John Curl's Blowtorch preamplifier part IV

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Crossovers WILL effectively destroy measured square wave response, if more than 6dB/octave, but 'transient perfect' designs (usually active) can also work OK. The problem is that 6dB/octave allows a lot a 'bleed' between the two speaker drivers, and is not considered very practical with many direct radiator based designs for a number of reasons, including establishing ultra flat frequency response.
I personally prefer 18/dB/oct Bessel roll off Xovers, when I can't use 6dB/oct. There was an interesting paper from Yamaha, given at an AES in 1976, that made me try them with some success. Isn't that when I first met you, Zung?
 
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May-be, on your side, you could try to say something interesting about audio, apart your LMDBT and your crazy crusade against audio pros ?
You are one of the few who attack constantly others, never providing anything useful or positive.
Attack, like the ones quoted below?
"Do you remember the two old guys, Statler & Waldorf in the muppet show ? He his the two all alone.
With a big difference: They were funny.
"
"He guys, do-you realize we all are arguing deaf, without reading what the others wrote ?"

Oh, yes, please move on !
No thank you. I like this forum.
You on the other hand gave it a try: "I join the long list of those who, before me, reacted the same way, harassed by the same few people: Goodbye.https://www.diyaudio.com/forums/the...wtorch-preamplifier-iii-2330.html#post5832646"
 
Crossovers WILL effectively destroy measured square wave response, if more than 6dB/octave, but 'transient perfect' designs (usually active) can also work OK. The problem is that 6dB/octave allows a lot a 'bleed' between the two speaker drivers, and is not considered very practical with many direct radiator based designs for a number of reasons, including establishing ultra flat frequency response.
I personally prefer 18/dB/oct Bessel roll off Xovers, when I can't use 6dB/oct. There was an interesting paper from Yamaha, given at an AES in 1976, that made me try them with some success. Isn't that when I first met you, Zung?

John,
Have you ever paid attention to crossovers where one part has Fr1= H(s) and the complementary part Fr2 = 1- H(s).
In that case you will have a perfect transition no matter how steep H(s) is because [H(s)]+[1 - H(s)] = 1.

Hans
 
It's a matter of an elephant memory (a figure of speech, elephants don't excel). 45 years later, I can still derive the 5 fundamental semiconductor equations starting from the Boltzmann transport equation, or transform the Schwarzschild metric around a black hole using the ingoing/outgoing Eddington–Finkelstein coordinates and determine the new geodesics around the event horizon, or prove the Bell's theorem, to name a few. Didn't make me a CEO with a golden parachute, tough ****, but it helped me living to my expectations for as long as it's written in my genes :rofl:.

Now, back to audio myths and legends 😀.

And yet you hang around here with us, a bunch of ignorant dumbo’s.

Having you here Syn08, I have come to realize, means we are truly blessed.
 
New Old info for QUAD ESL owners. Their HV supply is not regulated.
The HV supply affect the HF response progressively as the Hv is reduced.

If you use a 'variac' on the ESL power, you can change the HF response by varying the ac line voltage. When I adjust the ac line voltage upward, i get flat response >20Khz. If I adjust the ac line voltage to a lower voltage, the response drops off well before 20KHz.

I doubt if any magazine testing the QUADs checked and adjusted their ac line voltage before running FR tests.


THx-RNMarsh
Intriguing information, but I don’t understand it.

The HV voltage is only to supply the membrane with a constant charge despite its movement between the two stators, independent of frequency.

To achieve this constant charge, a very high ohmic resistor is placed in series with the membrane.
A higher HV voltage will lead to a higher charge, increasing the gain of the LS somewhat.
So when the membrane charge would drop for whatever reason, gain for all frequencies will drop to my feeling and not just the high frequencies.

The parts that are determining the frequency response are audio transformers and filters that have nothing to do with the HV voltage.

Maybe I’m overlooking some important thing, so maybe you can fill in the gap or provide a link.

Hans

P.s. Looking at the power supply, I see two VDR’s in the power line.
So there is even some voltage regulation.
 
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What do other members think about that type of behavior, are we all going to start doing too so we can fight back?
I remember your use of psychological terms to describe another member whom you've never met, which were deleted by the forum mod/s due to the severity. You do remember that page and "Mark: why do you so want to be hall monitor in the lounge? It's an honest question as this thread seems to be affecting you badly. In the last day (at least UK time) you've started off with diagnosing a personality disorder and ended with nearly threatening a moderator.", don't you?

John, I asked Richard whether he'd ever measured square waves from his speakers and he immediately started talking about crossovers,
That would be called "dodging".
 
