John Curl's Blowtorch preamplifier part II

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um, 10 us = ~1/8”, 3mm sound prop distance in air

I don't have my chair, speakers that closely aligned – do you? multiple drivers lots further apart on the cabinet – even the tweeter cone/dome has modes on that scale...

You've hit directly upon the prevailing yet inaccurate view.

If you have exactly one entity being imaged via two speakers, and the image is being created exactly in the middle of the soundfield, then what you speak of is exact and accurate. edit(that being the head in the vice concept).


When more than one image is being generated via two speakers, the human mind will create the central images physically centered when we enter the sweetspot, and we will use our ability at sub edit (10) microsecond discernment to localize other non central images with respect to the central (or reference) image. edit(differential amplitude as well, but one windmill at a time)

The problem is not one of absolute location, to which you speak...it is a problem of location relative to a reference image.

jn
 
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10us of ITD detectability is about correct, maybe even less. Such is human auditory system.

The rumor about 10 us is from the experiment with spark gaps. There were 2 spark gaps, near 2 ears. 10 uS caused audible shift of the image. It is rounded number, for rounded person, in rounded conditions.

In real conditions in Siberia we used to kill mosquitoes routinely, when they were flying around our heads. Without any calculations, or conscious attention.
 
I don't have my chair, speakers that closely aligned
It seems that our ears are very sensible to the energy. We can feel very fast overshoots, and slow slew rates as well. This for the speed accuracy, witch has nothing to do with phase alignment at the crossover of an enclosure. Their deficiencies are here anyway, no need to add one more. But the important point where Jneutron' asserts seems very relevant is about charge for the amp.
I thing (I'm sure of that) that most of the differences some can find between speakers cables are caused by this. (mountain looking impedance curve).
On my side, i have a near flat impedance enclosure, and cables witch sound different on some enclosures sound the same on mines.
Same thing for the amp. It seems obvious that an amp will behave better if ration V/A is constant on all the bandwitch than to see a speaker/cable where the impedance vary from 6 ohms to 150, and goes near 0 at HF because capacitance of the cable.
Poor sounding amps on a set of speakers can behave well on mine (tested). And never the contrary. May be it is because they tend to oscillate on the poor soundung system due to capacitive load ? Response curve modified because internal impedance+ wire resistance vs impedance of the enclosure ?

My experience is different from yours.
I'm not an audiophile. I don't want my system to *make* good sound.
I want my system to be *transparent*. As a sound engineer i can compare some of my original mix's mirror copy to their industrial reproduction (CD vs Vinyls). I can make direct comparisons, i'm not inventing an ideal dreamed reproduction. See what i mean ?

I have a pretty good system, believe-me, improved all the years long, very fast amp, high end horns...As long i don't find major deterioration in known sources reproduction (and I'm pretty intolerant) i'm satisfied. *Separation between instruments*, good localization, high dynamic, fidel tonal balance and respect of little dynamic details (like attacks on notes) are my concerns.
On an other side, i don't cut hairs in four and my cables are not cryogenic threated by virgins.

But i can understand a customer prefer agreeable reproduction, witch hide recording defects, adding pleasure. Some kind of pretty makeup. My position is special, due to the history of my life.
 
don't we expect speaker identical models speaker terminal impedance to match even a little? , maybe even better than 10%?

Now, an interesting question (well a hint at it).

When I connect an inductance meter to a wide range driver and sweep it for inductance and resistance vs frequency, The inductance and resistance measured is dependent on the constraints placed on the cone. If I measure face up, no baffle, I get one set of numbers, if I place it face down on a smooth flat surface, I get another. The inductance at any frequency is dependent on the velocity and effective mass of the cone. ((edit: For an eminence sigma pro 18A, over 500 hz, the measurements are independent of the cabinet, but below 500, totally dependent. If I wish to cross over this driver below 500 hz, I have to measure the driver in the cabinet before I can calculate the inductor..))

Now, how does the inductance and resistance of the coil depend on the velocity? If one speaker has a bass line, but not the other, what will the mid or hiband impedance of the driver be?

In other words, how much will the driver's impedance at any frequency be dependent on the motional response to another frequency? Can an asymmetrical stereo signal content cause one driver to react a bit different than another?

jn
 
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The rumor about 10 us is from the experiment with spark gaps. There were 2 spark gaps, near 2 ears. 10 uS caused audible shift of the image. It is rounded number, for rounded person, in rounded conditions.
In 74, nordmark showed 1.2 uSec with dither.

Greisinger's work with speakers is closer.

Bose knows how to impress potential buyers. Respect.
Actually, I was referring to the 901's ability to create a much larger than life image.. caused by the non specular reflection of a dihedral wavefront.

jn

ps..I should be ashamed of myself for using such words...but yet, I am not...:D
 
I'm not an audiophile. I don't want my system to *make* good sound.
I want my system to be *transparent*.

