# More Math I Never Did

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Guest

Sat Dec 15, 2018 5:45 am

Inductors.

Where:

D=diameter
l=length
N=number of turns
L=inductance

Then it is L=(N^2 x D^2)/((18 x D) + (40 x l) <"ell", not one there<<

https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html

It says 0.43891 uH.

I got all these small coils, many are adjustable. I did not buy them per se, I did but as a package an just having too much time on my hands wonder if I can do anything with them. I wouldn't mind fucking around with some 315 MHz right now but this coil looks too small for that. The 315MHz is a frequency used for some RF remote controls. I got a receiver board here and wonder what I might do with it.

I don't deny that I have too much time on my hands and I do not deny that my education was not, umm, perfectly whatevered. Does that calculation seem right ? I will find some kind of device and make it oscillate, I have some fast transistors laying around. Not GHz but good enough for this I think.

Whatever. Bitch and moan or pick on me, or tell me what I ask. That is not clearly defined. Is that figure right is the min question. Whether or not I can count on that formula is a good thing to know.

Actually the problem is that it seems too easy, and this 18 times this and 40 times that, how in the fuck did that come about ?

Though I don't completely understand it I did study how the trig tables, sine and cosine, are derived. I found it fascinating but had to return the book. As such I am wondering if this is derived from measurements or theory.

Why the fuck would it be 18 times diameter and 40 times the length ? Just how did that happen ? We know how Ohm's law happened, we know about coulombs n shit. We know about capacitive, oh NOW, the plates of a capacitor. that is easier I think, area versus distance and all that. As it relates to Pi, well so does inductance, but the plates.

I dunno. So WTF, anyone want to tel me ? (and why the inductance formula came out in mH when they didn't say a damn thing about that ?)

John Larkin
Guest

Sat Dec 15, 2018 7:45 pm

On Fri, 14 Dec 2018 19:47:37 -0800 (PST), jurb6006_at_gmail.com wrote:

Quote:
Inductors.

Where:

D=diameter
l=length
N=number of turns
L=inductance

Then it is L=(N^2 x D^2)/((18 x D) + (40 x l) <"ell", not one there

https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html

It says 0.43891 uH.

I got all these small coils, many are adjustable. I did not buy them per se, I did but as a package an just having too much time on my hands wonder if I can do anything with them. I wouldn't mind fucking around with some 315 MHz right now but this coil looks too small for that. The 315MHz is a frequency used for some RF remote controls. I got a receiver board here and wonder what I might do with it.

I don't deny that I have too much time on my hands and I do not deny that my education was not, umm, perfectly whatevered. Does that calculation seem right ? I will find some kind of device and make it oscillate, I have some fast transistors laying around. Not GHz but good enough for this I think.

Whatever. Bitch and moan or pick on me, or tell me what I ask. That is not clearly defined. Is that figure right is the min question. Whether or not I can count on that formula is a good thing to know.

Actually the problem is that it seems too easy, and this 18 times this and 40 times that, how in the fuck did that come about ?

Though I don't completely understand it I did study how the trig tables, sine and cosine, are derived. I found it fascinating but had to return the book. As such I am wondering if this is derived from measurements or theory.

Why the fuck would it be 18 times diameter and 40 times the length ? Just how did that happen ? We know how Ohm's law happened, we know about coulombs n shit. We know about capacitive, oh NOW, the plates of a capacitor. that is easier I think, area versus distance and all that. As it relates to Pi, well so does inductance, but the plates.

I dunno. So WTF, anyone want to tel me ? (and why the inductance formula came out in mH when they didn't say a damn thing about that ?)

I have no idea of the origin of that equation. A true EM model of a
wound inductor would be a nightmare.

This one

https://hamwaves.com/inductance/en/index.html#input

seems to work pretty well, in that the Ls and Qs measure about right.

https://www.dropbox.com/s/cz8b1s8p397ww2g/Sol_2.jpg?dl=0

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Guest

Sun Dec 16, 2018 6:45 am

I almost dumped this thing. The question was, in part, how the answer got to be in milli or micro, but I looked and saw that the variables entered were <1, fractions of an inch. I guess that means that formula works in inches.. OK, but I just didn't think of it fast enough. The answer was adjusted to the nearest convenient decimal place.

