This is a tutorial for simulating a sub woofer in a Devastator cabinet using Hornresp
It is a work in progress for now. The simulation will be a Mini Devastator 18" using a SAF184.03.
Real quick refresher for the Devastators. The Devastators use two resonators, one on the front of the sub and one on the back. The front resonator is a quarter wave resonator (QW) and the rear resonator is a Helmholtz resonator a.k.a bass reflex/ported/vented. The Devastator is a 6th order band pass arrangement. The horn section is non flared, just a straight tube. The driver is in an offset alignment with no throat chamber. You might notice OD in red in the input menu, Offset Driver is what that stands for.
First I am going to talk about this mystery screen that welcomes us when we open up Hornresp. I have data populated in here from my Mini Devastator with my SAN184.03s. The input Window is one of the most intimidating parts of the program, it is not that hard to work with once you get more familiar with what everything means.
The first box is for the space in which we are simulating the subwoofer system. Right now it is set for being in the middle of an open field with one boundary underneath the enclosure. This is comparable to what we are use to seeing in WinISD.
This box is for the input voltage into the woofer. I will touch on this later, right now it is 1 watt into 5.5 Ohms. I am skipping over Rg and Fta since they are not required for Devastator simulation.
The data in these boxes represents the cross sectional opening of our front QW/horn resonator. It is expressed in cm2, I added a shot of what that corresponds to in the cabinet.
This is staring up the horn, I removed the bottom, the port board and rails that would be obscuring this viewing angle. The cross sectional area of the horn is inside the red boxes. 22.5"x8.5" is the calculated area for this box if memory serves me.
This is the length of our QW/horn resonator. The top number is from the top end of the horn to the center of the woofer. The bottom number is from the center of the woofer to the bass of the horn. I added a CAD screen shot to show roughly how the two segments line up.
The boxes highlighted below represent the parameters of the sub woofer we are simulating, more on that later.
Vrc is the volume of the rear chamber/Helmholtz resonator expressed in liters.
Lrc is the length of the rear chamber, not super critical, but it can show rear chamber resonances in more detail. Standing waves become more of an issue once the chamber exceeds 48 inches.
Ap is the cross sectional area of the port expressed in cm2.
Lpt is the length of the port expressed in cm. Vtc and Atc are not used for simulating a Devastator.