John Curl's Blowtorch preamplifier part II

[jneutron]

Originally Posted by jcx

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

[Wavebourn]

JCX, it is not about 3 mm difference. It is about 3mm smearing, imagine the mosquito 3 mm wider than it is when in front of your nose! Scale it on the 1 meter distance, is not it scary? !

[PMA]

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

[jneutron]

Originally Posted by Wavebourn

JCX, it is not about 3 mm difference. It is about 3mm smearing, imagine the mosquito 3 mm wider than it is when in front of your nose! Scale it on the 1 meter distance, is not it scary? !

Scary is a recorded mosquito reproduced on a Bose 901 system.

jn

[Wavebourn]

Originally Posted by PMA

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.

[Wavebourn]

Originally Posted by jneutron

Scary is a recorded mosquito reproduced on a Bose 901 system.

Bose knows how to impress potential buyers. Respect.

[Esperado]

Originally Posted by jcx

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 ?

Originally Posted by Joshua_G

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.

[Esperado]

Originally Posted by Wavebourn

Bose knows how to impress potential buyers. Respect.

I had spend some times to listen to video demonstrations conferences of different gurus about their high end (hum) enclosures.
They all use the same actor's methods. All is on the speech and the perfume of paradise. Great respect too.

[jneutron]

Originally Posted by jcx

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

[jneutron]

Originally Posted by Wavebourn

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.

Originally Posted by Wavebourn

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...