How do you calculate 1/4 & 1/2 waves?

How do you calculate for rear & front wave alignment?

Say your sub (rear-fire/sealed) is 30" from the back of the vehicle (magnet 40"), with 92" from the back of the magnet to the dash. Do you add 40+92, and divide 6780 by 132 for 51.36 hz or is it just 6480/92 for 73.69 HZ?

What other factors are there?

 

282/30 is your null point from the trunk. All multiples of that too.

IMO don't worry about the front.

And measure from the radiating surface, not the back of the magnet

 

The further away a box is from the listener the deeper it will sound, is this correct? What if it's in a closed off trunk or truck bed?

 

Not in a car. Just like with headphones, in a car your ears are directly modulated by the woofers at lower frequencies.

Depends on how soundproof the trunk is. Mine sounds pretty much the same seat up or down.

I would not put woofers in a truck bed that was not somehow connected to the cab.

 

What if it was a ported blow-through, but the subs were at the back of the bed... ?

 

Your lowest resonant frequency will be lower but the range you "hear" is the same. I've played with a box in the back of my hearse compared to it on the seat beside me. Same range. Placing it somewhere in between causes cancellations though.

 

 

Can you mount a subwoofer inside-inside a box?

 

Which begs 2, nope make it 3 questions....

1: Did you try figuring out what frequencies were being canceled? I'm curious if the math supports what you were hearing.....

2: Did you try facing the box forwards and to the rear while moving it front to back? I would assume the frequencies affected would be lower when facing the rear but I've never had the chance to test for it.

3: Does this mean you're working on the hearse again....that seems to have slipped onto the back burner for a while.....

 

Generally the wave should be longer if the woofers are pointing to the rear and not forward, as the sound has to travel further and reflect off a surface before going forward to your cab.