Topic: Filtering venue echo

[JimmieC]

Is there a mic pattern (ie., M/S or using figure-8) to minimize or cancel out some of the echo / reverb from the venue?  The reverb kind of adds a nice sound to the instruments but not the vocals.  Kind of muddy sound.  I went up to the stage and it sounded the same. 

[nulldogmas]

What kind of mics? "Avoid omni/binaurals" would be my first suggestion.

[page]

What kind of mics? "Avoid omni/binaurals" would be my first suggestion.

Yeah, the tighter the pattern, the better to a point (figure 8s won't help you as you get the slap back from the rear of an indoor venue). Most people use hypers or shotguns for this purpose.

[JimmieC]

I always run AKG ck61 cardioids and pretty much always DINa nowdays with active bar.  I wondered / thought I remember people using a figure-8 to filter some house reverb (especially in a church) from their recording but can't find it now.  Might have been dreaming though.

[acidjack]

M-S can definitely help, since the "S" information consists of a lot of that reverb. If the M is a super/hypercardiod or a shotgun, that's more direct sound still. Of course, boominess from a high ceiling or something is hard to fix with a mic pattern other than just getting closer. Some rooms just sound bad.

[Chuck]

In bad rooms I use the CK-63's and try to get closer to the source.

[Gutbucket]

Getting the most direct verses reverberant sound pickup at a given recording position is exactly what the recent thread I started is all about- PAS table (printable) - good imaging with high direct/reverberant pickup ratio.  However, the technique described there of pointing super/hypercarioids directly at the PA speakers and consulting the table for the most appropriate spacing between microphones to get decent imaging is not a substitute for moving closer to the PA or the on-stage sound sources, which is the first thing you should do if you are able.  This technique just makes the best of a bad sounding room from the position you are stuck with.

[Gutbucket]

I wondered / thought I remember people using a figure-8 to filter some house reverb (especially in a church) from their recording but can't find it now.  Might have been dreaming though.

Jimmie C,
More details than you probably want, but the figure-8s in a church story is probably Tony Falkner's "Phased Array" of parallel arranged 8's.  He's a highly esteemed British classical music location recording engineer.  Supposedly he used that arrangement to reduce problematic strong reflections off the hard side walls of a church decades ago.  With that parallel arrangement, the least sensitive quadrants of the figure-8s would face the side wall reflections (and the floor and ceiling above and below the vertical axis of the microphones as well).  However as page mentions, that configuration would be equally sensitive to sound arriving from behind the microphone position as it would be for sound arriving from the front.   

From what I've read and the interviews with him I've heard or watched, I didn't get the impression that he's used that configuration often.  It's primarily interesting as a creative solution to a specific problem at a particular location.  I suspect it was reported in an interview long ago and then was repeated in magazine articles and other places.  It probably doesn't apply very widely and I doubt it was ever intended to. Here's a PDF describing that setup and and some analysis of it by Eberhard Sengpiel at his www.sengpielaudio.com site. I agree with Sengpiel that the spacing described seems too narrow to get a good stereo image on playback given the parallel arrangement.  Yet since it was used by Tony Falkner, I have to assume it worked well enough that he was satisfied, and I'm certainly in no position to question his judgment!  Apparently he used it slightly farther back than would be normal for the type of classical recording he was doing in churches (which is typically much closer than what we are often doing using AUD mics to record PA speakers in bad sounding rooms) and the church probably had decent sounding reverberation other than the problematic sidewall reflections, so I suspect the lush reverberance picked up by the rear lobes of the 8’s countered the center-heaviness of that narrow parallel spacing.  The material may have been well suited to something like that.  A wide playback image which spreads the sources arrayed across the stage out towards the speaker locations isn’t always called for.  That spacing is similar to what is commonly used with omnis to record solo classical piano and I can envision it working quite well for something like that.  For all I know that may have been what he was recording with it.

Confusing things in this little aside, the more recent but less well known 4-microphone array (using cardioids IIRC) which Tony Falkner uses these days and refers to in the interview I watched as a “phased array”.   It works something like an antenna array to increase forward directionality and appears somewhat like a variation on some of the 4 channel setups tapers use on one stand with one narrow spaced pair between a wider spaced pair.  However the microphone spacing/angle/pattern relationship in such an arrangement is critical to avoid comb filtering problems and he monitors and adjusts things very carefully before the recording is made so that it works well.  For those reasons I wouldn’t recommend that as a taper setup without a good understanding of what is going on, a lot of double-checking before recording, and a significant forethought.

