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John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
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Old 7th March 2019, 10:17 PM   #15111
billshurv is offline billshurv  United Kingdom
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John Curl's Blowtorch preamplifier part III
Dumb question. Wouldn't extrusion be easier at that size?
 
Old 7th March 2019, 10:22 PM   #15112
Joe Rasmussen is online now Joe Rasmussen  Australia
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Originally Posted by jneutron View Post
Ground loops on the other hand, I am nefarious about, ground loop hum and noise bugs the living daylights outta me..no stone unturned..

jn
On that one, hear, hear!

(Was that my bone toss to you? No, I meant it seriously).
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Old 7th March 2019, 10:34 PM   #15113
simon7000 is offline simon7000  United States
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Originally Posted by jneutron View Post
Or maybe your application is not sensitive to 5 microsecond ITD.. Tell me, in Yankee stadium, where is the sweet spot? Which seat? Or MSG?

Humans are sensitive to that level of ITD, but as I said before, I'm the messenger. And I don't listen to any soundstage to that level of discernment.

jn
If we are discussing changes in localization due to settling time of a long cable loudspeaker system, yes an apparent position shift probably would show up in the empty arena testing in seats close to and between a pair of loudspeakers. In actual use any air motion (wind or even HVAC) would cause changes greater than 5uS.

Now as your supposed expertise in magnetics and loudspeakers..... Hospitality Electronics Supply carries glue, cones, surrounds and voice coils. So the ball of proof is now in your court.

Last edited by simon7000; 7th March 2019 at 10:36 PM.
 
Old 7th March 2019, 11:03 PM   #15114
jneutron is offline jneutron  United States
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Quote:
Originally Posted by billshurv View Post
Dumb question. Wouldn't extrusion be easier at that size?
It would be far easier to just buy the d##m gear. 50 bucks for five, or the whole regulator assembly for 50.

But anybody can do that!!! Me, in for a milling fixture at 300 dollars, various plastic, brass, aluminum, hardened tool blanks, live center.. By the time I learn how to do it well, I've probably made a 500 dollar gear. Ain't gonna learn if I don't try. I ain't in it for the money..

Quote:
Originally Posted by simon7000 View Post
If we are discussing changes in localization due to settling time of a long cable loudspeaker system, yes an apparent position shift probably would show up in the empty arena testing in seats close to and between a pair of loudspeakers. In actual use any air motion (wind or even HVAC) would cause changes greater than 5uS.

Now as your supposed expertise in magnetics and loudspeakers..... Hospitality Electronics Supply carries glue, cones, surrounds and voice coils. So the ball of proof is now in your court.
That's only half the battle. What magnetic structure? I can easily make my own vc, but I need dimensions and tolerances for the gap it goes into.

Also, I am thinking about the former.. Does anybody know if an IR 50 watt laser can kerf 5 mil aluminum? I know copper is out as it reflects, but I was thinking of a slot pattern on the former to eliminate eddy current drag, a friend has a CNC laser.

I'll check that source, thanks. All the recone kits I googled were 100 bucks give or take, why waste my money on that when I can waste it on ten dollar gear efforts.

Jn
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Old 7th March 2019, 11:22 PM   #15115
Joe Rasmussen is online now Joe Rasmussen  Australia
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Originally Posted by jneutron View Post
The only technical explanation I could shoehorn into what he is doing is the possibility of ITD stabilization. Perhaps his system is good enough that localization is impacted by what he does. Perhaps he tried it (despite the explanation being incorrect) and found a clearer soundstage.
Hi Jn

Not sure how soundstage and localization came into the picture?

Note perhaps a softening of the tone? That would be good all round.

No, in my mind, as I have now stated a number of times, this is about distortion.

I think the reason that this has all happened in the last few days was when Richard Marsh mentioned the 8R resistor in parallel with an 8 Ohm speaker and I knew exactly what he meant. You can hear what that resistor does.

It also seems that many speaker designers (without telling) include parallel resistors inside commercial speakers, but other designers vehemently dislikes it, they consider it bad form. I went to see Ulrik Schmidt, SB Acoustics driver designer and brought up the point with him. He too said he knew speaker manufacturers were doing it, hush hush!

But it is very wasteful of power. It is a crude, but it does something. But the speaker industry don't want to talk about it openly. Me? I don't use parallel resistors, but EQ the current phase angle. Others think I do it to flatten the impedance, but in fact it is the current I am looking at.

So hopefully that will give you some context and maybe give you an idea where I am coming from.

So many people have heard that simple 8 Ohm resistor trick (it is even mentioned when using a Nelson Pass amp in a recent issue of Stereophile, using 16 Ohm with 16 Ohm speakers).

I am convinced that what we are hearing is that the amplifier's current is EQ'd and that it leads to lower distortion.

