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New Fi Q15 owner here. I just wanted to share about my project and also had a few questions and was hoping for some feedback/opinions.

Recently got my hands on BB6 pro and built a pretty bitchin' (and simple) PR setup for my buddy's Saturn ION that piqued my interest to try it again, but bigger and with more power. I used a Resonant Engineering SEx10 paired up with a TC sounds VMP12 (stock 390g mms) in a prefab 1.8cf sealed 15" box. Made a speaker ring adapter for the 12 in the 15" hole, and then cut a hole in the side of the box for the 10". We were very pleased with the amount of LF output this little bad boy has, and still being super clean all the while. He put down 136db peak at 47hz on 525w with one of the rear seats folded down, and 1 window down.

Before doing all this PR business, I had already placed an order with Fi Audio for a Q15 optimized for vented enclosures (dual 2, low QTS, cooling option, and spider pack) that I had planned to stick in my current 3cf slot ported (17x28x2.5" port) -- which I did. It sounds great in my 2000 Toyota Tacoma Ext cab which I calculate cabin gain starting at about 95hz. I hit 141.7db at 45hz with 1 door open. 1.7kw RMS was metered during the SPL burp. Amp is Rockford Fosgate T1500-1bdCP seeing about a 2.5-3ohm load.

I ran the same SPL test on the new PR setup just last night. Loudest I was able to get was about 137db at 45hz @ 1.7kw. The PR setup models 2-4db quieter through the entire musical bass range than the traditional vented enclosure, but this doesn't bother me much. All it did was get rid of the fat response peak that ended up getting rid of almost all the "boom" for a much more solid sounding bass. The best way I can describe it is a well engineered, flat response HT subwoofer. Low low bass, 20-35hz is where this setup really excels. Not so much in SPL, but instead just beautiful, full, even sounding bass that has remarkably *low* group delay at that frequency for how loud it gets. Effortless low low bass, low or high volume. The high bass also seems to have been enhanced a fair bit. It no longer sounds "hollow" and doesn't need a bunch of EQ on the top end. I'm crossed at 110hz with my midbass. All in all, I'm happy with the tradeoffs and think that I'll run this PR setup for a good while.

This brings me to my question though.... I bought a woofer that was designed/optimized for a vented box but i'd say my PR box is more akin to a sealed box than a vented one with respect to how the active driver behaves in the enclosure. I'm wondering what it is that Fi does exactly to their woofers to optimize (High QTS) it for a sealed enclosure. What I've noticed is that now in the PR enclosure, the active woofer MOVES a ton more than it ever did in my vented enclosure. It behaves almost identically to how it would in a sealed box, just goes louder and lower. With all this additional movement, and lack of atmosphere venting into the box to cool the coils, I noticed the dust cap getting pretty warm but not anything ridiculous. Never smelled coils... A disclaimer though, according to BB6, I shouldn't be able to overdrive (mechanically; xmax) either the passive or the active woofers with 1.7kw (can't make any more power) until I get down to 15hz. My subsonic can't go any lower than 20hz 6db/oct (JBL MS-8) which is what it is currently set at. At 15hz the box starts walking on me though :)

*If I would like to stay with this PR enclosure, do you think it would be worth my while to either A) sell this woofer and get a high QTS version, or B) send this one back to Fi and have them re-work it for the higher QTS. What should I expect to experience if I were to go to the high QTS woofer? Would it better cope with all the extra excursion i'm now seeing?

Below are some BB6 graph screencaps I took comparing my Q15 in a sealed box, my vented box, and my new PR box.

Acoustic Elegance PR18-1600

Green = Q15/PR18 Passive Radiator enclosure
Pink = Q15 vented enclosure
White = Q15 Sealed

Cone Displacement (xmax)

Group Delay


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