Why use 40hz test tone to set gain when amp crossover is set at 80hz?

[RazorRust]

 

I set the gain on my amp using a 40hz -5db test tone.

 

I open a song in audacity, peak amplitude is -0.8db.

 

I apply a 40hz LPF in audacity and make sure the peak amplitude is below -5db.

 

But then I realized the LPF on my amp is set to 80hz not 40hz.

 

If I apply a 40hz LPF in audacity, peak amplitude drops from -0.8db to -4.8db.

 

If I apply a 80hz LPF in audacity, peak amplitude drops from -0.8db to -2.9db.

 

Just trying to wrap my head around why I should use 40hz test tone to set my gain instead of a 80hz test tone.

 

 

[Dafaseles]

40 hz is said to be the middle ground between 80 hz and 20 hz. It's only to simplify things. That being said, i know plenty of people who will actually set their gains with a sweep, rather than a test tone. But, to my knowledge, you can't do that with a DD1, you have to use an oscilloscope

[Kyblack76]

Depends, but, 40hz at -7.5 is what i roll with, or did. 

 

Edit- also, i cut my subs at 55hz. Because, well, they are subs. My mid range, is cut at 55..... 

[Kyblack76]

Also, 40hz and 1khz is "industry standard"