Hi all,
I thought this would be an interesting discussion to have here, since most of the members are into home HiFi.
A little preamble before the question...
There are lots of techniques used in the recording world that are intended to capture a stereo image of a given acoustic event.
At the small scale, we have something like an acoustic guitar, where the fret/finger noises will be slightly to the listener's right, and the strumming hand will be slightly to the left.
Medium scale would be something like a church organ.
At the large scale, we might have a big orchestra.
Here's a brief overview of the usual mic techniques:
- Spaced omnidirectional mics: These would be two mics that pick up sound equally from all directions, and they're usually positioned a metre or two apart. Different instruments in the stereo field will have different levels and arrival times at each mic.
- Coincident (XY) cardioid: A pair of directional mics, positioned close to each other but facing in different directions (they're 90-degrees apart, with the capsules aligned) in order to pick up sound from different places. This technique relies on level differences between the two mics to create the stereo image, since the mics are always in-phase with one another.
- ORTF: Like XY, but the mics are at 110 degrees, and the capsules are separated by a small distance of 17cm, introducing some phase differences.
There are some more esoteric mic techniques involving figure-of-eight mics (they're dipole), but going through all the permutations would take forever.
So, the question is this: which mic technique should be used for reproduction with a conventional stereo system?
Interested to hear what you all think.
Chris
I thought this would be an interesting discussion to have here, since most of the members are into home HiFi.
A little preamble before the question...
There are lots of techniques used in the recording world that are intended to capture a stereo image of a given acoustic event.
At the small scale, we have something like an acoustic guitar, where the fret/finger noises will be slightly to the listener's right, and the strumming hand will be slightly to the left.
Medium scale would be something like a church organ.
At the large scale, we might have a big orchestra.
Here's a brief overview of the usual mic techniques:
- Spaced omnidirectional mics: These would be two mics that pick up sound equally from all directions, and they're usually positioned a metre or two apart. Different instruments in the stereo field will have different levels and arrival times at each mic.
- Coincident (XY) cardioid: A pair of directional mics, positioned close to each other but facing in different directions (they're 90-degrees apart, with the capsules aligned) in order to pick up sound from different places. This technique relies on level differences between the two mics to create the stereo image, since the mics are always in-phase with one another.
- ORTF: Like XY, but the mics are at 110 degrees, and the capsules are separated by a small distance of 17cm, introducing some phase differences.
There are some more esoteric mic techniques involving figure-of-eight mics (they're dipole), but going through all the permutations would take forever.
So, the question is this: which mic technique should be used for reproduction with a conventional stereo system?
Interested to hear what you all think.
Chris
Hi chris!
As you have outlined yourself, the microphone technique is chosen to suit the subject being recorded. All the different techniques result in a stereo image compatible with a conventional stereo reproduction system.
Perhaps your question should be: "What are the upsides and downsides of the different microphone techniques in contributing to a convincing stereo image?"
I do mean stereo.
My question is which mic positions ought to give the most accurate stereo image, when reproduced with a stereo HiFi system.
A lot of captures are done with a main stereo pair of mics (usually with one of the techniques I outlined), usually with spot mics blended in as necessary.
I just thought it'd be an interesting discussion to have.
Chris
My question is which mic positions ought to give the most accurate stereo image, when reproduced with a stereo HiFi system.
A lot of captures are done with a main stereo pair of mics (usually with one of the techniques I outlined), usually with spot mics blended in as necessary.
I just thought it'd be an interesting discussion to have.
Chris
Here goes my attempt to kick off the discussion! 
The stereo effect depends on (a) the difference in time of arrival at the two microphones, and, (b) the difference in frequency balance picked up by the two microphones.
Compared to recording with microphones facing straight ahead but separated (A/B), recording with microphones angled to each other but with capsules coincident (X/Y) will have less stereo width.
The reason for this is that since the angled microphones are positioned at the same point in space there will be no differences in timing. The entire stereo effect is created from the differences in frequency balance.
The stereo effect depends on (a) the difference in time of arrival at the two microphones, and, (b) the difference in frequency balance picked up by the two microphones.
Compared to recording with microphones facing straight ahead but separated (A/B), recording with microphones angled to each other but with capsules coincident (X/Y) will have less stereo width.
The reason for this is that since the angled microphones are positioned at the same point in space there will be no differences in timing. The entire stereo effect is created from the differences in frequency balance.
Attachments
There is an AES article from the 1970's where Belgian researchers recorded an orchestra with many different basic stereo microphone techniques, carefully level matched, and then did a blind listening test where they asked for preferences. All microphone techniques had their own strong and weak points, but overall ORTF was the clear winner.
