Possibly really hifi query re mono listening

[Kosmische]

Mods

Please feel free to stick this in another forum - not sure which would be the right one.

As I've said in the header, this might be a more hi-fi type question but I was sure the folks on the forum would be able to help.

So - to say a little more about myself, I am a passionate music lover. I play the piano and previously played drums and saxophone. I was however born entirely deaf in one ear.

When I listen to CDs etc on my hi-fi, I just listen in stereo. I've placed one speaker slightly further forward than the other, and have adjusted the balance as well. I don't know how much I'm still missing of the recordings I'm listening to, even so.

However what prompts this email was that I was listening to a King Crimson CD last night on headphones. I use a separate headphone amp which maybe isn't such great quality, and I had a cable made up by someone one of your kind posters previously recommended to me, to enable mono listening.

My issue is that I noticed that I was missing parts of the music that I know are definitely there, as I've heard them clearly when listening on speakers. I actually wondered whether I was listening in stereo but when I swapped the headphones around I wasn't sure if there was any difference.

Is my perception that various parts of the music are missing just an expected function of listening in mono? If so, is there I can do about this? Would it make any difference if I spent some money on a better amp that has a dedicated mono option eg one of the SPL range?

Hope someone can help as I do love to listen on headphones!

[James Perrett]

If the polarity of the signal is reversed in one channel compared to the other then they will cancel out when the signals are summed to mono. That's why it is often handy to be able to choose how a mono signal is derived and a good monitor controller will offer switchable choices of listening to both channels, one or the other channel or even one channel subtracted from the other.

[RichardT]

Is there a reason why you want to listen in mono on phones? Do you not like the stereo effect on phones?

[zenguitar]

Is there a reason why you want to listen in mono on phones? Do you not like the stereo effect on phones?

The OP is deaf in one ear.

Andy

[ef37a]

"In the Court" was released in '69 and so it is likely that some parts of the mix were 'phase flipped'. People back then were listening to records on mono Dansettes (bleugh!) and would never notice the missing parts. Equally when they got a stereo system they would not notice. Only when you have the ability to switch instantly between mono and stereo would the problems be heard.

This is why the Doc always castigates the designers of monitor controllers if they omit a mono check button!

I have not heard that record for years! I have the original vinyl but no CD, must get one.

Dave.

[Hugh Robjohns]

I don't know which album you were listening to but, as others have said, if you're listening to an electrically summed mono and parts are missing the only reason can be that those parts are carried in opposite polarities on the two channels -- something that is done occasionally to create a super-wide effect in stereo.

If you can identify the KC album and track perhaps we can confirm if that is the case.

[RichardT]

Is there a reason why you want to listen in mono on phones? Do you not like the stereo effect on phones?

The OP is deaf in one ear.

Andy

Ah - sorry for missing that, Kosmische.

[Drew Stephenson]

This is probably a reflection of my limited brain power more than anything else, especially before my second coffee, but I would have expected a slightly different sound from an electrically-summed-to-mono source than a two-speakers-in-a-room source because of the interactions of the room (and any head-related transfer function for anything other than perfect side-on positioning)?

[Ariosto]

If the polarity of the signal is reversed in one channel compared to the other then they will cancel out when the signals are summed to mono. That's why it is often handy to be able to choose how a mono signal is derived and a good monitor controller will offer switchable choices of listening to both channels, one or the other channel or even one channel subtracted from the other.

As we are talking about inverted phase I would like to check that I am on the right track. I make mono (single channel) recordings of spoken voice. I have found that using the back of my R101 Royer ribbon mic works very well for my voice. When I edit in Reaper I invert the phase. Is this correct? It sounds very good so I'm hoping that this is the way it should be done.

[ef37a]

If the polarity of the signal is reversed in one channel compared to the other then they will cancel out when the signals are summed to mono. That's why it is often handy to be able to choose how a mono signal is derived and a good monitor controller will offer switchable choices of listening to both channels, one or the other channel or even one channel subtracted from the other.

As we are talking about inverted phase I would like to check that I am on the right track. I make mono (single channel) recordings of spoken voice. I have found that using the back of my R101 Royer ribbon mic works very well for my voice. When I edit in Reaper I invert the phase. Is this correct? It sounds very good so I'm hoping that this is the way it should be done.

