ruffrecords

  That said I push the phase button on a Neve 1081 to fix the polarity of a top and bottom snare mic on one of the pream modules.    Now that I’ve said that I guess I’ll never work in this business again. ;D.   Some body stop me!  LOL
I see this snare miced top and bottom thing and the need to flip the phase/polarity switch a lot. The interesting thing is that whenever you mic a snare top and bottom you run into phase problems not polarity ones. At some frequency the distance between the mics will be half a wavelength so even if both mics have the same polarity their outputs will be 180 degrees out of phase with each other. Only if the path lengths from the source of the snare sound to the top mic and to the bottom mic are identical will there b no phase difference. And given the shape of the snare drum this is very difficult to achieve.

Edit: and if you use room mics too......

Edit: Remember a half wavelength at 1KHz is just 6 inches.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


abbey road d enfer

Re: Low output ribbon/ dynamic microphone phantom-powered circuit
« Reply #41 on: January 20, 2020, 06:40:40 PM »
Why I put the phase switch in the circuit is because the mic might somehow be reverse-phased as compared to a second mic used at  the same time. I am not mistakenly reversing pin 1 with either pin 2 or 3. I am simply reversing the two wires of the capsule-pins 2 and 3. I have made a few preamps where I add a phase-reversal switch and the sound does change. Not a lot but it does change. It's just a coil and reversing the two wires should not change the sound but there is a subtle change in sound. Not a hum sound but, using headphones, I hear a slightly lowering in bass frequencies or even an out of phase sound. Don't doubt me. I have been doing this for years-decades actually and I hear a slight difference using only one microphone  and switching its two leads.
So you are listening via two paths, one lectronic and one via air and bone conduction. Indeed when you reverse the polarity of one of teh paths, something is bound to hapeen.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

Re: Low output ribbon/ dynamic microphone phantom-powered circuit
« Reply #42 on: January 20, 2020, 07:50:26 PM »
... one lectronic and one via air and bone conduction. Indeed when you reverse the polarity of one of teh paths, something is bound to hapeen.

I bet more would happen if you chose the bone conduction path to switch polarity on.

Whoops

That said I push the phase button on a Neve 1081 to fix the polarity of a top and bottom snare mic on one of the pream modules.   

Hi fazer
I also vouch on the Free Hall pass for you,
I actually gave a call to the central offices of the International Studio Police and told them they had my word that you are an experienced Engineer and that you totally understand the concepts of Polarity and Phase.
They will send a "Distinction" Diploma in your name

 ;D

Although the concepts were not directed to you or John, they are relevant to a new member that I'm trying to help in this thread, that is having a problem in wiring a Polarity reverse switch on a mic circuit, and unlike yourself and most of us doesn't understand the concepts of phase and polarity.
Learning that and making it more clear might help with the problems he has with the circuit or not. But I think it might be relevant to achieve a fix
« Last Edit: January 20, 2020, 08:20:35 PM by Whoops »

Whoops

The interesting thing is that whenever you mic a snare top and bottom you run into phase problems not polarity ones. At some frequency the distance between the mics will be half a wavelength so even if both mics have the same polarity their outputs will be 180 degrees out of phase with each other.

yes,
but not in all the frequencies, overall if you change the Polarity of one mic relative to the other (top and bottom) you get more Low Mids and body of the snare (compared to not flipping polarity). This is what I generally find with the mics and position I use

Saying this, you are right, it's a Phase issue,
in the studio when I mix I will move or align the waveforms (DAW) of top and bottom mic and flip polarity, and them check them against the Overheads or room mics. Check them by ear and visually the waveform also, try stuff and listen again. Sometimes I align the overheads also with the snare mics if I want a tighter sound for a song.
Sometimes I delay them from the snare mics even longer if I want more ambience, well I try and listen, and in the end I choose what I think sounds best for the song.

