Going from a single 12" to dual 8" subs

[damarble]

Any opinions on how this might work out?

I currently have a single JL 12" in a sealed box powered by a MTX amp. Don't know the specs of either because they came with the truck. This setup sits behind my rear seats facing rearward to bounce off the hatch. It's hooked to my factory head unit and I usually keep the bass at the middle mark.

I need to have my cargo area permanently empty for an upcoming mod. My thinking is I could use 8" subs in the side rear speaker locations and nix the speakers.There seems to be enough air space behind the trim panels to make fiberglass sealed enclosures of the right size.

Can a pair of 8s adequately replace a 12 in this situation? I'm not seeing any other options.

 

[Anime]

Easiest option, assuming the cargo area won't be blocked off or interfere, is to throw a single 10" in the stock sub box location behind the right rear panel. If you're willing to modify the panel for it, you can build a custom box that will fit behind the panel and house a 12" just fine.

The sides of a Sport have more than enough area for an 8" on each side, especially if using fiberglass to fill it in. Mask off the area, fabricate the back of the boxes with fiberglass, then pull it out and finish the front. You'll have secure drop-in enclosures.


As for what would be the best, it's hard to say. You can get two 8's to go pretty loud, but you might have issues with them facing each other and cancelling out unless you run one of them out of phase or something. You might be able to angle them slightly but that will only help so much. A single 12" will usually go lower than dual 8's, but it really, really depends on how well the enclosure is matched to the sub, how much power it's getting, and the overall system. Either will sound good if properly designed and with quality components.

Pick what sounds best for you.

 

[rhauf]

8" sub, (about 7 inches of moving cone area) = 22 square inches of surface area. (or 44 inches for two)

a 12" sub, (about 11 inches of moving cone area) = 35 square inches of cone area.

so the pair of 8" subs will be more efficient than the 12, as the total cone area will be bigger.

look at the resonant frequency of the subs as well (remember the enclosure impacts this, smaller enclosure raises it etc) and remember that whatever that pitch is (say its 60 hz) you're bass will drop off at 12db/octive below that (in other words, 30 hz will be down 12 db and completely worthless etc) for this reason, i would much rather have one high quality sub (any size) with a low resonance frequency, than a bunch of crappy subs that just play loud w/ higher resonant frequencys (and "one note" bass)

what is the reason for the upgrade? louder, or deeper bass?

 

[aznboi3644]

8" sub, (about 7 inches of moving cone area) = 22 square inches of surface area. (or 44 inches for two)

a 12" sub, (about 11 inches of moving cone area) = 35 square inches of cone area.

so the pair of 8" subs will be more efficient than the 12, as the total cone area will be bigger.

look at the resonant frequency of the subs as well (remember the enclosure impacts this, smaller enclosure raises it etc) and remember that whatever that pitch is (say its 60 hz) you're bass will drop off at 12db/octive below that (in other words, 30 hz will be down 12 db and completely worthless etc) for this reason, i would much rather have one high quality sub (any size) with a low resonance frequency, than a bunch of crappy subs that just play loud w/ higher resonant frequencys (and "one note" bass)

what is the reason for the upgrade? louder, or deeper bass?

I don't know where you got your numbers from but your math is all WRONG

How to calculate cone area
Cone area = pi x (r x r)
pi = 3.14 r = radius of sub

One 8" = 50.27
One 10" = 78.54
One 12" = 113.1
One 15" = 176.71
One 18" = 254.47

Two 8" = 100.53
Two 10" = 157.08
Two 12" = 226.19
Two 15" = 353.43
Two 18" = 508.94

Three 8" = 150.8
Three 10" = 235.62
Three 12" = 339.29
Three 15" = 530.14
Three 18" = 763.41

Four 8" = 201.06
Four 10" = 314.16
Four 12" = 452.39
Four 15" = 706.86
Four 18" = 1017.87

 

[damarble]

Easiest option, assuming the cargo area won't be blocked off or interfere, is to throw a single 10" in the stock sub box location behind the right rear panel. If you're willing to modify the panel for it, you can build a custom box that will fit behind the panel and house a 12" just fine.

This was my first idea but I'm worried about security. The cargo area will be open and exposed to the legions of meth heads that rape this city.

what is the reason for the upgrade? louder, or deeper bass?

I'm not really upgrading, per se, just removing my set up from the cargo area and trying to fit it in the passenger area somehow without loosing volumn and quality.

 

[Anime]

You mean the cargo area will be open with the rear plastic interior panels removed?

If you just mean it will be visible through the windows, the stock location is BEHIND the plastic panel and very secure, especially with a color-matched cover.

 

[damarble]

You mean the cargo area will be open with the rear plastic interior panels removed?

Yup. The back is getting cut off and converted to an open bed.

 

[Anime]

Oh. Well in that case you don't have much of a choice. Go with the two 8's. You might try making their enclosures so they angle towards the front instead of straight at each other.

You could always modify the rear seat area as well, if the rear seat is coming out to make space for the front part of the bed, theres plenty of space there for a sub box, with the top of the box providing the surface for the front of the bed.

 

[damarble]

Nope, seats are staying, so 8" it is. What effect would it have if I angled one forward and one rearward?

 

[Anime]

One forward and one rearward would likely have a similar effect to them facing each other, with part of the waves cancelled out where they meet in the middle.

Interior spaces of a vehicle have interesting sound properties, so there's really no telling where the best positioning is, other than general theory, which says you don't want speakers facing each other directly, even if they are somewhat apart.

I'd say both forward, upward, or angled forward and upward is the way to go. Since you'll be cutting up the rear panels for the bed part, you can probably modify what's left to get a clean looking spot for the woofers to face out of.

 

[BigBoom]

other than general theory, which says you don't want speakers facing each other directly, even if they are somewhat apart.

i know a guy that had 32 12's in his excursion...16 on each side in two separate boxes and said the more parallel he put the boxes, the louder it got. not doubting the theory...just saying what happened from his experience

 

[damarble]

Thanks for the input guys.

 

[Anime]

i know a guy that had 32 12's in his excursion...16 on each side in two separate boxes and said the more parallel he put the boxes, the louder it got. not doubting the theory...just saying what happened from his experience

Using a large number of woofers to build sound pressure is somewhat different than using just a few to get bass frequencies. If you want to, sure, you can build a HUGE box with 32 woofers all facing each other down a hole from front to back, and get enough SPL to blow the windshield clear out of any vehicle. Of course the SPL will make it LOUD, BUT it will only be loud at the frequences the design doesn't minimize or cancel clear out.

On the other hand, if you have just two woofers, the LAST thing you want is their sound waves cancelling each other out, especially in the really low frequences. Face them directly at each other in-phase, and they'll do exactly that. Do it out-of-phase, though, and they'll actually work together. Plenty of bandpass boxes work like this, with a push-pull system of 2 or 4 woofers, each pair facing each other, to get super high sound quality, and very accurate bass.