Re-Post: Guest Post: How to Use Amps and Iso Cabs on Stage, Part 1

Throughout the month of April I am taking a break from writing in order to focus on other things.  As a result I am re-posting some of my most popular articles.

Kevin McPeak is the Creative Director at EastLake Church in Chula Vista, California. He isKevin McPeak a proponent of both tubes and digits.  You can follow Kevin on Twitter @kevinmcpeak or find him on Facebook.  Kevin has kindly agreed to lend us some of his expertise in technical issues and will be posting from time to time.

Q: I play electric guitar and love my amp sound, but we donʼt use amps on stage because of stage volume. Is there some way I can use my amp so it does not impact stage volume?

Well, first off, letʼs identify the problem, because that will help us find a solution. The reasons that our mix engineer wants us to keep stage volume under control are many:

  • stage volume blurs front of house (FOH) mix clarity
  • stage volume creates ever-increasing demand for volume from stage monitors
  • stage volume leads to “hot spots” and “cold spots” where instruments are either too loud or too soft
  • stage volume dramatically limits the FOH engineerʼs ability to create a thoughtfully and musically designed mix.

So letʼs be clear: amps arenʼt the problem in and of themselves; the problem is that amps tend to get treated like personal monitors and turned up too loud. Furthermore, many amps donʼt sound their best without running at a decent volume. How the heck do we solve the problem?

First, you may want to give amp modeling a shot. The technology of amp modeling has come a long way in the past few years, so if you tried it before and you didnʼt like it, you might want to try it again. The versatility and tone quality of most amp modelers has gotten quite good.

But letʼs say that youʼre like me and youʼre one of those finicky tube amp people. Youʼve spent a lot of time on your tone and have finally found something you want to stick with, but itʼs dependent upon that magical combination of guitar, whiz-bang pedals, and amp. And at least for me, part of getting the tone I like involves turning up the amp a bit and letting the tubes do what they do, and that requires me to run at a higher volume. When thatʼs the case, what can you do to keep your tone intact but keep the FOH engineer from throwing darts at you?

A few years back, I decided to solve this by purchasing an isolation cabinet for my beloved amp. An isolation cabinet – also commonly called an iso cab – is an enclosed box within which a speaker and a microphone are mounted. The iso cab also commonly features sound baffling to help reduce the amount of sound that emanates from the cabinet once itʼs closed up.

What does it look like? Iʼm glad you asked. First off, hereʼs how it looks from the outside (itʼs the box on the bottom):

As you can see, it functions much like any other speaker cabinet in an important way: It gives me something to set my amp on. (After all, we couldnʼt put these tube amps directly on the floor, could we?) Bear in mind that the cabinet is a completely enclosed box. But how do we see whatʼs inside? Check out the picture below:

Once you open up the cabinet door, you can see the microphone and stand that are used to pick up the natural tone of the amp and speaker. (See below for a closer look.)

The idea is then to take the microphoneʼs signal from the iso cab and send it back to the mixer, where the FOH engineer can use as much – or sometimes as little – of it as he/she needs to create a workable mix. But the use of the iso cab allows me to open up and let the amp sing a little bit without generating angry looks from everyone else in the room.

For the tone purists, itʼs reasonable to ask if the iso cabs alter the sound in any way. The short answer is that they do. My experience has been that iso cabs can inhibit spaciousness a bit, but thatʼs not unreasonable if you consider that the sound is being picked up in a small, padded box. However, for the purposes of live sound, the benefit thatʼs gained by using a favorite amp more than offsets a modest alteration in tone.

So, if youʼve got a favorite tube amp that you want to use in a live setting but your FOH engineer keeps giving you the stinkeye when you bring it in, itʼs time to start thinking about getting yourself an isolation cabinet so you can turn it up to 11 and let that amp sing.

Have another technical question you would like Kevin to answer?  Post your question in the comments.

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