Originally Posted by sivadselim
It's ridiculous to recommend that someone with a perfectly functioning stereo receiver, that they seem quite happy with, purchase an AVR just so they can high-pass a pair of Paradigm Mini Monitors.
To the contrary, not doing it seems ridiculous to me, especially if used with movie soundtracks with LFE added to the mains. The monitors will still see all
of the LF information and distortion will increase throughout the midbass and midrange of the monitor's LF driver. Remember the driver/enclosures acoustic roll off does not in any way apply an electrical roll off to the signal. With no filtering applied to the monitors, whatever output they have in the sub's passband will not be coherent with the sub and depending upon placement and the room will have comb filtering as the three wavefronts combine at the MLP.
Below tuning, any ported system's excursion increases dramatically: in the case of the speakers Arny gave as an example, with a tuning of about 45Hz, then playing BHD, WOTW, M&C etc which have a lot of LFE at any sort of level will have the monitor's MB excursing far more than needed trying to reproduce the LFE rather than merely it's own passband material, say >75Hz. Distortion for a given driver depends upon the linearity of it's motor/suspension system and distortion increases with increasing excursion, and what type and how much depends upon the transfer function of the m/s.
As Arny stated, below tuning ported systems increasingly lose control of cone movement. The following are examples I have saved, mainly pro and sub drivers, but the same general behaviour applies to all ported systems. Unibox generally does sims at the rated power of the drivers, so that is the level most are shown at, and the tuning of the box Fb, is shown on the upper right of each. The red line is the rated Xmax of the driver. For some reason Excel is crashing for me at the moment or I would have added a few 'hifi' drivers too.
Knowing that this increasing excursion below resonsnce ids a problem, all
ported speakers should include a HPF. For my own, I design them as a system. Here is the Beyma 15G40 I used as the LF component in my bass guitar rig.
Note: the basic alignment is not a classical 4th order, but SBB4.
With complimentary 2nd order filter to make it a 6th order ported.
and the FR's without and with filtering.
Likewise the JBL2226 and 2241 had similar alignments when used as the bottom of my PA for well over a decade before I broke it down and I used a set of 2225 in my own speakers in this alignment before I started building the new ones.
My first experiments with high passing small monitors wre with my Proac Tablettes about 25 years ago, and they sounded much cleaners with the HPF than without, as well as measuring considerably better.