Dirty-South Blues Harp forum: wail on! > Micing an amp w/ two mics
Micing an amp w/ two mics
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1528 posts
Feb 18, 2019
5:47 AM
After another gig this Saturday, haunted by feedback, I wonder if it is a good idea to mic your amp with two (2) mics, in case you need to increase your volume?
My ignorance of sound tchnology is monumental but I know that the decibel scale is logarithmic and does not ... work like an ordinary scale.
I recall that I´ve sometimes seen this solution.

This time I followed a suggestion and used a Fender Vibrolux that already was on the (really crowded) stage, in lieu of hassling with my own. On my suggestion that it perhaps needed to be miced, the arranger said, "What! That one is 50 Watts!" and then turned to other things. I took that as a no.
Of course it should have been miced, and I was on or over the feedback threshold all evening. Really tiresome. (And this despite a feedback blocker (a simple thing), as well as a Harp Octave.)
1908 posts
Feb 18, 2019
8:35 AM
Needless to say, this is all just my opinion. Others may present other ideas. I hope they do... I always like hearing different ideas on managing live harp on loud stages.
*************** IMHO
If you mic the amp, then only one mic to the PA would be needed. You could experiment with what part of one speaker you aimed it at. I would start halfway from the center to the edge with a Shure SM57. The only time you might try 2 mics is in a studio, so you can capture different sounds and pick or mix for a recording. Live stage and loud volume, and you are asking for feedback trouble with 2 mics.

Unless you have a really small amp not on the edge of feedback, if the amp is miced to the PA it should not be put in the monitors, just in the front of house. Putting it in the monitors while you are playing at the volume limit of feedback would push you over into feedback. If you are having feedback problems and you mic the amp, you just amplify your feedback to the house and punish the audience.

Was the amp behind you? Could you have moved it to be beside you? You can push an amp louder if you are to the side, in a sonic "dead zone." Visualize an hourglass shape of sound, with the amp at the center narrow part.

Were you plugged into the Normal or Vibrato channel? There are extra 12AX7s involved in the Vibrato channel. Using that channel may increase the likelihood of feedback when you are struggling for volume. Did you use reverb? Reverb increases the chance of feedback and adds a 12AX7.

What harp mic did you use? Do you have volume control on that mic? VC can help you manage when you are playing on the edge of feedback.

If I had some ringing/feedback with a rig like this on a loud stage I would prefer a directional mic if I had one with me, not an omni bullet mic. A super cardiod mic is less likely to pick up amp sound and feed back. I like my 585SAV for a situation like this when I am pushing limits for volume. A Shure SM57, SM545, or SM58 with volume control would do, however, these low z mics benefit from an impedance converter when played through a high z amp input. There are other directional mics that help with loud volume situations, like the EV RE-10.

In a loud edge-of-feedback situation on a loud stage I would always choose to use the normal channel in order to maximize my volume. I would sacrifice some brown sound and effects in order to be heard.

If I had feedback issues while using the anti-feedback pedal and Harp Octave I would simplify and try the Normal channel without any pedals first and adjust eq to minimize feedback. Then I might try one pedal at a time to judge what got me the most volume before feedback with the best sound.

Sometimes in live gig situation, particularly with a loud band in feedback troublesome venues, you have to choose between optimal harp sound quality at lower volume, or acceptable harp sound at adequate volume. Sometimes you cannot have the sound you want at the volume required.

I have not played through a Vibrolux, but it should be a manageable amp and pretty loud. Maybe the band was playing way too loud for the room/stage?

Sitting in locally with a loud blues band, I experienced playing harp through a Fender Super Reverb that the owner had miced to the PA! The amp owner and harp player continually struggled with feedback despite the massive power of the amp through 4-10" speakers.

The first time I was asked to sit in using this amp I chose to use the normal channel. They first turned off the mic to the PA, and then the band and the sound guy still made me turn down. The harp was too loud for the stage and the room. No feedback, either!

Even with a smaller and weaker Blues Junior, you will get the most volume before feedback from the clean channel where your signal goes through fewer 12AX7s. You may not get the effects you like, like reverb, but you get a warm sound with enough volume for your playing to be heard.

In a live situation I will always choose to be heard rather than seek optimal harp sound and have feedback or not be heard over the band.

Doug S.
1529 posts
Feb 18, 2019
12:39 PM
Thank you Dougharps for your exhaustive answer.

Yes, the band was loud, they always are (it´s hopeless), and the amp was in an unfavourable position: at the back, partly shielded by one of the drums, and not elevated to any higher position -- all far from ideal.
Also I used delay, but I don´t think I´d even played if I had had to be completely dry: that is just too dull.

The mic is very feedback resistent (an EV) and compares well to the Audix Fireball, for instance, in that respect.
As a matter of fact I happened to use one of the Bright channels: my very quick soundcheck indicated more output from that one, and no overbearing brightness; the Normal sounded a bit dead.

There were dozens of mics (SM57´s and other) at the venue so I could have used that, but once we got started I couldn´t be bothered with rigging up a mic, not even in the break, so I just had to sweat it out.

I thoroughly regret that I took the "advice" from the sound guy and did not mic up the amp. And I´m glad you tell me that in cases where even that does not suffice, it´s no use in introducing another mic.

Once again I regret the cursed day that I took up this instrument, but there you go.

Cheers /Martin
2840 posts
Feb 18, 2019
6:35 PM
I just let go of loud bands some years ago. My harps and my voice were taking too much damage trying to hear myself, and most amps I used just didn't cut through. The duo thing is very satisfying these days. 12w amps, 2 or 3 different mics, and that's it. I can set the sound up in about 30 minutes. Guitar, harp through small amps, 2 vocal channels through small 4 channel p.a., and I'm done. Time to play and BE HEARD! With decent tone quality.

I had some great times with 4 piece and bigger bands over many years but this is so much more satisfying in the long run.
Music and travel destroy prejudice.



201 posts
Feb 21, 2019
7:43 AM
The best way,for me, to prevent harp feedback,is distance from the AMP.Though,a SM545,through a 65w Music Man 2x10,with a master volume,gives me a lot of control.Setting the volume on8/9 then cut back on master a few #,No feedback.With this set up i can play with the guitar, same volume...i`ve been using this set up since 1978.....And just one sm57 mic on amp...

Last Edited by nowmon on Feb 21, 2019 7:44 AM

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