Designing with Cabin Gain in mind

[JonJT 10+ year member]

I'm used to designing boxes only for home use where room resonance doesn't come into effect until the frequency reaches single digits. I'm thinking that designing a ported fox with an F3 point in the low 20s is overkill for most vehicles and will yeild a setup with a boomy low end. Do you guys usually design with cabin gain in mind or do you just EQ out the peaks after installation?

If I can, I'd like to take gain into account as it will decrease the size of my boxes.

I have an 02 maxima, if that helps.

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[helotaxi 5,000+ posts]

You can map the transfer function of the car and apply it as an EQ curve in some of the box design software. The small room effects of the cabin also lowers the tuning of a ported enclosure so you might have to experiment a bit to make sure that the end result is what you were after once you put it in the car.

 

[JonJT 10+ year member]

Hmmmmm, well now I guess I just have to figure out teh transfer function of my car and see what I can do.

Do you know how to do this?

 

[helotaxi 5,000+ posts]

Use a small sub for which you have the response plotted in a large room with no acoustic coupling (up off the floor). Use the same sub with the same signal in the car in the approximate position of the sub you are planning on using. Subtract the first curve from the in-car curve and the result is the cabin gain.

 

[JonJT 10+ year member]

I was afraid you were going to say that. The only sub I have is a 3 CF ported beast that won't fit in the car. Maybe I can build something small with one of the Koda 8s I have although, thats a lot of work for a transfer function.......