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Author Topic: Quick and dirty and cheap Laptop RTA  (Read 11441 times)

Dan Richardson

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Re: Quick and dirty and cheap Laptop RTA
« Reply #10 on: June 23, 2011, 01:55:34 pm »

I have a laptop and TrueRTA software, I'm thinking about a Behringer ecm8000

I routinely use an RTA to ring out feedback nodes preshow. DesktopRTA identifies the loudest frequency, which is all I care about.
(Well, actually I use Audio Kit on my iPhone or iPad, but it was Desktop RTA on the laptop before that.)
For that application, the mic in the phone or laptop is plenty good enough.

If you want some nice eye candy with a lot more information available, grab a copy of the Easera Systune demo.
Free, not time limited, and has a great spectrogram display, so you can see what just happened before you looked at the screen.
http://systune.afmg.eu/
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Re: Quick and dirty and cheap Laptop RTA
« Reply #11 on: June 23, 2011, 02:03:51 pm »

I routinely use an RTA to ring out feedback nodes preshow. DesktopRTA identifies the loudest frequency, which is all I care about.


Dan....

Not arguing with your method or experience, just wanting to know why you don' just do a few sweeps with a parametric EQ to identify said "nodes".  Put a bit of boost on the band, sweep until the node shows, then narrow it down and cut it.  Lather, rinse, repeat.  A lot quicker than sorting out the visual info, then transferring it to your EQ and then confirming the results by ear.

Why not just do it by ear in the first place?
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Dan Richardson

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Re: Quick and dirty and cheap Laptop RTA
« Reply #12 on: June 23, 2011, 03:14:28 pm »

Dan....

Not arguing with your method or experience, just wanting to know why you don' just do a few sweeps with a parametric EQ to identify said "nodes".  Put a bit of boost on the band, sweep until the node shows, then narrow it down and cut it.  Lather, rinse, repeat.  A lot quicker than sorting out the visual info, then transferring it to your EQ and then confirming the results by ear.

Why not just do it by ear in the first place?

[thread hijack]

My application is a little unusual.
4 chorus mics over largely untrained elderly singers, and a rock band onstage. I need every dB I can get.

I preprocess them with a Xilica XP4080M. I use this piece for two reasons.
It has mic preamps, and it can do .03 octave filters with single Hz precision from 20 to 20k.
I can add 8 notches and the mic still sounds the same, only it doesn't feed back.
RTA says it's ringing at 423, I type in 423 and hit Page Down as many times as I want dBs of cut.
Cursor arrow to the next filter, up the gain, and repeat. It's very fast. The knob interface is not.
Sweeping the computer interface isn't good either, because there's significant lag.
Xilica's hardware is excellent, but their program is awful. I wish Lake would write everyone's interfaces.

Anyway.

I notch each mic independently in the processor's input stages.
Inputs 1-4 are routed to outputs 1-4, and those output settings are linked.
Then I bring up all 4 at once, and use the output EQs to notch the combined mics.
Inputs 1-4 are also routed to outputs 5-8, and those output settings are linked.
I bandpass outputs 5-8 300-3k with a gradual slope at the top, and notch them viciously.
When the chorus is shouting a rocker, like The Ramones' Sedated or Fugazi's Waiting Room,
I can use 5-8 to get another 3-6 dB of intelligibility without getting any additional high hat.

Works pretty well.

[/thread hijack]
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Re: Quick and dirty and cheap Laptop RTA
« Reply #13 on: June 23, 2011, 03:27:02 pm »

[thread hijack]

My application is a little unusual.
4 chorus mics over largely untrained elderly singers, and a rock band onstage. I need every dB I can get.

I preprocess them with a Xilica XP4080M. I use this piece for two reasons.
It has mic preamps, and it can do .03 octave filters with single Hz precision from 20 to 20k.
I can add 8 notches and the mic still sounds the same, only it doesn't feed back.
RTA says it's ringing at 423, I type in 423 and hit Page Down as many times as I want dBs of cut.
Cursor arrow to the next filter, up the gain, and repeat. It's very fast. The knob interface is not.
Sweeping the computer interface isn't good either, because there's significant lag.
Xilica's hardware is excellent, but their program is awful. I wish Lake would write everyone's interfaces.

Anyway.

I notch each mic independently in the processor's input stages.
Inputs 1-4 are routed to outputs 1-4, and those output settings are linked.
Then I bring up all 4 at once, and use the output EQs to notch the combined mics.
Inputs 1-4 are also routed to outputs 5-8, and those output settings are linked.
I bandpass outputs 5-8 300-3k with a gradual slope at the top, and notch them viciously.
When the chorus is shouting a rocker, like The Ramones' Sedated or Fugazi's Waiting Room,
I can use 5-8 to get another 3-6 dB of intelligibility without getting any additional high hat.

