Most 12" subs require either 1cuft or 1.25cuft in a sealed box. If your sub has a mounting depth of 6.5 inches, then you will need AT LEAST 8.5 inches of vertical space to accomidate several factors, the base of the box which would more likely be done with 3/4" MDF, the woofer mounting "ring" with surround and one-way excursion which (depending on your subwoofer) could be around (safe to say) 3/4", then you would need to allow room for the sub to pass air without acoustic obstruction (i.e. your seat or the floor depending on which way you are firing your sub) at least 1/2". If you are going to build your own box and lift your seat to fit the subwoofer, then put your subwoofer under the seat so you have an idea of which way is best to fire. I have two 12" shallow Rockfords under my seat. My box is much to small for my subs which exhibits the danger of a blowout if I run power closer to manufacturer rated power input and requires an amp with at least +12db or +18db to really "pound", but it has really nice low-end thumps. What kind of subwoofer do you have? Check out my setup and if you have any questions then feel free to ask.

http://www.cardomain.com/ride/2961992/12

 

the sub requires .8-1.6 cuft and the seat lift lifts the seat 2.5 inches and forward 2 inches... is there enough room?

 

There's enough room, you have a lot of width down there to compensate for air space, even for a ported box. As for the box, you will have to get creative. A ported box will be much louder but a sealed box will give you harder "thuds" at lower frequencies. Yeah you should have just enough room to fit that sub and a box after a lift.

 

i wanna build this thing... someone want to send me or 4x4tiger the dimensions and preferred wood? and all the specs and things to build it successfully.

 

I'll try to come up with a schematic along with building materials for a 6.5" mounting depth 10" subwoofer in a ported and sealed box. I'll research a 2.5" seat-lifting kit (as I'm not familiar with those) and figure dimensions for you guys. Hey rolltide4x4, what kind of subwoofer setup are you running, how big, how many, and what kind of sub?

 

Umm, first of all a blowout? With running a smaller than recommended box, power handling increases due to the increased cushion recieved. So bit lost there.

Then adding 12-18dB of boost isnt really a safe scenario. Keep in mind every 3 db is double. So, thats a lot of peak at one certain frequency. Can cause some serious damage to the speaker.

 

The shallow Rockfords are paper cone with a plastic dust cap. I used to have a 12" in my truck with a box that yielded less than .5 cuft with the sub dropped in. I ran it with my current P300.1 amp with +6db bass boost and 4 weeks after owning it, the dust cap popped off the cone and a hole tore in the cone near the surround. The shop I bought it from didn't honor the warranty because it was installed in a "faulty box" (and neither did Rockford), which is ironically the box they built for me. So I bought another one, no warranty, and the same thing happened again. You SHOULD be able to run more power in a smaller box as long as the construction of the woofer can handle the pressure but you would need more power since the compression of the smaller box is greater than that of a larger one. That's why larger woofers that are more concave can handle the pressure better because the cone doesn't flex as much as the more flat subwoofers like the shallow Rockfords and shallow Sonys meaning more cone wear. Also I mentioned that since I'm currently using a box smaller than individual driver requirements, I'm running a low-power amp with sufficient bass boost ready at hand, not saying that you would need one as a general standpoint or even to run all the time. And my setup is only one voice coil per sub, both are dual 4 ohm, run parallel to 2 ohms to push a bit more power from my amp. And how can adding 4x the bass boost (@ 45hz per say) cause some serious damage to the speaker? The biggest damage to speakers anyone can do is overtuning the source unit and amp to overdrive the subwoofer that cannot handle that kind of power (for SPL competitions and leads to the voice coil burning out, the voice coil bottoming out, or the cone assembly, frame, and surround come apart), miswiring the impedance (which results in more amplifier issues than subwoofer destruction), and obstructions. I hope some of this stuff I put made sense. I am very familiar that you can put more power into a smaller box, but only if the sub is built to handle the pressure (i.e. butyl rubber surround, a somewhat deep concave cone made of some kind of plastic or kevlar, stitched surround to cone, and a bumped magnet assembly to prevent bottoming out).

 

Ok, I was misunderstanding what you meant by blowout... I didnt quite catch that you were using the current series of RF's, WHICH ARE HORRID. The cones are the most fragile I have ever seen. But at the same time, there are always other factors to the damage of a speaker. Obviously, more was being asked from it than was available.

And as you say, overpowering your sub is the most dangerous part. Well, adding that much boost is overdoing it. After you set your gains, which are meant for level matching and to give the most power without clipping. Then making the amp give more, will send the speaker a clipped signal with very high peaks. Which will not only begin to damage the voicecoil, but may have also been a key factor in adding more stress to the cone then needed. The VC wouldve never bottomed out due to the box size but the stress from the overcompressed box led to the "blowout" you described.