This is a nice tool in the analog realm:
https://littlelabs.com/ibp.html

But when doing Live sound , I will just flip the Polarity of one of the snare mics, and I find that's good enough.
Overheads usually have quite a good amount of HP filtering when doing Live PA sound
« Last Edit: January 20, 2020, 08:34:12 PM by Whoops »

abbey road d enfer

Although the concepts were not directed to you or John, they are relevant to a new member that I'm trying to help in this thread, that is having a problem in wiring a Polarity reverse switch on a mic circuit, and unlike yourself and most of us doesn't understand the concepts of phase and polarity.  Learning that and making it more clear might help with the problems he has with the circuit or not.
As a mod, I suscribe 100% with this approach. Our group is very much dedicated to education and busting myth. It starts with proper terminology.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

abbey road d enfer

The interesting thing is that whenever you mic a snare top and bottom you run into phase problems not polarity ones.
Both. Distance between mics in a typical drum set-up is about 1 meter All frequencies below 170Hz will be "polarity-sensitive". Indeed, everything above 170Hz will be "phase-sensitive" too. For phase issues to become "problems", the levels picked up from a particular source must be comparable (typically within ca. 10 dB). The usual fix is via balancing, either electrically or acoustically, and EQ.
The two main causes for concern are the kick and the snare, because most often the SE tends to balance the mics in a pair almost equally. Actually it is wise to EQ the mics in a complementary way, boosting the desirable qualities (oomph in the distant kick mic and attack in the batter mic) and attenuating the less desired. Same for the snare, where the top mic takes care of the skin and the bottom one favours the wires.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

fazer

Quote
Now that I’ve said that I guess I’ll never work in this business again. ;D.   Some body stop me!  LOL

Haha  :D  You'd get a free hall pass if it were up to me. 
As would everyone else. 

Quote
Hi fazer
I also vouch on the Free Hall pass for you,
I actually gave a call to the central offices of the International Studio Police and told them they had my word that you are an experienced Engineer and that you totally understand the concepts of Polarity and Phase.
They will send a "Distinction" Diploma in your name

Thank you gentlemen for coming to my defense.  Very much appreciated. 
I'm told I have to take a vocabulary test by the principle and vow to learn the new terminology.   ;)

Seriously learning the audio foreign language is the first step in progressing in the field.   I fully support that idea.   

It seems like we have taken this thread over from its original intention.  So lets talk politics.   No lets not.

Lennie

Re: Low output ribbon/ dynamic microphone phantom-powered circuit
« Reply #48 on: January 23, 2020, 08:27:51 PM »
As I already told you in the previous post what you mean is "Polarity Reverse" , "reverse-phased" is something that doesn't exist

I know exactly what you mean. I use a polarity-reversing switch in  the circuits I have built. But if two loudspeakers are wired in parallel and you reverse the wires of one of the speakers, wouldn't this make them out-of-phase with each other? They are not 'out of polarity' with each other.

Whoops

Re: Low output ribbon/ dynamic microphone phantom-powered circuit
« Reply #49 on: January 23, 2020, 10:21:41 PM »
wouldn't this make them out-of-phase with each other?

No.

The signal that one speaker outputs is with the polarity reversed compared to the other.

When you are listening in the center of the 2 speakers (and sound reaches you ears at the same time from both speakers) if you move 1 meter to one side then you ears are receiving the sound of one speaker with a phase difference relative to the other, and that is independent of having both speaker with the same Polarity or not.

Understand that "out-of-phase" doesn't exist although a lot of people use that term wrongly when they mean in reality "Reverse Polarity"

Well,
back to your circuit, can you do the recordings so we help you out troubleshoot the circuit?
« Last Edit: January 23, 2020, 10:28:36 PM by Whoops »


Lennie

No.

The signal that one speaker outputs is with the polarity reversed compared to the other.

When you are listening in the center of the 2 speakers (and sound reaches you ears at the same time from both speakers) if you move 1 meter to one side then you ears are receiving the sound of one speaker with a phase difference relative to the other, and that is independent of having both speaker with the same Polarity or not.

