Reducing Mic Bleed

[wesg]

I'm listening to a multitrack recording of a recent gig, and being able to solo the tracks has revealed that some of the channels have really bad mic bleed. The worst offenders are Leslie Lower, and the two congas (soft hitter), and these mics spend a significant amount of time sending all-noise-no-signal to the FOH due to the nature of the program (the instruments are not always in use).

 

The good news is that the leakage is fairly representative of a decent mix.

 

Are there any useful tricks I can use to reduce the impact of these on the FOH mix when performing live?

 

I'm nervous about using gates on the channels, because I worry about screwing up the mix every time they get used.

 

Would running those mics out of phase make sense, or is it likely to cause more harm than good?

 

Similarly, would a shelving EQ around the ranges created by the sources cause more harm than good?

 

I also plan to work on mic position as my #1 weapon in this battle, stage volume #2. The one thing I don't like about the Leslie 760 is that you can't pull off the bottom cover like on a 122/147. I may have to get creative there. BTW I close mic'd the Leslie upper rotor with an XY pair on that gig. Panned hard left and right it sounds amazing in my headphones. Big SNR, too. Wish I knew what it sounded like out front!

 

Wes

[Tomm Williams]

Are you using any gates or downward expanders ?

[Tomm Williams]

Ooops just saw your comment about gates. What concerns you about them ?

[Craig Vecchione]

I can see gates on the Leslie being very difficult to set, as the dynamic range is nearly infinite. You're liable to not trigger the gate on the lowest passages, or not have the gates effective if they're set to be more sensitive.

[trevcda]

Have you considered your mic selection? A mic with a tighter pattern will tend to pick up less of axis signal and improve channel isolation.

[Audiopile]

Maybe equip the conga player and keyboardist with microphone foot switches to punch-in and out. Or volume pedals... as it might be difficult for the musician to confirm if the switch switched on at punch-in time.

[dboomer]

 

Would running those mics out of phase make sense, or is it likely to cause more harm than good?

 

Probably won't make any difference either way as the wash is likely so far out of phase to make any difference.

 

The problem is simple Mics just pickup what the hear. So stage volume or isolation boxes are gone be the only thing to achieve what you are looking for. Going to super-cardioid patterns might help if your stage environment is big enough. In a small club it probably won't make much difference ... but that all depends.

 

 

[Tomm Williams]

I can see gates on the Leslie being very difficult to set' date=' as the dynamic range is nearly infinite. You're liable to not trigger the gate on the lowest passages, or not have the gates effective if they're set to be more sensitive.[/quote']

 

 

I"ll certainly defer to your knowledge on the Leslie as I've never worked with one, on the congas I would think gating wouldn't be too tough.

[Audiopile]

 

 

Leslie

In my limited experience:

 

Leslie noise: Most all Leslies I've been around were tube models, and there's was live AC conductors combined with the audio conductors in it's umbilical cable, and there's bearings and belts moving, and hornflairs rotating. The total combination can be "pretty noisy"... especially if the bearings aren't oiled, and the tubes are tired or loose in their sockets, and the caps are getting tired, and there's belt slap, and especially if the rotating horns are left on "high speed".

 

 

 

[agedhorse]

One thing to determine is if the bleed is direct or coming from reflections off of walls or surfaces. This may dictate what may work.

[Pro Sound Guy]

Starting up a B3 is like kick starting an old Harley.

Leslies make mechanical noise. You cant get around that.

Typically the organ signal will mask the mechanical noise.

A thing of pure beauty.

[wesg]

Tom - my concern with gates is that I may wind up "pumping" the sound if you know what I mean? I have been playing with software gates in my DAW and I do get this effect on individual tracks, but it does seem to get lost in the mix.

 

Trev - I *have* thought about mic selection. The day I have recorded, we were using AKG supercardiod dynamics for the vocals and SM57s for the congas. We have some kind of Audix conga/tom mic coming for the congas, hopefully these will be a bit better. The Leslie lower was using a Beta 58 (yeah I know) but was poorly aimed; the pattern wouldn't have helped much. Kick was mic'd with a CAD D12, I think.

