Can you just eye ball 4th orders?

I must be confused what cabin gain is. Back to school for me. Where would my box peak outside of my truck?

Outside your truck pointing in a direction with no immediate reflections and measured 1-3ft away you box should peak at tuning. Then running the same volume on the radio same amp same frequency sweep test track and same meter distance in the truck, the difference between the two should be the gain.

This is easiest to measure with a sealed box since the graphs are generally smoother.

Smaller vehicles usually gain at lower frequency larger vehicles gain at higher frequency. That super tight kick in the chest bass is often caused by cabin gain where as most vehicles have a null in the same frequency range.
 
Outside your truck pointing in a direction with no immediate reflections and measured 1-3ft away you box should peak at tuning. Then running the same volume on the radio same amp same frequency sweep test track and same meter distance in the truck, the difference between the two should be the gain.

This is easiest to measure with a sealed box since the graphs are generally smoother.

Smaller vehicles usually gain at lower frequency larger vehicles gain at higher frequency. That super tight kick in the chest bass is often caused by cabin gain where as most vehicles have a null in the same frequency range.

And if my peak turns out to be 33 hz. outside of my truck and 31 hz. inside of my truck is that cabin gain or cabin loss?
 
Again, take the box outside of the vehicle out in the desert somewhere and measure your SPL 1 meter away and see if you have any "loss" compared to the numbers you get in the vehicle.

I have to take my bench seat out to get my box out. That ain't going to happen. My box is in so tight it isn't even bolted down.
 
Again, take the box outside of the vehicle out in the desert somewhere and measure your SPL 1 meter away and see if you have any "loss" compared to the numbers you get in the vehicle.

And where do you put the meter? Are the doors open or closed? Are the windows up or down? Do I do a full competition burp or a sweep? What if the wind is blowing 50 m.p.h.? I'm guessing that I need 10 foot speaker wires to do this. You guys make it sound so easy when there is a lot of variables.
 
I gained two hertz?

No you gained db below the box peak. Your cabin gain allowed you to play louder at a lower frequency. Cabin gain couples with the box response curve and amplifies the response curve.

Where it amplifies the response curve is different vehicle to vehicle.

Large vehicles usually have higher frequency cabin gain than smaller vehicles. This also has a side effect of making certain vehicles perfect for midbass and that hit you in the chest kick drum. And others can very well struggle.
 
No you gained db below the box peak. Your cabin gain allowed you to play louder at a lower frequency. Cabin gain couples with the box response curve and amplifies the response curve.

Where it amplifies the response curve is different vehicle to vehicle.

Large vehicles usually have higher frequency cabin gain than smaller vehicles. This also has a side effect of making certain vehicles perfect for midbass and that hit you in the chest kick drum. And others can very well struggle.

Is my situation good or bad? It sounds like if I want to peak at 32 hz. then I need to tune my next box to 34 hz. Is that a correct assumption?
 
Is my situation good or bad? It sounds like if I want to peak at 32 hz. then I need to tune my next box to 34 hz. Is that a correct assumption?
No not necessarily.

Say you gain 3db at 30hz that gain is fixed it's not a single peak though it's it's own response curve you may gain 3db at 30hz but 1.5db at 32 and 1 at 34. This is why you have to measure the difference inside to outside. Do you get the whole response curve of the peak.

Raising the tuning may raise the overall peak by letting the cabin gain roll off and the box take over. This typically means less efficiency. Knowing the actual response curve helps you couple the cabin gain to the box response curve. It becomes much more predictable to model. Most sub box programs give you the free air response curve. Some have features to help predict cabin gain but nothing beats an actual measurement
 
No not necessarily.

Say you gain 3db at 30hz that gain is fixed it's not a single peak though it's it's own response curve you may gain 3db at 30hz but 1.5db at 32 and 1 at 34. This is why you have to measure the difference inside to outside. Do you get the whole response curve of the peak.

Raising the tuning may raise the overall peak by letting the cabin gain roll off and the box take over. This typically means less efficiency. Knowing the actual response curve helps you couple the cabin gain to the box response curve. It becomes much more predictable to model. Most sub box programs give you the free air response curve. Some have features to help predict cabin gain but nothing beats an actual measurement

That's too much for an old man like me. You still never answered my meter location, doors, and window locations while metering my box outside of my truck. Do I face my box toward or away from my truck? Burp or music?
 
That's too much for an old man like me. You still never answered my meter location, doors, and window locations while metering my box outside of my truck. Do I face my box toward or away from my truck? Burp or music?

I've answerd that numerous times. The mic goes in front of the box 1-3feet from the subs. Both inside and out of the vehicle. And when measuring the response curve outside the vehicle you want to face the box away from any hard surfaces that could reflect back at the mic.

You don't have to use your current box. A simple spare sub in a sealed box could just be sat on top of the seat inside and then ran outside with a decently long run of speaker wire.

Idk if you could use a pressure meter to measure the response curve, I don't see why not but I've never done it that way.

You use a frequency sweep not really tones but I guess if you had to manually record every hz 28-80hz you could run the 52 different test tones.
 
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