Is this assuming only one pair of mics for the whole recording ? In many cases the stereo image is the results of fusing many individual tracks, all recorded with different techniques. Taking the acoustic guitar example, I wouldn't care much about "soundstage" at the recording stage. I'd be more interested in using dissimilar mics aimed at different parts of the instrument, to get the richest tone possible.
I second the Yamaha handbook for mic techniques. Neumann has some great video freely available too.
I second the Yamaha handbook for mic techniques. Neumann has some great video freely available too.
This thread appears to be about capturing a stereo image of a real acoustic event, not achieving a "rich tone" while synthesising a stereo image from a multitrack recording of what might be multiple events - that would be a different thread. If an acoustic guitar played in a particular room had a thin tone then that is what we should capture.
@DF96: I agree in theory but practice isn't as clear cut as neither microphones nor venues are perfect.
I happen to sometimes record lives performances. A typical live recording will mix the sound of a stereo pair with what you get from a few well placed spot mics (mics close to the instruments).
First off, the "natural soundstage" you get at a venue is more often than not not very interesting. Having the possibility to pan a bit the instruments can create a much more convincing experience when replayed on stereo. In a way, just choosing where to put your stereo pair is already a choice on what sound you're trying to achieve (when you have a choice...).
The closed mic'ed tracks (often made with more specific mics than just small diaphragm mics) also give you access to some extra details and tone. Adding them back to the mix gives a final result that is just more convincing when replayed. Maybe artificially so ? But the whole hifi experience is artificial anyway.
This being said, all this varies a lot depending on the kind of music you're recording. In my view, there's no such thing as a single proper technique for stereo music. Only a collection of tools available to create the best illusion possible, under the constraints we get and according to the priorities we set.
I happen to sometimes record lives performances. A typical live recording will mix the sound of a stereo pair with what you get from a few well placed spot mics (mics close to the instruments).
First off, the "natural soundstage" you get at a venue is more often than not not very interesting. Having the possibility to pan a bit the instruments can create a much more convincing experience when replayed on stereo. In a way, just choosing where to put your stereo pair is already a choice on what sound you're trying to achieve (when you have a choice...).
The closed mic'ed tracks (often made with more specific mics than just small diaphragm mics) also give you access to some extra details and tone. Adding them back to the mix gives a final result that is just more convincing when replayed. Maybe artificially so ? But the whole hifi experience is artificial anyway.
This being said, all this varies a lot depending on the kind of music you're recording. In my view, there's no such thing as a single proper technique for stereo music. Only a collection of tools available to create the best illusion possible, under the constraints we get and according to the priorities we set.
I accept that sometimes the main stereo mikes need to be assisted by a few spot mikes. However, I believe this should be done as little as possible. Every extra mike can create frequency comb effects etc.
The OP included 'hi-fi' in the thread title. For me this implies that there is an acoustic stereo event to be captured, which implies mostly or exclusively acoustic instruments in a suitable room which could contain an audience even if it is in fact empty for the performance. I recognise that few modern recordings are made in this way.
The OP included 'hi-fi' in the thread title. For me this implies that there is an acoustic stereo event to be captured, which implies mostly or exclusively acoustic instruments in a suitable room which could contain an audience even if it is in fact empty for the performance. I recognise that few modern recordings are made in this way.
For classical music I would agree, as the formations have evolved over time to be somewhat balanced, in the absence of sound reinforcement. For more modern styles of music, spot mics can be essential.
One additional factor to consider is the disconnection between visual clues and audio clues when going from a live event to a recording. I readily admit I'm not familiar with the literature on that topic but my gut feeling is that the brain more easily filters out noise/process music in a live setting than with recordings. As such recordings need to be more rich in clues to elicit a similar feeling. Multitrack work can provide this.
Btw, I found this article in my bookmarks, which is somewhat relevant: Orchestral Recording - Mixonline It's an interesting piece on the evolution of classical orchestra recording, from the perspective of sound engineers.
One additional factor to consider is the disconnection between visual clues and audio clues when going from a live event to a recording. I readily admit I'm not familiar with the literature on that topic but my gut feeling is that the brain more easily filters out noise/process music in a live setting than with recordings. As such recordings need to be more rich in clues to elicit a similar feeling. Multitrack work can provide this.
Btw, I found this article in my bookmarks, which is somewhat relevant: Orchestral Recording - Mixonline It's an interesting piece on the evolution of classical orchestra recording, from the perspective of sound engineers.
the room acoustics are going to be the dominant factor. You can get a good sounding recording in an excellent room with an average mic pre and a pair of Shure SM67s.
The problem is with accurate methods, they can give you an accurate picture of a crappy room.
Of course it will be better with a better mic.
Cheers
Alan
The problem is with accurate methods, they can give you an accurate picture of a crappy room.
Of course it will be better with a better mic.
Cheers
Alan
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