How big a box for a couple Qs? Big trunk!

[CadillacMatt 10+ year member]

Hey guys! After doing much research on this forum and around the web I've decided I'd like to upgrade my low end to 2 15" Fi Qs, but I need some help with the box.

Ok... from the threads I've read 32Hz ported is an excellent sweet spot for this sub, giving both excellent low end properties and volume without sacrificing SQ. I've decided on that. As far as size, Fi recommends a ported enclosure of 2.8cuft-4cuft. My trunk is quite massive, as far as car trunks go, I have 40" depth, 19" height and 48" width to work with. Before I go and pick a box, I have a few questions -

1. What would I gain from choosing either the smaller (2.8) or the larger (4) enclosure, assuming I can fit them?

2. If a sub requires, say for example 3cuft, and I have two of them, must I get a 6cuft enclosure?

3. Two subs in a ported box... divider in between with a port for each sub, or one chamber?

Thanks for any help you can give

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[skateboardkid 10+ year member]

The smaller ported box might increase power handling, the larger box would be more efficient, needign less power to get loud.

 

[Rashaddd 5,000+ posts]

Bigger enclosure means higher efficiency, yes if you have two of a sub you need twice as much space, and its up to you if you want to do separate chambers or a single chamber, most people do single

 

[CadillacMatt 10+ year member]

The smaller ported box might increase power handling, the larger box would be more efficient, needign less power to get loud.

I plan on running an AQ2200D to these bad boys so I don't think power should be an issue... I think you're actually the one who first suggested that amp //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif. Does it make a difference in the sound tho? I'm getting them with the BP Power as well ftw

Bigger enclosure means higher efficiency, yes if you have two of a sub you need twice as much space, and its up to you if you want to do separate chambers or a single chamber, most people do single

Is there any acoustical advantage to segretating/joining the chambers?

 

[CadillacMatt 10+ year member]

^^

 

[mcsoul 10+ year member]

The volume is net, you have to account for the port displacement.

I would do 7 cubes net, maybe a little more. Your power handling should

be fine. You need to be carefull, because you should fire the subs to

the rear and not have a box so big that it chokes off the cabin when the

sound tries to bounce back through.

You don't need BP power with the AQ 2200. I would not get it in your situation.

It's more for burping. An extra 100w a sub is not going to hurt you, and will be

swallowed by impedance rise.

Here this will work, but still may choke off the cabin. If your not walling the trunk

to fire forward you may want to consider 12's.

Use .75" MDF

H 17.5" x W 40" x D 24"

a single 4"wide x 16" high (internal box hight) x 16" deep

slot vent to the right or left of the two woofers. Add some internal

bracing and an extra front face to make the actual depth 24.75"

This box is a little too big for your trunk, it could choke off the bass.

I do not know how to do cut sheets or 3d plans.

 

[CadillacMatt 10+ year member]

I would do 7 cubes net, maybe a little more. Your power handling shouldbe fine.

Is that including the port displacement?

You need to be carefull, because you should fire the subs tothe rear and not have a box so big that it chokes off the cabin when the

sound tries to bounce back through.

I think I have enough space but if not, couldn't I face the subs forward into the pass. compartment with the ports firing forward? I have bench seats so it's all one piece they don't fold down. I have the top of the seat pulled forward about 2" so the bass comes straight into the cabin (about 4-5x louder than before).

 

[mcsoul 10+ year member]

My changes to my above post inlude port displacement

7.2 or so cubes net at 32Hz or a little less. As long as your

bracing does not take up major displacement (and it does not

need to).

 

[mcsoul 10+ year member]

Sorry man, I neglected to take into account

speaker displacement. The box is jacked.

 

[CadillacMatt 10+ year member]

You don't need BP power with the AQ 2200. I would not get it in your situation.

It's more for burping. An extra 100w a sub is not going to hurt you, and will be

swallowed by impedance rise.

According to Fi it boosts anywhere from 200-500W, without BP I think the AQ2200D would be a waste of power (might as well get the AQ1300) because the subs are 1000wRMS wired into one ohm.

Thanks for your insight man I'm trying to get a general idea of what I have to work with, I've never built a box but I have access to everything I need at my work (save materials) so I think it might be fun to tackle.

 

[alex5857 10+ year member]

he's saying you dont need BP because the subs will easily handle the 2200