Helmholtz Resonator Calculator – Exhaust Drone Killer
The Helmholtz resonator calculator below, calculates the theoretical optimum dimensions for a Helmholtz chamber to reduce drone in an exhaust. (If you are looking for a J-Pipe or 1/4 Wave resonator calculator, click here).
Helmholtz Calculator – Some tips
Neck diameter – I believe it is optimum to use a 2 inch neck diameter.
Always use the internal diameter. Exhausts are usually given with outer diameter and exhaust wall thickness is usually 1.5 or 1.2mm.
Temperature – Probably the most critical part and one most likely to be wrong, experimentation could be needed. From the research I have done, the temperatures in the chamber are much lower than I expect. People are quoting 50-90 celsius.
I believe minimum volume for the chamber should be 1.5 litres. The smaller the chamber the less DB attenuation there will be.
Neck cross sectional area should probably be less than 50% of the chamber cross sectional area where neck enters.
