Microphone Directionality

F

Farshock

New member
Right, baisicly i've just been reading through on recording and it says something like this ( Can't be bothered finding the page to reference it right now )

" Remember condenser microphones will capture more room sound than their ribbon or dynamic counterparts "

Assuming these microphones are gain matched and are the same directionality as stated, why will a condenser pick up more room sound?

Cheers,
Matt
 
A condenser mic has a very light-weight diaphragm, which reacts to transients faster and has a higher sensitivity. Ribbons are very light as well, but the motor reacts differently compared to a capacitive transducer and also requires a high amount of gain. Ribbons are also figure of eight patterned by default, so there are null points on each side. Dynamic mics have the weight of the coil attached to the diaphragm. They react slower.
 
They don't. This is a myth repeated ad nauseum by people who have never accurately tested it. I have, and I posted the results here. Microphones respond to sound according to their polar pattern and frequency response, including proximity effect for a directional microphone, period. Transient behavior makes little difference for ambient noise, as the noise of concern is generally broadband and sustained.

Set up an experiment for yourself and see, people have been misleading themselves.

What is true is that since dynamics are very low sensitivity, people have a tendency to place them very close to the source, otherwise signal-to-electrical noise would be unacceptable for quieter sources. That will create a difference in signal-to-ambient noise as well. But if you put a condenser with the same polar pattern as a dynamic (ideally the polar patterns will be similar across the frequency spectrum) the same distance from a source, and control for frequency response, you will find that the ambient noise is almost exactly the same (unless such ambient noise is swamped by electrical noise in the case of the dynamic, which very quiet noises could be).
 
They are mics, they convert sound to signal. Dynamics tend to "need" to be closer to the source, so the ratio of source to room is generally less. But that's why we treat rooms. Or just use stuff like an sE Reflexion filter or portable vocal booth. Takes part of the room out of the equation and makes a less direction mic more directional.

Lots of little ways to balance the source to the environment. Different tools (mics) for different jobs. Sometimes the room / ambiance is the subject needing to be captured. And sometimes the source is just too loud to get close enough to achieve a proper balance. But that's why we have studios and knobs / sliders. And that's why mics have polar patterns to tailor their sensitives to sounds from various directions.
 
mshilarious said:
They don't. This is a myth repeated ad nauseum by people who have never accurately tested it. I have, and I posted the results here. Microphones respond to sound according to their polar pattern and frequency response, including proximity effect for a directional microphone, period. Transient behavior makes little difference for ambient noise, as the noise of concern is generally broadband and sustained.

Set up an experiment for yourself and see, people have been misleading themselves.

What is true is that since dynamics are very low sensitivity, people have a tendency to place them very close to the source, otherwise signal-to-electrical noise would be unacceptable for quieter sources. That will create a difference in signal-to-ambient noise as well. But if you put a condenser with the same polar pattern as a dynamic (ideally the polar patterns will be similar across the frequency spectrum) the same distance from a source, and control for frequency response, you will find that the ambient noise is almost exactly the same (unless such ambient noise is swamped by electrical noise in the case of the dynamic, which very quiet noises could be).
Click to expand...

Thank you,

I had a feeling this would be the truth, baisicly this has just became a widespread myth?

Atleast i didn't have to find out and understand the physics behind why different transducers would react differently to reflections, i think that could've been hell if it existed.

Cheers, Matt
 
PhilGood said:
A condenser mic has a very light-weight diaphragm, which reacts to transients faster and has a higher sensitivity. Ribbons are very light as well, but the motor reacts differently compared to a capacitive transducer and also requires a high amount of gain. Ribbons are also figure of eight patterned by default, so there are null points on each side. Dynamic mics have the weight of the coil attached to the diaphragm. They react slower.
Click to expand...

Sorry just jumping in here, sometimes ribbon microphones can have a different directionality than figure 8 though?

Take for example beyerdynamic ribbons,

Through use of 2 small ribbons that both capture the sound, a hypercardiod pattern is made
and i do believe that any polar pattern can be made? except perhaps omni.

cheers, matt
 
Well quasi OMNI, basically blumlein mixed to pure mono. But if you're going to be using two mic elements and putting them in that configuration why would you advertise it as a mono ribbon and not a stereo ribbon (Royer SF-12) for twice the price?
 
Farshock said:
Sorry just jumping in here, sometimes ribbon microphones can have a different directionality than figure 8 though?

Take for example beyerdynamic ribbons,

Through use of 2 small ribbons that both capture the sound, a hypercardiod pattern is made
and i do believe that any polar pattern can be made? except perhaps omni.

cheers, matt
Click to expand...

Hello Matt,

No, the hypercardioid pickup pattern (I assume you mean M160) is not due to the fact that microphone uses 2 ribbons. For example, M130 also has two ribbons, but it is fig8. In ribbon microphones the patterns other than native Fig8 are achieved whether with infinite space behind the transducer (this was implemented in RCA77, RCA Varacoustic, Beyer 360, Oktava ML11, ML19, ML219, and some others). Or applying effective damping behind the ribbon, with appropriate response shaping devices, such as horns, or resonators. This way took some famous ribbons, such as Shure 330, Beyer M160, M260, M500, etc.

