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Opinions on cab micing please

Gwardar

Gwardar

May 24, 2009
408
22
Australia
#1
Dear All,

I need some opinions on what would be the best way to mic up a bass cab for live sound reinforcement.

The cab is Mesa 4x12, front ported with tweeter. Here are some ideas so far:

kick drum mic for lows and DI for highs
only one mic (say SM57) for both lows and highs
two instrument mics (SM57) but EQ-ed for lows and highs
kick drum for lows and SM57 for highs.

Which one would be the best setup (or none of them)? Also -where to put the mics (point at the centre, tweeter, port, etc)?

Basically what I have for my disposal is a kick drum mic, some other instrument mic (can be SM57, yet to buy this one) and a DI from amp (either Ampeg SVT VR or Mesa M-Pulse, not sure yet).

Many thanks,

MP
 
#2
DI and a Mic would definately be the best way to go for sure. Concentrate the DI for the lows while using the mic for the highs. The more centered to the cone you point it, the more crisp highs you will hear. I prefer an AKG D112 Mic on my 810 cab. If you really wanna get crazy, ha ha.... SM57 on tweeter, kick mic on one of the 12's and the DI out to the board. But seriously, most venues will just run a DI out and call it a day. This way there is no need to worry about feedback or vibrations on the stage causing unwanted sound to the mic. Hope this helps.
 
#4
9 times out of 10 when you use both a DI and a mic on your cab, you will get phase cancellation that sometimes can be severe and rob you of some serious low end.

My soundman uses a Radial Phazer out front specifically to remedy the phase cancellation between my bass DI and the mic on my cab.

I would highly suggest you use one if you plan on blending the two.

Oh, and skip the kick drum mic and use a 57 instead.
 
#5
Eric Moesle said:
9 times out of 10 when you use both a DI and a mic on your cab, you will get phase cancellation that sometimes can be severe and rob you of some serious low end.
(...)
Click to expand...
That is an excellent point. Thanks for highlighting it. Surely there are a few inverting stages on the way and it's hard to say which way it would turn out as they are separate paths.

Would you suggest 2x SM57 (one EQ-ed for treble, one for bass) or just one will suffice?

Thanks.

MP
 
#6
Note that the SM57 slopes from -10db to 0db from around 40Hz up to 200Hz. That'd be the fundamental notes between an open E string at -10dB sloping up to 0dB at a G string's octave.

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The 57 does gain a decent amount of low frequency response up close. But I'd imagine some EQ would still be needed to accurately reproduce the sound of your cab. And then you'd need another for your cab's tweeter (unless you turn it off to get your sound).
 
#8
You should be fine with one 57. A kick mic will have a scoop as previously mentioned. DI will give you a clean signal, but you wont have the sound of your cab figured into it. Most times the DI will sound pretty good, but I always prefer a mic. I think micing the tweeter is a bad idea, you should get plenty of high end off the mic.

The engineer will eq at the board for the amount of highs and lows, no need for separate mics. It's live sound, not a multitrack recording. Point the mic straight on at the speaker, don't angle it. I like my mic placed pointing at the junction of the cone and dust cap. I don't know why, it just always seems to sound good there. Experiment a bit if you have a chance, but most likely the sound guy will just put it where he thinks is best. Most times you should trust them, they know their room and their system. Lastly, try to get them to mic the bottom speaker, there's less chance you'll knock into it.
 
#12
Inverting the phase will definitely solve alignment issues if the two signals are 180 degrees apart. The solution could also involve experimenting with forward/backward mic placement in concert with phase inversion. Either way, as kedo said, if you mix two signals (mic + DI), it'd be a good idea to make sure at least one of them has a phase switching feature. It shouldn't matter which one you switch, as long as you don't switch them both. In that case, you'd be right back where you started.
 
#13
For my Mesa 12" cabs I just use my Heil PR-40 whenever possible. Plenty of low end and attack for what I need. The RE-20 and 421 are also good choices for stand-alone miking. I don't like to run dual-signals, usually. Just one or the other. That cab sounds great (I had the full 412 before I got the "modular" version) when you turn it up and the speakers start to bark so I definitely try and mic when I can!
 
#14
kedo said:
Also... if phasing issues occur, many mixing consoles have a phase inversion function on each input.....
Click to expand...

That would only be a remedy if the phasing was exactly 180 degrees out of wack, which it almost never is.

You need a VARIABLE phase adjuster like on the Radial Phazer to be effective in 99 percent of the circumstances.

I can tell you from my experience over the past two years of two gigs every weekend, the correct setting on my Radial Phazer was different in EVERY venue and was NEVER exactly 180 degrees apart.

Even playing the SAME VENUE on different nights the phase differential will change, simply because my amp's speaker will be at a slightly different distance or angle from the mains each time after tear-down and setup.
 
#15
Ya, springing for a good mic like the Heil or EV is the way to go IMHO. However, if you use a DI for lows below 100hz, and a 57 or 58 for everything else, it'll do a really good job for you and you can keep phasing issues at bay pretty easily.
 
#16
57+DI is utopia for me, whether I'm on stage or behind the desk. It's a great combination to work with, and it's very 'mixable' from a sound engineers' point of view.

I've had a little experience with high-end dynamics, and IMO the advantages you get don't warrant the cost for live. YMMV, but that's just how I see it as a bassist and a sound engineer. :)
 
#17
Well the big advantage is you can use one line without requiring a blend. A lot of times I can only get one line because we're a pretty big band now with horns and 5 of us who sing. And my one line sure ain't gonna be a DI if I can help it ;)
 
#18
Eric Moesle said:
That would only be a remedy if the phasing was exactly 180 degrees out of wack, which it almost never is.
Click to expand...

That's not exactly right. Using the polarity ("phase") switch will almost always have a "better" and "worse" setting, because for it to make no difference the phase would have to be exactly 90 degrees out, which is just as unlikely.

But I am curious about the piece of gear you speak of. Is it a delay unit? Phasing issues are highly dependent on the position of the listener and the frequency of the signal.
 

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