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Author Topic: Advice when running multiple Guitar Amps on Stage  (Read 1001 times)

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Elantric

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Advice when running multiple Guitar Amps on Stage
« on: March 15, 2013, 09:13:01 PM »

I should relate one bit of advice when running multiple Guitar Amps in a large room / concert hall.

If you do not manage the acoustic phase cancellation that physically occurs due to multiple Non Time Aligned Audio Point Sources (i.e. Multiple Guitar Amps spread across a large stage in a Large Concert Venue) , you may find the audience will report that your Live tone sucks compared to the opening Acts Guitarist who only used one 1965 Fender Deluxe Reverb close mic'ed with one Shure SM57.

More technical discussion on Audio Time alignment is here
http://sound.westhost.com/ptd.htm

True, Many classic Guitar tones we all know (Brian May) are the result of Multiple Guitar Amps with CAREFULLY PLACED Microphones located both near the Amp's Guitar Speaker and far away which creates phase errors in a controlled studio environment, This creates a resonant peal thick tone due to phase errors  -and its important the resulting dominant resonant tone frequency does not conflict with the key of the song   - so it often handy  to have the same tools  / knowledge to tune your Live rig for the specific venue, key of song, guitar type used - all play a factor in distant mic placement.

Typically The recording Producer listens to the combined "mix" of all sources for the guitar being recorded (DI Box, DSP Modeler direct out, room mics, etc)  - and instructs the recording engineer to move the room microphones until it sounds good with the current song being produced. There are no hard and fast rules, and often its takes several pages and days of math analysis for a PhD to explain in full scientific detail the same "audio phase error "phenomena that a producer / engineer with good ears can set up with multiple mics in seconds for the benefit of the song and delivering "thicker sound" for the guitars. 

I suggest get a set of good closed headphones  - like Audio Technica ATH-M50S
http://www.amazon.com/gp/product/B004ZG9TMA/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1

and have a friend play guitar, while another friend moves a few mics to separate locations (near and far from amp) in a separate room  and record all elements on separate tracks and mixed to mono  for analysis / playback review.

DO this for a day or two and you should have  better first hand knowledge of phase errors due to multiple point sources


On the cheap, one method is use a Yamaha 01V Mixer as a Guitar "Pre-mixer" - before your FOH Board feed.

http://www.soundonsound.com/sos/jul98/articles/yam01v.html


Each night, be sure all your Guitar Cab mics are consistent: set at the exact same distance / position relative to the speaker.

Run every guitar amp mic into a separate channel on the 01V , then employ the individual "Channel Delay" controls (with its 0.1 millisecond resolution)  on each channel of the Yamaha Mixer to assist with restoring time alignment and minimize the Phase cancellation for all the guitar amps in that specific room.

I see band Riders for touring bands , and many do specify "Yamaha Mixer Only" - for this specific reason, because bulk of Mixers lack the unique Channel Delay controls that are built into most high end  Yamaha Digital Mixers.

But know that most Professionals who are reading here understand all that  - been there, done that,  bought the T-Shirt.

and in 2013 many major acts have opted  / or have tours managers who insist the whole band USE no onstage guitar amps, and In Ear Monitors for the whole band  with better management of all stage audio sources to allow the FOH Mixer more complete control over the bands Live sound.


The biggest complaint most FOH Mixers inform is lack of ability to "Turn Down the Guitar" when confronted with acts with guitarists with large multi-amp rigs.

I also recommend buy PlexiGlass Shields to place in front of the guitar cabs, to assist your FOH Mixer's job, and improve the audiences's opinion of your live act, and sell more CD's.
http://www.thegearpage.net/board/showthread.php?t=1055062




Quote
there are plugins that will phase align tracks to counter any phase issues. Record away...

My point is, often the "phase issues" are desired and in the case of Brian May, an important part of his final Guitar tone on the recordings

skip the books and explore the following strategy that can become a useful tool in your arsenal of knowledge so you can employ multiple point sources on future recordings and live sound

Quote
I suggest get a set of good closed headphones  - like Audio Technica ATH-M50S
http://www.amazon.com/gp/product/B004ZG9TMA/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1

and have a friend play guitar, while another friend moves a few mics to separate locations (near and far from amp) in a separate room  and record all elements on separate tracks and mixed to mono  for analysis / playback review.

