Synergetic Audio Concepts - Tech Topics (2001) about a my MATLAB program PolarSum. This details a different way to view directivity data. It also
describes processing the data with filter functions and adding multiple sources to calculate their combined directivity response.
A process is described for measuring impedance of loudspeakers at higher drive levels common of typical usage. Most often impedance is measured at
very low drive level which may not reveal some problems. This is done with standard, off-the-shelf software and hardware that is relatively inexpensive.
A short article on how to do small and large signal impedance measurements with a TEF analyzer. Waterfall (3D) impedance measurements showing how impedance
resonances behave as a function of time are also mentioned.
There are always questions about the "correct" phase response when measuring a loudspeaker or some other band pass device. In this article I
examine the correct phase response of a text book device (a band pass filter). I then describe a method to determine the correct propagation delay
for an arbitrary device under test so that its true phase response may be measured. This is a great companion / follow-up to the Subwoofer Alignment
article.
Does a square wave, or any clipped wave form, contain DC? I examine a square wave and see what causes it to have its square shape. This leads
into an easy to understand explanation of phase and its effects in the time and frequency domains. This is a very general introduction to Fourier
analysis and the correlation between the time & frequency domains with no math cited.
I have heard the question "How do I align a subwoofer with a full range loudspeaker system?" asked many times. I thought it might be interesting to delve
into this to see if I could come up with an answer. The task of adding a subwoofer to a loudspeaker system to increase the low frequency bandwidth should
typically entail three primary items.
It is this last item that is perhaps the most challenging. This is the one that we will primarily investigate.
A white paper on the anechoic chamber modifications and calibration that were necessary to accurately measure the complex data of directivity balloons
of loudspeaker systems. The facility detailed in this paper is operated by NWAA Labs in southern California.
John Murray gives a very good explanation of the Quadratic Throat Waveguide without a lot of the math. This also covers some of the history of the
development of conventional constant directivity horns.
This paper details using software modeling (EASE SpeakerLab) to predict the directivity response of a loudspeaker system using the individul driver directivity measurments
and crossover filter transfer functions. This paper was presented at the 123rd Audio Engineering Society convention, October 2007.
