18hz f3 sub possible with two 15" subs?

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Hello all,

I am finishing my Aviatrix towers for music/movies. I am looking into building it's center channel next and a sub to go along with it. The towers should play an f3 of 40hz at around 89dB.

I was thinking about taking the 2.5-way tower mentality to a sub, but can't find info on something like this anywhere. Has anyone heard of playing two subs in a sealed box with two chambers and have the main sub play with a lowpass of 40 hz and the other sub with a low pass just before the main subs f3 value. So if the main sub has an F3 of 25hz, in a ported box for say, then the secondary sub will have a 2nd or 3rd order low pass to where it stops playing around 25 hz or so but will play everything below.

This way the dB won't be very high as the towers I have should hit around 92dB. But on the other hand, the subs might be able to stay mainly flat down to 18hz or so?

Or control the main bass from an AV receiver, and only have a low pass on the secondary sub to take it down around that 25 or so hz?

Have anyone seen this before, or is it a bad idea for good sound?

Its a complex arrangement needing two sub amps and different
active filters, that can't achieve anything more than simple EQ.

An Eminence LAB12 in 100L tuned to 20Hz with a 200W sub
amplifier with low enough x/o settings to go below the
normal 80Hz, should easily handle your set up.

rgds, sreten.
MiniDSP 2x4 for EQ?
Depending on how big your room is LFE may be for free so you can build a box that'll reach F3 at 25hz! I've tried the subwoofer method with one each on the LCR and tbh it was better with my usual 4 sub setup on LFE only with 2 front 2 rear and all speakers set to small with a 60-80hz crossover.

Sent from my A0001 using Tapatalk

A DTS-10 is a big potent tapped horn using two LAB12 drivers.
IMO it is overkill for the capabilities of the other speakers, in
the above system, it will go way louder than is actually needed.

Assuming the L and R floorstanders are not high passed, their good
bass extension implies maximum low bass levels will be limited, if
you want to bring in a sub underneath them. Like I said one LAB12
in a vented box should easily do the job, though I've not modelled it.

rgds, sreten.
Last edited:
thanks everyone for the replies so far. I will look into the DTS-10. I think it is
strange that towers employ the 2.5 for lower sustained bass, but subs don't.
seems like a good way to extend bass down low without raising the overall
SPL of the sub.


Its simply not a good way to do it for a subwoofer, EQ is far simpler.

2.5 way works for passive speakers because of the need for BSC,
(baffle step compensation), and the gradual transfer function does
match moreorless the the acoustic phenomenon of baffle step.

It doesn't work well in subwoofers, which is why it is never used.

rgds, sreten.
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