It is perfectly possible to make an omni ribbon.

Best, M
 
Marik said:
Hello Matt,

No, the hypercardioid pickup pattern (I assume you mean M160) is not due to the fact that microphone uses 2 ribbons. For example, M130 also has two ribbons, but it is fig8. In ribbon microphones the patterns other than native Fig8 are achieved whether with infinite space behind the transducer (this was implemented in RCA77, RCA Varacoustic, Beyer 360, Oktava ML11, ML19, ML219, and some others). Or applying effective damping behind the ribbon, with appropriate response shaping devices, such as horns, or resonators. This way took some famous ribbons, such as Shure 330, Beyer M160, M260, M500, etc.

It is perfectly possible to make an omni ribbon.

Best, M
Click to expand...

Ah thanks for clearing that up for me, I always assumed it had something to do with combining the two directionalities to create a new one.

Can a ribbon be true omni though? Correct me again if i'm wrong, but i thought that two combined figure 8's ( Actually i thought any two combined patterns to create omni, such as in double capsuled condenser microphones ) would still behave with some directionality on high frequencies ?

Cheers,
Matt
 
Farshock said:
Can a ribbon be true omni though?
Click to expand...

I don't think so.

An omni (pressure) microphone has a diaphragm as the front of a sealed box.

As a ribbon is only held at two ends and not at the sides you would not be able to seal the box and therefore could not get an omni pattern.

You could, however, get all other patterns by damping (as dynamic and condensers do).
 
Farshock said:
Can a ribbon be true omni though? Correct me again if i'm wrong, but i thought that two combined figure 8's ( Actually i thought any two combined patterns to create omni, such as in double capsuled condenser microphones ) would still behave with some directionality on high frequencies ?
Click to expand...

Hello Matt,

Actually, the pure pressure omni operated capsule has more directivity on the top of the band, as a result of the physical size of the capsule. In other words, the smaller the capsule, the higher the corner, and less directivity.

The omni pattern can be obtained by either:

1) combining two cardioid capsules (done in two-sided capsules)
2) true pressure operation. The main condition is stiffness controlled system operation, i.e. the capsule diaphragm is tensioned and tuned to the top of the audio band.

In order to get an omni pattern in ribbon we need to make it operating as a pressure mic, which achieved by enclosing the space behind it. The trick is, since the ribbon operates as a mass controlled system, this space should be of infinite volume--that's the reason they make long and (often) elaborate labyrinth system, but the omni pattern is perfectly possible. We already know that directivity depends on a physical size of the diaphragm, so the peculiarity of the response is ribbon's dimensions are different in vertical and horizontal planes. In other words, in horizontal plane it is excellent (in fact, it is as good as possible can be, because the ribbons are very skinny), and in vertical... well, it depends on the length of the ribbon, but 1" ones can be at least as good as any LDC.

The part about principles of operation might be confusing. For further reading, not long ago I made a big post on GS. Please check it out:

Gearslutz.com - View Single Post - ultra-thin diaphram, fast, small diaphrgam condensers?

Best, M
 
Farshock said:
Sorry just jumping in here, sometimes ribbon microphones can have a different directionality than figure 8 though?

Take for example beyerdynamic ribbons,

Through use of 2 small ribbons that both capture the sound, a hypercardiod pattern is made
and i do believe that any polar pattern can be made? except perhaps omni.

cheers, matt
Click to expand...

I probably should have made my statement more clearly. I thought that's how I typed it, but I didn't. The thought in my head is that most ribbon motors are be default figure of eight, but yes their directionality can be changed through mechanics just like any transducer.
 
mshilarious said:
They don't. This is a myth repeated ad nauseum by people who have never accurately tested it. I have, and I posted the results here. Microphones respond to sound according to their polar pattern and frequency response, including proximity effect for a directional microphone, period. Transient behavior makes little difference for ambient noise, as the noise of concern is generally broadband and sustained.

Set up an experiment for yourself and see, people have been misleading themselves.

What is true is that since dynamics are very low sensitivity, people have a tendency to place them very close to the source, otherwise signal-to-electrical noise would be unacceptable for quieter sources. That will create a difference in signal-to-ambient noise as well. But if you put a condenser with the same polar pattern as a dynamic (ideally the polar patterns will be similar across the frequency spectrum) the same distance from a source, and control for frequency response, you will find that the ambient noise is almost exactly the same (unless such ambient noise is swamped by electrical noise in the case of the dynamic, which very quiet noises could be).
Click to expand...

Link? I must have missed that post.

I look up to you very much and respect your knowledge a great deal, but I'd really like to see just how you measured the ambient levels vs. close source to determine the accuracy. How many sample sources did you try? I'm assuming it was a rather large pool you conducted the tests from since you're results are so defining.

Perhaps I'm wrong, but I'm afraid I'm going to have to respectfully disagree with you. To make such an assertion with 100% certainty for all microphones in all categories is a little far fetched when it isn't even true among mics that fall under the same category.

