Can output impedance measurement/plot be added to the amplifier test repertoire?

[egellings]

There's some good info in post 86, too.
Random thought in my head: Sometimes I wondered why some people don't read anything in a thread and keep asking questions to things that have been answered 5 different ways already. Then I realised trying to figure out illogical behaviour is illogical. Then I started ignoring people who exhibited this behaviour, once a pattern was established. For really serious offenders, there's the ignore button, too!

I sometimes will ask a question already answered earlier in a thread because I jumped into the thread later and simply missed the answer posted earlier.

 

[mike7877]

I sometimes will ask a question already answered earlier in a thread because I jumped into the thread later and simply missed the answer posted earlier.

Me too. I think it's forgivable in some cases - threads can be pretty long. But when people like that keep asking the same questions, over and over and over and over, page after page, and they keep getting really good answers, over and over and over and over from different people, put in different ways - people putting in real effort trying to inform them of something they have no interest in knowing (even though they keep asking) because they're not there to learn, only to argue. Don't you find people like that annoying?

 

[egellings]

Me too. I think it's forgivable in some cases - threads can be pretty long. But when people like that keep asking the same questions, over and over and over and over, page after page, and they keep getting really good answers, over and over and over and over from different people, put in different ways - people putting in real effort trying to inform them of something they have no interest in knowing (even though they keep asking) because they're not there to learn, only to argue. Don't you find people like that annoying?

Agree. Once I happen upon a reasonable answer to a question I have in a thread, I'm done asking then.

 

[Piere]

Once you get to a reasonably low level of amplifier Zo, not much, outside of generating advertising copy. You need some, though. You wouldn't want to drive your speakers with a voltage controlled current source, either. Nice thing is that modern day S.S. amplifiers come with a plenty low Zo, so it's usually not an issue. With vacuum tube amplifiers, it can become an issue.

Yes give people points, no matter what, and they will do everything The funny thing is that in the old tube amplifier days bass performance of serious loudspeakers was sometimes tuned to the high Zo of the amplifier. Doing measurements for reviewing and judging amps are imho only meaningful if you can associate them to its audible consequences in a unambiguous and generally accepted repeatable way. But I can't think of today's quality amplifiers tested by Amir, that fail on the point of low Zo.

 

[egellings]

Yes give people points, no matter what, and they will do everything The funny thing is that in the old tube amplifier days bass performance of serious loudspeakers was sometimes tuned to the high Zo of the amplifier. Doing measurements for reviewing and judging amps are imho only meaningful if you can associate them to its audible consequences in a unambiguous and generally accepted repeatable way. But I can't think of today's quality amplifiers tested by Amir, that fail on the point of low Zo.

Analog audio amplification is a long-ago solved problem. Any improvement in specifications will be inaudible. With feedback-using S.S. amps, low Zo comes with the territory. Tube amps, however, need to work on that. I think that designing a speaker to work specifically with high Zo amplifiers would work, but then that speaker would lock the user into just one particular type of amplifier.

 

[Deleted member 48726]

I have been stating facts to inform a few people who are unaware of certain realities. A couple others seem to think that because the information isn't useful to them specifically there's no reason to collect it. When I sense trolling, I'm pretty quick to disengage. I thought I was being helpful, but I'm not always right (see that right there? self-awareness! the ability to correct previous misperceptions)

I'd like to see more transparent capacitive and inductive load frequency responses of which I think says a lot more of real world applications than a somewhat arbitrary value derived seemingly for marketing purposes. Also above a certain threshold it's of no concern.

With that said testing if the manufacturer spec is in line with reality is generally a good idea. I'm not sure what value it brings though. I mean; if an amp spec says it haves a DF of 350 at 1 kHz and measures 250 what does that bring of value IR to buying decision? A Hegel amp claims a DF of 1000 but measures 700?

Do you have certain amps in suspicion or is it in general?

 

[fpitas]

I'd like to see more transparent capacitive and inductive load frequency responses of which I think says a lot more of real world applications than a somewhat arbitrary value derived seemingly for marketing purposes. Also above a certain threshold it's of no concern.

With that said testing if the manufacturer spec is in line with reality is generally a good idea. I'm not sure what value it brings though. I mean; if an amp spec says it haves a DF of 350 at 1 kHz and measures 250 what does that bring of value IR to buying decision? A Hegel amp claims a DF of 1000 but measures 700?

Do you have certain amps in suspicion or is it in general?

I can't exactly answer your question, but Amir certainly finds amps that don't meet spec for say, power. I guess you have to take it for what it's worth to you.

 

[SIY]

I mean; if an amp spec says it haves a DF of 350 at 1 kHz and measures 250 what does that bring of value IR to buying decision? A Hegel amp claims a DF of 1000 but measures 700?

