Why cannot i get much air flowing in a single cab

[Tony Starks]

You must be registered for see images attach

Ive been messing with subs for awhile now but ive noticed that nothing will ever beat a trunk. I put my old 2 10's which were 250 rms each on a matched amp in my buddys trunk and it was louder than my 2 12 alpine type s' 500 rms. By louder I mean feeling more spl, is it because of the box? My box was built to spec and to fit behind my bench seat. I just need someone else whos experienced with these type of problem

Heres the setup:

2 12's Alpine Type S 500rms
Alpine MRP-500 Monoblock

Box is made of 3/4th MDF

 

[great white]

Anytime you "fire" a speaker in to a sound absorbing material within a few winches (IE: your seat) you're going to loose spl.

Just the way it works.

A regular cab truck is about the worst you can get for trying to make either SPL or SQ in a vehicle.

Also, it's hard to tell from your pictures, but your box looks kind of small for 2 12's. Looking up specs on those, it appears the recommended box is .85 cuft net. that's 12x12x12 plus whatever additional volume your cone, spider and magnet take up. Also don't forget that you have to use inside dimensions on your box as MDF is pretty thick stuff and takes up a fair amount of space. Any bracing also takes away from interior volume.

Your box kind of looks like plywood in those pics, which is not the best choice for a box. The box has to resist flexing when the sub driver moves. That means mass. Plywood has a lot of air space in the layers that make it up. MDF is not strong mechanically (IE: holding weight) but it is very good at isolating the positive wave from the negative because it is very dense and essentially solid as face as acoustics are concerned. If the box flexes, it allows the negative wave to be reproduced and this cancels when it sees the positive wave. Basically, it's opposite the side of the cone you want and cuts down on your SPL (SQ also, but it sounds like you're not as concerned with that).

Your box is also not square, so you have to do some calculations to see how much volume you are loosing in the triangular portion.

You can play with those dimensions in which ever way you can get it to fit (subs only care about volume in a sealed box, not shape).

Maybe if you post up the dimensions of the box and the thickness of your material we can see if your box really is "to spec"....

 

[Tony Starks]

Anytime you "fire" a speaker in to a sound absorbing material within a few winches (IE: your seat) you're going to loose spl.

Just the way it works.

A regular cab truck is about the worst you can get for trying to make either SPL or SQ in a vehicle....

thanks that makes a lot more sense. I think im about done with car audio, ive improved nothing in being "louder". Do you have any ideas on what could improve it? Thanks though!

 

[great white]

thanks that makes a lot more sense. I think im about done with car audio, ive improved nothing in being "louder". Do you have any ideas on what could improve it? Thanks though!

Have a re-read of my post. I was editing while you were typing....

I've got a single 10 in my truck and it's louder than I can ever use. It shakes the mirrors and rattles the door handles easily and it's only a cheap sony 'Splode driven off a old 150W RMS pioneer amp. It's in an extended cab though:

You must be registered for see images attach

You must be registered for see images attach

Thats a clarion 10 in the pictures. It developed a rattle and I swapped it out for a Sony 'splode I had sitting on a shelf.

 

[Half Assed]

You aren't moving air because there is no air to move. That's why I don't like subs that fire into a seat. You have that box sandwiched in there.

Throw the box on the passenger seat for a few days and you will see a big difference.

Not much you can do except try to make a box with the ports at the top of the seat or a center console sub box.

 

[96Z71ECSB]

Remove one 12" speaker and cover the hole temporarily with a piece of wood.
A single 12" will probably hit harder than two 12" in that box.
If your satisfied, make the box out of MDF as great white suggested and make sure the box is air tight when you're done.
You may want to build the box a little wider (towards the cab corners) to take advantage of all the room back there.
I've seen a lot of single cab trucks, with a single twelve behind the seat, that hit pretty hard. Of course, it was all box behind the seat and nothing else.
You may want to bridge your amp to mono also. Use it's low pass filter too (if it has one).

 

[Blaine Davies]

You aren't moving air because there is no air to move. That's why I don't like subs that fire into a seat. You have that box sandwiched in there.

Throw the box on the passenger seat for a few days and you will see a big difference.

Not much you can do except try to make a box with the ports at the top of the seat or a center console sub box.