[JimmieC]

Thanks so much Gutbucket.  It was the AB figure-8s.  It would be nice if the - portion of the figure-8 (facing away from the stage) could be used to cancel out the reverb. 

In the past at this venue, I have tried recording stereo hypers and cardioids to separate channels, and the hypers sounded similar to the cardioids recording.  The event that I recorded last weekend is continuing all week with classes, dances, and such but may be when it is over I will ask the organizer if I could get a sample of Saturday nights sbd (multichannel) recording for comparison.  I'm betting the vocals have reverb.  All the amps were both DI and mic'd.  There was over head mics for the drums but could not hear them in the mix (probably for a reason).

Next time, I'll try the AB figure-8s and / or get closer but might have to give up on this venue.  It seems the building was designed more for heritage and music was a second thought.

[Gutbucket]

Glad to help.

Instead of A-B 8s, try an A-B spaced, parallel arrangement of supercards or hypercards.  That arrangement provides the greatest possible 'forward looking bias' of any 2-channel stereo mic arrangement, maximizing the pickup of sound arriving from directly in front over the sound arriving from all other directions.  In other words, that setup gets you the most direct sound verses reverberant sound possible from that recording position, even more than what the PAS approach provides with the microphones pointed directly at the speakers.*  For best imaging, you'll want the mics spaced relatively widely if possible, to compensate for having no angle bewteen them.  Because of that parallel arrangement to reduce pickup as much a possible for everything except sound from in front, the pair will be acting more like A-B spaced omnis in terms of imaging.  You might try them something like 30" apart if you can.

*[edit- one way to understand that is to imagine the combined polar pattern of the two mics used together as a pair, rather than the polar pattern of each individual microphone by itself.  For example: Two cardioids pointed in opposite directions collectively produce an omnidirectional pickup pattern.]

[bombdiggity]

If you've already got it on your recording I'd suggest editing with an fft filter aimed at the very low end of the spectrum.  When you have more mud than sound you'd want to listen to sometimes a little filtering can get at the worst of the reverberant frequencies. 

[2manyrocks]

Could be interesting to download the trial version of Izotope RX3 advanced and see if the DeReverb tool would be useful in this situation-especially while it's on sale. 

[noahbickart]

Use an MS plugin (au or vst). Decrease the S information and boost the M to your taste.

People forget that *any* stereo track can benefit from MS processing.

[DSatz]

Just to qualify noahbickart's suggestion, the L/R -> M/S -> L/R approach works best if a coincident miking setup was originally used, and less well (sometimes quite poorly) if the microphones were spaced apart.

In general the notion of "filtering" or other post-processing to decrease reverberation is a "holy grail" type of quest that can only be achieved to some given degree, never absolutely (unless the reverberation came from separate microphones and was recorded onto separate tracks in the first place, and you can go back to the original multi-track recording and remix--obviously not what we're discussing here).

Apart from that type of situation, you'll always have to give up some degree of the naturalness and believability of your recorded sound quality--quite possibly a lot of it. In the end it may not be worth the cost. The universe doesn't guarantee a technical fix for every possible kind of mishap.

For example, even with M/S (in its conventional, two-microphone or two-signal form), when you decrease the reverberance by lowering "S", you are also cross-blending the left and right channels. So you can get a recording with less reverberation, but it will also have less stereo separation. And as I said, that whole approach really only works well when the original recording was X/Y (or was M/S itself); any kind of spaced recording will have comb filter effects when you go to derive the "M" and "S" signals from your left and right channels.

If you suspect in advance that you're going to need this type of post-processing, you might consider double M/S or even Soundfield recording, if those are possible options for you.

--best regards

[TSNéa]

I read somewhere you could use a noise gate in post processing... and that doesn't sound (!) so stupid: if not perfect, it could attenuate part of the unwanted sound / reverb, but I guess it may not be so easy! Say it's a cheap solution! 
I never tried it.

FWIW.