shotgun inside... at DVinfo.net

Renton Maclachlan · October 22nd, 2009, 05:33 PM

I've noticed that several have said Shotgun mics should preferably not be used inside (best outside), rather, that a hyper-cardioid should be used inside instead.

1. I thought a shotgun WAS a hyper-cardioid.
2. What is the issue with shotguns inside?

Seth Bloombaum · October 22nd, 2009, 06:07 PM

This is more of a guideline than a rule. It's *almost* guaranteed that you'll wish for a hypercardoid if you try to shotgun from above in a typical home.

You're right - a shotgun is a hypercardoid with a longer interference tube. For that matter, a hyper is a cardoid with a longer... An omni has no interference tube.

The issue is that while the longer interference tube reduces off-axis sound, it doesn't do so equally across frequencies, and, worse, develops a lobe of sensitivity at the back which responds very non-linearly.

Use it near ceilings or walls, get a reflection of non-linear response. This can be heard very readily if you know what you're listening for. If you don't know what's going on, you may notice that the sound is more "hollow" than expected.

In summary - all mics are going to catch some room sound. Smaller and live-er the room, more room sound. The longer the interference tube (generally), the more colored the reflected sound will be.

Close study of the polar patterns of your favorite mics will help to tell the story. Below, the polar pattern of the Rode NTG2, a medium/short shotgun. Notice that the off-axis response is different at different frequencies.

This is definitely a case where your mileage varies. Every room is different for reflectivity, mikes are slightly different, since the manufacturers are always working to reduce these effects.

Carl Hoang · October 29th, 2009, 05:45 AM

What's the rule of thumb when not to use shotgun for inside?

Rob Neidig · October 29th, 2009, 09:00 AM

Carl,

I'd say you generally don't want to use a shotgun inside where there are lots of reflective surfaces. So in a room that has hard wood floors, or a kitchen with tile or linoleum, for instance. Anyplace where you get a very "echo-y" sound. A hyper will be better in those situations. Now if there's too much echo, a hyper isn't going to be great all by itself either. You may have to lay down sound blankets, etc. to get rid of some of the echo. In a carpeted living room or bedroom, though, I think a shotgun like the Sennheiser 416 can work quite well.

Have fun!

Rob

Steve House · October 29th, 2009, 10:26 AM

Quote:

Originally Posted by Carl Hoang

What's the rule of thumb when not to use shotgun for inside?

Pretty much any space that has not been acoustically treated such as a soundstage might be is going to be too reflective for a shotgun. For that matter, 'guns can encounter the same problem outdoors, on the tarmack at an airport or on a paved tennis court for example. The problem comes about due to the way sound entering the front of the mic interacts inside the tube with its reflections coming in through the side ports of the interference tube. Other types of directional mics like a hypercardioid do not use the interference principle and so don't have the same drawbacks.

Jimmy Tuffrey · October 30th, 2009, 01:58 AM

Standing next to stone walls can do it too. Especially if your in a corner with two walls and the stone pavement.

Dean Sensui · October 30th, 2009, 03:46 AM

Also, keep in mind that some shotguns are actually bi-directional and have poor rejection from the rear.

Marco Leavitt · October 30th, 2009, 10:27 AM

This issue can get murky. At SOME distances in SOME interiors, the shotgun will win, in others the hypercardiod. If you've got a very bright space and you can't get close enough it's more of a question of which will sound worse, as they're both going to sound like crap. Some people believe that shotguns actually will attenuate echo better than hypercardiods in very large reverberant rooms, but I'm not committed to that.

Steve House · October 30th, 2009, 10:52 AM

Yep, it's all a continuum. The really nasty effects occur when the reflected sound arrives so close to the direct sound that you get comb filtering effects inside the tube. As the time lag of the reflection gets longer it transitions into reverb and then again into echo and the effect changes for each. It's a very arcane art.

Dan Brockett · October 30th, 2009, 10:54 AM

Why not go through all of the nice sound samples I recorded both indoors and outdoors with hypercardioids and shotguns and decide for yourself? Much more accurate than discussing it As I Hear It - Choosing the Right Microphone

Dan

John Willett · November 1st, 2009, 04:14 AM

Quote:

Originally Posted by Dean Sensui

Also, keep in mind that some shotguns are actually bi-directional and have poor rejection from the rear.

All shotguns pick up from the rear - it's the law of physics.

A gun mic. is normally a super-cardioid capsule wirh an interference tube that makes it more directional at higher frequencies.

