New and have no clue.

[shutter]

Hello everyone my first post here. After reading some of the posts in here, I realize a lot of this is way over my head.

I want to get this subwoofer for my truck:

Helix Precision P8W Specs:

• Power Handling: 300W RMS (600W Max.)
• Sensitivity: 87 dB @ 1W
• Impedance: 4 Ohms
• Resonance Frequency: 42 Hz
• Qms: 4.2
• Qes: 0.27
• Qts: 0.26
• VAS: 18 Liters
• Linear Cone Excursion: ±1/4”
• Top-mount depth: 4-9/16"
• Bottom-mount depth: 5-1/8”
• Cutout Diameter: 7-7/16”
• Sealed box volume: 0.28 cu. ft
• Ported box volume: 0.48 cu. ft.

I want to put it in a sealed box. But don't have any clue how to determine the box actual size. Can anyone help me out? Please?

It's a single cab truck (Ranger) Have four infinity speakers now, and looking for alittle help on the low end.

 

[weltersys]

A cubic foot is 12 inches x 12 inches x 12 inches, 1728 cubic inches.
A box volume of 0.28 cu. ft is 1728 x .28 =428 cubic inches.
The interior dimensions of the box height x width x length need to equal 428 cubic inches plus the area the driver occupies in the box.

Disregarding the driver volume, a 9 x 9 x 5.28 inch (interior dimension) box would be 428 cubic inches.
As a rough guess, the driver might occupy 100 cubic inches, so the depth would be increased by about 1.2 inches, a 9 x9 x 6.5" interior.
Any shape box that will fit the driver and adds up to around 528 cubic inches interior will work fine.

 

[Phenoholic Anonymus]

Shutter,

The woofer you want to use is not very usefull for a sub, ported or closed. In a closed box it will strugle to put out much under 90Hz. Maybe this will help to get some grip on Qts, Vas and their relation. Box volume calc online tool.

For a closed box, look for Qts 0.45 - 0.6 and low Fs.

 

[GM]

In a closed box it will strugle to put out much under 90Hz.

You seem to be forgetting how much cabin gain affects this. Once factored in, the recommended 0.28 ft^3 may be sufficient if the specs are reasonably accurate to get solid output to well below Fs and since it's already somewhat over-damped, it actually needs some VC heating [thermal power compression] to increase Qts a bit.

GM

 

[Phenoholic Anonymus]

I am not very informed about caraudio. I reckon there is a online cabingain tool somewhere. Could someone point the topicstarter to this?

 

[GM]

I don't recall seeing one per se and the only thing I have is an overlay chart of numerous car models's gain curves that gets posted periodically, though a single cab's truck curve would be even greater.

JBL often includes an approximate response sim with their car audio woofer's specs, so browsing a few of these should give some idea what to expect at minimum.

The general rule is no different than for a room though, so one can probably get an accurate enough estimate once the cab's net Vb and longest dimension is calculated.

GM

 

[Inductor]

Phenoholic Anonymus,
I would second you, unless OP is happy with that driver.
It's worse than the JBL GTO804 8" subwoofer for the same sealed enclosure.
http://manuals.harman.com/JBL/CAR/Boxes and Parameters/GTO 804D.pdf

 

[bjorno]

..and have no clue..

Hi, Nor do I,but a wild guessing cam be done. Your Cabin-Gain surely starts higher up in frequency than what I estimate for typical Sedans.

b

 

[Phenoholic Anonymus]

I think the Topic starter wants to get lower bas. Can you tell us about the Infinity speakers that need a little help? Are these doormounted? Would be nice if the subwoofer gets lower, cabin gain or no cabin gain.