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Audiophile help please - Ohms and power

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Dundarave:
Another, simpler (I think) way to look at this is from an impedance-matching perspective:

For maximum power transfer between any amplifier circuit and its load, the output impedance of the amp needs to match the speaker.  Any other load impedance will, theoretically, reduce the amount of power delivered to the load.  It’s as simple as that.

That’s the theory.  The reality is that the impedance of anything is dependent on the frequencies involved, but practically speaking, matching an 8 ohm speaker with an 8 ohm amp is always going to deliver the most power to the speaker.

DW1961:

--- Quote from: Dundarave on July 30, 2020, 11:02:51 pm ---Another, simpler (I think) way to look at this is from an impedance-matching perspective:

For maximum power transfer between any amplifier circuit and its load, the output impedance of the amp needs to match the speaker.  Any other load impedance will, theoretically, reduce the amount of power delivered to the load.  It’s as simple as that.

That’s the theory.  The reality is that the impedance of anything is dependent on the frequencies involved, but practically speaking, matching an 8 ohm speaker with an 8 ohm amp is always going to deliver the most power to the speaker.

--- End quote ---

Yes, I do understand that the  impedance changes depending on what sound is begin generated, but keeping it static is all my head can handle. Thanks for that simplistic explanation. However, I do need to do some calculations, so I'm missing something in the formula (see post below).

retrolefty:

--- Quote from: Dundarave on July 30, 2020, 11:02:51 pm ---Another, simpler (I think) way to look at this is from an impedance-matching perspective:

For maximum power transfer between any amplifier circuit and its load, the output impedance of the amp needs to match the speaker.  Any other load impedance will, theoretically, reduce the amount of power delivered to the load.  It’s as simple as that.

That’s the theory.  The reality is that the impedance of anything is dependent on the frequencies involved, but practically speaking, matching an 8 ohm speaker with an 8 ohm amp is always going to deliver the most power to the speaker.

--- End quote ---

 I have the understanding that audio amps normally have a much lower output impedance rating then the speakers they drive by a factor of 50 to 150. In fact there is a quality specification parameter called damping factor covers this topic
 ( https://en.wikipedia.org/wiki/Damping_factor ).

As most solid state audio amps normally use significant negative feedback (Vs tube amps} to maintain a linear output voltage it should be considered as having a very low output impedance Vs normal speaker impedance. Your point is about when most efficient power transfer occurs, but most all audio amps are not designed and used for best efficiency, that doesn't sell amps.  :-DMM

Dundarave:

--- Quote from: retrolefty on July 31, 2020, 01:35:29 am ---
--- Quote from: Dundarave on July 30, 2020, 11:02:51 pm ---Another, simpler (I think) way to look at this is from an impedance-matching perspective:

For maximum power transfer between any amplifier circuit and its load, the output impedance of the amp needs to match the speaker.  Any other load impedance will, theoretically, reduce the amount of power delivered to the load.  It’s as simple as that.

That’s the theory.  The reality is that the impedance of anything is dependent on the frequencies involved, but practically speaking, matching an 8 ohm speaker with an 8 ohm amp is always going to deliver the most power to the speaker.

--- End quote ---

 I have the understanding that audio amps normally have a much lower output impedance rating then the speakers they drive by a factor of 50 to 150. In fact there is a quality specification parameter called damping factor covers this topic
 ( https://en.wikipedia.org/wiki/Damping_factor ).

As most solid state audio amps normally use significant negative feedback (Vs tube amps} to maintain a linear output voltage it should be considered as having a very low output impedance Vs normal speaker impedance. Your point is about when most efficient power transfer occurs, but most all audio amps are not designed and used for best efficiency, that doesn't sell amps.  :-DMM
--- End quote ---

Lol, I’m not going to argue the point, as I was only talking about “maximum power transfer”, but an amp driving a 4 ohm speaker to have a reduced impedance factor of 50 to 150 below 4 ohms has got to have a pretty insignificant output impedance!

ejeffrey:

--- Quote from: Dundarave on July 30, 2020, 11:02:51 pm ---Another, simpler (I think) way to look at this is from an impedance-matching perspective:

For maximum power transfer between any amplifier circuit and its load, the output impedance of the amp needs to match the speaker.  Any other load impedance will, theoretically, reduce the amount of power delivered to the load.  It’s as simple as that.

--- End quote ---

The maximum power transfer theorem only applies to linear (and stable) sources and loads, so while it kind of hints at the right answer (making the load *closer* to the source impedance increases power output), it is wrong if taken literally.  If you put a power matched speaker on a typical audio amplifier the power transfer will be zero as you will blow a fuse or power transistor.


--- Quote ---That’s the theory.  The reality is that the impedance of anything is dependent on the frequencies involved, but practically speaking, matching an 8 ohm speaker with an 8 ohm amp is always going to deliver the most power to the speaker.
--- End quote ---

(Solid state) audio amplifiers are almost always very low impedance -- a small fraction of an ohm, not 8 ohms or similar.  An amplifier described as an "8 ohm amp" just means that is the type of speaker it is designed for.

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