Anyway, part of the reason I even asked is for speakers. Now let me tell you something. You take a sealed cabinet and put a low impedance woofer in it, it is going to suffer some low end loss which COULD be helped by a port or passive radiator.
but the rolloff is twice as bad when it goes under the resonant frequency. Could be 20dB/octave, who knows ?

With a sealed cabinet the rolloff is 3dB/octave. Or 6 depending on how you look at it. But if you look to the bottom octave it is not buried 16dB down like it is an a cabinet with a port or passive radiator, it actually has more output down there.

As such it can be reasonably equalized electronically. Trying to overcome 20dB is impossible, but say 9dB is not.

This does not have to happen in the amp. this EQ could be n the crossover. They put 3 ohm woofers in some speakers and with the coil in series can barely eek by with a 6 ohm rating. The impedance at 19KHz is like 2.5 ohms, but at 100Hz it is 40. They CAN claim a higher impedance because of that.

But what is happening is that the woofer is getting a tilted response, some maybe 15dB up in the lowest octave which will really bring it out in a sealed system because the thing rolls off at a reasonable rate, not like 20dB/octave. This works best with solid state amps and the higher the damping factor the better.

So that bottom octave CAN be had with 8" woofers and at 110dB. What happens with ported or passive radiator speakers is that they DO have greater output, but form the port odr passive radiator it is out of phase. They try to tel you it doesn't matter but they are full of shit. YOU COME AND LISTEN, I can demonstrate, well I will be able to soon.

Bottom line is fuck all this shit, I stick with the old designs. In my project list are a pair of Boston Acoustics A-150 and Audio Research AR-93Q. I got a pair of EPIs, I think 100C that have a great low end as do my Nova Six, ELCHEAPO Radio Shack speakers. And I prefer them to the biggest JBLs, Macs, almost anything in the mid/hifi range. No ports. Less efficient. But better sound. the bass is tight, it is almost surprising to some how well controlled the bass is yet still responsive to the lowest octave. Most ported speakers are like, m, , loose. You can control the woofer electronically but you can't control the air. With a sealed cabinet for the woofer, you CAN control the air. there is nothing like it. I stand by this until death, speakers should not have holes in the cabinet. Period.

If you heard my system you would not argue. (not saying you are but...)

So they can keep their little one note bass box and the balsa wood "speakers" and I will keep my three bucks that they are worth along with the three hundred they get the idiots to pay for their fucking junk.

Anyone wants to argue, we make a date at a REAL stereo shop.

Guest

Sun Dec 16, 2018 6:45 am

I went off on a tangent. Sorry. But that is for real. Fuck ports, give me coils !

Yuo cannot buy a really good speaker crossover coil with an air core. I want to but will have to wind it, thus my question.

John Larkin
Guest

Mon Dec 17, 2018 3:45 am

On Sat, 15 Dec 2018 21:00:02 -0800 (PST), jurb6006_at_gmail.com wrote:

Quote:
I almost dumped this thing. The question was, in part, how the answer got to be in milli or micro, but I looked and saw that the variables entered were <1, fractions of an inch. I guess that means that formula works in inches. OK, but I just didn't think of it fast enough. The answer was adjusted to the nearest convenient decimal place.

Anyway, part of the reason I even asked is for speakers. Now let me tell you something. You take a sealed cabinet and put a low impedance woofer in it, it is going to suffer some low end loss which COULD be helped by a port or passive radiator.
but the rolloff is twice as bad when it goes under the resonant frequency. Could be 20dB/octave, who knows ?

With a sealed cabinet the rolloff is 3dB/octave. Or 6 depending on how you look at it. But if you look to the bottom octave it is not buried 16dB down like it is an a cabinet with a port or passive radiator, it actually has more output down there.

