placing a room mic on amp / phase

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joninc
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placing a room mic on amp / phase

Post by joninc » Wed Mar 25, 2020 3:46 pm

I'm wondering if any of you have any rules of thumb when it comes to placing a room mic on a amp - i've had very mixed results over the years with this and sometimes I luck out but more often than not, when I listen to the close and room I have major phase problems making the room mic unusable.

ex: i have a close mic up on the grill and I want to add a mic back maybe like 5 feet for some room ambience but i am really struggling to find a placement that's in phase with the close mic... i keep moving it back a few inches and checking and it doesn't seem to get better/clearer... lots of bad comb filtering.

so i'd love to know any tips from those of you who do this regularly - specifically for repeatability since i record 98% of the time in my own studio. (I have 2 large booths at either end of my studio that I typically record the amps in. They are roughly 10 x 25 with some good acoustic treatment on the outer walls and ceiling panels.)

do you like to point the room mic away from the amp?

how far do you typically place it from the amp?

mic polarity/type that you favour for this application?
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Re: placing a room mic on amp / phase

Post by A.David.MacKinnon » Wed Mar 25, 2020 7:20 pm

Im going to give the classic “it depends” answer but it really does depend on a number of factors.
How loud are you hoping to mix the room mic? Is it panned to the same spot as the dry?

Lots of times I’m tracking bands live in the same room. In those cases bleed becomes my room mic. It usually shows up in the vocal and overhead more than anywhere else. When it comes time to overdub, if the band mics are still up I’ll use the vocal or oh mics for my room and track them along with the close mic for any overdubs.
Beyond that, I never have tons of luck if the room mic isn’t fairly far away. My old space was quite big and very, very live sounding so it was pretty easy to drop a room mic almost anywhere in the room 10+ feet away from the amp and have something useable. Now I’m in a small space and it’s much harder. Pointing a cardiod mic away from the amp works sometimes. Using a figure 8 and pointing the null towards the amp can help. Heavy compression can make a huge difference too.

If the room mic doesn’t need to be loud and it will be panned opposite the clean signal you can often get away with a less than stellar sound. In context it give you the sense of space you need.
If you want to mix it loud and panned with the dry signal it’s harder. Sometimes I find it easily to just use one mic and back it up enough to get my space that way. In a small room I find that easier than dealing with the phase issues of two mics.

One other thing, if you can do it you might try cracking the door on one of the booths and putting the mic in the other room.

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Re: placing a room mic on amp / phase

Post by A.David.MacKinnon » Wed Mar 25, 2020 7:46 pm

You might also try delaying the room mic. Being able to extend the room mic distance beyond the haas effect range might help your phase issues. You’d also be able to “tune” the phase by changing the delay time while listening to the phase relationship.

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Re: placing a room mic on amp / phase

Post by drumsound » Wed Mar 25, 2020 9:30 pm

I often end up with the mic I set up as talkback becoming the room mic. I think the key is often to have the mic higher, not on the plane the amp is on. I think a room mic at speaker level can have really weird interactions with the floor, but up in the air some (or a lot) works better for me.

Omnis are great, especially 635a, its already a little "band limited" and just kinda works.

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Re: placing a room mic on amp / phase

Post by Nick Sevilla » Wed Mar 25, 2020 9:31 pm

joninc wrote:
Wed Mar 25, 2020 3:46 pm
... ex: i have a close mic up on the grill and I want to add a mic back maybe like 5 feet for some room ambience but i am really struggling to find a placement that's in phase with the close mic... i keep moving it back a few inches and checking and it doesn't seem to get better/clearer... lots of bad comb filtering.
Hi David,

I've been recording guitar cabs for a while... from 1 to 4 mics.

Typically, I use a "room" mic only to add girth to the sound, and use a large condenser, or even a tube condenser
when possible. If I need a larger room sound, I go artificial with reverbs or delays.

I never find good results at beyond 3 feet. Usually inside of 2 feet is best. Especially in a room that does not sound good.

Usually, to get the guitar to "bloom" anywhere from 12" to 24", checking for phase, not for the signal to begin
at the same time, just for it to begin in the same direction of the close mic. It should be NOT time aligned,
just let it sit back in time from the close mic, in a spot where it adds dimension to the sound. I point it towards
the speaker, usually pointing down at it from just slightly above the speaker, or the height of the edge of the cabinet.

You mention "comb filtering", which means that wherever you were placing the room mic, there is a node or
a peak around the main guitar frequencies. So, don't put it there. Move in closer.

Cheers.
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Re: placing a room mic on amp / phase

Post by losthighway » Thu Mar 26, 2020 7:10 am

If you're on a digital platform the wise 'delay the room mic' recommendation can be auditioned in milliseconds (sorry). Zoom in, grab the room mic track and slide it slightly right. Listen, adjust, repeat.

Also a figure 8 with the null pointed at the amp is good.

Overall I find the room mic on guitar amp sound only works on really sparse mixes, or as a production choice to shift the soundscape during a specific moment of a song (say where the drums drop out and there's a guitar and vocal only segue). In something bigger, or busier it just fogs things up.

