Topic: Does an omni have broader pickup on the vertical axis as well?

[acidjack]

This would be easier to explain in pictures, but..

Pattern plots typically are only 2-dimensional, at least the ones I see. 

What I am wondering is, an omni obviously picks up 360 degrees of sound.  But is the range of its pickup vertically the same as horizontally? 

To be more concrete - Would an omni mic 15' in the air pick up a person standing and talking below and just in front of it (i.e., in the horizontal plane, within the pickup pattern of an omni or cardiod mic) to any greater degree than a cardiod? 

I think the answer is "no", but I am curious what the experts know.

[SmokinJoe]

Yes, those plots apply to "up and down" as much as they do "side to side".  Maybe not perfectly as he says (the big fat body of an AKG414 has got to cause some sort of interference directly underneath it), but for most purposes, yes, it's even all around, and if you step forward one step you are back in the "wide open" zone.

[JasonSobel]

there are a couple of 3D renderings posted here:
http://www.taperssection.com/index.php/topic,795.0.html
I think these are very helpful/useful.

[SmokinJoe]

Good pix Jason!

When it's chatty, I frequently run hypers and point them upwards maybe 20degrees if I can.  The result is that directly under the stand is that big null spot as shown at 4:00 and 8:00 on the plots.  It certainly doesn't cut out all the chatter, but I think it does help a bit.  http://www.archive.org/details/enb2009-09-25.akg414.flac16f  you can still hear some chatter, but it sounds more distant and easier to ignore.

[Javier Cinakowski]

smoking joe, that sounds like you have it backwards?  Why would you want the rear lobe pointing downward toward the crowd behind you?  If you point your mics facing slightly downward, the rear lobe points upward toward the ceiling.  Those distant reflections are much more pleasing than the crowd behind you....    The crowd in front of you is going to picked up no matter if you point the mics upward or downward.  The front lobe is just too big to limit the folks in front of you, unless you angle them drastically upward, then you are not capturing the music properly.  my $0.02

[datbrad]

smoking joe, that sounds like you have it backwards?  Why would you want the rear lobe pointing downward toward the crowd behind you?  If you point your mics facing slightly downward, the rear lobe points upward toward the ceiling.  Those distant reflections are much more pleasing than the crowd behind you....    The crowd in front of you is going to picked up no matter if you point the mics upward or downward.  The front lobe is just too big to limit the folks in front of you, unless you angle them drastically upward, then you are not capturing the music properly.  my $0.02

With all due respect, I have to challenge this regularly peddled myth of rear lobe sensitivity in comparison to the main lobe using hypers.

Have been using the AKG 463 hypers extensively for 15 years, and have never had any issues with audible rear lobe pickup in concert recording.

The masking effect is what we are talking about. Even though there is a measurable rear lobe on hypers, the massive proportional difference between the sensitivity of the main front lobe in contrast to the sensitivity of the rear lobe means that sounds picked up by the front lobe will mask anything being heard at the same time by the rear lobe.

I have experimented with this both in live concert settings, as well as in test scenarios in my home listening room. Bottom line, the only time the rear lobe of a hyper can be distictly heard is when there is almost no sound pressure hitting the front lobe on axis, and significant sound pressure only hitting the mic directly at the rear, 180 degrees off axis.

Example you can try yourself. Place a single hyper mounted on a stand with a person standing 2 feet from the front of the mic, on axis, and a second person standing 2 feet from the rear of the mic, exactly 180 degrees off axis. If the person in front started to sing or speak, then stop and allow the person in the rear to sing or speak, immediately you would notice the extreme difference in gain due to the weak sensitivity comparing the front and rear lobes.

But, and here is where the masking comes in, if both people started to talk or sing at the same level, the proportional difference in sensitivity would cause the sound from person in the front to almost totally mask whatever sound is being picked up from the person facing the rear lobe.

This is exactly the same thing that happens in classic auditory masking with most microphones. Say for example when you are taping FOB with a low stand, and even though there is chatter and racket around you that you can hear live at the show, because of the masking effect from far louder sound pressure from the music, you can barely hear these noises that are within the same field of pickup as the music.

As far as the difference in pickup of people around a rig, comparing cards to hypers, I have definately heard this distinction while using each pattern at the same venues, and it's clear that hypers have a wider proportion of music to ambient noise than cards, and even more so compared to omnis. Shotguns are obviously the best at rejecting ambient noise, but you pay a price with coloration and often hollow sounding results.

YMMV

[Javier Cinakowski]

I appreciate your respectful tone and clear points though I do have a bit of disagreement.  First, your points about the insignificance of the rear lobe do not show that pointing the front lobe up or down will reduce crowd noise.  My point to smoking joe was that the front lobe is too broad to make any significant change in the crowd pickup.  The rear lobe is tight enough that slightly angling the microphone will provide results. 

The AKG hyper that you mention doesn't have drastically different sensitivity from the front to rear lobe.  The ck63 is only down about 5dB in the rear lobe through a significant portion of the frequency range.  The hyper actually is down less in the rear lobe than the full size ULS shotgun!

Additionally, the guy standing directly behind your mic stand is likely going to be 5dB louder than the music when he is yelling "freebird" at innapropriate times.  This will negate the sensitivity difference of the lobes and the masking effect you speak of.  By angling the mics slightly downward you are pointing the rear lobe above said jackasses head.

