2-12" Infinity KAPA series making weird noise in box

Not to sure what the problem is so I came here in hopes of some feedback. A friend of mine just lent me his system cause he doesnt have wheels for the summer but I'm not sure if he's ever run them because I'm getting a really weird sound on the bass hits comming from the box... I think.

I'm running two 12" Infinity KAPA's that have a 1200w peak and 430rms I believe. They are in a "BASSWORX" factory box where both subs are seperated and seperately ported with what looks like about a 1.5"X10" square port. All being Run off an 800rms MTX Thunder amp.

The issue is that when the bass hits (with the volume up) i get a weird snap, almost scratch sound. I've checked the subs and they dont seem blown. I had them running out of the box, and they sound perfectly fine. If I place them in the box but lift the sub up a bit (as to let air pass in and out of the sub hole itself) I get no weird noise but it's not until tighten the subs down that I get the weird snapping noise. And it looks like the subs are flexxing back with the pressure after every hit (like the sub hits and the air has trouble leaving the port so it snaps back at the cone) Which leads me to believe that it might be a port issue. I feel that if the speakers had enough air movement that this back pressure would be let out elsewhere and not force the sub to snap back against itself.

Not to sure if this is the issue though because I dont have a whole lot of knowledge when it comes to car audio so I was hopping to get a litle help on here.

 

I've narrowed it down to the subs themselves. I know I have a bit of trunk rattle but the noise I'm concerned about is deff commin from the subs. like I said, when the sub is lifted of the box(unscrewed) as to allow air to pass in and out of the 12" sub hole it's half sitting in, there is absolutely no unwanted noise. It's not until the sub is firm in the enclosure that the air seems to be not exiting fast enough so it pushes the sub's cone back out on each reverb. Which leads me to believe it's the ports not tuned to the drive of my 1200w peak subs thats creating this issue.

I brought the gain way down and put on the HF filter as someone else suggested on another forum. The sound stopped but now I have no punch when sitting in the car, slightly defeating the purpose of the subs altogether.

So what I'm wondering, is if anybody out there has experienced this before and remedied it by porting larger or some other fix. This is the box my buddy would like to keep the subs in cause it's desinged to fit his truck. So if it's just a matter of changing the ports to tune the box for the subs then some advice would be greatly appreciated.

If a whole new box is in order to handle these subs then some guiding on that would appreciated as well.

Not too sure of the specs off hand but:
Subs: 2-12" Infinity KAPPA Series 122.7
Amp: 1-MTX Thunder tc8001

 

Well, not too sure what you mean by are the subs moving out of the box... If you mean like that might be where the vibration is coming from, like the sub not being caulked or sealed to the box and vibrating the metal on wood. I don't think this is the case.

When I look at the subs you can see a sort of snapping motion in the cone. I think that the box isnt alowing the right amount of air to move so when the really punchy bass hits, the cone pushes out then normally should just go right back. But the air has trouble exiting the slotted ports and pushes back on the sub when it is trying to go back... (if that makes any sense, I'm just guessing this is the issue)I found the specs on the subs for what the factory recomends for inner volume and port dia./length for proper tuning of this enclosure. I'm Currently building a new box (thankfully my dad has quite the woodshop) and hopping that a properly tuned enclosure will solve this issue. Got it all cut and ready to assemble, just gotta pick up the hardware or steal the one's outta the Bassworx box (aside from the port that is...lolz) and throw it all together. Each enclosure was recomended to have an internal volume of 2 cu/ft with a 4" dia X 12-1/4" long port. Hopping to get my hands on some Polyfill (wish I could afford that Blakhole5 stuff ) to line the inside a bit so I made the cu/ft just a hare larger, like 2.2 cu/ft or so. I'll let you guys know how it goes with the new box when im done but any further input would be greatly appreciated.

Another guy said that it is known as "unloading" and its cause the box isnt tuned for those subs. Sorry if it's long but here's the post if it helps anybody else who might have an idea about this issue.

(QUOTE) Originally Posted by DeadlySones
The subs are unloading. You need to set the subsonic filter higher. Them BASSWORKS boxes are tuned really high. Usually around 45-48hz. When you play lower notes at high volumes the sub unloads and causes this fast snap your witnessing.

Its an easy fix, turn up the subsonic filter to stop this at the expense of loosing some lows, or else, get another enclosure built for them designed to play what you like to hear.

HTH(QUOTE)



(MY REPLY)
Fooled around with the amp, lowered the Gain and turned on the Subsonic Filter. The filter helped out alot and lowering the gain and other levels reduces the snap back but at the cost of that punch I would like to feel. Just running it on low for now so I dont wreck the subs but I would really like to either make this enclosure work with these subs by tunning the box to the specs of the subs (but would not know where to start) Or just make a whole new box for the subs if I just can't make this one work for whatever reason.

Here are the specs if anyone feels like helping out a guy who knows very little about about car audio tunning and thought this system install would have been alot simpler. Any help would be appreciated though.

Subs: 2-12" Infinity KAPPA Series 122.7

Speaker Type-Passive
Speaker-Diameter 12"
Nominal (RMS) Output Power-350 Watt Response Bandwidth-18 to 250 Hz
Input Impedance-1/4 Ohm
Sensitivity-92 dB
Magnet Type-Neodymium
Connectivity Technology-Wired
Additional-Features Dual voice coil

Enclosure: Bassworx Dual 12" Slot Ported (Mod#GPH212BK)

Amp: 1-MTX Thunder tc8001

Amplifier signal to noise ratio-75 dB
Amplifier continuous power/channel qty-400 Watts x 1 Amplifier output-1 channel
Amplifier high level inputs-Yes
Amplifier input signal voltage-0.1 to 5V
Crossover type-Active crossover
Crossover slope-24 dB
Crossover low pass frequencies-40 to 200 Hz
Crossover bass boost frequency-40 Hz
Crossover bass boost gain-0 to +18dB
Amplifier total output power-2400 Watt
Amplifier/Amplifier Class-Class D
Amplifier distortion factor-0.25%
Amplifier Output Details-400 Watt - 4 Ohm - THD 1.0 %
-1 channel(s) , 800 Watt - 2 Ohm
-THD 1.0 % - 1 channel(s)
Additional features-Subsonic filter
-Input level controls