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Re: placing a room mic on amp / phase

Post by joninc » Thu Mar 26, 2020 12:42 pm

thanks for the feedback - some good (and conflicting :) thoughts for me to try... I think getting off the same plane as the close mic/speaker might be key and possibly using the null as mentioned in a fig 8 makes sense to me too. The rooms sound good, I think it's more to do with the placement and perhaps I need to also try being much father away.

As far as the context: This is for when I'm going for something vibey and want the guitar to have more personality and more of a sense of space in the song. It's very different sounding than adding reverb IMO. This isn't typically dense rock or something where there's not a lot of room to breathe .. more singer songwritery type stuff. I'd generally be panning this away from the close mic to add more width.
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Re: placing a room mic on amp / phase

Post by vernier » Thu Mar 26, 2020 4:20 pm

Adding a second mic is ok if you have a cool sounding room ...the size and liveliness adding coolness to the finished product. As for phase issues, I never had it, but also hardly ever use a room mic on guitars.

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Re: placing a room mic on amp / phase

Post by digitaldrummer » Fri Mar 27, 2020 7:40 am

when I use room mics (for drums or guitars) I usually either put them in fig-8 with the null facing the subject (amp, drums, etc.) and that gets more reflections off the opposing walls (as mentioned earlier), or I'll put it in Omni mode, or in cardioid mode I'll face it opposite of the subject and put it up in a corner, or even down in a corner, just so it gets weird reflections. although sometimes, that also can be pretty dead depending on how your room is treated. either way, it's not the same sound as the mic on the cabinet and that's usually what I'm going for. And then more than half the time I never use it anyway. :-)
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Re: placing a room mic on amp / phase

Post by Recycled_Brains » Fri Mar 27, 2020 8:57 am

I generally have the same problem. I'm always recording heinously loud amps, so the room really gets filled up.

I'm wondering if putting the room mic behind some sort of barrier or gobo or whathaveyou would help, so that there is almost no direct sound hitting the mic.

I think Tony is on to something. The impulse is to point it at the cab, just further away, but I think that (especially) 4x12s are extremely directional. The random mic in the room not pointing anywhere near the amp is probably worth a shot too.
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Re: placing a room mic on amp / phase

Post by losthighway » Fri Mar 27, 2020 12:08 pm

Recycled_Brains wrote:
Fri Mar 27, 2020 8:57 am
I think Tony is on to something. The impulse is to point it at the cab, just further away, but I think that (especially) 4x12s are extremely directional. The random mic in the room not pointing anywhere near the amp is probably worth a shot too.
I second this, or third it as it were.

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Re: placing a room mic on amp / phase

Post by vvv » Fri Mar 27, 2020 12:21 pm

A search will reveal a thread I started on about the same topic in this last year.

The advice I received that I found most useful in mic'ing loud amps in my little (12 x 15") room was to place my room mic (as said above - and I note that I use ribbons for the far mic) about mid--room with the null facing the amp.

That did result in more usable 2nd mic's, but ultimately, in such a small room, I had to add processing to get a room effect with the 2 mic's.

In reality and current practice, I find the second mic most useful as more or less an EQ; ex., the room mic is typically dark, so as a primary mic it's pretty different from a track done with the close mic, and combining the two (I usually do this) so that one is 2/3 and the other 1/3 of the mixed-down track, and the second guitar the opposite proportion, can give me more flexibility and/in variation of the guitar tracks.

FWIW, more useful to me to get an actual room sound is a 2nd mic in the hallway ... in particular, the amp and close mic in the bathroom and a second mic out in the hall - where the ambient area is actually different - can work pretty well for setting off the rhythms from the leads.

And then, and I really dig it sometimes, there's M/S.
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Re: placing a room mic on amp / phase

Post by joninc » Fri Mar 27, 2020 1:46 pm

I'm mostly using smaller combo amps - fender deluxe, blues jr etc... sometimes an ac30 - so it can be loud but not usually crazy distorted/heavy - at least not on the stuff where i'm looking to use a room mic.. think more Mark Ribot / Tom Waits / Tbone burnett...

looking forward to trying these ideas ASAP.

Also VVV, could you share the link? I can't find that thread...
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Re: placing a room mic on amp / phase

Post by vvv » Fri Mar 27, 2020 7:49 pm

bandcamp; vlayman;
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Re: placing a room mic on amp / phase

Post by MoreSpaceEcho » Sat Mar 28, 2020 11:21 am

losthighway wrote:
Fri Mar 27, 2020 12:08 pm
Recycled_Brains wrote:
Fri Mar 27, 2020 8:57 am
I think Tony is on to something. The impulse is to point it at the cab, just further away, but I think that (especially) 4x12s are extremely directional. The random mic in the room not pointing anywhere near the amp is probably worth a shot too.
I second this, or third it as it were.
Fourthed.

I'll add that I never had any luck panning the room mic to the same spot as the close mic, just never seemed to work. But panning it opposite, maybe 9 and 3, can be really cool. Or the close mic panned center and the room hard l or r. You can get a really nice sense of space/depth that I don't think you can really get any other way, just slapping a reverb on isn't the same.

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