 

Mark - if you ever bump into a Leslie 760 or 770, they are for all intents and purposes loud Leslie 147s with solid-state amps mounted on the steel lower back panel, which doubles as a heat sink. Running AC through the cable isn't as bad as you'd think, because the signal level is WAY hotter than anything found in pro-audio, typical signal levels are around 3Vrms or more. Not an issue at all with the Leslie 122, that one uses a balanced signal and we get common mode rejection in the push-pull output stage (no preamp in a Leslie). The Leslie 122 is also fairly immune to power supply noise for the same reason...crappy filter caps can still sound okay.

 

I need to figure out a better way to mike my Leslie lower rotor for live work. One side of the cabinet gets hit with my monitor, the other side gets hit with the band. I thought putting a road case in front of the grille to keep the band noise out would be enough, but it's not. (It's nice to have multi-track recordings to learn this stuff -- I never get to hear myself from the FOH). Maybe I should mike the front instead of the side, but leave my baffle in place... (see stage plot context).

 

BTW, am totally not worried about mechanical noise from the Leslie. It's way too quiet to notice. New bearings, grommets, and windscreens all help here.

 

Andy - Good observation, thank you; I completely overlooked the bounce factor. We were playing in a less-than ideal location that day. An outdoor stage that was basically a box made out of galvanized roofing material. I wonder if this explains why there is so much bass in the kick. Or maybe it was that echoey stage floor. We don't run a bass-heavy mix, and the bass player's stage volume is very reasonable IMO.

 

Here is what the kick drum sounded like: https://soundcloud.com/wesgarland/raw-kick/s-qdc42 coming into the board.

 

BTW the stage may have been ghetto and the mics may have been bleedy and the power ground was noisy enough to cause problems with bass and keys... but the crowd was great, the band sounded good, everybody had a blast, and the pay was good.

 

Thanks for any insight! I've come a long way since I came here trying to put a band PA together on $1500 three years ago, but I still have a heck of a lot to learn.

 

Wes

[Pro Sound Guy]

Power ground was noisey? You mean you had a ground loop?

[Crownman]

The last time I had really bad stage bleed while micing a leslie we turned the cab so that when the mics were on it the leslie can was between the mics and the rest of the instruments. For the congas get some Audix D2's and some mic clips. I've had good luck using them.

[wesg]

PSG - "noisy ground" = bass amp ticked when ground not lifted (only through internal speaker, not PA). Piano made a loud THUMP about 300ms after signal started, I thought it was a badly-configured gate at first. Fixed by going DI. Wierd wierd wierd.

 

Crownman - I think what you're describing is how I set up (see stage plot 3 posts up)? ... Isolation was terrible. I should post a recording. The drum is on the stage-right side of the Leslie in this configuration. Isolation for the top horns was fine, but I could also get a bit closer to the source. Conga player ordered new mics already, either D2 or F2. He wasn't real clear on what he finally settled on. Either way, I can't wait to try them out, both have a hypercardioid pattern which will hopefully work better than 57s in that environment.

[wesg]

Tom Williams - thanks for providing "Downward Expander" google-food. That's exactly what I'm doing in Audacity with a "Noise Gate" plugin. I wouldn't mind having one of those available on a few mic channels, like congas and maybe drum overheads. I should shop around. Our drum overhead is currently not much more than a full band mix. I'm going to move the overheads dramatically on the next gig to get a lot more cymbal and tom signal.

[Tomm Williams]

Tom Williams - thanks for providing "Downward Expander" google-food. That's exactly what I'm doing in Audacity with a "Noise Gate" plugin. I wouldn't mind having one of those available on a few mic channels' date=' like congas and maybe drum overheads. I should shop around. Our drum overhead is currently not much more than a full band mix. I'm going to move the overheads dramatically on the next gig to get a lot more cymbal and tom signal.[/quote']

 

 

 

I use a Valley Gatex which is a four channel unit with two levels of downward expansion. You can find them easily under $100 and Valley still services them although they have been discontinued for years.