But how? You cannot ignore it when in a room full of people heard it. Even putting an 18 Ohm series impedance (a switchable Hypex NCore amplifier modified by Menno Vanderveen) at ETF17 (held in Denmark) and the whole room heard the amplifier being switched back and forth. I told Menno I believed the improvement was caused by a reduced current phase angle of the amplifier. He did not disagree. He is looking for the answer to this question too.

So please, everything I have posted in recent days (and even further back) is entirely down to one thing:

Distortion, and what is the mechanism for what we are hearing?

I believe that there is a rational explanation and if we can find it (join the search), then we shall all be better for it.

John is right, my world is very different from yours. And so is his I suppose. But the world needs guys like you too. But I am more a Faraday kind of guy, maybe you are more the Maxwell kind. Yet they became close friends.

Some quote Dylan, but I will quote Lennon: "Come together."

[Friday here, needs to make myself scarce and get to work, not yet retired.]
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Old 7th March 2019, 11:22 PM   #15116
Tournesol is online now Tournesol  Belgium
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Trying to calm down people that I respect or/and like in this forum, which are fighting together, I would like to make a diversion and ask a question that interest-me. A serious question about something I never tried: to drive an electro-dynamic speakers in current.

As all the speakers I had worked with seems to have been optimized to offer a flat acoustic response curve (as much as possible) with a flat *voltage* response curve, driving them in current will imply to correct the response curve in order to have the same current at each frequency out of a current source than with the voltage source. or, if you prefer, to have the same power at each frequency between the 2 amps. I hope I'm clear and you will agree with this working hypothesis.

Now, i've read and been told that the speaker will produce less distortion with the current source than with the voltage source. Why ? (What are the physical factors at work ?)
What is the difference between the two amps. I believe the damping factor. Right ?
So what about the impact on the waterfall ?

I apologize if my questions seems trivial, or ridiculous, I try to be virgin about the things I never experienced and learn as much as possible.
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Last edited by Tournesol; 7th March 2019 at 11:49 PM.
 
Old 8th March 2019, 12:19 AM   #15117
Joe Rasmussen is online now Joe Rasmussen  Australia
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Originally Posted by Tournesol View Post
I apologize if my questions seems trivial, or ridiculous, I try to be virgin about the things I never experienced and learn as much as possible.
If they are not trivial to you, then they are not trivial.

I will come back and make some comments later. But quickly, it is not about damping factor, and it is not so much about current drive versus voltage drive. I design amplifiers that typically have 2-5 Ohm output impedances (solid state front and tube output stages). So I do not lean towards straight-out current drive and more towards voltage. More later...
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Old 8th March 2019, 12:30 AM   #15118
Indiglo is offline Indiglo  Australia
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At the risk of being flamed to death:


The distortion comes from the non-linearity of the loudspeaker motor design.
Many patents have been applied either from engineering an improved voice coil assembly or the implementation of a feedback mechanism.


Some engineering type folks were trying to explain and provide soultions to this age old problem with the loudspeaker transducer several hundred pages ago.


JBL's differential drive transducer is one example of an engineering approach.

Trying to fix the distortion mechanism via the crossover is just fixing the symptom.
 
Old 8th March 2019, 01:33 AM   #15119
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by Joe Rasmussen View Post

I am convinced that what we are hearing is that the amplifier's current is EQ'd and that it leads to lower distortion.

But how? You cannot ignore it when in a room full of people heard it. Even putting an 18 Ohm series impedance (a switchable Hypex NCore amplifier modified by Menno Vanderveen) at ETF17 (held in Denmark) and the whole room heard the amplifier being switched back and forth. I told Menno I believed the improvement was caused by a reduced current phase angle of the amplifier. He did not disagree. He is looking for the answer to this question too.
Switching amplifiers too? I figure anyone could hear an 18 Ohm resistor switched in and out. You've departed from speakers again BTW. There exist many amplifiers that have virtually immeasurable change in distortion with output current phase angle (within reasonable limits certainly those of almost any speaker).
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Last edited by scott wurcer; 8th March 2019 at 01:36 AM.
 
Old 8th March 2019, 01:38 AM   #15120
RNMarsh is offline RNMarsh  Thailand
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Hi,

I often do simple Proof of Concept tests without refinements. What JR has done is a refinement. I was just curious to know if I am thinking on the right path or not. i did that maybe 15-20 years ago. There was even one Monster cable which included a parallel R at the cable end connector.

-RNM

:-)
-------------------------------

I think the reason that this has all happened in the last few days was when Richard Marsh mentioned the 8R resistor in parallel with an 8 Ohm speaker and I knew exactly what he meant. You can hear what that resistor does.

So hopefully that will give you some context and maybe give you an idea where I am coming from. The parallel 8 Ohm was one of those -- some 15 or more years ago I tried it.

"So many people have heard that simple 8 Ohm resistor trick (it is even mentioned when using a Nelson Pass amp in a recent issue of Stereophile, using 16 Ohm with 16 Ohm speakers).

-----------------------------


THx-RNMarsh

Last edited by RNMarsh; 8th March 2019 at 01:46 AM.
 

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