Howdy, recently i've been interested in the idea of building large sealed subwoofers (18" drivers, ~200L) but recently came across some papers which i haven't seen discussed anywhere online showing some complex effects of nonlinear distortions, particular in larger boxes when user with higher input power. I've had a bit of a read over the papers but the implications still are unclear to me how much of an issue this is and finding what balance of box and driver parameters are ideal to avoid it.
The papers basically show at higher power levels a rapid breakdown of speaker behavior particular in larger boxes due to nonlinearity in effective stiffness between the motors suspension and the compliance of the air in the box. I've seen a handful of old comments online mentioning nonlinearity of air being an issue but often not giving good explanations why. It seems most transducers are generally only linear within a few mm of xmax, the newest paper gives a full complex mathematical formula for showing these effects using wave digital filters but the math is a bit above my level and i'm unsure how i could substitute in my own values for transducer/box to find the limitations of my own designs and where the limits lie. Has anyone got more information on this topic or done any of their own research or have thoughts? It mentioned while the graphs look concerning in theory higher order box designs (BR, bandpass ect) should have even worse issues than sealed :O
Here are the papers and a borrowed image from one.
First and newest paper is not public so you will have to track down your own copy...
but the older three are free to read:
The papers basically show at higher power levels a rapid breakdown of speaker behavior particular in larger boxes due to nonlinearity in effective stiffness between the motors suspension and the compliance of the air in the box. I've seen a handful of old comments online mentioning nonlinearity of air being an issue but often not giving good explanations why. It seems most transducers are generally only linear within a few mm of xmax, the newest paper gives a full complex mathematical formula for showing these effects using wave digital filters but the math is a bit above my level and i'm unsure how i could substitute in my own values for transducer/box to find the limitations of my own designs and where the limits lie. Has anyone got more information on this topic or done any of their own research or have thoughts? It mentioned while the graphs look concerning in theory higher order box designs (BR, bandpass ect) should have even worse issues than sealed :O
Here are the papers and a borrowed image from one.
First and newest paper is not public so you will have to track down your own copy...
but the older three are free to read: