STEvil

If you wire to .66 with two amps strapped each amp will see .33 ohm. You'd be better off at 1.5 for daily, then each amp would be at .75 ohm. this.

The 21's are fun but only really good for home audio.

Miss the "Sealed" box part he put in there? No, ignored it. Sealed is junk for L7's.

double baffle, double side walls, and probably double the back wall too.. Port in the back looks like it needs to be finished into the box so its not a zigzag. Might be better move the walls tighter to the sides of the box of the truck and just do a sealed 4th order with subs inverted.

subs up port back. or, if you want to get creative, face them down (need space under the box and an angle is a good idea like a clamshell) with port back.

No reason you cant run the 18 at lower output while still having the ability for "reference" levels at 20-30hz where the 10 and 12 would shit the bed.

If the trunk and box are not pretty much perfectly sealed from the cabin it wont get loud..

nope, dont care at all.

pedestrians dont always have the right of way. Thats in russia (or somewhere near russia I think), their road laws could be different. That said, ignorance on the roadway on part of pedestrian, cyclist, or motorist is going to have dire consequences.

$500-1000 for a wall, depending on the shop and how much work you do yourself. Build a box for the 4 12's. Subs up, port back, put them on a 1000-1500w amp, call it a day.

MOSFETs die from voltage drops and heat. Heat causes more resistance which means they use more power to put out the same amount of power as they were before. Voltage drop means they use more power to put out the same amount of power. Heat and/or voltage drop will rise as more power is used thus creating more heat/resistance/voltage drop and inducing a "cascading" effect until the parts burn out. One part can be weaker than the rest and go out first, but often if you have been seeing overly large voltage drops then more than one mosfet may be on the edge of blowing up or may have blown up.

the small magnet is a bucking magnet. Arcing 12v across probably altered the magnetic field.

suv/station wagon/van works best with subs up/port back... unless you wall it, then you can do a killer bandpass enclosure Of the two amps, i'd say the 5K would be the better choice as long as you are careful when setting it up so it doesnt clip to death. I've no experience with it btw. Just make a post in the amp section asking for experiences with the amp brand.

the yellow things are tantalum capacitors. Kind of looks to me either the MOSFET, resistor, or capacitor is cooked.

If you dont list the amps we cant say yes or no, because each could be rated at either RMS or peak.. As to cabin gain, it will always be a gain, just only to a point. There is a possibility that the vehicle could lessen SPL if you put the subs and/or port in the completely wrong direction, but without knowing your enclosure style there is no "correct" direction to tell you yet.

english?

that could have just been a poor connection from the ipod to the amp. Those 3.5mm plugs are notorious for that. But if you lose the humm then it makes it look like the head unit is the issue, not the amp.

Only thing with vehicles I watch these days is King of the Hammers or tough trucks.. edit well, anything offroad based I guess..

what do you mean it wouldnt play music properly?

... aside from n8 being correct, i'd try to jam a pair of 10's into it at least..

depends whats going in it. Could glue a couple 3/4 or 1" sheets together but I imagine keeping the air bubbles out of that would be hell..

3mm would probably break or vibrate and sound like shit.

those burn marks dont look like they came from the mosfets. Might be the legs on the 'fets vibrated and cracked the solder causing the burning on the board..

No, thats it, rest of the post was answered sufficiently before I posted.

why wouldnt we know who cadence is?