Works pretty well.

[/thread hijack]

Yup, hijack.  I had forgotten  what your gig was......

I think this is a little different than the OPs usage, but valid anyhoo.  I use GraphiQ's in pretty much the same way because that's what I have.  Running them on my laptop allows me to do sweeps just like I'd do with my KT410.

The only difference I see at this point is whether you turn up the input until it shows visually or whether you sweep with a boost until you hear it.  The GraphiQ will also sets filters for me automatically which  can then be locked down or changed to parametric for tweaking to taste.  Quick fixes on rogue mics are then addressed by inserting a SOLO unit on the channel.

Lotsa fun.

Keep up the good work.

Now back to your original sponsor........
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duane massey

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Re: Quick and dirty and cheap Laptop RTA
« Reply #14 on: June 23, 2011, 10:43:12 pm »

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Duane Massey
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Rob Spence

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Re: Quick and dirty and cheap Laptop RTA
« Reply #15 on: June 25, 2011, 12:32:42 am »

One problem with ringing out rooms when empty is you pull out frequencies that may not be problems once the room fills up. Then, during the show you may have other ones resulting in too many frequencies pulled down and taking out too much program.

Not that ringing out is bad but you need to be aware of the results.
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Marsellus Fariss

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Re: Quick and dirty and cheap Laptop RTA
« Reply #16 on: June 25, 2011, 04:20:52 pm »

I will be touring with a support act in August and September. One 50 minute set with little set up time and little or no sound check. I have a laptop and TrueRTA software, I'm thinking about a Behringer ecm8000, well, I said cheap :D Can I plug the mic into a channel on the FOH desk and patch from the channel out directly into the laptop mic in? With phantom on for that channel and not assigned to any outs obviously. Would the 1/4" to 1/8" patch cord be TS or TRS? Would this work? I will have some specific effect cues and I want to be able to grab "bad" freqs in a hurry so I'm not fudging around with EQs instead of hitting my cues. Thanks in advance, Sean.


First of let me say that I use SMAART every night when I mix. I run one input from the headphone/monitor bus of the console into it and monitor that in spectrograph mode. The other side is fed from an unused pre via it's direct out just as you described. This allows me to solo any input or aux send (feeding wedges across the room of 500+ people) and have a look on the spectrograph. I find so many uses for it it's really awesome.

Examining an instruments tone to determine what action to take such as finding that note that's poking out on an upright bass during a show with no soudcheckor finding the fundamental of a kick drum or floor tom and duck that frequency at the channel a little is very helpful sometimes.

Ringing out problem mics or wedge mixes in a split second with no mistakes during a show or after doors when you've gotten no sound check. There's all types of situations where you might have to ring things out and locate feedback when you really don't want to or shouldn't have to but there you are. With this rig I can crank the gain to SMAART and see the ringing develop before people can even hear it. On stage during a soundcheck I might ask an experienced musician to cup a hand and move it VERY SLOWLY toward a hot mic and all I need is the slightest little wisp of a ring for a half a second and I can find it the first time everytime. I wouldn't do this with novices however.

As far as ringing out a room at soundcheck remember two things:

Your the opener. You shouldn't hack up the house graph if it's not recallable. Your not going to have a lot of time for soundcheck anyway if the headliners take every minute for themselves and this is not unusual. Your the opener. If you think you really need to so some serious EQ'ing to the rig (which you won't really have time for) then insert a PEQ across the mix bus or your subgroups or something and bypass the house graph the headliner is using.

Don't fight empty room. If you've got major feedback problems then you have to cut a few bands but more then a few and your going to just hack up the graph because of the empty room that's going to settle down and tighten up with people arrive. Just cut a few and leave it until show. Monitor on your spectrograph what was ringing and if if it happens again during the show then cut it then.

To the skeptics of using the spectrograph method I say I'm not leaning on it because I can't use the old school methods of using the ear and the graphic and strips. I did that for 15 years. I'm saying sometimes I'm wrong and it takes me a few try's to pull the right band and this method gets it right in a second the first time every single time and lets me see stuff I can't hear. It's saved my ass so many times I can't even count. Why would you not want to do that? I honestly don't know why it's not a feature built into digital desks these days.   

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Re: Quick and dirty and cheap Laptop RTA
« Reply #16 on: June 25, 2011, 04:20:52 pm »


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