Opinions on box design...

[draggindakota]

Longtime lurker here with my first post.

I'mcurrently designing an under seat box for my F150 extended cab and trying to use what equipment I have on hand. This isn't my first box build, but it would be my first ported box.

Right now I've got it designed as ported and downfiring, but I'm not opposed to going sealed as well. 

Box specs are:
1.72 ft^3 before woofer displacement, 3" x 6" rectangular port approx. 21.25" long (obviously will vary due to final box volume and tuning), shooting for 34 Hz tuning. Max box height is 8" outside.

I'm looking for opinions on the design so far. Sub choice is either a 10" Kicker CompVR(4 ohm DVC) or an 8" Kicker CompS (8 ohm SVC), as I have both available. The 10 would be getting 300 watts and the 8 would be getting 200 watts, based on what amps I have on hand.

Here is what I'm getting in WinISD for both subs:
 

The outputt isn't really that different even with the 8 getting 100 watts less, but the 10" curve is a lot smoother. I don't have a lot of experience with ported designs.

My one concern is clearance for sub excursion. I've only got about 1" clearance and I'm not really sure how much is needed for a down firing sub.

Thoughts?

[bcbrassard]

1" is 25 mm/2.5 cm. What are the specs on the sub?

[Joshdashef]

If I am remembering this right, the xmax specs shows the maximum excursion of a subwoofer - but some exceed this measurement. I think you should be fine with 1" clearance underneath the sub, but I would try to design it so you can have another half inch or so. 

The CVR10 has xmax of 14 mm (0.55 inches). Manual for CVR10

The Comp8 has xmax of 8.6 mm (0.34 inches). Manual for Comp8

Couldn't find a CompS8 but I'm guessing the Comp8 is what you meant? (It is a 4 ohm SVC instead of a 8 ohm SVC)

Besides xmax I would consider the DVC sub to be the better option because you can run it at either 2 or 8 ohms, allowing more power from your amplifier if it is stable at 2 ohms. Whereas the SVC would only allow you to wire at 4 ohms (or 8?), getting less from your amplifier. 

[YukonXL04]

If your not flush mounting the woofer, you'll need more than 1 inch. The frame of the sub sticks out roughly 1/2 inch, plus the surround usually sticks out more past that, leaving basically no room for excursion. I generally try to leave 2-3 inches from the surround to the floor, so your bass has room to escape from under the box.

[ckeeler11]

That box is to big and the response curve shows it. I would cut it down to about 1.0 cu ft.

[draggindakota]

The sub specs are:

10: 

fs: 33.2  SPLo: 85.5  Xmax: .501  Re: 6.71  Qms: 8.93  Qes: .640  Qts: .597  Vas: 1.42  Displacement: 75.3 in3  400w RMS

8: 

fs: 40    SPLo: 85.6 Xmax: .34  Re: 3.85   Qms: 8.892  Qes: .574   Qts: .540  Vas: 0.65  Displacement: 31.4 in3  200w RMS

I'll probably end up doubling up the baffle so the sub can be flushed and give a little extra clearance. If needed I could probably space the rear seat up a bit

1 hour ago, ckeeler11 said:

That box is to big and the response curve shows it. I would cut it down to about 1.0 cu ft.

What about the curve indicates the box is too big? Honest question. The manual recommends 1.25 min / 1.75 max ft3 ported for the 10" and 0.66 / 1.2 ft3 for the 8".