The rear lobe is normally about 10dB down in level from the front at low frequencies. The published polar-patterns should show you what;s happening.

October 22nd, 2009, 05:33 PM	#1
Renton Maclachlan Trustee Join Date: Jul 2007 Location: New Zealand Posts: 1,180	shotgun inside... I've noticed that several have said Shotgun mics should preferably not be used inside (best outside), rather, that a hyper-cardioid should be used inside instead. 1. I thought a shotgun WAS a hyper-cardioid. 2. What is the issue with shotguns inside?

October 22nd, 2009, 06:07 PM	#2
Seth Bloombaum Inner Circle Join Date: Sep 2003 Location: Portland, Oregon Posts: 3,420	This is more of a guideline than a rule. It's almost guaranteed that you'll wish for a hypercardoid if you try to shotgun from above in a typical home. You're right - a shotgun is a hypercardoid with a longer interference tube. For that matter, a hyper is a cardoid with a longer... An omni has no interference tube. The issue is that while the longer interference tube reduces off-axis sound, it doesn't do so equally across frequencies, and, worse, develops a lobe of sensitivity at the back which responds very non-linearly. Use it near ceilings or walls, get a reflection of non-linear response. This can be heard very readily if you know what you're listening for. If you don't know what's going on, you may notice that the sound is more "hollow" than expected. In summary - all mics are going to catch some room sound. Smaller and live-er the room, more room sound. The longer the interference tube (generally), the more colored the reflected sound will be. Close study of the polar patterns of your favorite mics will help to tell the story. Below, the polar pattern of the Rode NTG2, a medium/short shotgun. Notice that the off-axis response is different at different frequencies. This is definitely a case where your mileage varies. Every room is different for reflectivity, mikes are slightly different, since the manufacturers are always working to reduce these effects. Attached Images __________________ 30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.

October 30th, 2009, 03:46 AM	#7
Dean Sensui Inner Circle Join Date: Oct 2001 Location: Honolulu, HI Posts: 2,054	Also, keep in mind that some shotguns are actually bi-directional and have poor rejection from the rear. __________________ Dean Sensui Exec Producer, Hawaii Goes Fishing

October 30th, 2009, 10:52 AM	#9
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	Yep, it's all a continuum. The really nasty effects occur when the reflected sound arrives so close to the direct sound that you get comb filtering effects inside the tube. As the time lag of the reflection gets longer it transitions into reverb and then again into echo and the effect changes for each. It's a very arcane art. __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

October 29th, 2009, 05:45 AM	#3
Carl Hoang Regular Crew Join Date: Nov 2006 Location: Maple Grove, MN USA Posts: 65	What's the rule of thumb when not to use shotgun for inside?

October 29th, 2009, 09:00 AM	#4
Rob Neidig Major Player Join Date: Dec 2005 Location: Eugene, Oregon Posts: 222	Carl, I'd say you generally don't want to use a shotgun inside where there are lots of reflective surfaces. So in a room that has hard wood floors, or a kitchen with tile or linoleum, for instance. Anyplace where you get a very "echo-y" sound. A hyper will be better in those situations. Now if there's too much echo, a hyper isn't going to be great all by itself either. You may have to lay down sound blankets, etc. to get rid of some of the echo. In a carpeted living room or bedroom, though, I think a shotgun like the Sennheiser 416 can work quite well. Have fun! Rob

October 30th, 2009, 01:58 AM	#6
Jimmy Tuffrey Major Player Join Date: Jul 2007 Location: Bristol U.K. Posts: 244	Standing next to stone walls can do it too. Especially if your in a corner with two walls and the stone pavement.

October 30th, 2009, 10:27 AM	#8
Marco Leavitt Inner Circle Join Date: Jul 2002 Location: Albany, NY 12210 Posts: 2,652	This issue can get murky. At SOME distances in SOME interiors, the shotgun will win, in others the hypercardiod. If you've got a very bright space and you can't get close enough it's more of a question of which will sound worse, as they're both going to sound like crap. Some people believe that shotguns actually will attenuate echo better than hypercardiods in very large reverberant rooms, but I'm not committed to that.

October 30th, 2009, 10:54 AM	#10
Dan Brockett Inner Circle Join Date: Feb 2006 Location: Los Angeles, California Posts: 2,109	Why not go through all of the nice sound samples I recorded both indoors and outdoors with hypercardioids and shotguns and decide for yourself? Much more accurate than discussing it As I Hear It - Choosing the Right Microphone Dan