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Ok hard to explain? I over-heard a salesman once explaning a scene in a movie to a customer. In the movie a plane came flying towards him. I rumble sounded great as the plane approached and flew above, but when the plane flew past the sweet spot and towards the rear the rumble died off. He claimed it was because there was no subwoofer in the rear.


Unfortunately I will never get a chance to ask em.


He suggest 2 subs. Can he be refering to just placement. One in the rear and one in the front of the sweet spot. Or can you really connect a second sub in such a way that one can recreate the correct effect. Like biwiring a second sub to a rear or surround channel ?


Sorry if it sounds weird, but I hope you get the drift?


Teddy Thanks
 

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Low frequencies are not directional. However, the distortion caused by them (vibrating walls, shaking pictures, etc.) is directional. A 2nd sub will give you more output, especially if you place it next to the first one (acoustic coupling gives you an extra boost). Placing multiple subs in different areas of the room can lead to setup headaches (too many room modes to get a flat response, etc.).


Proper room placement and processor setup should be the first thing to investigate if imaging is a problem...
 

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Although, if the receivers setting were not correct, and the sound of the plane was not on the LFE channel, the change of sound to the rear channels may indeed cause the reduced bass sound. But generally it is a BAD idea to have multiple cubs around the room. Keeping the subs on 1/3rds of the front wall helps with the modal problems you can encounter by keeping the sub in the minima of an acoustic wave. But generally, it will not change the low frequency distribution in the room, only make you use less power to reach the given level you want. If you add another sub the same exact size you will actually reduce the amount of amplifier power required by 1/2.
 

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One thing we never seem to focus on when we use the term "Bass" is that bass comes in a number of flavors. A very small amount is infrasonic bass, a bit more is deep bass, and then we come to your not so deep bass that makes up the majority the bass content of movie soundtracks.


I am not disagreeing with anything the other posters said, particularly about multiple subwoofers creating set-up complexities. However, suppose, as Teddy suggests, you really want to hear the sound of an airplane (not an explosion) panning forcefully across the room, front to back? If you're like me and don't have full range surround speakers what do you do? One solution is you help them out with a surround subwoofer. This is not to be confused with an LFE subwoofer that handles the deep stuff. The surround subwoofer handles the higher, directional bass. The stuff you're supposed to be able to localize. Will a sub in the rear of the room cause added problems? Probably, but maybe its also worth the trouble.

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...but when the plane flew past the sweet spot and towards the rear the rumble died off. He claimed it was because there was no subwoofer in the rear
Or of course it might be due to the fact that the plane is flying off into the distance, and that's what's supposed to happen. :D


Larry
 

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"Or of course it might be due to the fact that the plane is flying off into the distance, and that's what's supposed to happen. "




That was part of my point Larry, but yeah, if you set your rear speakers to small in your receiver, all that low bass energy should be routed to your subwoofer, that is if you have LFE + Main or something like that set in your subwoofer settings. If you don't have your receivers speaker settings this way, you definatly could be missing some low bass as your generally smaller rear speakers cannot handle the sub-bass frequencies your looking for.
 
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