The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: "Arny Krueger"
Subject: Re: Cancel speaker resistance?
Organization: www.pcavtech.com & www.pcabx.com
X-Newsreader: Microsoft Outlook Express 6.00.2479.0006
X-Mimeole: Produced By Microsoft MimeOLE V6.00.2479.0006
NNTP-Posting-Date: Tue, 17 Sep 2002 08:43:24 EDT
Date: Tue, 17 Sep 2002 12:43:24 GMT
"Richard D Pierce" wrote in message
> In article <3D868192.F61269AB@webaccess.net>,
> Chuck Simmons wrote:
> >> I've studied quite a few impedance curves, and they do strongly
> >> to follow a pattern. Peak in the LF range dip, Peak in the
> >> range, dip, peak at the high end.
> >> http://www.pcabx.com/product/amplifiers/mag%20left_hi.gif
> >The first two peaks are mechanical. The first peak is the first
> >principle mode of the diaphragm and suspension. Very small
> >don't have the second peak which I suspect is due to the second
> >principle mode of the diaphragm. The third appears to be
> >rather than mechanical because it is present in voice coils not
> >attached to diaphragms. A voice coil with a stiff mass load and a
> >suspension has only two peaks corresponding to the spring mass
> >and to the self resonance of the coil and stray capacitance.
> You're right about the first peak at 40 Hz: it's the fundamental
> cone mass/system compliance resonance. The system compliance is
> the combination of the mechanical suspension for the cone and
> the acoustic compliance of the enclosure.
> You're wrong about the second peak, though. This is a two-way
> loudspeaker system, a woofer and tweeter. The second peak at
> 1800 Hz is a combination of things. First the rise above 200 Hz
> is the beginnings of the lossy inductance in the voice coil.
> That eventually gets shunted by the lower impedance of tweeter
> voice coil. If both drivers present a resistive load above
> mechanical resonance, and a constant-voltage crossover topology
> were used, then the impedance would be constant. However,
> neither condition is likely to hold, especially in that it is
> most likely NOT a constant-voltage crossover alignment, so you
> have the second peak at 1800 Hz. The third rise in
> impedance above about 6 kHz is primarily the lossy inductance of
> the tweeter voice coil.
> The self resonance of the coil and stray capacitance never
> really happens, at least not in the audio band, and if it ever
> does, it is a VERY low Q. One of the problems is that the
> first-order models are insufficient to explain the gross second
> order effects that drivers have. For example, assuming the plot
> was derived from a real speaker, as opposed to a simulated load,
> you'd find that the tweeter inductance rise is not the classic
> doubling of inductive reactance with each octave, rather is
> goes roughly as the square root of frequency. You will also find
> a resistive component that goes as the square root of frequency.
> This is due to the fact that the inductance is a complex, lossy
> mechanism resulting from frequency-dependent eddy current losses
> in the magnet structure: the higher the frequency, the more
> significant the losses.
While you are looking at this Mr. Pearce, I'd like your opinion of
the text that I've posted with the impedance plot at
"PCABX's loudspeaker simulator was designed to simulate the resistive
and reactive portions of the load presented to amplifiers by a
hypothetical 2-way sealed-box loudspeaker system whose nominal
impedance is 4 ohms. It is a "reasonable worst case simulation" of
about 95% of the roughly 50 better-quality loudspeaker systems that
were studied. The simulator is mostly made up of highly linear film
capacitors and air core inductors, but the woofer portion of the
simulator uses an iron core choke and non-polarized electrolytic
capacitors in order to simulate the fact that woofers present a
somewhat nonlinear load. All of the 8 ohm resistors are non-inductive
wirewound types. The remaining resistors are standard wirewound
"Components in the lower right hand corner (660 uF capacitor, 50 ohm
resistor, 18 millihenry choke), upper right hand corner (1 millihenry
choke and 50 ohm resistor) and upper left hand corner ( 3-8 ohm
resistors and a 10 ohm resistor in parallel) simulate a nominal 4
ohm woofer and the crossover's low pass filter. The 4 resistors in
parallel simulate the voice coil resistance of the woofer. The 18
millihenry inductor simulates the air in the sealed box and
suspension springiness. The 660 uF capacitor simulates the mass of
the cone. The 1 millihenry choke simulates the inductance of the
voice coil and the crossover's low pass filter."
"The remaining components simulate the tweeter and tweeter's side of
the crossover. The 0.26 mHy choke with the series combination of the
50 ohm resistor and the 1.33 uF capacitor simulate the lossy
inductance of the tweeter. The three 8 ohm resistors in parallel
simulate the resistance of the tweeter's voice coil. The 5 uF
capacitor and 0.13 millihenry choke simulate the tweeter crossover
and the voice coil resonance of the tweeter. There is some
interaction with parts in the woofer side of the simulator,
specifically the 0.26 millihenry and 1.0 millihenry chokes, to
complete the simulation of the load presented by the tweeter and its
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup