what is your current tuning frequency and how many square inches of port area you runnin total. i tried forward firing through the ski hole with my single hertz sx 10 years ago and figured out real quick that unless you seal the baffle off perfectly against the interior trim you just get a bunch of nasty hollow sounding reflections and massive cancellation. it looked sick but on the termlab it dropped 1.2db compared to rear firing into the trunk. sedans are tricky because you are fightin that massive pressure pocket that develops at the windshield. if you really want to chase the number keep the subs and port pointed back and focus on building a solid divider wall that isolates the trunk completely from the cabin. that way you force all that air through the rear deck or a cut out and stop the wave from wrapping around the box. stayin rear firing usually nets higher numbers in trunk cars because you get that extra loading off the trunk lid and quarter panels before the sound wave even hits the cabin.
Update incoming
trunk vs cabin firing for 2x NVX NSW 12s in a sedan
Trying to squeeze every bit of output out of this trunk build for some weekend competitions. Currently packin 2x NVX NSW 124s on a VAD1000 and it slaps for a daily setup, but I want to get that meter number up. Right now I got them ported and facin the rear, but I heard some guys swear by cabin firing through the rear deck. Has anyone actually seen a gain doing that in a sedan? I'm worried about cancelation if I seal it off against the seat vs keepin the air space open. Any of yall tried flipping these into the cabin with a proper baffle and noticed a difference on the termlab? Trying to see if it is worth the extra wood work or if I should just focus on better deadening behind the box.
Replies (3)
Replying to SarahV
back when i was running 4x 12s in an old civic i thought forward firing was the cheat code to get my score up. i spent a whole week glassing a baffle to my rear deck only to find out i actually lost 0.8db not 1.2db because i failed to account for phase alignment at the mic position. you mentioned the trunk lid loading which is definitely key but remember the cabin acts as a giant resonant chamber. instead of chasing that full seal you should check your phase relationship between the port and the subs at your competition frequency. if you flip the box and hit a dead spot on the meter it usually means the path length difference is causing destructive interference at the dash. my advice is to keep it rear firing but try tuning your port length using precision rings or internal spacers to find the sweet spot for your specific cabin resonance. sometimes just shifting that peak frequency by 2hz makes a way bigger difference than trying to force the air through a tiny factory opening in the deck. just keep an eye on your excursion if you start playing below that new tune or you might smell coil before you get that trophy.
Replying to SarahV
You are actually off by a bit on the claim that rear firing is universally higher because of trunk lid loading. In many sedans, the peak pressure gain isn't just about the trunk lid but the resonance of the rear deck itself interacting with the windshield. With my 3x Fi SP4 18s, I found that if your rear deck isn't reinforced with heavy sound deadener or additional bracing, that lid flex actually steals energy from your peak score by acting like a passive radiator. Instead of just a divider wall, tonight you should try a simple back-to-basics test. Take a piece of cardboard or 1/2 inch mdf and block off the top half of your trunk opening right at the edge of the sub box. Use a cheap tension rod to hold it firm. If your meter number goes up, you know you have an issue with the wave wrapping around the top of the box. If it drops, your box is already loading correctly off the trunk structure and you just need to focus on reducing the mechanical vibration of the quarter panels. When you check for the sweet spot, use a single 30 second sine wave at your box's tuned frequency rather than music to ensure you are seeing a true steady state number on the meter.
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