Parameters of the enclosure
Characteristics: | ||
|---|---|---|
Port resonance fb | ||
Quality factor Qlb of vented enclosure |
Vented-box systems can be modeled by an equivalent circuit comprising an acoustical compliance Cab, an acoustical mass Map and a resistance Ral representing losses due to box leakage and jet stream in the port. The parameters are important for the loudspeaker system development and also for end-of-line testing as they can indicate a leaky enclosure and damping material blocking the port entrance. Asymmetrical shape of the port orifice may cause a rectification of the air flow generating a dc pressure inside the enclosure and a dc component in the voice coil displacement.
KLIPPEL R&D SYSTEM (development)
Module | Comment |
|---|---|
LSI Box identifies the linear lumped parameters of the vented box system in the small and large signal domain. While the port resonance is relatively independent on the amplitude, the quality factor Qbl decreases significantly with amplitude. This is caused by the nonlinear resistance Rbl(pbox) varying with the sound pressure inside the enclosure. | |
MSC also measures the lumped acoustical parameters of the box in less than 1 s and indicates leakages inside the box and damping material blocking the port. |
Example:
- The figure above shows the setup of the Motor and Suspension Check (MSC) used for measuring the lumped parameters of a vented-box system. No additional sensor is used, and the transducer can be measured via long cables. The measurement provides full immunity against production noise.
Application Notes:
AN 1 Optimal Voice Coil Rest Position 
AN 2 Separating Spider and Surround
AN 3 Adjusting the Mechanical Suspension
AN 5 Displacement Limits due to Driver Nonlinearities
AN 15 Checking for Compliance Asymmetry
Templates of KLIPPEL products
Name of the Template | Application |
|---|---|
LSI Woofer+Box Nonl. P Sp1 | Nonlinear parameters of woofers operated in free air, sealed or vented enclosure with a resonance frequency fs < 300 Hz at standard current sensor Sp1 |
Diagnostics VENTED BOX SP1 | Comprehensive testing of vented box systems using standard current sensor 1 |
SIM closed box analysis | Maximal displacement, dc displacement, compression, SPL, distortion using large signal parameters imported from LSI BOX |
SIM vented box analysis | Maximal displacement, dc displacement, compression, SPL, harmonic distortion using large signal parameters imported from LSI BOX |
Standards:
- IEC Standard IEC62458 Sound System Equipment – Electroacoustic Transducers - Measurement of Large Signal Parameters
- IEC Standard IEC62459 Sound System Equipment – Electroacoustic Transducers – Measurement of Suspension Parts
- AES2-1984 AES Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement
- IEC Standard IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
Papers and Preprints:
W. Klippel, et al. “Fast Measurement of Motor and Suspension Nonlinearities in Loudspeaker Manufacturing,” presented at the 127th Convention of the Audio Eng. Soc., 2009 October 9-12, New York, NY, USA.
R. H. Small, “Direct-Radiator Loudspeaker System Analysis,“ J. of Audio Eng. Soc., Volume 20, pp. 383 – 395 (1972 June).
R. H. Small, “Closed-Box Loudspeaker Systems, Part I: Analysis,” J. Audio Eng. Soc., Volume 20, pp. 798 – 808 (1972 Dec.).
A. N. Thiele, “Loudspeakers in Vented Boxes: Part I and II,” in Loudspeakers, Volume 1 (Audio Eng. Soc., New York, 1978).
W. Klippel, “Measurement of Large-Signal Parameters of Electro-dynamic Transducer,” presented at the 107th Convention of the Audio Eng. Soc., New York, September 24-27, 1999, Preprint 5008.
W. Klippel, “Dynamical Measurement of Non-Linear Parameters of Electro-dynamical Loudspeakers and their Interpretation”, J. of Audio Eng. Soc. 30 (12), pp. 944 - 955, (1990).
W. Klippel, “Nonlinear Modeling of the Heat Transfer in Loudspeakers,” J. of Audio Eng. Soc. 52, Volume 1, 2004 January.