4 cubic feet, tuned to 22 Hz, port area >= 64in^2

[hispls 5,000+ posts]

Don't you divide it by 4? I thought cabin peak was quarter wave not half wave

Probably get a peak at 1/4 as well, but that would put you up at or over 100hz in most cars. You may be thinking "quarter wave" box (transmission line varient)

 

[Kangaroux 5,000+ posts]

[quote name='hispls']Probably get a peak at 1/4 as well, but that would put you up at or over 100hz in most cars. You may be thinking "quarter wave" box (transmission line varient)[/QUOTE]

"We can use these response graphs to enable us to control the design so we get the response curve we are shooting for. So in the 30 to 35 Hz range we usually find that this is the common range of quarter wave resonance in vehicles."

Pulled from @Moble Enclosurs blog: Why is 30-35Hz used most commonly?

 

[emilimo701 10+ year member]

Looks decent. What's wrong with that one?

I might just do that. All that would need to be done would be to cut a couple more pieces that need to be longer, and one needs to be shorter. I have extra board left anyway.

IIRC, it would have been ~4.1 cubic feet after displacement, tuned at just under 23 Hz. The way it's taped up now, I think the port would be an extra 3/4" wider all the way through, which would bring the tuning frequency up slightly. Per your advice, that wouldn't be a bad thing at all. Maybe I should even ditch the last 180-degree port turn?

 

[emilimo701 10+ year member]

[quote name='Kangaroux']"We can use these response graphs to enable us to control the design so we get the response curve we are shooting for. So in the 30 to 35 Hz range we usually find that this is the common range of quarter wave resonance in vehicles."

Pulled from @Moble Enclosurs blog: Why is 30-35Hz used most commonly?[/QUOTE]

Regarding the cabin gain curve, I intend on measuring that once I find my mic/Firebox, hopefully this weekend. When I do, I'll post the graphs.

It will be a frequency sweep tone (maybe I'll try pink noise too), with a plain old FFT done on the raw recorded file in MATLAB. Then possibly convolved with a Hanning window.

however I forgot to mention something very important:
This setup is being designed for open air. It will be used more sparingly than my other woofers (Polk SR 12", and Orion XTRPRO 10" for when I need more cargo space for stuff), most specifically it will be the subwoofer that I use for tailgating, with my hatch up, and all that goodness.

 

[hispls 5,000+ posts]

[quote name='Kangaroux']"We can use these response graphs to enable us to control the design so we get the response curve we are shooting for. So in the 30 to 35 Hz range we usually find that this is the common range of quarter wave resonance in vehicles.
Pulled from @Moble Enclosurs blog: Why is 30-35Hz used most commonly?[/QUOTE]
My bad, yeah, quarter would be @ 25-30. Still there's a bigger peak @ half wave. You may get a bit of a bump at 1/4 wave if you're tuned in the mid/low 20's

[quote name='emilimo701']I might just do that. All that would need to be done would be to cut a couple more pieces that need to be longer, and one needs to be shorter. I have extra board left anyway.

IIRC, it would have been ~4.1 cubic feet after displacement, tuned at just under 23 Hz. The way it's taped up now, I think the port would be an extra 3/4" wider all the way through, which would bring the tuning frequency up slightly. Per your advice, that wouldn't be a bad thing at all. Maybe I should even ditch the last 180-degree port turn?[/QUOTE]

If you just do a 45 or roundover on that last corner the wall will act as an extension of the port anyway and I'd definitely rather not see the opening to the port too close to the woofer.

 

[Moble Enclosurs 10+ year member]

Very true. 1/2 wave resonance is more efficient in car audio and is very important to understand as far as tuning goes. As mentioned before, you do not have to tune low to play low. Most of that is how the phase correlates to the response curve more than the gain. In fact, most of the response we encounter in such a small "room" is due to gain, so its importance is needed. Usually, there will be that very common heard of -6dB difference from 1/2 wave resonance to quarter and full wave efficiency....not exact, but this is a great point to mention for those interested in SPL mainly. (hint hint)

 

[Calikid 5,000+ posts]

that;s probably too low