Tb'er Fdeck has come up with a new variable High Pass Filter that has a fixed 12db/octave filter at 35 hz and another variable 12db/octave filer from 35 to 140 hz. Francis sent me one to try. I've been so busy pumping out cabs that I hadn't had the chance to try it. My big thing is obviously how does it affect the performance of my cabs. I took a Crazy 8 and got it loud enough for port chuff. I love the word chuff. It's an onomatopoeia. Which means that the word sounds like what it describes. What does port chuff sound like? Chuff. Fortunately the C8 goes very loud before you hear it. Which I'm very happy about. So, got it to chuff.Plugged in the Fdeck HPF. Didn't even have to get it past the initial 35 hz. Chuff gone. Took the HPF out. Now don't try this at home. One great thing about the Faital drivers---they go really far without farting out. I played it SO loud (as loud as my 12" 3012ho) and got it to make the nasty sound when the voice coil hits the back plate. Fortunately I don't have to buy the owner of the cab a new woofer. Put in the HPF and dialed it up at the highest setting. The clack was gone. As I expected---but so was the low bass. Kept dialing it down. I wasn't a whole lot past the lowest setting when I didn't really notice the missing bass. But no more voice coil smack. The interesting thing---the C8 actually got LOUDER. I think it was because I was no longer using my amp's recources amplifying crap I didn't want to amplify anyways. The C8 as well as the 88 go substantially louder with the HPF. Substantially louder. I would tell my customers that the C8 would be fine handling a jazz trio gig with drums at piano trio volume. Let me up that to a quartet with the HPF. Or maybe---shall I say it?---a jazz group with guitar! I then tried it with electric bass with a C8 + C88 stack. Just set it on the lowest setting. It went louder and sounded more effortless. I boosted the bass until I started chuffing (it was hard to tell--that stack goes really loud---I had to discern between the chuffing and half of my house making weird sounds). I then dialed the HPF up just a bit. Only enough so that I didn't feel like I was compromising the bass sound. Big difference, I'm recommending it for e-bass too. I didn't ask for a cut on this nor do I want one. I know that Francis isn't making a bunch of dough here---just a labor of love. I'm just happy that it makes my cabs sound better! And by the way--in my typical narcissism I failed to mention that it would give any amp and speaker a bigger dynamic range.