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Low bass (<40Hz) multiple subs?

andrew

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It's quite common to have multiple subwoofers running <80Hz with, as I understand it, the idea being to smooth the response across multiple seating positions My question is whether this has any merit when the subs run <35Hz. I get that having multiple subs running <40Hz might help in terms of output but isn't it the case at these very low frequencies there isn't much room re-enforcement / room modes and thus the notion of multiple subwoofers to smooth response isn't that useful?
 

q3cpma

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Why would you run them this low? One of the advantages of subwoofers is that you can relieve your loudspeaker's woofer from low frequency duty and possibly avoid using their port.
 

andreasmaaan

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It depends on your room's dimensions and construction materials. In many rooms, you're probably correct that the walls will be lossy enough / the room will be small enough that sub-40Hz frequencies will mostly escape the room and/or be pressurised. But it's not possible to generalise. My room is concrete construction with a minimum dimension of just under 5 metres (floor-ceiling) and there are modes present in the 30-40Hz region.

If your longest dimension is ~4m and/or/especially if it's a drywall construction, you may not have any problems there.

The best thing to do would be to take measurements if possible.
 

Worth Davis

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measure and buy some subs...you are gonna die when you see how messed up a basic, untreated room is under 200hz.

tons of bass traps, and a pair of GIANT subs is the always the starting point for a closed room
 

Kal Rubinson

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measure and buy some subs...you are gonna die when you see how messed up a basic, untreated room is under 200hz.
Agreed.

tons of bass traps, and a pair of GIANT subs is the always the starting point for a closed room
Suggested edit: tons of bass traps, capable DSP and a pair of GIANT several subs is the always the starting point for a closed room
 
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andrew

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Why would you run them this low? One of the advantages of subwoofers is that you can relieve your loudspeaker's woofer from low frequency duty and possibly avoid using their port.

The mains are active, sealed, speakers and a combination of DSP, room-treatment and good-luck with positioning see the mains delivering smooth in-room performance down to 40Hz. I’m just using the sub(s), then, for the final octave where the mains don’t quite have the same impact.



It depends on your room's dimensions and construction materials. In many rooms, you're probably correct that the walls will be lossy enough / the room will be small enough that sub-40Hz frequencies will mostly escape the room and/or be pressurised. But it's not possible to generalise. My room is concrete construction with a minimum dimension of just under 5 metres (floor-ceiling) and there are modes present in the 30-40Hz region.



If your longest dimension is ~4m and/or/especially if it's a drywall construction, you may not have any problems there.



The best thing to do would be to take measurements if possible.



The room is large (7.5m x 6m) with a leaky construction (i.e., glass windows with drapes). I’ve done a bunch of measurements in the past and, looking back, can get flat performance from 20 to 50Hz with a single subwoofer plus a bit of DSP. Hence the thinking that the only benefit of adding another subwoofer is to get more output or, better put, to reduce the distortion for the same output via sharing the load across two subs. I’m thinking, though, that this isn’t worth the cost as the existing sub (an SVS SB-16 Ultra) does a good job, we don’t listen at very high volumes and I seem to recall that distortion at <40Hz isn’t particularly audible.
 

HLee

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20Hz sound has wave length of 340/20=17meters.
multiple subwoofers would make mixed resonance of standing waves unless the dimension of your room is bigger than 17/2=8.5 meters.
IMO, two front subwoofers will be enough
 

Kal Rubinson

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IMO, two front subwoofers will be enough
But if both are in front, the mix will be less heterogeneous and still favor some modes.
 

PolkFan

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Unless you own one heck of a nice amplifier i would highly recommend using the THX crossover at 80hz and move your subs around your room until you find a ideal spot
 

Prana Ferox

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Another advantage of multiple subs is it's much easier to get the decibel output down low with more driver surface area than it is to just keep adding watts. Whether 1 16" driver can keep up with your mains, as far down as you're looking to go, depends on your mains and your desired SPL / sub boost. If all you're going for is flat (assuming you're counting room gain) and you don't get that loud, 1 sub may be plenty.
 
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