John Curl's Blowtorch preamplifier part III

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#4,062
jneutron said:
My point is, any energy that enters the listening space must come from the cone, otherwise a cone position system does not reflect what we hear.
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Obvious.
So, a servoed system will work only inside the frequency domain where a speaker works perfectly in piston. With a more important margin than a conventional speaker, because, as the speaker is more "under constraint" it will tend more easily to fractionate its membrane.
If we analyse all this, plus the limitations of the system, the best benefit will be for relatively little speakers (Piston) in closed boxes, and limited the the low end frequencies, IE, sub basses. The servo will be used to extend the reproduction under the resonance frequency. A perfect application to reduce the volume of several discret subwoofers, dispatched in the room in order to minimise the resonances modes (GedLee idea). There is an actual revival of this technology in several little Bluetooth speakers in the market.
 
#4,065
Tournesol said:
National Semiconductor was founded in Danbury, Connecticut. Did they moved their headquarters in Salem by a full moon night ?
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There was also this...

Of course for any single or double blind test to be valid, output levels of the units under test should be
matched as closely as possible. 0.1dB difference in output levels at a single location for a single listener is
recommended, but 1dB level matching has proved to be sufficient.
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Sometimes the inmates are not edited.
 
#4,067
Markw4 said:
Speakers are interesting, but I just happened upon a piece of TI applications information that reads as follows:

"In listening tests at TI's sound room evaluating different circuit components used in the LM4702 demo amplifier, there was one part whose negative effect on audible signal quality was undeniable. A DC blocking capacitor on the input of the LM4702 degraded sound quality. In multiple listening tests, with different participants and at various locations around the country, the negative effects of even the best film and foil polystyrene DC blocking input capacitors in the audio signal path was confirmed. It is therefore recommended that DC blocking capacitors not be used in the signal path for mid to high-end audio equipment. Where DC offset from another signal source may be a problem then the use of a DC servo circuit that keeps DC offset from appearing at the output of the amplifier is recommended."

This is the document that contained the above information: http://www.ti.com/lit/an/snaa031a/snaa031a.pdf
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W O W ! It has filtered down to mainstream now. And, they also LISTENED. Next thing you know, they will be saying its because of DA.

OMG

Texas Instruments. Time to celebrate. Walt Jung will be happy, also. We can all die in peace now.


;-) Its a happy day ! Future EE's will listen to a TI more than to an I.

Those who stick to It Doesnt Matter are now in or soon will be in the minority. It's all done now but the crying and shouting.


THx- Richard
 
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#4,069
Tournesol said:
Ah ah, the kind of sentence that made the legend of La palice.
ex: "Five minutes before his death, he was still alive."
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That is so funny yet so true also. It always amazed me knowing people who are alert and talking, typing out messages and then, Poof, Gone. Contributing right up to their end.

Some one on DIYAudio was giving out advice and experience and then ended with.... well, i have to go to the hospital now.........


THx-Richard
 
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#4,071
I doubt many people have taken that particular app note very seriously. It does smack of a project given to the new grads to keep them amused and teach them how to write in the company style. It's not up there with some of the great app notes of our time such as say some of Jim Williams output. (actually not sure he ever did a duff one).
 
#4,072
billshurv said:
I doubt many people have taken that particular app note very seriously. It does smack of a project given to the new grads to keep them amused and teach them how to write in the company style. It's not up there with some of the great app notes of our time such as say some of Jim Williams output. (actually not sure he ever did a duff one).
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Yeah, right. Sure.

It's a dead horse issue.


-RM
 
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#4,074
You have any evidence otherwise? I am sure there are some ex NatSemi employees here who could chip in. Personally I think the chances that they did any form of rigorous capacitor testing to be absolutely zero.

A significant amount has been written in the Audiophile Press about how different types of passive components affect perceived sound quality
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Pretty much sums it up.
 
#4,078
For those who are not familiar with French and Belgian humor, Jacques de Chabannes (1470-1525), seigneur de La Palice was a legendary figure famous to had said "truths" so obvious that they are funny.
As the dB was originally set to be the smallest difference in level that a human ear is able to perceive, I found this sentence: "1dB level matching has proved to be sufficient." worthy of him.
Well, laughed enough, now it's time to go back to the witch hunt ;-)
 
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#4,079
In response to a Q:

Google "dipole magnet pole profile"

Look for the Cockroff Institute paper by Neil Marks.

They add shims to flatten the field as you get closer to the edge.

I've never seen gap or pole pieces in speakers that were anything other than pure cylinders.

Nor, have I seen any reference to a pole piece extending past the front plate.

jn
 
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