 

 

[StratGuy22]

Is the bleed affecting things during the gig or are you talking about mixing down the multitracking after? You have to understand that live isn't going to be perfect unless you can isolate everything live. I think its just nature of the beast that the mics will pick up some overflow.

[wesg]

The sound at the live performance is good enough for sure. I'm using the multitrack recording to study what's going on with the band while I'm busy performing. Sometimes I run sound from the stage, on this event I had some hired help, but even so, I am too busy to strap on a pair of headphones during the show.

 

I don't expect a live recording to have anywhere near studio isolation, but some of it is, like, really bad. My thinking is that if I can reduce clutter without significantly increasing system complexity, then the guy running the board has the possibility of getting a better mix in the end.

 

For example, listen to that kick track I posted - you just can't turn that up without turning up the bass guitar also..and you can't fix that with EQ, either. So, the kick bleed problem needs to be resolved at the source if we want to get a more present kick sound in the mix. I'll be talking to the drummer about that this week to see if we can make improvements in mic positioning.

 

Wes

[DanCostello]

Gating a kick is pretty common, and pretty easy if the drummer can hit hard enough to reliably trigger the gate.

[philw44]

In my experience, you don't really need a lot of level from the bass Leslie speaker, nor do you need much frequency range. You can probably cut everything from below 60hz and above 300hz. If it's still bad then get a mic with the tightest polar pattern possible?

 

For the congas, if you want a really pro solution to this... I suggest getting some percussion drum triggers (I think ddrum make some). You attach these to your congas and run an xlr out to your mixer. With your gate, set the trigger as the 'key input'. Now the mic gate will only open when there is physical contact with the conga skin. That could be quite pricey and complicated though if you haven't got a top-end digital mixer...

[wesg]

Hi, Phil!

 

Thanks for telling me about those triggers. I didn't know about them, they may prove an interesting option. The conga player ordered Audix D12s, I am hoping that the tighter pattern than the 57s should be enough, but if not, that makes an excellent "Plan B".

 

Re. the Leslie lower -- Leslie speakers use an 800Hz 2nd order crossover. I figure there is meaningful information up until about 2kHz. When I have enough EQ, I will do my best to shelve it around there. I have been known to boost lows and cut highs with a graphic to get a 24dB shelf.

 

Wes

[TimmyP]

For the Leslie bottom, stick a little bitty mic through one of the lower slots. Or get a Kelly Shu Flatz with a Beta 91, and put it just inside the rear panel.

[wesg]

Through the slats - that's an interesting idea. I have PVM 480s I could try that with, they should fit through the slats on the 760.

 

The boundary mic is interesting, too. I didn't know if those would be a good choice or not, there is a fair bit of mechanical noise that vibrates the cabinet. But the Kelly Shu Flatz thing you mentioned might just do the trick. Might even be an ideal "permanent" mic.

 

Since posting here last, I've acquired a Leslie 147 and an RE20. The RE20 won't go through the slats (!!), but the lower back panel comes off on the 147. I should be able to get the RE20 in nice and close.

[Phil O'Keefe]

Through the slats - that's an interesting idea. I have PVM 480s I could try that with, they should fit through the slats on the 760.

 

The boundary mic is interesting, too. I didn't know if those would be a good choice or not, there is a fair bit of mechanical noise that vibrates the cabinet. But the Kelly Shu Flatz thing you mentioned might just do the trick. Might even be an ideal "permanent" mic.

 

Since posting here last, I've acquired a Leslie 147 and an RE20. The RE20 won't go through the slats (!!), but the lower back panel comes off on the 147. I should be able to get the RE20 in nice and close.

 

I use a RE20 on the low rotor of Leslies a lot, and I usually do take off the rear panel. Be careful about the amp and the noises that come from over on that side - the solenoids click quite a bit when the speed settings are changed, which causes a click that can be really obvious if you mic from the wrong direction. You also have wind noise, which tends to be greater on the opposite side, so it's a bit of a PITB to get the mic position just right - usually I use a couple of windscreens (a barrier type perforated steel Stedman screen, as well as a foam filter over the RE20) to deal with the wind noise of the spinning drum.