# Quartet12 question



## poppc (Nov 6, 2010)

Hi everyone,

I've been reading about subwoofers for a couple of months now, as I'd like to build my own, but still have many questions.

I came across the Quartet12 kit at CSS and I believe it would be a great kit for a first sub. I modeled the TRIO12 with the 12" PRs in a 20" cube box (in BassBox Pro) using the parameters on CSS's website. The graph I got was different than the one shown in the spec sheet - not as flat, but with more output under 20Hz. Then I noticed that the kit comes with a modified amp with a HPF. My questions is, would I be able to get output in the sub-20Hz frequencies with an unmodified amp (I'm sure there is a reason for the amp being modified the way it is and I'd like to find out what that is)? I also noticed that the kit may be purchased with a Reckhorn B-1. If I were to get the Reckhorn, wouldn't I be able to do with it what the modified amp does (and maybe more)? Thanks.


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## Mike P. (Apr 6, 2007)

The amp is modified to the HPF frequency to protect the sub from over excursion which would be an issue without one.


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## GranteedEV (Aug 8, 2010)

I'm not an expert on PRs, so feel free to correct/teach me if I made any technical errors but basically, use of Passive radiators makes a speaker a bass reflex design. As such, you tune them to a certain frequency via the use of added mass. 

With a ported design, we want a high pass filter because driver excursion unloads below port tuning.

With a passive radiator design, the passive radiators themselves go crazy below their tuning, especially at their resonant frequency. Without a high pass filter you're inviting damage.

If the Quartet12 and its HPF are too high for you, then switch to SDX15 or Tempest-X2 and 18" Passives!


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## poppc (Nov 6, 2010)

GranteedEV said:


> I'm not an expert on PRs, so feel free to correct/teach me if I made any technical errors but basically, use of Passive radiators makes a speaker a bass reflex design. As such, you tune them to a certain frequency via the use of added mass.
> 
> With a ported design, we want a high pass filter because driver excursion unloads below port tuning.
> 
> ...


Thank you for the reply. I am, by no means, no expert at all. The software I used to model this also has a graph for cone displacement and, according to this, Xmax is not reached until about 12Hz, whereas the HPF on the Quartet12 amp is set at 18.7Hz. I'm not sure what the maximum displacement would be for the PRs, but from all I've read so far it is usually higher than that of the drivers. In this case the software shows the highest displacement to be 31.8mm at about 11Hz. This is why I thought I could get away with an unmodified amp and could use the Reckhorn to set the high pass filter lower, to something like maybe 15Hz.


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## Mike P. (Apr 6, 2007)

> The software I used to model this also has a graph for cone displacement and, according to this, Xmax is not reached until about 12Hz, whereas the HPF on the Quartet12 amp is set at 18.7Hz.


This is the cone excursion graph for the TRIO12 kit, both with 500 watts of input power. Pink is with a HPF at 18.7 hz, yellow is without a HPF and Xmax is reached at 19 hz. Something is not right with your modeling.
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## poppc (Nov 6, 2010)

Thanks Mike,

It all makes sense now. There is probably something I'm not doing right when entering the PR parameters in BassBox. Some of the parameters must be changing with adding mass, but I'm not sure which ones to leave for the software to calculate.


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