No, I'm saying the speaker terminals are the most sensitive place to measure any difference due to upstream changes. Audibility is a different question, one to be answered the same no matter where you measure. Unless someone holds to a form of mysticism by which an interconnect can change the acoustic output of a speaker without altering the input voltage it's hard to see a scientific objection.
Acoustic measurements potentially mask upstream changes with, for example, the relatively high distortion added by that particular loudspeaker that may not appear in the next. Playing music changes the voicecoil temperature which changes the electrical characteristics which changes the acoustic performance. Play the same song twice and you're unlikely to get the same measurements. Standing in a different place in the room for the second measurement will almost certainly cause differences well above Redbook resolution. It's an unworkable, nonsensical proposal with no benefit. Even assuming the microphone reacts the same way as the ear, counter to a century's research.
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Right. I thought we were talking about (or at least I was) measuring an audible "effect" (difference)? Are we?
Then it's time for a better mic and measurement technique (such as very nearfield). Are you saying it can't be measured (with a mic)....or that you would rather not with your particular setup?
I'm really starting to worry about you amp guys (and the whole electro-"acoustics" thing)
Well - you have had your leg pull.
More seriously though, do you truly believe that all of the views you express and questions which you pose on this thread are totally valid? Or is your avatar actually your clue as to your purposes?
At the speaker terminals is far and away the easiest and most reliable. If the speakers aren't pathological, a change of x dB in volts at the speaker terminals (within the speaker's passband) will translate to a change of x dB SPL in the radiated output. A voltmeter or spectrum analyzer is a far more precise and repeatable instrument than a transducer. Especially in a room.
What would the mike measurement prove? I have no idea- you seem to be focused on doing that, not me. I wouldn't use a relatively low resolution transducer in a noisy measurement to try to get data if there were a clean, high res way to get the same data- and there is. Difficulty and expense are not virtues, except to the tweak set.
Agreed. Some of us listen to sound waves fully, with our ears, while others listen fully, with their eyes and knowledge, to sound waves, silver waves, price waves, purity waves...and lord knows what else
Strange??
So "backwards" is of similar effect as EM? EM which can be measured and audibly (or not) correlated to sound waves? So what is the measure of "backwardness" and how is this audibly correlated to sound waves?
I think you already know what I am going to suggest and you are mainly asking if I have quantified my results in graphical form for you. Correct?
Measurably, various types of shielding can affect (even audio) frequencies to a greater degree at higher frequencies, thus audibly shifting the phase of the higher frequencies in relation to the lesser affected lower frequency waveforms. Admittedly, some shielding is almost symmetrical in its affect.
I doubt that anyone has bothered to come up with a definable "backwardness quotient," since the term reactance is already fairly well understood by many.
Thank you.
Posted by RDF
You do realize that every word of that paragraph echoes the sentiments on the "non-believers"....don't you? How would you hear that which disappears into the non-linearities of your speakers/room?
Allow me to simplify/clarify what I glean from that: Cables measure differently, but it is inaudible.
Posted by SY
I don't know either. That's why I thought you were doing a listening test. But, it's a damn sight more relevant then measuring cable output, which apparently, has been done repeatedly.
What if Tubeguy gets every cable right? How will we figure out how w/o measuring the speakers/room he heard it in?
I mostly appreciate/agree with your posts but you have stated you would investigate if tubeguy picks the cables consistently. How else would you go about trying to do that?
Eric
You do realize that every word of that paragraph echoes the sentiments on the "non-believers"....don't you? How would you hear that which disappears into the non-linearities of your speakers/room?
Allow me to simplify/clarify what I glean from that: Cables measure differently, but it is inaudible.
Posted by SY
I don't know either. That's why I thought you were doing a listening test. But, it's a damn sight more relevant then measuring cable output, which apparently, has been done repeatedly.
What if Tubeguy gets every cable right? How will we figure out how w/o measuring the speakers/room he heard it in?
I mostly appreciate/agree with your posts but you have stated you would investigate if tubeguy picks the cables consistently. How else would you go about trying to do that?
Eric
That is as unfortunate. You did note where I specified 'that particular speaker' in italics? Or that there is no reason to discard sensitivity for no proven gain?
Let me ask, let's say you do measure a difference with a microphone. What will it tell you? What do you know about the fine-grain repeatability of acoustic measurements?
