Once I upgrade to the Ultramega drivers and BBPR in my Larger subs, should I use a High Pass Filter and if so, what frequency should I use? I would be using a 24db/octave Linkwitz-Riley active filter, and I can hit the frequency very accurately if indeed this is recommended.
Hi LR,
Yes, to blend your sub to your main speakers and system you will need a high pass filter.
If you are using a HT device like a prepro or AVR then you would use the filter it provides.
If you are using the sub in a 2 channel system, then you will need a filter such as the NHT X-2 or something similar. If you use a specific SUB AMP or some of the more recent PRO AMPS, you will find that they generally have high pass filters in them.
As far as what frequency, you should use, it will depend on your usage.
If it is for HT and the PrePro/AVR is used as a XO then it will be you choice as to what works best with your mains. 80Hz is the most common, but depending on the capability of your mains and how the system couples with the room and the sub placement, you may want to experiment.
If it is 2 channel, then you want as little "overlap" as possible of the frequencies produced by BOTH the sub and the mains. If your mains are left to roll off naturally and not low passed, then you would want to find the frequency where the sub "rolls in" and the mains roll off.
The frequencies that both produce if too large can cause muddiness and wooliness due to the same frequency being launched into the room from two dissimilar distances from the ear, thus causing arrival issues. This is not as much of a problem in HT, where bass is often transient and dynamic non musical sonics. However if you are listening to fine bass musical passages, the detail and harmonic overtones will be distorted (muddy/boomy/wooly)
