Saturday, May 14, 2022

Can I downfire or upfire that subwoofer? Do the math!



 Not all subwoofers can be upfired or downfired. Some subwoofer drivers need to be mounted on the vertical plane, firing into the room.

Determining this is easy: just make sure the woofer's suspension is strong enough to prevent gravity from pulling the driver down less than 5% linear excursion.

The formula looks like this:

We need to know a subwoofer driver's resonant frequency and Xmax. Resonant Frequency is simply the frequency that the driver will "ring" at. Xmax is maximum linear excursion. Our goal is to not lose 5% of linear excursion.

Example of the formula using a Rockford Fosgate R2D2-12 Prime Subwoofer driver, we can use it for upfire and downfire:


Example of the formula using an early 1990s Rockford Fosgate Punch 12. We should use this one to fire into the room: 


I hope this helps you with your subwoofer design!