The sound of comb filtering

Got speaker theory questions? This is where you'll find the answers.
Post Reply
Message
Author
User avatar
doncolga
Posts: 1967
Joined: Thu Jul 01, 2010 3:01 pm
Location: Statesboro, GA
Contact:

Re: The sound of comb filtering

#1 Post by doncolga »

TimpBizkit wrote:http://www.youtube.com/watch?v=zMzws30ZluI
This time caused by the difference in arrival time from the mouth to 2 different microphones
Very cool man. Thanks for the link.
Donny Collins
Built:
Two 18" Tuba 30's 3012 LF
Two 26" Tuba 30's Lab 12
Two OmniTop 12's DL 2512 (Melded Array)
Presonus Studio One DAW
Harrison Consoles MixBus 32C DAW

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: The sound of comb filtering

#2 Post by Bill Fitzmaurice »

TimpBizkit wrote:http://www.youtube.com/watch?v=zMzws30ZluI
This time caused by the difference in arrival time from the mouth to 2 different microphones
That's not comb filtering. When the hand held mic is brought close to his mouth there's a major bass boost that's caused by microphone proximity effect.
They're selling something. Caveat emptor.

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: The sound of comb filtering

#3 Post by Bruce Weldy »

Bill Fitzmaurice wrote:
TimpBizkit wrote:http://www.youtube.com/watch?v=zMzws30ZluI
This time caused by the difference in arrival time from the mouth to 2 different microphones
That's not comb filtering. When the hand held mic is brought close to his mouth there's a major bass boost that's caused by microphone proximity effect.
They're selling something. Caveat emptor.
True about the bass proximity creating the extra low end. The other issue is phase cancellation that happens when two mics are picking up sound from a single source.

That video shows both things happening.....but, they totally blew the description of what's actually happening. It's not comb filtering as Bill says.

If you want a real world example of how to see the difference phase cancellation can cause - mic a snare drum on the top....then put another mic on the bottom. Bring up both channels and listen. Then flip the phase reverse on the bottom mic channel. You'll hear an instant volume increase and it really fattens up.

This happens a lot with micing choirs etc. with multiple mics. It's hard to catch sometimes....it just sounds dull and listless. Move 'em farther apart to overcome the cancellation......or just use two mics instead of three or four.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Steven Gustafson
Posts: 36
Joined: Tue Nov 27, 2012 3:18 am

Re: The sound of comb filtering

#4 Post by Steven Gustafson »

Here's a link to what Ivan Beaver and Mike Hedden of Danley Sound Labs will identify as "finger lobing."

The time effect on line arrays. This was a demo of a DSL Jericho (J1) vs. a Meyer Mina. Pretty cool.
http://www.youtube.com/watch?v=cPHpusei0jQ

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: The sound of comb filtering

#5 Post by Bill Fitzmaurice »

That just shows to go ya' that you can skew data/tests to give just about any result. At the correct listening distance versus array height that does not happen. No one listens to an 8 box pro-touring array that close.

The issue with arrays is that it takes a certain distance from the array for the individual wave fronts from each element to coalesce into a single coherent wavefront. My 40 inch high TLAHs loaded with 4 inch woofers and 3/8 inch tweeters do so about eight feet out. A massive pro-touring array may need 50 feet. This applet shows how it works:
http://www.acoustics.salford.ac.uk/fesc ... fract4.htm

Steven Gustafson
Posts: 36
Joined: Tue Nov 27, 2012 3:18 am

Re: The sound of comb filtering

#6 Post by Steven Gustafson »

Cool. Plus, unless is the park is empty, no one is walking their way to the stage.

User avatar
Bill Fitzmaurice
Site Admin
Posts: 28620
Joined: Tue May 02, 2006 5:59 pm

Re: The sound of comb filtering

#7 Post by Bill Fitzmaurice »

TimpBizkit wrote:http://www.youtube.com/watch?v=fbn2cGJHB9Q more comb filtering, love that phaser pedal effect!
Let him off, he's just testing!
That is comb filtering, and proves that no matter how much you spend it's money wasted if you don't know what you're doing.

Post Reply