As such it can be reasonably equalized electronically. Trying to overcome 20dB is impossible, but say 9dB is not.

This does not have to happen in the amp. this EQ could be n the crossover. They put 3 ohm woofers in some speakers and with the coil in series can barely eek by with a 6 ohm rating. The impedance at 19KHz is like 2.5 ohms, but at 100Hz it is 40. They CAN claim a higher impedance because of that.

But what is happening is that the woofer is getting a tilted response, some maybe 15dB up in the lowest octave which will really bring it out in a sealed system because the thing rolls off at a reasonable rate, not like 20dB/octave. This works best with solid state amps and the higher the damping factor the better.

So that bottom octave CAN be had with 8" woofers and at 110dB. What happens with ported or passive radiator speakers is that they DO have greater output, but form the port odr passive radiator it is out of phase. They try to tel you it doesn't matter but they are full of shit. YOU COME AND LISTEN, I can demonstrate, well I will be able to soon.

Bottom line is fuck all this shit, I stick with the old designs. In my project list are a pair of Boston Acoustics A-150 and Audio Research AR-93Q. I got a pair of EPIs, I think 100C that have a great low end as do my Nova Six, ELCHEAPO Radio Shack speakers. And I prefer them to the biggest JBLs, Macs, almost anything in the mid/hifi range. No ports. Less efficient. But better sound. the bass is tight, it is almost surprising to some how well controlled the bass is yet still responsive to the lowest octave. Most ported speakers are like, m, , loose. You can control the woofer electronically but you can't control the air. With a sealed cabinet for the woofer, you CAN control the air. there is nothing like it. I stand by this until death, speakers should not have holes in the cabinet. Period.

If you heard my system you would not argue. (not saying you are but...)

I don't like music. I never listen to it voluntarily.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

John Larkin
Guest

Mon Dec 17, 2018 3:45 am

On Sat, 15 Dec 2018 21:02:05 -0800 (PST), jurb6006_at_gmail.com wrote:

Quote:
I went off on a tangent. Sorry. But that is for real. Fuck ports, give me coils !

Yuo cannot buy a really good speaker crossover coil with an air core. I want to but will have to wind it, thus my question.

Why not do a crossover electronically, before the power amps?

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Guest

Mon Dec 17, 2018 8:45 am

>"Why not do a crossover electronically, before the power amps?"

Been done, is done. I screwed up, that impedance was at 19Hz, not KHz.

Active crossovers and multiple amps are the best way to go but are too complicated for most people.

>"I don't like music. I never listen to it voluntarily. "

Well you are more picky than I. I am quite picky about what I will feed my speakers. I also can't stand distortion. Yes my ears are half shot but I can still hear some things.

Now after I thought about it, wondering why the answer was in uH was stupid.. I put in the measurements and they are like .034 and all , below one. So instead of 0.000000000X H it was in uH. OK.

But what if I put the dimensions in metric ? They do not have different Henries as far as I know.

For example when I was playing around with BASIC I wrote a program that would recalculate the displacement of an ICE when bored out. In that one if the measurements were put in in English the result would be, if the input was metric then so would be the output.

This does not seem to apply here. If I put in 2.54 instead of 1, what then ? A metric Henry ? I find that hard to believe.

Anyway, this is what happens when idle hands find no Devil. And that is why I put it in basics. It doesn't belong in design or repair.

default
Guest

Mon Dec 17, 2018 2:45 pm

On Sun, 16 Dec 2018 18:18:25 -0800, John Larkin
<jjlarkin_at_highlandtechnology.com> wrote:

Quote:
On Sat, 15 Dec 2018 21:00:02 -0800 (PST), jurb6006_at_gmail.com wrote:

I almost dumped this thing. The question was, in part, how the answer got to be in milli or micro, but I looked and saw that the variables entered were <1, fractions of an inch. I guess that means that formula works in inches. OK, but I just didn't think of it fast enough. The answer was adjusted to the nearest convenient decimal place.

