Headphone speaker Impedances

[otlew]

There seems to be some conflicting opinions about this subject. Can anyone sort this out? The first excerpt is from an Arizona Outback article written by Mr. Steve Gholson as follows;

Again you can see that the headphones with the matching impedances of 600 ohms (#1) will have much more power delivered to them than the headphones with 60 ohms impedance (#2). The point that I am trying to make here is that you can take any headphone impedance above or below the output impedance of the detector and none will have as much power delivered to them as the ones that have been matched to the impedance of the detector. Remember, maximum transfer of power takes place when the impedances are matched in a circuit.

This longer excerpt is from an Article by Mr. Bill Whitlock of Jensen Transformers (audio experts I guess). It seem to agree with the power optimization concept of Mr. Gholson, but with audio....well if you have an opinion...

Understanding, funding and eliminating AV Ground Loops

By Bill Whitlock of Jensen Transformers


2.2 - MATCHING AND TERMINATION

A common misconception is that audio outputs and inputs must be impedance matched. Circuit
theory tells us that when source and load impedances are the same, maximum power is
transferred.

Although useful in some passive signal processing systems, this concept does NOT
apply to modern audio signal interfaces. Their goal is to transfer voltage, not power!

If Zi is made to match Zo, half the signal voltage is lost and the output drives an unnecessarily heavy load.

However, impedance matching or termination is required for video and RF cables because the
signals have much shorter wavelengths! As a general rule, cables begin to exhibit

 

[OldBeechnut]

Interesting OT, Many point at the Ohm's but I feel it's the big picture, (Total Electrical Specifications) And the only way to get the best results is to take them for a spin...cause once I see what does, and does not work.......the numbers start to have a meaning. From these three I tested, I got a feel for what works with the Excalibur... the big factors...........input watts, Ohm's, Resonant Frequency, Frequency Response, SPL and speaker design. My opinion....Now we need Critter....Wish some of the old-timers would chime in with their experience.............

 

[OldBeechnut]

OT, Sorry this is off subject....Take a look at this....It's Factor!.....? Notice what is missing?

Must be one of the first excaibur's after the Sword, the Sword never had the HI/Lo filters either, but the sword endcaps were machined, this one is cast..

 

[deepdiger60]

There seems to be some conflicting opinions about this subject. Can anyone sort this out? The first excerpt is from an Arizona Outback article written by Mr. Steve Gholson as follows;

Again you can see that the headphones with the matching impedances of 600 ohms (#1) will have much more power delivered to them than the headphones with 60 ohms impedance (#2). The point that I am trying to make here is that you can take any headphone impedance above or below the output impedance of the detector and none will have as much power delivered to them as the ones that have been matched to the impedance of the detector. Remember, maximum transfer of power takes place when the impedances are matched in a circuit.

This longer excerpt is from an Article by Mr. Bill Whitlock of Jensen Transformers (audio experts I guess). It seem to agree with the power optimization concept of Mr. Gholson, but with audio....well if you have an opinion...

Understanding, funding and eliminating AV Ground Loops

By Bill Whitlock of Jensen Transformers


2.2 - MATCHING AND TERMINATION

A common misconception is that audio outputs and inputs must be impedance matched. Circuit
theory tells us that when source and load impedances are the same, maximum power is
transferred.

Although useful in some passive signal processing systems, this concept does NOT
apply to modern audio signal interfaces. Their goal is to transfer voltage, not power!

If Zi is made to match Zo, half the signal voltage is lost and the output drives an unnecessarily heavy load.

However, impedance matching or termination is required for video and RF cables because the
signals have much shorter wavelengths! As a general rule, cables begin to exhibit

 

[tvr]

The two sources don't contradict. Max power transmission is with matched impedance. The statement about "If Zi is made to match Zo, half the signal voltage is lost and the output drives an unnecessarily heavy load." assumes a constant power output for the drive circuit; not always a valid assumption.

The argument about wave length is true. Wave length for 1 kHz is about 980,000 feet, so the reflections of an impedance mismatch don't create the really bad standing wave reflections in our relatively short headphone wires. What we use for speakers and drive circuits are low power and we don't necessarily care about a little power loss. Recall what Mel did with the transformer, got more voltage to the speaker to make it louder; even though it changed the impedance match some, the results are now more usable.
tvr

 

[otlew]

Yes and Mr. Gholson was addressing headphone matching and Mr. Whitlock is speaking to audio and video. So I suppose it is situational. I know the 150 ohm Sun Rays sound sweet on the Sovereign, and that's about all I need to know. As far as the transformer voltage, well the Sovereign does have volume control as Mel stated.

The two sources don't contradict. Max power transmission is with matched impedance. The statement about "If Zi is made to match Zo, half the signal voltage is lost and the output drives an unnecessarily heavy load." assumes a constant power output for the drive circuit; not always a valid assumption.

The argument about wave length is true. Wave length for 1 kHz is about 980,000 feet, so the reflections of an impedance mismatch don't create the really bad standing wave reflections in our relatively short headphone wires. What we use for speakers and drive circuits are low power and we don't necessarily care about a little power loss. Recall what Mel did with the transformer, got more voltage to the speaker to make it louder; even though it changed the impedance match some, the results are now more usable.
tvr

 

[otlew]

Well guess the low pass filter used today is BIG improvement, NOT.

 

[Tin Fin]

otlew,

In the first case, Whitlock is speaking specifically of "passive signal processing systems" - that means regular, analog headphones. He then says this is not true with MODERN audio signal interfaces - that means digital devices, i.e., are not analog. So the impedance match is best on analog headphones; but with something like an mp3 player, computers, or similar device, the impedance matching does not have to be identical for good, or best, results. In Gholson's write up, I would read that to be about analog devices - headphones. Modern detectors have digital processors, but the audio signal is analog on most of them; that might not be true on some of the newer models though.

 

[otlew]

Great explanation, as I had failed to condider digital audio vs. analog. It sounds like we are definitely into the comparing apples to oranges here .

otlew,

In the first case, Whitlock is speaking specifically of "passive signal processing systems" - that means regular, analog headphones. He then says this is not true with MODERN audio signal interfaces - that means digital devices, i.e., are not analog. So the impedance match is best on analog headphones; but with something like an mp3 player, computers, or similar device, the impedance matching does not have to be identical for good, or best, results. In Gholson's write up, I would read that to be about analog devices - headphones. Modern detectors have digital processors, but the audio signal is analog on most of them; that might not be true on some of the newer models though.