Speaker resistance and sound energy

resistance"

their DC resistance value.

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No, it's their nominal _impedance_.

value.

No.

resistance"

their DC resistance value. But shouldn't the conversion to sound be accounted for somehow since it's a sink on energy delivered?

inductance is lossless, so where does the sound producing energy come from?

DC resistance is usually a healthy fraction of the rated AC impedance, like 3/4 maybe. Which indicates that speakers are pretty inefficient.

Of course, impedance is usually a wild function of frequency, not a steady 8 ohms. And if there's a crossover, there will be series capacitors that will look open to an ohmmeter, and inductors too.

Sound is produced by the voice coil moving in the magnetic field, with a component of the motion being mechanically lossy because of the sound produced. It's like a motor driving a load, where the mechanical load reflects back as electrical resistance.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

sentence:

of resistance"

their DC resistance value. But shouldn't the conversion to sound be accounted for somehow since it's a sink on energy delivered?

inductance is lossless, so where does the sound producing energy come from?

look

--
No, it's like a voltage source driving a motor which is driving a load 
where the mechanical load reflects back as electrical resistance.

"M. Hamed"

** Not exactly. 8 ohms ( or whatever) is the"nominal impedance" of the speaker - usually measured with a 250 or 400Hz tone.

The DC resistance of the voice coil is about 80% of that number or about 6.4 ohms.

The impedance of most ( bass or full range ) speakers in the range of 250 to

400 Hz is RESISTIVE too.

So, we have two resistances that dissipate heat, one the copper wire and the other due to losses in the moving suspension, magnet assembly and sound radiation.

Sound radiation accounts for barely 1% of the input power, in most cases.

A good circuit model for a loudspeaker is not a simple one, it would have many inductances, resistances and capacitances involved - plus the resistances would each have temperature co-efficient.

... Phil

resistance"

their DC resistance value. But shouldn't the conversion to sound be accounted for somehow since it's a sink on energy delivered?

inductance is lossless, so where does the sound producing energy come from?

Speakers are rated in impedance a combination of resistance and inductive reactance. And a real speaker would have different impedances at different frequencies, air density, cabinet design, cone compliance, magnet design, etc..

I think I remember reading somewhere that speakers are rated in impedance at 1,000 cycles - but doubtless that wouldn't hold true for a tweeter... would it?

Thank you for the thorough explanation. As it often happens my false assumptions led to false conclusions.

I remember a couple years ago I created a toy speaker out of magnet wire and a strong magnet. I remember how I carefully wound the coil to measure 8 Ohms DC. How naive I was :-)

assumptions led to false conclusions.

strong magnet. I remember how I carefully wound the coil to measure 8 Ohms DC. How naive I was :-)

You were only about 20% off. In audio, that's high precision.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom timing and laser controllers 
Photonics and fiberoptic TTL data links 
VME  analog, thermocouple, LVDT, synchro, tachometer 
Multichannel arbitrary waveform generators

assumptions led to false conclusions.

a strong magnet. I remember how I carefully wound the coil to measure 8 Ohms DC. How naive I was :-)

You trying to start an audiophoolery fight?

Mikek :-)

I like the way they used to (maybe still?) describe horn loudspeaker transducers as "motors".

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

The "motor" part of a loudspeaker is the linear motor, not the entire assembly.

Or drivers.

--

John Larkin Highland Technology Inc

jlarkin at highlandtechnology dot com

Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

^^^^^^^^^^^

See above

--
"For a successful technology, reality must take precedence  
over public relations, for nature cannot be fooled." 
                                       (Richard Feynman)

The cone is part of the transducer (the entire loudspeaker). It is not part of the motor.

Richard Feynman is a man for whom I have great respect. I have learned much from reading books by Feynman, and much more from watching videos of his lectures. Yet still I see quotes of things Feynman has said, which I had not seen before, that are valid today, years after his death. Thanks. Eric