title: An extended lumped-element model and parameter estimation technique to predict loudspeaker responses with possible surround-dip effects.
abstract: Lumped-element models have long been used to estimate the basic vibration and radiation characteristics of moving-coil loudspeakers. The classical low-frequency model combines and simplifies several important driver elements, predicting only a single mechanical resonance wherein the diaphragm (e.g., cone and dust cap) and the inner portion of the surround move together as an effective piston. Even if the diaphragm maintains piston-like motion with increasing frequency, the flexible surround eventually vibrates out of phase, producing another resonance whereby a noticeable "surround dip" may occur in the radiated pressure spectrum. The classical model is unable to predict this behavior. This paper explores an extended lumped-element model that better characterizes the distinct diaphragm, surround, spider, and other properties of a loudspeaker in a plane rigid baffle. It extends effective modeling to mid frequencies and readily predicts a surround dip in the radiated response. The paper also introduces a method to estimate model parameters using a scanning laser Doppler vibrometer, a surround resonance indicator function, and a constrained optimization routine. The approach is validated by its ability to better predict on-axis pressure responses of several baffled loudspeakers in an anechoic environment.
authors.affiliation: Acoustics Research Group, Department of Mechanical Engineering, 435 Crabtree Building, Brigham Young University, Provo, Utah 84602.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Sagers
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Leishman
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Blotter
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000669:Amplifiers, Electronic; D004301:Doppler Effect; D004867:Equipment Design; D007834:Lasers; D008962:Models, Theoretical; D009038:Motion; D011312:Pressure; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013018:Sound Spectrography; D013997:Time Factors; D014160:Transducers, Pressure; D014732:Vibration