Will XT32 boost frequencies below 20hz?

I have designed a subwoofer system of (8) 18" subwoofers in an IB configuration to maximize low frequency extension without overexcursion.  This particular solution requres an external miniDSP unit and the use of biquad or Linkwitz Transform equalization.

Without the filter the subs reach excursion at 15hz and will bottom out quickly after attempting to play anything below 15hz. 

With the filter the subs can play with smooth curve all the way to 3hz without overexcursion as long as each sub receives no more than 90w.

There are other SSF options available, but this is what I would like to try first in the way of protecting the subs from overexcursion.

I would like to take advantage of the XT32 processing power of my Denon AVR4311ci, but am concerned that it might push the subs to overexcursion as the processing they apply is an unknown.  Specifically I'm concerned that it might apply boost in the regions of 5hz-30hz that could allow the subs to bottom out on a deep note in a movie.  Excursion in th danger region of 5hz-15hz could easily be affected by wide parametric boosts by XT32 in the 20-30hz range. 

If XT32 applied only cut to peaks and did not apply any boost, this would be a moot point. 

This concept really applies to most well designed ported subs as well, as boost applied to the low end could alter the effect of the SSF designed for that system.

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4 Comments

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    Zac Vasilinda

    After reading a little further into the Ask Audyssey threads I now see that no boost is applied below the roloff point that Audyssey determines.  So the question becomes is the rolloff point that Audyssey comes up with reliably close to the actual f3 of the speaker?.

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    Zac Vasilinda

    Also, on my Audyssey readout on the receiver of the Boost applied it looks like there is considerable boost being applied to my large ported subs that I'm currently running, all the way to the tuning frequency which is 20hz.  The EQ display of what Audyssey has boosted stops at 20hz.  I'm assuming that the readout is only designed to display down to 20hz.  Or am I wrong and Audyssey has determined a 20hz roloff point and is showing me that it has only boosted the frequencies down to 20hz? 

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    Zac Vasilinda

    I'll attach graphs of the frequency responses of the subwoofer system so maybe it can be estimated as to where Audyssey will determine the rolloff and stop applying boost.  Unfortunately those graphs are on another computer, but I'll update when they're available.  Thanks.  Zac.

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    Chris Kyriakakis

    The roll off point that Audyssey finds is not the anechoic f3.  It is the in-room roll off that is affect by proximity to walls and other acoustical factors.

    What product do you have? Onkyo doesn't show the filters and Denon doesn't show the sub filter so I want to make sure you are looking at the right information.  The roll off that Audyssey found is where the AVR has set the crossover to the speakers.  

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