Of course you are correct in your description/ set up. I might conclude the same if that is what I thought always happens.
I would have to look at each result to tell what is what and which is correct.
Are there any dbt that correlate with the larger body of data and visa versa?
There certainly are plenty of disagreement as to what/which conclusion is the final word.
THx-RNMarsh
Richard, what exactly do you mean by 'the larger body of data'?
I mean, one 'larger body of data' is 'everybody knows amps have to be broken in'. I would not consider that 'body of data' on the same confidence level as data from a controlled test.
As Anatoly France once, long ago, remarked: 'if 50 million French citizens believe something that is wrong, it still is wrong'
jan
John:
Unfortunately this needs qualification and may be a more significant issue. Most amps that are competently designed will have essentially flat response from at least 50 Hz to 15 KHz into a resistive load. However very few amps will have exactly the same response into a reactive, dynamically changing load like a loudspeaker. The differences may be small but there is plenty of evidence that even small frequency response errors are audible. In some cases the differences can be pretty significant. And its very possible that the response changes under dynamic conditions since the load changes under dynamics and the amps output impedance is not just a simple resistor. its more of a synthesized impedance that changes with current and frequency and to some degree with what just happened.
As for distortion, looking at the measurements of speakers done by SoundStageNetwork.com | SoundStage.com | Loudspeakers There is a higher correlation between low distortion and sonic preference than flat response and sonic preference. I believe that humans can adapt to many response deviations and essentially remove them after time much like not seeing the different colors of light sources once adapted.
That's my experience too - once a system works at or beyond a certain quality level then FR seems to have little or no relevance to the perceived, subjective impact. In fact, over the years I've used this as a quick and easy "test" - on an amplifier that had tone controls, that was temporarily working at a competent level, I could spin the treble control all the way from one end to the other, and the "change" in the sound was imperceptible - i.e., I was "listening" to the musical performance, not to the amplifier, or speakers; and this changes how the mind reacts, it seems - IME.
lets say several different people review a particular speaker system. They are from different cultures and have different sources and amps and rooms etc. Just about everything a DBT would not allow in a single test (changing equipment while trying to determine the sound of one of them). This is quit common if reading many reviews of that speaker.... very different systems be played in very different rooms.
Yet, the many comments about that speaker's sound character is the same or very similar from one review and another. That can be valid data as well
Myself, I have read descriptions of a speakers sound and later heard that speaker and had the same impression of its character. The first time this happened was with a MagnaPan speaker.
Now, if reviews all said something different about the sound character of this speaker system, that would be a problem and in fact very unusual in my experience.
THx-RNMarsh
Last edited:
Thinking about it I'm not so sure the variations under dynamics will be smaller. Its entirely possible they could be larger. The dynamic conditions I'm referring to are the nature of the lad. A speaker can easily have different impedance curves with level. There are many factors that affect its static impedance. Further if a voice coil is moving out of its linear range in the magnetic field all bets are off. Finally given the nonlinear nature of energy storage in a speaker its effective impedance after a big transient may well be different if the spectrum of the transient were spread out over time.
Given that few amplifiers are real pure voltage sources across the audio spectrum there is many ways to depart from "flat".
Yes, these load tests are done at a 1W power level, and are not intended to cover large signal behavior.
At that point, the amp is the least of your worries!
I haven't seen any data showing enormous speaker impedance changes with level (not counting VC burnout)- do you have any references on that?
While I do think that deviations in frequency response are possible with low damping factor, I doubt that one of my amps will change level with changes of load impedance to any extent. Not only is my damping factor over frequency almost constant, but it is very high, especially when compared to low rent speaker wire.
Its all a matter of proportion and sensitivity. Ohms law is a difficult task master.
If your tolerance is .1 dB what source impedance is necessary to handle the impedance variation of a typical 4 Ohm speaker?
Designing with a pretty constant and low output impedance across the band will minimize the effect. However if the speaker designer was counting on a higher source impedance you could have undone all of his work.
Here is a plot showing response variations when a 1 Ohm resistor is added: Speaker Wire . The plot is 5 dB per division which is huge. .5 dB may be enough to change the perceived balance. In the world of Metrology 10 MegOhms input impedance can degrade the accuracy of a measurement of a low impedance source. I'm not suggesting our ears are 10 PPM accurate but its not an issue to ignore.
If your tolerance is .1 dB what source impedance is necessary to handle the impedance variation of a typical 4 Ohm speaker?
Designing with a pretty constant and low output impedance across the band will minimize the effect. However if the speaker designer was counting on a higher source impedance you could have undone all of his work.
Here is a plot showing response variations when a 1 Ohm resistor is added: Speaker Wire . The plot is 5 dB per division which is huge. .5 dB may be enough to change the perceived balance. In the world of Metrology 10 MegOhms input impedance can degrade the accuracy of a measurement of a low impedance source. I'm not suggesting our ears are 10 PPM accurate but its not an issue to ignore.
Yes that is true of course. But amp Zout increase the response variations of speakers, which are already there due to the speaker's impedance response variations. And of course this increase in response variations is the same in whatever angle you look at it.
Jan
In the mid 70ies, Accuphase had an integrated amp designated 202. Aside from being built like few others ate the time, it had a dampung factor switch at the back, which allowed the user to change at will the damping factor in three steps, normal, medium and soft. If memory serves, that was 60:1, 6:1 and 1:1, or some such, not sure about that, been too long ago.
Anyway, a friend bought it and we fiddled around with that cotrol switch. On his speaker, AR 3a Improved, the "medium" position produced the best sound, while on my speaker, AR5, the "normal" did best in terms of sound.
How is this explained?
Anyway, a friend bought it and we fiddled around with that cotrol switch. On his speaker, AR 3a Improved, the "medium" position produced the best sound, while on my speaker, AR5, the "normal" did best in terms of sound.
How is this explained?
- Status
- Not open for further replies.