I am not saying your points are wrong, I am saying that mine are a bit more than a unfounded "myth"

 

[SmokinJoe]

JC, you bring up a valid point.  Yes, there is somewhat of a tail, and yes tipping it down in the back would seem to be "not in the direction of goodness", but I believe you gain more in the front than you lose in the back, for an overall gain.  The guy who is 10' feet behind me goes from 20db attenuation to 10db attenuation, but the person standing right next to me went from -5db to -30db, and to me that is an overall gain.   I'm not talking about pointing them towards the sky... I'm talking about pointing them up at the stacks.

[datbrad]

I appreciate your respectful tone and clear points though I do have a bit of disagreement.  First, your points about the insignificance of the rear lobe do not show that pointing the front lobe up or down will reduce crowd noise.  My point to smoking joe was that the front lobe is too broad to make any significant change in the crowd pickup.  The rear lobe is tight enough that slightly angling the microphone will provide results. 

The AKG hyper that you mention doesn't have drastically different sensitivity from the front to rear lobe.  The ck63 is only down about 5dB in the rear lobe through a significant portion of the frequency range.  The hyper actually is down less in the rear lobe than the full size ULS shotgun!

Additionally, the guy standing directly behind your mic stand is likely going to be 5dB louder than the music when he is yelling "freebird" at innapropriate times.  This will negate the sensitivity difference of the lobes and the masking effect you speak of.  By angling the mics slightly downward you are pointing the rear lobe above said jackasses head.

I am not saying your points are wrong, I am saying that mine are a bit more than a unfounded "myth"

 

Your points are well taken. I personally always run the hypers absolutely parallel to the ground, neither pointed up or down, so I have never heard what the rear lobe might do pitched downward. However, I have in practice found that the hypers do cut crowd more than cards in most situations.

When I look at the frequency plot for the CK63, the sensitivity difference that is significant for front to rear lobe is in the upper frequencies, where the majority of intelligibility of the sound is found. Hypers move towards omni response looking at the lower frequencies with sensitivity front to back being very close, but that is not where the detail from the chick chattering or that "freebird" guy is picked up. That comes from the higher frequencies that do fall into the traditional plot of the hyper, with the front lobe being much more sensitive.

Good discussion.

[Javier Cinakowski]

yeah, the plot really doesn't look very favorable for the "freebird" guy on second look.  Unless he has a really deep voice...

:-)

[stevetoney]

I agree that this is an interesting discussion.  I like DATBRADs test, so to test if any of this makes a difference, Brad how about taking your test one step farther. 

Use the same setup as your first test, but do it in your 'stereo room'.  Put your mics on a stand several feet above your head and repeat the test twice, once with the mics angled up and once with them angled down. 

For interest and to test the masking effect on the rear lobe, it would be interesting to see how much difference you perceive when the music is playing versus when it's just spoken word being picked up by the mics.

If you don't have enough literal headroom for the mics on a stand in your house, just put them as high as you can and do the test while you and your buddy are sitting on the floor.

[datbrad]

I agree that this is an interesting discussion.  I like DATBRADs test, so to test if any of this makes a difference, Brad how about taking your test one step farther. 

Use the same setup as your first test, but do it in your 'stereo room'.  Put your mics on a stand several feet above your head and repeat the test twice, once with the mics angled up and once with them angled down. 

For interest and to test the masking effect on the rear lobe, it would be interesting to see how much difference you perceive when the music is playing versus when it's just spoken word being picked up by the mics.

If you don't have enough literal headroom for the mics on a stand in your house, just put them as high as you can and do the test while you and your buddy are sitting on the floor.

Steve, Sounds like a good test. I will have to try it sometime.

[DSatz]

Back to the original question ...

For microphones that are radially symmetrical in a way where the part of them that faces the direct sound has the same shape whether you look at it horizontally, vertically or diagonally--you can reasonably expect the directional pattern to be the 3-dimensional projection of the 2-dimensional pattern in the spec sheet.

That includes many condenser and dynamic microphones, though certainly not all. Some microphones (including most large-diaphragm condensers as well as most ribbon microphones) are "side-addressed," so their symmetry is on a different axis, so to speak, from the one they're usually aimed along. Side-addressed microphones (when used in the usual way) never have the same directional pattern in the horizontal plane as in the vertical plane.

Generally the pattern in the horizontal plane is the one people are more interested in--but just as a tip: If you're using a side-addressed figure-8 as your "S" microphone for M/S recording, don't overlook the possibility of pointing the tip of the microphone toward the sound source; the pattern will tend to be more nearly symmetrical that way, again because what is facing the direct sound will be symmetrical along two axes rather than just one.

--best regards

P.S.: Would people PLEASE stop using "hyper" as a synonym for a shotgun (interference tube) microphone? They're not the same thing at all. A shotgun microphone can be designed around a hypercardioid capsule (though it doesn't have to be, and some are not), and unfortunately even some manufacturers' literature blurs the distinction occasionally, but they really are two different kinds of beast. I think the discussion here is stumbling over that distinction to some extent.

And again getting back to the topic while simultaneously following this path of digression, at mid and high frequencies many shotgun microphones don't have the same directional pattern (such as it is) in the horizontal vs. vertical plane, so their sound quality changes as you rotate them along their main axis; they have a definite "top" and "bottom" that needs to be observed when setting them up.