DO this for a day or two and you should have  better first hand knowledge of phase errors due to multiple point sources  - and understand when its desirable to employ them

and read the free web resources here:
http://www.sengpielaudio.com/Calculations03.htm

http://en.wikipedia.org/wiki/Phase_(waves)


http://www.sengpielaudio.com/calculator-timedelayphase.htm



http://mhsecure.com/products/CSGB/cs_pg2.html

« Last Edit: Today at 01:44:46 PM by admsustainiac »
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DF400

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Re: Advice when running multiple Guitar Amps on Stage
« Reply #1 on: March 15, 2013, 10:28:03 PM »

Good stuff, thanks for sharing! Although I have never played "arena" venues, I have played large enough venues where time delay became an issue - both for me and the audience. My sound guy very much prefers that we all run in-ears, I prefer one in - one out so I don't loose touch with the feel.

Although I truly hate thinking about these things before a gig - I very much appreciate your sharing this. If nothing else, it gives me a great appreciation for the Sound Eng. -

I continually hear about the Yamaha 01V, although it seems there is some pretty stiff competition these days.
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Elantric

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Re: Advice when running multiple Guitar Amps on Stage
« Reply #2 on: March 15, 2013, 10:58:51 PM »

Quote
I continually hear about the Yamaha 01V, although it seems there is some pretty stiff competition these days.

Even in 2013, very few live mixers sold today offer discreet "channel delay" for each channel on the mixer. a 24 channel Yamaha board has the typical onboard stereo FX, but it also includes 24 separate discretely controllable digital delay lines - one per channel

The concept originated on the 1996 Yamaha 02R - which soon migrated across the Yamaha mixer range  and the popular Yamaha PM5D live mixers.

http://www.soundonsound.com/sos/oct02/articles/yamaha02r96.asp

Read the manual here:
http://www.manualslib.com/manual/196612/Yamaha-02r96.html?page=114


Even todays popular Presonus "StudioLive" Mixers still lack this important feature, that 90% of folks who grew up with a Mackie mixing Board  never understand why this feature even exists.

I know several live acts who rely on the individual Yamaha channel delays with 0.1 millisecond resolution on the yamaha mixers to time align and control phase cancellation on Drum mics, choirs, symphonies, etc. Its a fundamental important audio control tool for pro Audio engineers.

BTW - the VG-99 includes a similar set of "Chanel Delays" - one for each A and B COSM signal chain.

See page 35 of the VG-99 Owners Manual

Quote
When mixing two channels, you can produce a more
realistic twin guitar tone by setting a channel delay in
one of the channels, thus causing the two guitar sounds
to be output at different times.

and in conversations with Bill Rupppert - he told me many dull COSM VG-99 patches can really change character for the better ( or worse) by making two identical COSM Signal FX chains, but then manipulating one of the COSM audio signal's CHAN Delay control, to adjust the phase of each COSM chain's final arrival time in the mix, by manipulating and implementing ultra small minute delay shifts in one VG-99 COSM channel, you introduce comb filtering due to phase errors which occur when the two VG-99 COSM signal chains are mixed in the VG-99 mixer stage - adjust to taste!

Makes for good experimentation for VG-99 owners.  (see Orange blocks for the Channel Delay controls)




Similar strategies can be obtained in a digital computer DAW, by recording a mono guitar track of a miced guitar amp, then make an exact copy to another channel - but then drag the track left or right on the timeline by a few SMPTE frames,  to create a thick phase error riddled "fixed flange" like tone.   
« Last Edit: July 09, 2013, 03:05:14 PM by Elantric »
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aliensporebomb

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Re: Advice when running multiple Guitar Amps on Stage
« Reply #3 on: March 16, 2013, 08:28:30 AM »

The Lexicon Vortex had a similar feature, to "morph" from one patch to another, it also had an A/B for patches so frequently the interesting part of the sound was the process of traveling from A to B and you could also control it via a pedal and also change the amount of time it took from traveling from A to B.

I had an idea about this yesterday too applicable to the VG-99, more later.

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rolandvg99

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Re: Advice when running multiple Guitar Amps on Stage
« Reply #4 on: April 17, 2013, 11:57:39 AM »

The 01V's channel delay is the main reason for me still owning one of the 01V96's. It's perfect for cleaning up stage clutter in the FOH. I usually run it in 16+16 channel mode. 16 channels for FOH and 16 channels for IEM and wedges. Very handy indeed as latency isn't what you want for monitoring. There are better mixers and preamps, but it's a trusted companion yet to fail me. These days I mainly use the ADAT out to feed 16 channels of IEM to my Moto 828 MKIII.
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