Signal phase, or more correctly, 'polarity' has to be relative to another signal (though the beardy tweaky hi fi nutters have been banging on about 'absolute phase' for decades, I don't think anyone has ever proved it a detectable reality?)

If the rear of your Royer sounds better to you than the front then do that! There is no need to flip the polarity that I can see?

Dave.

[Hugh Robjohns]

I make mono (single channel) recordings of spoken voice. I have found that using the back of my R101 Royer ribbon mic works very well for my voice. When I edit in Reaper I invert the phase. Is this correct? It sounds very good so I'm hoping that this is the way it should be done.

It's completely unnecessary, unless you're bothered about preserving the 'absolute phase' of the recording -- in other words making sure that a compression wave arriving at the microphone generates a compression wave leaving the speaker. Some people claim to be sensitive to the absolute polarity of soundwaves... but in my experience what they hear is more often due to non-linearities of the loudspeaker's behaviour!

Nevertheless, as the rear of a ribbon is of the opposite polarity to the front, if you're using the rear side you can invert the polarity (phase varies with frequency, and so despite the popularity of the term, "invert the phase", what you're actually doing is inverting the polarity!) to maintain absolute polarity of the recording.

[ef37a]

Morning Hugh, I know that in really 'professional' gear such as mixers, great pains are taken to preserve absolute polarity from any input to any output but is the same care taken with lesser equipment?

There are millions of hi fi amps and interfaces and other audio kit 'out there' and I cannot recall seeing a claim in a handbook that boasted "Absolute phase is preserved" (they would say "phase"). Nor can I remember any review of anything anywhere that did a test for it!

So, is 'AP' a property that all manufacturers follow in all their products so that 'we' don't have to think about it? I do know for a fact that guitar amplifiers do not preserve AP between brands and not even between different models of the same brand!

Dave.

[Hugh Robjohns]

There are millions of hi fi amps and interfaces and other audio kit 'out there' and I cannot recall seeing a claim in a handbook that boasted "Absolute phase is preserved" (they would say "phase").

I have, and some certainly do mention it, particularly amongst the higher-end gear. It's not something that budget hi-fi is going to worry much about, but I think the designers of the better stuff do try and maintain the same output polarity as the inputs.

Being me, I have checked my various hi-fi products and most do maintain absolute polarity. One notable exception amongst my own gear is a Meridian 502 (balanced) preamp which does maintain AP for all the main outputs, but the second tape loop is inverted for some reason!

Most audio mixers maintain AP for the main outputs, but it's surprisingly common to find (impedance balanced) Aux outputs are inverted, and sometimes the direct outputs (if present) and insert sends are, too. It all depends on how many op-amp stages are in the signal path, as most stages are configured to invert the polarity so you need an even number between input and output!

[Ariosto]

Many thanks for all that information, so I probably do not need to "invert the polarity" - to use the correct term. I must admit that could not hear any difference when I inverted the polarity. I only record in mono these days, unless it's a music recording, due to the requirements of the organisation that stores the material on their server.

[Ariosto]

Just one more point - if I was recording two people, one on front and the other on the back of the ribbon mic, I presume I would have to invert the back of the mic recording when editing in the DAW?

[Wonks]

Presumably you mean using the same mic but at different times?

No automatic reason to polarity invert one. Use your ears. Two people singing the same tune will have inherent timing and pitch differences, so it's very unlikely that the polarity of the mic will make much difference.

You are only likely to need to require doing so if you are using two of the same type of mic to record the same source at the same time, one front of mic and one back of mic, say to compare the tonality.

[Tim Gillett]

I remember as a 12 year old being briefly "on air" in a local radio station to receive a prize I'd won in a phone in competition. The DJ was on one face of the big studio ribbon mic and me on the other. I think that was pretty standard interview practice many years ago and a good use of the figure 8 pattern.

[Hugh Robjohns]

Just one more point - if I was recording two people, one on front and the other on the back of the ribbon mic, I presume I would have to invert the back of the mic recording when editing in the DAW?

If you're talking about using a single mic, one person each side, then no! There's no need or point, and trying to invert the polarity each time your guest is talking would potentially mess up the ambient acoustics at the edit points too!

