Limited Comparison of Microphones for Video Conferencing

Evaluation of several microphones for use in video conferencing such as zoom, teams, teamviewer etc.



Microphones evaluated:
1) ACO Pacific 7046 capsule on Josephson C617 preamp body (reference omni mic)
2) Logitech Brio Ultra on-board USB mic
3) Rode VideoMic with Rode VXLR+ XLR adapter
4) Audio Technica AT875R short shotgun
5) Shure SM7b with Shure MVX2U USB adapter

The first four mics are arranged in a roughly near coincident configuration as can be seen in the picture above. Simultaneous recordings of the four were made, three using a Sound Devices MixPre 3 and the Logitech Brio recorded to a DAW on the laptop. Synchronization between USB and MixPre 3 was achieved with a slate clapperboard at the beginning of recording for DAW alignment in post-production.

MixPre 3 gains for each microphone:
1) 40 dB - ACO 7046 + C617
2) 50 dB - AT875R
3) 61 dB - Rode VideoMic + Rode VLSR+

ACO 7046 is a reference measurement microphone with omnidirectional polar pattern. This captures the room ambient reverberation against which the other mics can be evaluated for their ability to reject room ambience.

Listen to the ACO 7046 recordings first to gain a sense of the room sound. It will also have the most accurate capture of the voice tone. Then proceed with the successive mic evaluation recordings and listen for overall tone and reduction in room reverberation.

The first four mics have recordings with speaker at 100 cm (~39 inches) and then at 50 cm (~19.75 inches). Listen to how each mic differs from the other mics and from itself at the two distances. Evaluation is best performed by importing the attached recordings into a DAW such as Reaper.

I prefer the AT875R + Shure MVX2U USB adapter for most situations but if I need to keep it very simple and some room reverberation is tolerable, then the Logitech Brio on-board mic is serviceable.

Recordings attached below:

 

Shure SM7b



The SM7b was recorded separately from the previous four, 15 cm (6 inches) from the mouth at an approximate 45 degree angle with respect to the mouth. This reduces P-pops and B-blasts from the speaker as s/he is talking across the microphone instead of directly into the microphone.

To keep the setup wiring simple, a Shure MVX2U USB adapter was employed with gain set to 60 dB.

SM7b is considered to provide excellent sound when the mic can be in camera view and especially if a number of different people will be using the mic. It nearly always suits any specific voice. However, it is a heavy mic requiring either a stout boom arm or desktop stand. It also has a low output and requires at least 60 dB of clean gain. Not recommended for casual use unless broadcast quality sound is desired.

Recording attached below:

 

I was just discussing with some friends what it might be like to use a "Shotgun" mic for gaming, how it would block out the keyboard sounds... and also if it could be a little further away from the face, giving more flexibility.

Did you do any testing in that regard, or have used it for such in the past with the shotgun mic you said you mentioned... AT875R

 

Even with a supercardioid you're not going to really have a great time blocking out desk sounds if you use anything but a dead silent mouse and keyboard. It's just a game of proximities IMO, which is why I've got a supercardioid dynamic shoved up within 1-3in of my face on a boom arm. Even then I get some keyboard sounds picked up, but I do have a bit of a *characterful* sounding keyboard.

 

Oh if you're gaming and have a desk mounted boom arm, then you definitely need a shockmount for the mic otherwise all the vibrations from the keyboard will transfer right through to the mic.

 

As @Lyander alludes inverse proportional law will be helpful for radiated sounds if you can keep the mic as far away from the keyboard as possible, while also keeping it in the null of the shotgun mic's polar pattern, approximately 100 degrees off-axis in this case. The person speaking need be in the 60 degree on-axis window.






As @Armaegis points out, conducted noise is also an issue. A dampening pad below the keyboard and shock mount for the microphone will help reduce that.

There is no magic solution. Different keyboards have varying levels of transient sounds they produce when keys are pressed. Mic position is critical to achieve best results, which is likely to reduce at best, but not eliminate key clacks, unless the keyboard is nearly silent to begin with.