Sub tuning and frequency response (1 Viewer)

[GeorgeJM]

If you have your sub tuned to 25Hz, from what I gather about ported subs, anything below 25Hz will cause the speaker to be "unloaded" -- IOW, it no longer has the enclosure to damp speaker movement. Additionally, as I understand it, this can cause speaker damage to put frequencies under the port tuning through the speaker. Yet I read all the time about people doing sweeps down to 16Hz with their SVS (and other) subs. What am I missing?

 

[Lee-c]

It depends how hard you push the sub when playing below it's tuning point. SVS's are extremely well built
and can take quite a bit before bottoming out the driver, even when playing frequencies below
the tuning point. But it's easier to bottom them out (takes less SPL) when playing frequencies below
the tuning point, than when playing frequencies at the tuning point or above.

 

[Zack_R]

I'm not an expert but here goes.

Regards to a ported sub, below the tuning point the restoring force to the driver is lost pretty quick. Ported enclosures roll-off at 24 db an octave.

So if your ported sub is tuned to 25 Hz. And my interpretation of tuning is the point where maximum air velocity is reached or the highest SPL through the port (resonator) is achieved. So at 12.5 Hz the db level is down ~24 dbs compared to ~25.

As Lee said, if you don't push too much power to the speaker it is possible to play well below the tuning point. If you see a graph of a 25 Hz tuned sub that is still showing about the same dbs as when at 25 Hz, this is due to the room boosting the dbs.

Yet I read all the time about people doing sweeps down to 16Hz with their SVS (and other) subs. What am I missing?

Certain SVS subs allow you to block a port or two which will lower the tune and allow you to play low frequecnies at higher volume with a much reduced risk to bottoming.