Anyway, part of the reason I even asked is for speakers. Now let me tell you something. You take a sealed cabinet and put a low impedance woofer in it, it is going to suffer some low end loss which COULD be helped by a port or passive radiator.
but the rolloff is twice as bad when it goes under the resonant frequency. Could be 20dB/octave, who knows ?

With a sealed cabinet the rolloff is 3dB/octave. Or 6 depending on how you look at it. But if you look to the bottom octave it is not buried 16dB down like it is an a cabinet with a port or passive radiator, it actually has more output down there.

As such it can be reasonably equalized electronically. Trying to overcome 20dB is impossible, but say 9dB is not.

This does not have to happen in the amp. this EQ could be n the crossover. They put 3 ohm woofers in some speakers and with the coil in series can barely eek by with a 6 ohm rating. The impedance at 19KHz is like 2.5 ohms, but at 100Hz it is 40. They CAN claim a higher impedance because of that.

But what is happening is that the woofer is getting a tilted response, some maybe 15dB up in the lowest octave which will really bring it out in a sealed system because the thing rolls off at a reasonable rate, not like 20dB/octave. This works best with solid state amps and the higher the damping factor the better.

So that bottom octave CAN be had with 8" woofers and at 110dB. What happens with ported or passive radiator speakers is that they DO have greater output, but form the port odr passive radiator it is out of phase. They try to tel you it doesn't matter but they are full of shit. YOU COME AND LISTEN, I can demonstrate, well I will be able to soon.

Bottom line is fuck all this shit, I stick with the old designs. In my project list are a pair of Boston Acoustics A-150 and Audio Research AR-93Q. I got a pair of EPIs, I think 100C that have a great low end as do my Nova Six, ELCHEAPO Radio Shack speakers. And I prefer them to the biggest JBLs, Macs, almost anything in the mid/hifi range. No ports. Less efficient. But better sound. the bass is tight, it is almost surprising to some how well controlled the bass is yet still responsive to the lowest octave. Most ported speakers are like, m, , loose. You can control the woofer electronically but you can't control the air. With a sealed cabinet for the woofer, you CAN control the air. there is nothing like it. I stand by this until death, speakers should not have holes in the cabinet. Period.

If you heard my system you would not argue. (not saying you are but...)

I don't like music. I never listen to it voluntarily.

Music evokes strong emotions in some of us. Some of us go to
irrational extremes to get a fix...

Wine Women and Song, are things worth consideration IMO.

John Larkin
Guest

Tue Dec 18, 2018 4:45 am

On Mon, 17 Dec 2018 07:50:52 -0500, default <default_at_defaulter.net>
wrote:

Quote:
On Sun, 16 Dec 2018 18:18:25 -0800, John Larkin
jjlarkin_at_highlandtechnology.com> wrote:

On Sat, 15 Dec 2018 21:00:02 -0800 (PST), jurb6006_at_gmail.com wrote:

I almost dumped this thing. The question was, in part, how the answer got to be in milli or micro, but I looked and saw that the variables entered were <1, fractions of an inch. I guess that means that formula works in inches. OK, but I just didn't think of it fast enough. The answer was adjusted to the nearest convenient decimal place.

Anyway, part of the reason I even asked is for speakers. Now let me tell you something. You take a sealed cabinet and put a low impedance woofer in it, it is going to suffer some low end loss which COULD be helped by a port or passive radiator.
but the rolloff is twice as bad when it goes under the resonant frequency. Could be 20dB/octave, who knows ?

With a sealed cabinet the rolloff is 3dB/octave. Or 6 depending on how you look at it. But if you look to the bottom octave it is not buried 16dB down like it is an a cabinet with a port or passive radiator, it actually has more output down there.

As such it can be reasonably equalized electronically. Trying to overcome 20dB is impossible, but say 9dB is not.

This does not have to happen in the amp. this EQ could be n the crossover. They put 3 ohm woofers in some speakers and with the coil in series can barely eek by with a 6 ohm rating. The impedance at 19KHz is like 2.5 ohms, but at 100Hz it is 40. They CAN claim a higher impedance because of that.