Do you have certain amps in suspicion or is it in general?

Good luck accurately measuring those numbers.

 

[solderdude]

I'd like to see more transparent capacitive and inductive load frequency responses of which I think says a lot more of real world applications than a somewhat arbitrary value derived seemingly for marketing purposes. Also above a certain threshold it's of no concern.

With that said testing if the manufacturer spec is in line with reality is generally a good idea. I'm not sure what value it brings though. I mean; if an amp spec says it haves a DF of 350 at 1 kHz and measures 250 what does that bring of value IR to buying decision? A Hegel amp claims a DF of 1000 but measures 700?

Do you have certain amps in suspicion or is it in general?

Perhaps O.P. is not so much interested in output Z's smaller than 0.1ohm but rather interested in the ones with an output Z well above that.
Such would be valuable info and can shed some light on expected deviations in FR one might get when one knows the imp. of their speakers.

An alternative could be an FR measurement with a challenging 'speaker emulating' complex load which would have to be well documented.

No matter how we look at it it would mean more work for Amir, measurements, connecting certain loads and reporting it.

 

[KSTR]

With that said testing if the manufacturer spec is in line with reality is generally a good idea. I'm not sure what value it brings though. I mean; if an amp spec says it haves a DF of 350 at 1 kHz and measures 250 what does that bring of value IR to buying decision? A Hegel amp claims a DF of 1000 but measures 700?

As the DF measurement is extremely sensitive to everything once output impedance is low enough, any value above 100 or so should be only used as rough orders of magnitude, notably as their practical relevance is close to zero once you have DF > 30, basically.
A tolerance band of something like +-6dB (a factor 0.5x to 2x) applied to any given factory spec is fully within bounds, and both your examples do fit right in.

 

[Deleted member 48726]

As the DF measurement is extremely sensitive to everything once output impedance is low enough, any value above 100 or so should be only used as rough orders of magnitude, notably as their practical relevance is close to zero once you have DF > 30, basically.
A tolerance band of something like +-6dB (a factor 0.5x to 2x) applied to any given factory spec is fully within bounds, and both your examples do fit right in.

That was a part of my point. Above a certain threshold it doesn't seem to matter.

 

[Mnyb]

If that's a serious question (?):

Audio Myth - "Damping Factor Isn't Much of a Factor"

Myth - "Damping Factor Isn't Much of a Factor" Myth - "A Damping Factor of 10 is High Enough" Myth - "All Amplifiers Have a High-Enough Damping Factor" Where did these Myths Originate? These myths seem to trace back to a well-known paper (PDF) written by Dick Pierce. His analysis shows that a...

benchmarkmedia.com

Yes this article highlights the real issue fr response variations due to high output impedance .

 

[Deleted member 48726]

Good luck accurately measuring those numbers.

I don't think of DF as a particular important value taking in account what else is influencing the value. So I'm not the one needing luck.

 

[Chrispy]

This was already linked? https://www.audiosciencereview.com/...-impedance-damping-factor-and-speakers.23968/

 

[Deleted member 48726]

This was already linked? https://www.audiosciencereview.com/...-impedance-damping-factor-and-speakers.23968/

There are a couple of other threads also. Actually I'm deeply sceptic in one of them I believe. -Where people where explaining to me the factors that drops the DF from high to low in any system. It started with me hearing some difference in amplifier swapping that got me on the wrong track believing the difference was due to the DF being 300 rather than 190. I've since been reading the subject and am convinced that it can't matter because of cables, passive crossover circuits and driver/cabinet equivalent behaviour.

I'll dig out the threads during the day. I believe I have them bookmarked.

 

[SIY]

I don't think of DF as a particular important value taking in account what else is influencing the value. So I'm not the one needing luck.

It was more of a general statement. It is very difficult to accurately measure low source impedances, and almost no-one trying to do so uses Kelvin connections.

 

[pma]

It is just another technophile BS, like seeking for 140dB 1kHz SINAD. Without taking into account the connecting cables and binding post connections the DF number, usually without frequency dependence shown, is a pointless number. You measure it at PCB output and get 1 order different number than behind the output binding posts.

 

[Philbo King]

Fortunately, as powered speakers slowly replace passive ones with RLC crossovers, this topic will eventually become an analog to the medieval 'how many angels can dance on the head of a pin?' question.

 

[fpitas]

Fortunately, as powered speakers slowly replace passive ones with RLC crossovers, this topic will eventually become an analog to the medieval 'how many angels can dance on the head of a pin?' question.

47?

 

[fpitas]

Fortunately, as powered speakers slowly replace passive ones with RLC crossovers, this topic will eventually become an analog to the medieval 'how many angels can dance on the head of a pin?' question.

True for the consumer, but the speaker designers will want the information. I know I would.