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The “Power Alley” - Discussion & Solutions To The Troubling Interaction Of Subwoofer Stacks
Opposing subs can create what’s termed a “power alley” - regions where LF energy is too hot. Here's a quick explanation and a few solutions.
Feb. 02, 2011, by Joe Brusi
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  Sound Reinforcement, Subwoofers

Fig. 10: Powerhouse alley with two subwoofers spaced 14 m (47 ft).

Figure 10 shows the alley for two single subwoofer boxes spaced 14 meters (47 feet). It is not as obvious graphically as it is audibly, but it can still be distinguished as an approximately 4 meter (13 feet) band with more intense color.

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Conclusion
The only real way to avoid the powerhouse alley is to place all subwoofers in a single location. With smaller scale applications, placing all the subwoofers in the center is normally not a possibility, but the larger shows may benefit from flying subwoofers in the center.

It is important, however, to understand what is happening, so as not to blame the speakers. And being aware of the zones that get created before taking mixing decisions.

For instance, if the FOH console is located in the centre, we could chose a mix that is somewhat bass-heavy when listened to along the center line.

Off to the sides destructive interference will kick in and establish some frequency balance between the low frequencies and the rest of the system.


Source: Live Sound International

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Comments (6) Most recent displayed first | All comments in chronological order
Posted by sally  on  10/25/11  at  09:29 AM
So with this, installing sub woofer must have proportionate to where you will install the device?

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Posted by sally  on  10/25/11  at  09:27 AM
So with this, installing sub woofer must have proportionate to where you will install the device?

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Posted by Amanda Bynes  on  10/17/11  at  06:45 AM
Thank you for this very useful information.

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Posted by Krooburg  on  02/08/11  at  12:37 PM
"With smaller scale applications, placing all the subwoofers in the center is normally not a possibility, but the larger shows may benefit from flying subwoofers in the center."

Nah, flying subs presents a whole other set of issues. Since the floor is an acoustic mirror, you've just created another boundary cancellation issue that didn't exist with the subs on the floor. And that cancellation is probably worse than the power alley you're trying to mitigate.


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