Understand that "out-of-phase" doesn't exist although a lot of people use that term wrongly when they mean in reality "Reverse Polarity"

Well,
back to your circuit, can you do the recordings so we help you out troubleshoot the circuit?
For weeks I have  been searching for  a wiring diagram so that I could build a circuit powered from the phantom power from my mixer but none of the 48 volts gets to the dynamic or ribbon mic.  I have come up with the perfect 4-transistor circuit.  The low level from my Shure SM7 is boosted by more than 20db which is enough so that there is no need to increase the gain control of my mixer and therefore not increase the noise level.  It uses 4 fet transistors and 3 resistors and 2 caps.  Really easy to build.

I am getting just a little confused. Thank you everyone who replied to my post.  I don't have a problem with my circuit.  As a matter of fact I have 4 orders so far from people who have heard the preamps I have built and want to purchase their own from me. I am leaving this forum for the time being. Best wishes to everyone.




Whoops

I don't have a problem with my circuit. 

You had low-end loss on one position of the Polarity switch.

So how did you solve it?

Your solution might help another member in the future that might get stuck with the same problem.

fazer

Quote
I am leaving this forum for the time being. Best wishes to everyone.

Hey Lenny Im glad to hear you have good working preamp boosters.  Why we all went south on things is Im not sure.  I hope you come back to this forum someday.  Its not like this always.   If you are selling your boards as a Kit,  I would be interested in one  for an old RCA mic I have.  An API does not have quite enough gain at times.  I love how a ribbon can completely hide the sibilance from a female talking voice without doctoring the EQ constantly.   Thanks for your contribution to the tread.

Ricardus

So like, wow. People scared him away. And here I wanted to build a pair of his circuits. Cheesum crimers.
Audio mastering for hire..

Whoops

Wouldn't believe so, learning doesn't scare anyone away,
and I'm pretty sure there's a lot of circuits around to keep you well Entertained

 ;)

Lennie

So like, wow. People scared him away. And here I wanted to build a pair of his circuits. Cheesum crimers.

I guess that you might say I was scared away.  Some day I will tell you why. Anyway, I have built three of the circuits and they have surprised the people who heard the difference in gain level and low noise. I have added a blue LED connected via two 1 meg resistors-one each to pin two and pin three of the male XLR. It must be a blue or otherwise clear bright LED. I don't know why though.  Len.
« Last Edit: January 26, 2020, 01:37:08 PM by Lennie »

abbey road d enfer

I guess that you might say I was scared away.  Some day I will tell you why.
You don't need to. Usually that means putting the blame on those who gave answers you don't like.  You ask questions, people give answers, they may not please you, that's the game.

Quote
  I have added a blue LED connected via two 1 meg resistors-one each to pin two and pin three of the male XLR. It must be a blue or otherwise clear bright LED. I don't know why though.
Powering leds with about 60uA requires very high efficiency types. Normal LED's operate at about 100 times more current. You can find high efficiency LED's in all the usual colours, green, red, amber, yellow, though.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

You don't need to. Usually that means putting the blame on those who gave answers you don't like.  You ask questions, people give answers, they may not please you, that's the game.

A person should be able to defend their circuit, justify why they did what they did.   I personally learn a lot when my stuff is scrutinised.    If I didn't want the flack from the big guns on here, I wouldn't post it.


 

If I didn't want the flack from the big guns on here, I wouldn't post it.

Ok, take this!

flak= german for FLug Abwehr Kanone  = antiaircraft gun

#smartass mode off  ;D

I appreciate the correction   :)


 

Related Topics

  Subject / Started by Replies Last post
9 Replies
3861 Views
Last post June 05, 2005, 04:22:26 PM
by
2 Replies
3473 Views
Last post August 10, 2005, 08:26:51 PM
by mfdu
0 Replies
1869 Views
Last post September 10, 2006, 11:50:27 PM
by PRR
17 Replies
5850 Views
Last post May 29, 2009, 12:10:31 AM
by dkelley