frequency cutoffs may well be in phase and additive over most of their band, but at or below system resonance may well be out of phase. This can put us in the position of having the sub with a higher cut-off frequency reducing overall system output below its cutoff frequency. This is why we usually recommend using identical subs all around. ...
Step 2: Location Location Location
Two Sub Midwall Placement—If you are running two subs, the ideal locations for them in a rectangular room are on opposing vertical or horizontal midwalls. Two subs configured in such a method work nearly as good as four subs configured via our 4 Corner Placement recommendation.
4 Corner Placement—In you are running four subs, the ideal locations for them in a rectangular room are the corners of the room. Assuming all subs are identical, this will achieve up to 12dB of increased output when compared to a single corner loaded subwoofer. ...
Step 3: Make sure all of your subs are playing the same tune
Trust me on this one. It becomes quite problematic trying to integrate multiple subs if they aren’t playing the identical signal. Stereo subs can work if your processor accommodates such a provision while also sending LFE signal to both, but at that point its really no longer stereo since the subs share mixed L/R info. ...
Step 4: Level Match ALL of the subs
It’s important to level match all of the subs relative to each other as closely as possible. Failing to do so may result in poor integration and even cause the ones set higher than the others to be overdriven during loud passages. This can result in considerably higher distortion than your system is capable of for a given SPL. The proper way to level match your subs is to use the internal pink noise generator of your processor and an SPL meter set for slow response “C-weighted”. ...
For the rest of the steps in Gene DellaSalla’s Home Theater Multiple Subwoofer Setup and Calibration Guide, read the rest at Audioholics.com.