If its just a bench in the truck, couldn't a box like the ones for the extended cab trucks be built to mount underneath the seat? so it the box would technically be as long as the bench & tapered with the angle underneath the seat to the floor, with enough room for the seat to slide along with breathing room for the release cables and handles etc. make all the measurments, (measure 8 times & cut once) then just pull the bench out, and start fabbing a box to go underneath the seat. (if the bench dosnt fit back on top of the box, just get some longer grade 8 bolts of the same tread pitch, and stick a bunch of washers in between the seat bracket & the floor & put a bunch of loc-tite on the threads) mount the subs facing up underneath each seat (cages mounted overhead of the speakers wouldn't hurt) carry the box on over the transmission hump under the bench, mount the amp right in the middle. drill a port hole with a hole saw bit on each side facing the door (one for each sub) and inside the entire box, route a piece of plastic 1&1/2-2" PVC acting as a "port conduit" from one hole to the other and make sure in the middle of it, cut the pipe in half, mount the pipes beside eachother, and secure each of them with a woodscrew long enough that it goes through thepipe & into theMDF, but not so long that it goes through the entire box. this would resonate the sound waves from inside the box out evenly to either side of the truck, also any breeze coming through the window while its open, though the weather stripping @ the door seal & the foot vents from your HVAC system would technically feed the box it's air supply and circulate it throughout the cab. with the PVC inside the sub box, you're creating a path for air & sound waves to flow through. (DO THIS ALL WITH THE TOP OF THE BOX OFF & SUBS OUT) also, if you drilled couple holes in the top of the box with a hole saw bit (similar size to the one you used for the port holes) underneath the amp and mounted a couple 12v fans (similar to computer fans for a CPU) underneath the amp, daisy-chaining the positives together and tapping onto the remote wire feed at the amp, and the grounds @ the amp ground as well. this would keep your amp nice and cool whenever the stereo is on. technically the fans would just run off of the stereo/radio fuse as well, even tho they wouldn't even draw more than an 1 amp anyway. after the top of the box lid is done (with the fans if you choose), make sure to just seal all the corners inside the box with silicone or something, then do the same to the lid before screwing it on top. (dont forget to drill a hole large enough to fit both sets of speaker wire to go to the subs before you screw the lid/top on) run the speaker wires with an excess amount of wire so that you can connect them to the subs and then bolt the subs in place)

just a thought in my head, i would try to fab one up for my front bench to give you a design to go off of, but my tahoe has more than enough room for a massive sub box behind the rear seat lol. heres a couple links to something similar to what im trying to draw out in my head, it would just have to be built for a front bench, not a rear.

http://www.supercrewsound.com/88ChevyECdual.html

http://www.supercrewsound.com/99ChevyECquad.html

 

[Tony Starks]

You must be registered for see images attach

ok this what I got, the box is made out of 3/4th MDF and the box's length all together 2 feet and 9.5 inches. I also put the box in the seat with me and it made no difference. Im going to read the specs for the subs over again and see how it compares. Thanks for all your help everyone!

 

[great white]

If its just a bench in the truck, couldn't a box like the ones for the extended cab trucks be built to mount underneath the seat? so it the box would technically be as long as the bench & tapered with the angle underneath the seat to the floor, with enough room for the seat to slide along with breathing room for the release cables and handles etc. make all the measurments, (measure 8 times & cut once) then just pull the bench out, and start fabbing a box to go underneath the seat. (if the bench dosnt fit back on top of the box, just get some longer grade 8 bolts of the same tread pitch, and stick a bunch of washers in between the seat bracket & the floor & put a bunch of loc-tite on the threads) mount the subs facing up underneath each seat (cages mounted overhead of the speakers wouldn't hurt) carry the box on over the transmission hump under the bench, mount the amp right in the middle. drill a port hole with a hole saw bit on each side facing the door (one for each sub) and inside the entire box, route a piece of plastic 1&1/2-2" PVC acting as a "port conduit" from one hole to the other and make sure in the middle of it, cut the pipe in half, mount the pipes beside eachother, and secure each of them with a woodscrew long enough that it goes through thepipe & into theMDF, but not so long that it goes through the entire box. this would resonate the sound waves from inside the box out evenly to either side of the truck, also any breeze coming through the window while its open, though the weather stripping @ the door seal & the foot vents from your HVAC system would technically feed the box it's air supply and circulate it throughout the cab. with the PVC inside the sub box, you're creating a path for air & sound waves to flow through. (DO THIS ALL WITH THE TOP OF THE BOX OFF & SUBS OUT) also, if you drilled couple holes in the top of the box with a hole saw bit (similar size to the one you used for the port holes) underneath the amp and mounted a couple 12v fans (similar to computer fans for a CPU) underneath the amp, daisy-chaining the positives together and tapping onto the remote wire feed at the amp, and the grounds @ the amp ground as well. this would keep your amp nice and cool whenever the stereo is on. technically the fans would just run off of the stereo/radio fuse as well, even tho they wouldn't even draw more than an 1 amp anyway. after the top of the box lid is done (with the fans if you choose), make sure to just seal all the corners inside the box with silicone or something, then do the same to the lid before screwing it on top. (dont forget to drill a hole large enough to fit both sets of speaker wire to go to the subs before you screw the lid/top on) run the speaker wires with an excess amount of wire so that you can connect them to the subs and then bolt the subs in place)

just a thought in my head, i would try to fab one up for my front bench to give you a design to go off of, but my tahoe has more than enough room for a massive sub box behind the rear seat lol. heres a couple links to something similar to what im trying to draw out in my head, it would just have to be built for a front bench, not a rear.

http://www.supercrewsound.com/88ChevyECdual.html

http://www.supercrewsound.com/99ChevyECquad.html

Ummm, no...

 

[great white]

You must be registered for see images attach

ok this what I got, the box is made out of 3/4th MDF and the box's length all together 2 feet and 9.5 inches. I also put the box in the seat with me and it made no difference. Im going to read the specs for the subs over again and see how it compares. Thanks for all your help everyone!

Hate to break it to ya but your volume is not even close to the oem recommended sealed box volume.

You 5.5" is actually 4" when accounting for the 3/4 mdf and your 8" is actually 6.5"

If i had time i'd do the calculations for ya, but i can tell just from the dimensions you don't have the interior volume you need.

So, box too small and right up against the sound absorbing seat....that's 2 strikes out of 3....