you could try shortening your port length to bump that peak frequency up higher which forces the subs to move more air and lower the impedance spike but you risk losing that bottom end authority entirely. another way is shrinking internal volume by adding wood displacement blocks which stiffens the suspension and raises the tuning but cuts total output capacity. with my 4 ds18s on two nxl2000s i find port length changes are way easier to dial in on the fly during testing than rebuilding the whole enclosure to change volume. i would personally shorten the port because it is faster to modify and lets you find that sweet spot for your meca score without sacrificing all the box displacement you already have. just watch your excursion because once that rise drops the power draw spikes hard.
Restart is you are having issues. New update available.
Box rise is killing my burp numbers on the 4 VXF 15s
Hit a wall trying to get my box rise under control for the next MECA show. Currently rockin 4 VXF 15s in a common chamber box tuned to 38hz, fed by 2 RP2000s strapped. On the meter, I am seein way higher impedance than I calculated, and the output is fallin off hard after 45hz. When I clamped it, the amps are barely seein half the rated power because of the rise. Has anyone had luck with a specific port ratio for these VXFs to keep the rise down during burps? Should I try shrinkin the total volume a bit to force more pressure even if it kills the bandwidth?
Replies (3)
Replying to LowEndFlex
Before tearing into the port, try checking your wiring series-parallel scheme to ensure you are not running too high of a final load for those RP2000s to handle efficiently at the burp frequency. My Kicker KX2400 really wakes up when I keep the final impedance closer to the bottom of the amp stable range despite the rise. Sometimes just rearranging the voice coil wiring to a lower nominal impedance before the rise kicks in helps the amp dump more current early on. This keeps your costs at zero since you are just moving wires rather than cutting wood. You might find that the extra current makes the subs play through the rise better without losing your low end.
Check your port velocity calculations against your cross sectional area before you trim anything else. I had a similar issue with my 3 Fi SP4 18s where I was so focused on impedance rise that I forgot about the backpressure inside the common chamber. I was hitting 154.2 at 42hz but my coils were heating up like crazy because the port was choking at the exit. Once I flared the outer port opening to smooth out the airflow, the impedance curve flattened out a bit and I picked up 0.8dB because the subs werent fighting the trapped air. You might think the rise is the only enemy but if your port is too restrictive for the volume of those 4 VXF 15s you will be dealing with massive thermal compression which makes the rise look way worse than it actually is. Get a better flare on that port entrance and exit and you might find the amp sees the power it needs without rebuilding the box internals.
Sign in to join this conversation.
Sign in to reply