How come I can't bottom my subs (1 Viewer)

[GabrielC]

TPM = Star Wars Episode 1: The Phantom Menace

bah, beat me to it :b

 

[Dustin B]

Vin, it's more volume related than F3 related. Maximum driver excursion will happen in the 30-35hz range with a sub tuned to 20hz (with the exception of below tuning). Below 30hz excursion will go down as the port takes over the bulk of the output until you hit the tuning point. Below the tuning point driver excursion will start to rise very quickly again. So a ported sub tuned to 20hz will bottom most easily at high volumes around 30-35hz and below 16-17hz.

That 30-35hz spike in TPM will be what does it for a 20hz tuned sub.

 

[VinhT]

Ah, thanks Dustin. I've always wondered why some SPL/response charts show two plots, driver and port.

 

[LorenzoD]

Vin, it's more volume related than F3 related. Maximum driver excursion will happen in the 30-35hz range with a sub tuned to 20hz (with the exception of below tuning). Below 30hz excursion will go down as the port takes over the bulk of the output until you hit the tuning point. Below the tuning point driver excursion will start to rise very quickly again.

So a ported sub tuned to 20hz will bottom most easily at high volumes around 30-35hz and below 16-17hz.

So, theoretically, how would a sub tuned to 16Hz react in this situation?

 

[MarcVH]

The graphs in the SVS tuning block chart seem roughly consistent with what's been said so far, and may provide some hint.

 

[Dustin B]

I was pulling my numbers out of the air by playing with a Shiva in a 140L enclosure using a 4" port in the free version of LspCAD Adire has for download (you can learn a lot about subs playing with it). It shows peak excursion to be in the 30-35hz range for both a 16hz and a 20hz tune. And excursion starts to go up rapidly again below the respective tuning points.
But the graph Marc mentioned shows something different.
Link Removed
Here we see a 20-39CS+ tuned to 20hz and with a port blocked tuned to 16hz. The red lines are cone excusion and you can see the dips that indicate the tuning frequency. Peak excursion above tuning occurring at 29hz and 25hz.
I just noticed I was still modelling my room, a HP rumble filter and a receiver crossover in LspCAD. When I take those out, then it matches the above graph as well.