But what is happening is that the woofer is getting a tilted response, some maybe 15dB up in the lowest octave which will really bring it out in a sealed system because the thing rolls off at a reasonable rate, not like 20dB/octave. This works best with solid state amps and the higher the damping factor the better.

So that bottom octave CAN be had with 8" woofers and at 110dB. What happens with ported or passive radiator speakers is that they DO have greater output, but form the port odr passive radiator it is out of phase. They try to tel you it doesn't matter but they are full of shit. YOU COME AND LISTEN, I can demonstrate, well I will be able to soon.

Bottom line is fuck all this shit, I stick with the old designs. In my project list are a pair of Boston Acoustics A-150 and Audio Research AR-93Q. I got a pair of EPIs, I think 100C that have a great low end as do my Nova Six, ELCHEAPO Radio Shack speakers. And I prefer them to the biggest JBLs, Macs, almost anything in the mid/hifi range. No ports. Less efficient. But better sound. the bass is tight, it is almost surprising to some how well controlled the bass is yet still responsive to the lowest octave. Most ported speakers are like, m, , loose. You can control the woofer electronically but you can't control the air. With a sealed cabinet for the woofer, you CAN control the air. there is nothing like it. I stand by this until death, speakers should not have holes in the cabinet. Period.

If you heard my system you would not argue. (not saying you are but...)

I don't like music. I never listen to it voluntarily.

Music evokes strong emotions in some of us. Some of us go to
irrational extremes to get a fix...

It mostly annoys me.

Quote:

Wine Women and Song, are things worth consideration IMO.

No objection at all to women or wine.

The only other character that I've heard of that didn't like music was
the fictional British sea captain Horatio Hornblower.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Jeroen Belleman
Guest

Tue Dec 18, 2018 10:45 am

John Larkin wrote:
Quote:
On Fri, 14 Dec 2018 19:47:37 -0800 (PST), jurb6006_at_gmail.com wrote:

Inductors.

Where:

D=diameter
l=length
N=number of turns
L=inductance

Then it is L=(N^2 x D^2)/((18 x D) + (40 x l) <"ell", not one there

https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html

It says 0.43891 uH.

I hate it when they do that. First the formula obscures the
physics, and second it is not in SI base units. Both are sins,
in my eyes. It appears to be in inches and mH, rather than in
meters and henries.

It's another variant of Wheeler's formula for air-core inductors.
The scaling appears to be for multi-layer inductors, because
it is slightly different from the one I use for single-layer
inductors.

Jeroen Belleman

DemonicTubes
Guest

Wed Dec 19, 2018 12:45 am

On Monday, December 17, 2018 at 8:39:22 PM UTC-7, John Larkin wrote:
Quote:
I don't like music. I never listen to it voluntarily.

Music evokes strong emotions in some of us. Some of us go to
irrational extremes to get a fix...

It mostly annoys me.

Wine Women and Song, are things worth consideration IMO.

No objection at all to women or wine.

The only other character that I've heard of that didn't like music was
the fictional British sea captain Horatio Hornblower.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Do you have Aspergers? A couple of the most capable designers I have worked with do and are annoyed and irritated by just about any type of music.

John Larkin
Guest

Wed Dec 19, 2018 5:45 am

On Tue, 18 Dec 2018 15:16:37 -0800 (PST), DemonicTubes
<tlackie_at_gmail.com> wrote:

Quote:
On Monday, December 17, 2018 at 8:39:22 PM UTC-7, John Larkin wrote:
I don't like music. I never listen to it voluntarily.

Music evokes strong emotions in some of us. Some of us go to
irrational extremes to get a fix...

It mostly annoys me.

Wine Women and Song, are things worth consideration IMO.

No objection at all to women or wine.

The only other character that I've heard of that didn't like music was
the fictional British sea captain Horatio Hornblower.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Do you have Aspergers? A couple of the most capable designers I have worked with do and are annoyed and irritated by just about any type of music.

