BillFitzmaurice.info

Does anyone have a good resource that quantifies this effect and what kind of gain can be expected in a mid sized SUV (e.g. 4runner). I'm toying with the idea of making my T39 my car subwoofer and was wondering how it would respond in car, obviously it would be much louder within it's intended passband but I have a feeling I may get decent response down to 35 or so based off my low power test a while back.

If you keep the power low you could probably have it dig down as deep as 25Hz or maybe even lower, although response seems to drop like a brick below 35Hz cabin gain is at its strongest there.

My previous car subs we're two eight inch woofers in an undersized enclosure. They kicked a## where the sub theoretically shouldn't have any effect eg. Have efficiency about 12dB down!

If you look at the specs sheets of for instance JBL and Infinity subs they show response with cabin gain in the graphs included.

150 Watts in to a 20" t39 will most likely thump the car to pieces!

For a sealed rigid enclosure cabin gain shouuld be 12dB/octave begining at: f=speed of sound/(2xlongest dimension). Your suv is neither sealed nor rigid, lol.

You can measure it by rta'ing any old sub outside your vehicle (no boundries nearby) and inside your vehicle (in your intended location) with constant amp power and then subract the two graphs. In the old days we would play test tones (25hz,30hz, ...) And use a RS SPL meter and graphing paper. Different spl levels will give you different in car results as panel flex comes into play at higher spl levels and can cause reinforcement or cancellations. Air seals may also open up at higher pressures.

Experience has shown that most suv's begin to show gain around 50-55hz @ 12dB/octave.