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Two 12" dual opposed subwoofers or four 12-15" ported subwoofers

Krillin

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I am considering a high end AV processor with bass management for multiple subwoofers. Cost is a concern and $3,000 is ideal for subwoofers but I can stretch the budget a bit if on sale.

From what I have read:
  • Two subwoofers really smooth out a room and the ideal placement is midwall on opposite ends in a rectangular room
  • Three subwoofers are not ideal at all with no real benefit over two unless the room is oddly shaped
  • Four subwoofers is the limit and where nothing can be gained beyond this. Corner placement is ideal.
I am considering:
  • Two Rythmik G22 dual opposed sealed subwoofers, totally inert cabinet with Direct Servo. Sixteen inches of total surface area per subwoofer. Frequency response of 14 - 200 Hz (-2 dB @ 14 Hz) with LFE inputs.
  • Four Rythmik FVX12 with Direct Servo. Twelve inches of total surface area per subwoofer. Frequency response of 14 - 200 Hz (-2 dB @ 18 Hz, -6db@14hz) with LFE input
  • Four Monolith 15 subwoofers. Fifteen inches of surface area but no Direct Servo. Frequency response of (-6db@14hz with two ports) with LFE input
My priorities:
  • I want to be able to watch Top Gun Maverick and feel like the jet taking off is really there in the room with me
  • I do not want to compromise musicality
  • Essentially I want it all
My concerns
  • That while four subwoofers is the ultimate, the increase in smoothness in sound may be minute over two subwoofers
  • That four 12" subwoofers may not have the same tactile presence as two 15-18" subwoofers
  • That the Monolith 15 without Direct Servo may not be the equal of the Rythmik
  • That my choice may leave me disappointed. When a T-Rex stomps through in Jurrasic Park I want to feel it.
So any advice? I'm tempted to go Rythmik G22's for dual opposed cabinet vibration cancellation.
 

alex-z

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Go with the quad Monolith 15 if you can afford it. While the Rythmik subs advertise extension to 14Hz, they do so through the use of internal DSP, and as you turn them up, compression will kick in. The Monolith 15 can maintain that same bass extension for longer.

Dual subs is the price to performance sweet spot.

Three subs is viable, because you can do mixed configs, such as using a big sub for 10-30Hz, and small subs for 30-80Hz.

Four subs is great for managing room modes, but is mostly beneficial for two rows of seats. I run quad subs myself, but purely for output headroom.

Eight subs is pointless outside of real theatres, where the front and back rows have a significant height difference.

Dual opposed drivers are beneficial in theory, but not less so in the real world. A well built cabinet + single driver should not have audible cabinet vibrations in the first place.

Direct Servo isn't a magic bullet. It improves distortion from non-linear sources like the suspension and motor geometry. However, I would still prefer larger subs, a larger driver has to move less for the same SPL, which itself results in reduced distortion. And obviously the larger driver + cabinet + amplifier combination is going to yield higher peak SPL.
 
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Holmz

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ryanosaur

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The servos are meaningless today. 10 years ago, different story. Modern design techniques have made up for the servo's gains in the past.

In a regular, closed rectangular room, pairs of subs make sense a la Welti / Devantier.
But Geddes has a strong case with his suggestions too.

End of the day, you really need to measure your room and add subs as needed if your goal is something so specific. Beyond that, consider what your goals are and look at adding a Dev if you have the space, which will crush your mid bass region, then something to give you the absolute bottom end like the newer dual 18 or 21" monsters GSG is working on.

There are many ways to address this issue!
 

maverickronin

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I just finished building two 12" dual opposed subs myself. For space reasons I essentially needed to use them as furniture and the force canceling lets you set stuff on them with out it dancing off the edge. Secondly they transfer less vibration into the floor and bother the rest of the house less.

If neither of those benefits apply to your situation then more and/or bigger single subs would probably be a better option.
 

Chromatischism

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My priorities:
  • I want to be able to watch Top Gun Maverick and feel like the jet taking off is really there in the room with me
  • I do not want to compromise musicality
  • Essentially I want it all

My concerns
  • That while four subwoofers is the ultimate, the increase in smoothness in sound may be minute over two subwoofers
  • That four 12" subwoofers may not have the same tactile presence as two 15-18" subwoofers
  • That the Monolith 15 without Direct Servo may not be the equal of the Rythmik
  • That my choice may leave me disappointed. When a T-Rex stomps through in Jurrasic Park I want to feel it.

So any advice? I'm tempted to go Rythmik G22's for dual opposed cabinet vibration cancellation.
Your intuitions are correct. As someone who has owned the Rythmik subs you are considering, the dual opposed configuration won't give the best movie experience. You won't feel the jets or the T-Rex. They will be preferred by roommates and neighbors, though, so it depends on your priorities. You didn't mention that as a concern, so I'll assume you just want the best movie experience. I recommend 2xFVX15.
 

Dal1as

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Funny you mentioned Maverick as I just watched it. A lot of ways to go about this but I will say go big or go home. The distortion specs measured in the reviews for the Monolith are damb good so no worry there.

I am using 3 Monolith 15s in a 16x22 room and have no problem with tactile feel or pressurization but have spent a lot of time with bass optimization and working out a good curve.

The beginning of Maverick was pretty freaking incredible.

Also most of the better large subs are pretty inert. I have a few items on my subs and they barely move. Maybe an inch during a 2 hour movie.
 
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