Probably not. I just don't like annoying noises.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Phil Hobbs
Guest

Fri Dec 21, 2018 3:45 am

On 12/18/18 3:54 AM, Jeroen Belleman wrote:
Quote:
John Larkin wrote:
On Fri, 14 Dec 2018 19:47:37 -0800 (PST), jurb6006_at_gmail.com wrote:

Inductors.
Where:

D=diameter
l=length
N=number of turns
L=inductance

Then it is L=(N^2 x D^2)/((18 x D) + (40 x l) <"ell", not one there

https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html

It says 0.43891 uH.

I hate it when they do that. First the formula obscures the
physics, and second it is not in SI base units. Both are sins,
in my eyes. It appears to be in inches and mH, rather than in
meters and henries.

Well, it's a variant of a formula from the National Bureau of Standards
in the 1920s. (I have a copy of the Bulletin C22 that has them.)

The usual simplified formula is

L(uH) = a**2 N**2/(9a + 10b),

where a is the mean radius of the winding, N is the number of turns, and
b is the pitch, both in inches.

So suck it up, cupcake. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

amdx
Guest

Fri Dec 28, 2018 3:45 am

On 12/20/2018 7:56 PM, Phil Hobbs wrote:
Quote:
On 12/18/18 3:54 AM, Jeroen Belleman wrote:
John Larkin wrote:
On Fri, 14 Dec 2018 19:47:37 -0800 (PST), jurb6006_at_gmail.com wrote:

Inductors.
Where:

D=diameter
l=length
N=number of turns
L=inductance

Then it is L=(N^2 x D^2)/((18 x D) + (40 x l) <"ell", not one there

https://www.electricaltechnology.org/2014/03/inductance-air-core-inductor-calculator.html

It says 0.43891 uH.

I hate it when they do that. First the formula obscures the
physics, and second it is not in SI base units. Both are sins,
in my eyes. It appears to be in inches and mH, rather than in
meters and henries.

Well, it's a variant of a formula from the National Bureau of Standards
in the 1920s.  (I have a copy of the Bulletin C22 that has them.)

The usual simplified formula is

L(uH) = a**2 N**2/(9a + 10b),

where a is the mean radius of the winding, N is the number of turns, and
b is the pitch, both in inches.

So suck it up, cupcake. ;)

Cheers

Phil Hobbs

Here's a handy program with many useful features, calculate turns, or
turns per inch, inductance and more. Click on >info< at the bottom of
each section to get a clue what the handy functions are. It shows Q and
handles Litz wire also.
If you want to go to the main site, see the the last link on the left
side of page here, > http://ham-radio.com/k6sti/

Two years ago I did an experiment comparing 5 coils with 7 to 12 turns
per inch to find what the optimum turns per inch is for highest Q. I
ended up winding a 6th coil with 11 turns,
My data showed 10 turns per inch gave the highest Q at 1MHz.
This program is in agreement with my experiment.
My best 240uh coil had 10 turns of 660/46 litz on a 6.62" diameter
polystyrene coil. Q measured 1400 at 1MHz and 1475 at 800kHz on my
Q meter.
Mikek

Guest

Wed Jan 09, 2019 9:45 pm

On Tuesday, December 18, 2018 at 8:19:20 PM UTC-8, John Larkin wrote:
Quote:
On Tue, 18 Dec 2018 15:16:37 -0800 (PST), DemonicTubes
tlackie_at_gmail.com> wrote:

On Monday, December 17, 2018 at 8:39:22 PM UTC-7, John Larkin wrote:
I don't like music. I never listen to it voluntarily.

Music evokes strong emotions in some of us. Some of us go to
irrational extremes to get a fix...

It mostly annoys me.

Wine Women and Song, are things worth consideration IMO.

No objection at all to women or wine.

The only other character that I've heard of that didn't like music was
the fictional British sea captain Horatio Hornblower.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

Do you have Aspergers? A couple of the most capable designers I have worked with do and are annoyed and irritated by just about any type of music.

Probably not. I just don't like annoying noises.

--

John Larkin Highland Technology, Inc

lunatic fringe electronics

You dislike even Chillstep and Metal?

Michael

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