@Markw4: you are no saint anymore. So really the pot/kettle bit is not helping anyone. Ignore or rise above.

Sorry, Bill. I wish I could engage in civil conversation with you, but it would leave an opening for Syn08's attack. In case you didn't notice, at first when he came back and started attacking people, I tried doing exactly as you now suggest. It didn't work.

Look at what just happened here: a short time ago Syn said he didn't want to awaken someone so he tried being civil for a day or three. He can't stand other people speaking what they sincerely believe to be the truth, so he starts cursing and making up exaggerated claims to the effect that lies are being told to help out somebody's audio business. His claims aren't true, and he is jumping to conclusions.
 
John,
Have you ever paid attention to crossovers where one part has Fr1= H(s) and the complementary part Fr2 = 1- H(s).
In that case you will have a perfect transition no matter how steep H(s) is because [H(s)]+[1 - H(s)] = 1.

He designed one back in the good old days - Symmetry Crossover.

I have worked with this as well, and sometimes it gives results, but
routinely the phase response of the drivers themselves joined with
low slopes is a problem.
 
Of course Hans, John Meyer and I used it with our reference 3 way horn loaded speaker with 3 separate amps back in 1974. Dr. Ashley published it in the AES back in the '60's, and later, I designed a 'Transient Perfect' Xover for Symmetry in 1977, and still later in 1984 or so, Vendetta Research made an inexpensive product with the same technology. Unfortunately these Xovers are problematic with more compromised speakers and and their effective interface, such as a direct radiator woofer with a horn mid-range. Big trouble! At least for me.
 
Sorry, Bill. I wish I could engage in civil conversation with you, but it would leave an opening for Syn08's attack. In case you didn't notice, at first when he came back and started attacking people, I tried doing exactly as you now suggest. It didn't work.
When I first joined the forum, certainly people really annoyed me (and still do). Luckily only one posts on this thread. Back then I gave as good as I got and got my knuckles rapped a few times. Then I realised that this is an audio forum. Somewhere for guys and gals who like solder fumes and sawdust to gather and discuss how to make music reproduction setups. It doesn't matter in the big picture. So with that epihany behind me I just ignore them now. No need to raise my blood pressure on their account. I have kids to do that for me.



Ok I still get a little cheeky when the odd windbag needs some air letting out but in general water off a slippery thing.


He can't stand other people speaking what they sincerely believe to be the truth,
If you have nothing to sell what's to worry about. If someone believes the truth to be in contradiction of Maxwell, Shannon, Fourier etc then there are a number of people on here, not just the piled high and deeps who will pull people up.



There is so much to investigate using real science, why invent flooby dust? I seriously hoped JN would discuss balanced interconnect and ground loops but he decided to argue zip cord which no one actually uses. Go figure. But no real loss to cloth eared me.
 
BTW, Steve Albini (one of the music producers I deeply respect, together with Ian MacKaye and a few others) offers a one year of training for the "audio professional" wannabes in his Chicago studio. Half of this time is dedicated to understanding, adjusting and repairing studio equipment,


If it ever makes it off the bench and into a box I have a preamp in build that is entirely done on pro audio principles. Balanced, lots of 8 legs and THAT chips and EQ. I don't need to run 50ft interconnects, but good to know I could! I have a number of reasons for having this as a baseline including upsetting delicate souls who cringe at even one extra gain stage. But I do expect Hans balanced MC headamp into a focusrite Scarlet to be just as good and more heretical.
 
John,
Have you ever paid attention to crossovers where one part has Fr1= H(s) and the complementary part Fr2 = 1- H(s).
In that case you will have a perfect transition no matter how steep H(s) is because [H(s)]+[1 - H(s)] = 1.

Hans
Unless very specific conditions are met, the 1-H(s) reponse is only 1st order. With these conditions met, one can achieve, for example, 2nd order slopes for both. But those functions don't really work as there is huge overlap, the individual responses peak 3dB or more and the phase difference is a whopping 120 degrees.
Edit: see for example http://www.bodziosoftware.com.au/Multi.pdf
 

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Of course Hans, John Meyer and I used it with our reference 3 way horn loaded speaker with 3 separate amps back in 1974. Dr. Ashley published it in the AES back in the '60's, and later, I designed a 'Transient Perfect' Xover for Symmetry in 1977, and still later in 1984 or so, Vendetta Research made an inexpensive product with the same technology. Unfortunately these Xovers are problematic with more compromised speakers and and their effective interface, such as a direct radiator woofer with a horn mid-range. Big trouble! At least for me.

Thank you John,

Hans
 
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