Whats the point of knowing the peak of ur cars cabin

[Hotdog]

Speed of sound ~1130 feet per second, divided by frequency then you get the length of that sound wave in feet. Then you can divide that by 4 to get the 1/4 wave or 2 for 1/2 and so on.

why cant you just grab a tape measure and measure the distance from the port to the windshield. Divide that number into the speed of sound to get your full wave length peak then divide by 2 to get 1/2 wave length or 4 to get quarter wave length?

example say it is 9 feet from port to windshield

1130/9= 125.5555555555556hz = Peak of vehicle at full wave length

125.5555555555556/2 = 62.77777777777778 = Peak of vehicle at 1/2 wave length

125.5555555555556/4 = 31.3888888888889 = Peak at Quarter wave length

my thinking may be wrong

it works out right in the wave length calculator though

Link --> Wave Length Calculator

You can do it that way cuz you are just reversing the order of operations, depends on which "unknown" you are looking for wavelength or freq.

Well my Logic may be messed up but it seems to me logically if you want to get loud that you should find out what frequency your 1/4 wave length is then tune your box there.. I really don't know I am just speculating on what makes sense. Can someone elaborate on my thought that has a clearer understanding of how it really works?

[AMI CUSTOMS]

You are on the money, that is exactly how I started for my SPL port of my wall, got the tape measure out measured from the center of the cone to the center of the glass, it was 5 ft exactly, so do the math and you get 1/4 wave of 56.5, so I knew I needed to land on 56 or 57 for peak. I took 10 hz out for cabin gain, tuned the port to 48 hz as a starting point, and BAM first try, 57 hz peak is my MAX SPL.

[Hotdog]

I took 10 hz out for cabin gain

Now that is the question.. how do you figure out cabin gain

[AMI CUSTOMS]

I took 10 hz out for cabin gain

Now that is the question.. how do you figure out cabin gain

TEST TEST TEST LOL

Oh yeah with termlab on old system

[AMI CUSTOMS]

It is very usefull in spl and sq. The resonant is where it will have a peak or be louder at a certain frequincy. Knowing this you can tune the box to peak here to gain SPL for an SPL ride. Or you can also use this to help maintain a flatter response throughout the sub frequency range. Achieving a more true sub stage for sq.

Subs up and port rear it should peak around 44hz

1sy part is correct, second part is not. the car does not resonate differently based on how your subs and port face. that would be like saying the FS of a sub changes depending on how you mount it.

Oh yes it most certainly will. Its all about 1/4 wave format. The distance of the wave from peak to peak. If it is a small difference like sub and port rea no not a change really. Set it in the back seat and not in cargo and it WILL change.

Im sure if you go from kick to windshield you will see that it peaks a few hz different. This is because of the effect in wave length.

wave length and box peak are different things than the resonate frequency of the car. they all play a part, but they are all different. you seem to be lumping them all together.

They all go hand in hand. If you understand them. You can use it to your advantage.

Wavelength is different with frequency. Knowing this you can know what the length is of each frequency or its 1/2 wave or 1/4 wave or so on. Speed of sound ~1130 feet per second, divided by frequency then you get the length of that sound wave in feet. Then you can divide that by 4 to get the 1/4 wave or 2 for 1/2 and so on.

Box peak you say? LOL first off at the terminology, but non the less. This is not and easy one. Free air will show final output (F0) at one thing in the vehicle is will react TOTALLY different as does your FB.

Resonant frequency of the vehicle. First lets define resonant frequency. -Frequency at which there is a response peak. Why do we get these peaks? Well lets go back to wavelength. So again lets use the speed of sound. Speed of sound ~1130 feet per second, divided by frequency then you get the length of that sound wave in feet. Then you can divide that by 4 to get the 1/4 wave or 2 for 1/2 and so on.

Guess what happens at the lengths? I will tell you, you get PEAKS! Now what happens when you design your enclosure to preform with or at the vehicles peak? MAGIC

Now since this may be a lot for you. Measure the length of the wave path in you vehicle. Your "peak" frequency goes hand in hand with wavelength. I will put money on it.

But yeah lets not "LUMP" it together lol

This what that MAGIC looks like btw....

[ahoz28]

I want the magic lol. Where did you have the mic and did you have a window open?

[TeamHT]

Outlaw I believe

[AMI CUSTOMS]

I want the magic lol. Where did you have the mic and did you have a window open?

Yeah that magic was outlaw usaci globe in the kick.

[Hotdog]

Ok.. I measured my Mountaineer (aka Explorer) I get a length of 12' 6" from where they place the termlab meter to the center of the rear hatch.

Now putting that into the wave length calculator and this is what you get.

now based on the 1/2 wave length frequency of 45.2hz it is just about right on the money because when I was on the termlab my peak was at 44hz.

[J.Reed]

OH my GOD. So the guy with only a few post trying to help, but gets called out actually KNOWS what he is talking about? LOL.

Measuring for it will USUALLY put you really close. There are other factors that will play a part and mod this. Roof shape, seats, dash and other unforeseen things messing with the wavepath. But generally it will put you really close. Some cars are just straight up weird though or with the enclosure design will NOT preform as thought. This is where Testing, testing and more testing comes in.

As for the expected cabin gain you can see. There are a few factors to even guess.. Enclosure volume, port area and tune, placement of the said enclosure. Even power can change it some. Testing is the only way to start to understand what is going on and why.