how do you figure out box rise?

[Kyblack76]

Also SLINKY

calm your tits... jesus.....

???

I am the calm one.

Good......

[bkolfo4]

Take your reactive impedance and subtract your nominal impedance from it and that is your box rise. Your nominal impedance is the load at the amp, for example let's say 1 ohm. You will need a clamp meter and a dmm to read voltage and amperage from the amp on a burp. So I will throw some hypothetical numbers out there to show how it is done.

Let's say your amp is wired to 1 ohm nominal and on a 50hz burp you produce 117.6 volts and 42.4 amps. To find out what you are working with you will need to take 117.6 and divide it by 42.4, which will give you 2.77 ohms. The 2.77 ohms will be your reactive impedance. Next you will take 2.77 and subtract 1 ohm from it. This gives you 1.77 ohms, this is how much box rise you will have. This is the method that on how to do so explained to me by Mike Singer about 6 years ago and is how he told me he figured out box rise in his vehicle. If I'm not mistaken he was told this information from Team Neo Eric, so this is not my info as I will give them credit for showing me how to do so.

I am glad you didn't make this up yourself, and I would advise you don't keep spreading this answer.

Subs have an impedance curve with a peak at Fs even when they are not in a box. Putting the sub in a box does not cause the sub to go from being a flat "1 ohm" to some higher number.

[Nightshade]

Take your reactive impedance and subtract your nominal impedance from it and that is your box rise. Your nominal impedance is the load at the amp, for example let's say 1 ohm. You will need a clamp meter and a dmm to read voltage and amperage from the amp on a burp. So I will throw some hypothetical numbers out there to show how it is done.

Let's say your amp is wired to 1 ohm nominal and on a 50hz burp you produce 117.6 volts and 42.4 amps. To find out what you are working with you will need to take 117.6 and divide it by 42.4, which will give you 2.77 ohms. The 2.77 ohms will be your reactive impedance. Next you will take 2.77 and subtract 1 ohm from it. This gives you 1.77 ohms, this is how much box rise you will have. This is the method that on how to do so explained to me by Mike Singer about 6 years ago and is how he told me he figured out box rise in his vehicle. If I'm not mistaken he was told this information from Team Neo Eric, so this is not my info as I will give them credit for showing me how to do so.

I am glad you didn't make this up yourself, and I would advise you don't keep spreading this answer.

Subs have an impedance curve with a peak at Fs even when they are not in a box. Putting the sub in a box does not cause the sub to go from being a flat "1 ohm" to some higher number.

Yeah I have never been 100% sure about what the hell box or impedance rise even is. I do know that the math behind this method is correct, but what it exactly accomplishes is not that useful. I have read the info at this link before http://www.atrendusa.com/blog/impedence-rise-car-audio/ but still don't see the point of it. Like I said before though this is how a few competitors attempted to show me how to calculate box rise and the math works out, but the information isn't really that valuable unless you are seeing that you have a ton of rise and take action to add power to compensate for it, or make modifications to the enclosure to help keep the impedance down.