This and the rest of your post might be a bit confusing. To *get* a good sound, we usually need to solve perfectly power supplies, shielding, EMI immunity. Sterile sound (as a result of ultralow THD only oriented design) does not necessarily mean "exact" or "natural" sound.
 

I'm not an audiophile. I don't want my system to *make* good sound.
I want my system to be *transparent*. …

Evidently, you are not interested in the sense of music realism.
It seem to me that this may be the major difference between you and me.

As a sound engineer i can compare some of my original mix's mirror copy to their industrial reproduction (CD vs Vinyls). I can make direct comparisons, i'm not inventing an ideal dreamed reproduction. See what i mean ?

I do see what you mean – apparently you have no interest in the sense of music realism.
The details between the original mix and the CD produced from it may be the same.
If the music was recorded and mixed without any consideration for music realism, the CD may sound the same as the recording and mixing. Both wouldn't have a sense of music realism.

I also worked for a while as recording engineer, so I have a clue about what can be captured in the process of recording and mixing. When a certain aspect isn't captured in recording and mixing, it wouldn't be there in the final product.

It's easier to have a mediocre recording and mixing than a really good one (good in the sense of music realism). For mediocre recordings, mediocre reproduction gear is good enough.

For a mediocre taste, mediocre recordings and reproduction gear are satisfactory.
 
It seems obvious that an amp will behave better if ration V/A is constant on all the bandwitch than to see a speaker/cable where the impedance vary from 6 ohms to 150, and goes near 0 at HF because capacitance of the cable.

The normal model of a speaker cable as t line is C per foot and L per foot. While the capacitive reactance of the cable will continue it's downward trend, the distributed inductance is still there. Until the cable starts to absorb the signal, the cable Z will remain as z = sqr(L/C). (for the lengths involved, R/G have not been invoked due to the KISS requirement.)

jn
 
Evidently, you are not interested in the sense of music realism.
It seem to me that this may be the major difference between you and me.

I believe you are misreading him. Music realism should not depend on the system adding something to the signal.

I do see what you mean – apparently you have no interest in the sense of music realism.
Again, I don't believe he meant that.
For a mediocre taste, mediocre recordings and reproduction gear are satisfactory.
That seems as somewhat of a slap in the face. I assume you hadn't meant it as such.
edit: I do indeed understand the gist of what you said, but it didn't come across very well.

While I personally am extremely discerning in what I consider as far as music reproduction fidelity, I am not interested personally in maintaining a system which can provide the ultimate soundstage or performance. It is not on my bucket list at this point in my life. I've no issue helping technically those who do this however..

jn
 
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never without H2

Any system, has significant H2 ..... if not from funky electronics, then from speakers, themselves. No one has heard reproduced music... not the recording engineer, mixer, producer, musician without some H2 in it. With systems with very low levels of H2 are produced, people generally do not like it and think it is not musical or it is unnatural. Its as if you need to put back a little H2 to be accepted and i am sure this has been done deliberately in some equipment to make it more musical and less sterile. HOWEVER --

When you listen mostly to LIVE music ...without amplification and loudspeakers.... it does sound closer to the system which is serile. And, if the front end of the chain is recorded with very low distortion and no EQ ... it sounds best or more like Live sounds with a playback that also has very low distortion. Thx-RNMarsh
 
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Greisinger's work with speakers is closer.

Didn't he also show that 20kHz brickwall filters were inaudible? Not that that 's relevant but I don't have much to say about this IAD stuff right now. If both channels are the same where does the difference come from (this with respect to the cable prop delay issue)? Moving cones, bobbing heads, I would love to have a demo since the discussion around building the central image and having the rest of the soundstage fill in (and supposedly being vulnerable to these issues) is intriguing.

EDIT - Is this work on Dave's website, he does love to share.
 
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jneutron said:
All transmission lines have a propagation speed, v = c/sqr(LC), c being lightspeed.
The high frequency speed is v =1/sqrt(LC), where L and C are per metre. This assumes that series resistance and parallel conductance can be ignored - not true for audio. You can choose to regard a slowly-rising audio signal as consisting of an infinite series of infinitesimal impulses but this is generally not a fruitful way of doing low frequency electronics.

If you use load which matches the line, the amp will NOT see any capacitance, no matter what the cable C is, no matter how long it is.
Possibly true, but potentially misleading to the majority of people who don't understand that line impedance varies with frequency. I say possibly true because the cable characteristic impedance is not a pure resistance at audio frequencies so a matched cable, even if achieved (unlikely), will present a reactance to the source.
 
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