 

im running 2 pioneer premeire 12" shallow mounts at 350rms each 700rms total
to a kicker 750.1 mono amp

 

Yeah bro, new Rockfords are horrible, since I've been owning them I usually burn out the voice coils matching barely less than RMS rated power so this time I'm running less than that (about 50W less per subwoofer) to relieve the fear of voice coil burnout but you know how everyone with a system in their cars and trucks are (since it seems that you are big and knowledgeable in mobile entertainment technology), sometimes we want to push our subs a little harder to get that extra "hit" on some of our favorite songs or when the mood desires it, that's why I push to have extra bass boost. And yes, my gain is set right, my head unit is set for -7 bass volume (between -15 and +6), LPF set on the HU at 80hz, no subsonic filter on the amp, Low Pass only, I don't have much bass at all and I don't run boost often. And no my subs never bottom out. I had an old Jensen that did, and I was at an audio shop that had a lot of Polk Momo subs and when the guy turned up his demo, I could hear that annoying "clicking" and I just left. I don't run my subs with enough power to bottom-out, but with bass boost I get that extra "thump" without putting my subs in danger. My only danger right now is overdriving my PAPER subs in my super small box. I know I'm not overdriving my subs, but I do have moments where I'm "pushing" them. I'm only using Rockford because their frame design fits best under my rear seats completely, unlike shallow Sonys, Kickers, Kenwoods, Earthquakes, and MTX. Only one I haven't tried is the new JLs, but I'm in total refusal to spend that much when I could put two MTX 9512-04's in my bed and fire them in the cab run by a hefty amp.

 

Yeah with the box i have when the subs would flex they would hit the floor and it caused my amp to overload so i had to install some spacers to give them about 2in more

 

LOL There's, ummm, alot wrong with all of that.
No subsonic filter is dangerous in a ported application, not a great idea mechanically for your subs in general.
Just because your HU is on -7 bass does not mean your gain sensitivity is not cranked to compensate. And buy better subs don't underpower them - you'll just end up clipping the amp in your quest for da bazz boust, and you're putting your subs in more danger than if you were overpowering them.
Get some quality 8s from Sundown or AQ, if you want to throw more power go with Digital Designs, and if you just have money to burn the RLi's are pretty beefy too. All those will fit under the seat with no modifications (I think, dont really know) and give you waaayyy more response and output than Best Buy brand shallows.

 

When I tuned the gain on the amp, I tuned it at +0 bass level on the head unit, then turned the level down so it wouldn't be hard on my 6 year old and 7 month old nieces and nephews but I could enjoy it at any moment's notice with the bass boost. Also my amp doesn't have a subsonic filter, and powers two subs in a sealed box, a box with about 1.45cuft without the subs in it. And no other 12" sub will fit in the F150 that doesn't require 1) the box to stick out or 2) a seat lift kit, either of which I don't want because of the passengers I normally have, friends over 6ft tall or kids that like to kick the seats and other things with dirty shoes. All other subs are made too high or the frame is attached to the bottom of a sub's magnet which doesn't give clearance where the floor rises to the back of the seat. And also, if bass boost is available on most if not ALL amps, then how does it become such a danger to your subs? I can understand the ugly sound and pressure of the amp's internal components if someone is trying to make 150dbs out of two 12" subs by using a 100W amp @ 4ohms with +24db bass boost in the back of their Corsica, but I'm running correct gain, lowered bass level on the headunit, and occasional +12db bass boost on the amp @ 2ohms 300Wrms in a box that is too small for flat paper cone 12" subwoofers, the only subwoofers that will fit my conditions without spending the money I don't have to run two yellowtop batteries, 1/O wiring, two 12" 9500 subs in the bed run by a 2300 watt RMS amp mounted under the seat. Trust me bro, I am very familiar with all the dangers in a sound system, but come on now, every once in a while who doesn't push their subs to a limit to satisfy their hunger for LOUD music that brightens their mood?

 

http://www.icixsound.com/iv/view_vid...e=&category=mv

Nothing good comes from bass boost.

Set your gain with the h/u subwoofer level all the way up, and after you're done turn the level back down. That way whenever you want more bass at times, it's safe.

 

I considered that until I realized it took most of my driving attention off the road an on my headunit pushing my touchscreen to slowly adjust th bass up as quickly as I could. And I'm not one of those people who is going to wait for a red light or to be parked to turn my bass up a bit, especially if I'm driving on the freeway.