I've had a weird observation over the last 2 years regarding tube mics vs. solid state that made me wonder. So based on what you've just posted I decided to verify it for myself just for my own clarification.

To make sure I'm not just full of myself I just did a test with several microphones, level matched at the same distance, capsules side by side and in polarity, with a source for ambient sound that would be consistent for my test. A fountain, TV on in another room, plus the heater running in my room.

Both sets of mics have the exact same capsule in all of them: K47 copy. One set is solid state, the other tube. I have 3 identical mics in each category just to rule out it being a specific mic. I set the channels all at 0 and then matched the peak levels between channels to my voice and then panned them hard left (SS mics) and hard right (tube mics). The results aren't even subtle. There is clearly more ambient sound being picked in all the tube mics vs. solid state in all the tests.

Next I tried mics that had K67, SS vs. tube. Same result.

I have a theory as to why, and I think it has to do with how the circuits work. This usually happens when something either loads the capsule, causing physical electrostatic damping, or part of the circuit is starved. This can happen when tubes mics are "grid starved" by the wrong value grid resistor.

In any case, the frequency response, polarity and patterns are all the same, yet my results do not match your accurate tests. If I can have such varying difference among mics in the same category, how is it you achieved such concrete evidence in your tests?

Care to elucidate?
 
Through more experimenting I think I'm answering my own question. I'm finding that the louder the source, the less variation in the ambient pickup. That stands to reason though, based on sensitivity. Would that still imply condensers pick up more room based on volume levels? I guess I need to try with some dynamic mics.

I'd load some samples, but my recoding rig is not here at my house, and my guitarist set up our studio like the 1970's, so everything is dead, dead, dead, or I'd go down there and do tests. I'll try and bring my rig back here soon, so you don't think I'm trying to BS anyone.
 
Post your files and let's analyze them. We also need a reliable polar pattern by frequency chart for the two mics.

But you need a theory of why your phenomenon occurs--capsule loading would not be dependent on angle of incidence. And I don't think I have seen much to indicate that condenser capsules can be significantly damped by loading. A simple test would be to measure on- vs. off-axis response in a single mic with a capacitive pad engaged and disengaged (ensuring that the test off-axis signal exceeds the higher self-noise of the mic with the pad engaged). That is about worst-case real world scenario I can think of. Also, directly measure its transient response, since that is the quantity that must necessarily be directly impacted by damping, as it is in a dynamic mic (it is of course trivial to measure the change in transient response by loading a dynamic mic).

My results were quite clear using the exact same methodology you did (on-axis voice, off-axis TV in another room), but with a condenser and a dynamic. The relative levels of the on- and off-axis signals were within about 1dB of each other when controlled for frequency response. I would say that the degree people claim dynamics magically reject room sound the difference must be at least 6dB.

Note finally that even if such a difference existed, it should be described in terms of the mic's measured polar pattern. I can't think of any reason why that would not be the case.
 
PhilGood said:
Through more experimenting I think I'm answering my own question. I'm finding that the louder the source, the less variation in the ambient pickup. That stands to reason though, based on sensitivity. Would that still imply condensers pick up more room based on volume levels? I guess I need to try with some dynamic mics.
Click to expand...

That is a statement that the microphone is a nonlinear device, which should not be true within the mic's dynamic range (above self-noise, below max SPL). Which could be an answer for dynamic mics--if the ambient sound is below the resulting self-noise of the mic/preamp combination, it will not be heard. The noise will be though.

One could achieve the same ambient noise "rejection" by adding the same relative level of white noise to the condenser recording.

I'll run a new test later tonight; my first test wasn't as clear as it could have been due to a hum in the amplifier (since replaced).
 
Intellectually, I would expect any two mic elements with the same polar pattern and same frequency response to produce almost exactly the same results, ignoring any masking caused by self noise. Sluggish transient response might reduce the level of some specific types of noise (crinkling paper, for example), but that would show up as lost high frequency response as well, since a transient is effectively just a very brief high frequency component to the sound.

Regarding tube mics, part of the difference there could be microphonics. Tubes do, to some extent, act as microphones in and of themselves. To the extent that any noise might be coupled from the floor through the mic stand, I could see this affecting the sound in ways that would not be obvious from a simple plot—particularly if we're talking about low frequency noise.
 
dgatwood said:
Regarding tube mics, part of the difference there could be microphonics. Tubes do, to some extent, act as microphones in and of themselves. To the extent that any noise might be coupled from the floor through the mic stand, I could see this affecting the sound in ways that would not be obvious from a simple plot—particularly if we're talking about low frequency noise.
Click to expand...

Ahh - you got here before me.

I was just about to mention that is was the possibility of the valve itself being microphonic.

Especially as it was noticed mainly with quiet, distant sounds and the gain would have been high.
 
Dynamics and Ribbons generally have greater SPL limits. Which allows them to be closer to loud sources. So the relative SPL / loudness of the source is greater than at distance where the source and the ambiance are one and the same. Content and position is king. Using various combinations there of, you can prove by samples to favor ANY of the types of mics. And many shootouts do this when combining more than one type of mic or polar pattern, just by keeping all of the other factors the same like distance. However indirectly or unintentional.
 
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