TheTubeGuy before doing the cable tests, I suggest that you do a test of something where we all agree that you might hear a difference (like a small equalization difference). That way you can quickly refine your procedure to hear smaller and smaller differences.
I was just reading in the newspaper that on 100 coin flips, streaks of 5 to 7 consecutive heads is not uncommon.
I was just reading in the newspaper that on 100 coin flips, streaks of 5 to 7 consecutive heads is not uncommon.
We don't need to measure the speakers, we only need to measure the signal being delivered to them. They're dumb- they only know what's fed to them, not how it got there.
Before starting the test, we'll obviously look for significant differences in frequency response, noise, and stability. Given his description of the equipment, this is unlikely to be anything remotely close to audibility thresholds- we've already discussed that part repeatedly. If I thought there were obvious, mundane differences, I wouldn't bother hauling my sorry old *** over to Florida.
That sums it up quite nicely. Thanks.
To measure 0.1db (your example) changes in mid band sound pressure? Actual (not calculated) sound pressure measured at the terminals?
Now you're adding if's. So TG can precisely and repeatably hear a 0.1db change in mid band sound pressure in his room, but a microphone cannot measure this? IOW, human ears are indeed more sensitive to sound pressure changes than microphones (as advocated by the believers). I disagree.
No, what would: In fact, I'll be happy to visit you after I'm done with Tom, and run a blind test with you- using a microphone ONLY, reliably detect a 0.2dB (I'll be generous here) EQ difference in the midrange. prove?
And again
?
TIA.
All this comes as news to me, that as a speaker designer, acoustic measurements cannot capture audible effects heard by humans in the soundfield. Are Toole, Olive et al all measuring electrically at the terminals as well?
cheers,
AJ
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@ SY
That makes sense. I guess I've always wondered how differences in amplitude and frequency could manifest itself as adding detail and the other wondrous things attributed to certain cables. I guess the ability to prove/disprove discrimination is as good as it will get.
@ RDF -
I agree on the difficulty/dubious usefulness of microphonic testing. Although I seriously ask you to reread that paragraph, with it's references to system/room/positioning anomalies rendering measurements useless. Compare that to the "disbelievers" claims that cables cannot be blindly identified, because any alleged differences would be swamped by system/room/positioning anomalies.
That makes sense. I guess I've always wondered how differences in amplitude and frequency could manifest itself as adding detail and the other wondrous things attributed to certain cables. I guess the ability to prove/disprove discrimination is as good as it will get.
@ RDF -
I agree on the difficulty/dubious usefulness of microphonic testing. Although I seriously ask you to reread that paragraph, with it's references to system/room/positioning anomalies rendering measurements useless. Compare that to the "disbelievers" claims that cables cannot be blindly identified, because any alleged differences would be swamped by system/room/positioning anomalies.
I am leaning with SY and company thinking that the measurements at the terminals will just be easier to deal with and tell you what you need to know in most cases, but mics are always worth a try. I don't see why they wouldn't expose something as long as you take the measurements really fast so to avoid any drastic change in the environmental variables, don't move the mic, and swap the cables somehow without moving the speaker - this is the part that realistically isn't going to happen unless you detach the terminals and extend them away from the speakers. Also probably trigger the recording in a separate room so that your body and it's placement in the room doesn't cause a change in the reflections.
In fact, that is exactly how small (~0.2dB) level differences are perceived. And it's just as often attributed to the electronics. This is why, when comparing boxes of gain, it is VITAL to have very precise level matching.
Ah, got it. The human ear/brain system has millions of years of evolutionary DSP that discards or most charitably suppresses 'mundane' elements like millimeters positioning differences to adjacent walls or changes in barometeric pressure. There's no reason to presume potential changes wrought by cables or caps are of the same type and dispensed in the same manner. Reverse it, if a 6 inch head move changes the perceived power response from a speaker by multiple dB, why design for flat? Answer: because the ear/brain is not a microphone/meter.
Too true. Actually it has been suggested that the head position is the reason for some reports of cable differences. In that after a person gets up to change the cable and returns to his chair, his head will be in a different position and the sound will be different. Of course it would be different even without the cable swap. This can be proved (sound change with head position) by moving a mic around and seeing how much things change with even small changes in position.
Yes.
Rather than continue to run in circles, lets put the horse back in front of the cart and worry about measuring what Tom heard after he confirms hearing it (unless the Jakob rule applies - where we have to prove that Tom/we heard nothing and measured nothing).
My intent all along.
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