As Tim says, it was standard practice (and actually still is in some corners of the BBC) to have a presenters on each side of a fig-8 ribbon. It's a well proven technique, and you obtain a balance by moving the mic closer to the weaker speaker, or moving the speakers closer or further away.

Matching 'phase' only becomes important when you have two (or more) mics picking up the same sound source...

So a classics are situations like mixing top and bottom mics on a snare drum, or combining two mics at different positions in front of a guitar amp.

[Ariosto]

Thanks Hugh - that is totally clear now.

[Kosmische]

"In the Court" was released in '69 and so it is likely that some parts of the mix were 'phase flipped'. People back then were listening to records on mono Dansettes (bleugh!) and would never notice the missing parts. Equally when they got a stereo system they would not notice. Only when you have the ability to switch instantly between mono and stereo would the problems be heard.

This is why the Doc always castigates the designers of monitor controllers if they omit a mono check button!

I have not heard that record for years! I have the original vinyl but no CD, must get one.

Dave.

It was actually a later one - Larks Tongues in Aspic. I was listening to the first, fourth and sixth tracks.

Who knows what that band could have become if Jamie Muir had stayed with them instead of buggering off to become a Buddhist monk.....!

[Kosmische]

If the polarity of the signal is reversed in one channel compared to the other then they will cancel out when the signals are summed to mono. That's why it is often handy to be able to choose how a mono signal is derived and a good monitor controller will offer switchable choices of listening to both channels, one or the other channel or even one channel subtracted from the other.

Sorry but the technicalities here are a bit beyond me but are you saying I could get something that might help with my problem? I'm not sure what a monitor controller is, I'm ashamed to say! Would you be able to recommend one and could you even show a pic of one?

I do recall I contacted one supplier - Studiospares, maybe - and they said they wouldn't recommend just a re-wired headphone cable but rather a device which might well have been the type of thing you're talking about. However, just to confuse me even further the guy who eventually did make up my modified headphone cable poo-pooed the idea of anything more complicated than a cable.

[Hugh Robjohns]

I've not checked those tracks to confirm opposite polarity content, but assuming that is the issue, a monitor controller won't help. Anything that sums both channels electrically -- whether a mono button on a monitor controller or headphone amp, or a properly wired mono headphone adapter -- will give the same results.

There is a solution, but its rare in professional gear and I've never seen it in hifi gear, and that's an all-pass filter. The idea is to shift the phase of one channel by +45 degrees, and the other by -45 degrees, so that anything that was previously in opposite polarity ends up being only 90 degrees apart and therefore no longer cancels out.

[Martin Walker]

Many thanks for all that information, so I probably do not need to "invert the polarity" - to use the correct term. I must admit that could not hear any difference when I inverted the polarity

I was on the fence for a long time about the claimed benefits of 'absolute polarity', but the best evidence for my ears was to download the files kindly provided by Matthias Carstens of RME:

http://www.rme-audio.de/download/polari ... tfiles.zip

I tried it out on headphones first, by listening to the 20 Hz Sawtooth.wav contained in this zip file - with polarity set one way the L/R signals are 'pulling' at your ears, but with polarity inverted both the signals 'push' at your ears, and the difference becomes obvious.

I then tried the same test on my loudspeakers, and could hear the 'correct' polarity' on those too.

Martin

[James Perrett]

If the polarity of the signal is reversed in one channel compared to the other then they will cancel out when the signals are summed to mono. That's why it is often handy to be able to choose how a mono signal is derived and a good monitor controller will offer switchable choices of listening to both channels, one or the other channel or even one channel subtracted from the other.

Sorry but the technicalities here are a bit beyond me but are you saying I could get something that might help with my problem?

It would help diagnose the problem although it may not be a solution to the problem. If the sound is present when you only listen to one channel then it would point to the sound cancelling out in mono. However a monitor controller that offers these functions is going to cost a few hundred pounds.

Probably the simplest and best thing to try is to remove the adaptor lead and just plug your headphones directly into the amplifier so that they are working in stereo. You can then try listening to the album to see if the missing sounds re-appear - turning the headphones round if necessary.

I notice that Canford used to sell a headphone amp with a mono switch and adjustable levels for each channel. This might be useful in your situation if the mono switch is after the level controls as you could set up something similar to your speaker arrangement with one channel more dominant than the other. Unfortunately it appears to be discontinued.