Free RTA

[Schniapereli]

At my high school, we have a very strange auditorium, with strange acoustics. They once had a professional bring in an RTA, (which came up with some pretty strange frequencies), but since then, our GEQ has been messed up, so now all the notches are just at 0.

I am looking for a completely free or extremely cheap RTA sort of system. I found this online which is (according to my own unprofessional, inexperienced opinion) pretty good.

I also have this little program which outputs pink noise, or white noise, or whatever.

So, I've got pink noise, an RTA, but no measurement microphone. What I'm wondering is,
can I use a different microphone, and just adjust the system. I could use an SM58 mic (edit,: or rather our MKE-2 since it is omni), output white noise, and fix the EQ to match the picture of the SM58 (MKE-2) frequency respone.

...right?

Is there a better way of doing this? Is there maybe a different program out there that just let's me tell it that I am using an SM58, and the computer calculates it accordingly?

I also have a RadioShack decibel measurement device with a microphone and an output. Is this maybe flatter, and thus better to use as a measurement microphone. (I just don't know how much to trust the quality from RadioShack)

I'm kinda lost here, so any information is helpfull.

[stantonsound]

I am not an expert with RTA, as I have only used mine once with my driverack and don't plan on using it again, but it doesn't sound like it will work too well. RTA's and the programs are ok tools, but that is all they are. Your ears are the best tools in your toolbox, so trust them before some piece of equipment. If it sounds terrible, fix it. If it sounds good, leave it alone.

Now that I am off of my soapbox, see if there is a tech in town that would stop by and use a rta mic for you and set it. Call it a teaching clinic, they will eat it up. The bigger companies will charge you, but a guy with a board that is trying to make a career of it will likely give you a hand.

[the_dude]

Unless you are fairly fluent in the ways of utilizing an RTA rig to get the most out of a PA, you're better off doing it by ear.

Using a 58 will make little bars in your rta go up and down. But If you're trying to get an accurate reading of a room, it will not be enough. A good measurement microphone is encompasses more then just a "flat" response. Other things to consider are the polar pattern, impulse response, and the time the diaphragm come to rest. (I think there's a big word for it but I don't remember.) Earthworks makes some of the best measurement mics around. The M30 is very common, and with good reason. Audix makes the TR40 which (I believe) is about one third the price and about two thirds the quality.

[kovacika]

A 58 wont really work, neither will most stock computer sound cards. Behringer makes a decent measurement mic , the EMC-8000. I wouldnt try to use an RTA with anything less than a sound blaster audigy 2 for a internal sound card. Best would be a USBPRE by sound devices but most external usb pre amps will suffice.
but just as said before, an RTA is only a guideline, use your ears.

[Hughesie]

True RTA

is pretty cheap, i got a free copy because of my school

but like all the rest said, i don't use it very much

[CURLS]

Bottom line there are plenty of free rta's out there however, there all going to be a bunch of crap without me explaining your waisting your time when it comes to free rta's and you might as well like previously mentioned just use your ear. Quite interestingly though you had he opposite point of view on which microphone to use, omnidirectional is the more optimal choice than a cardiod microphone so yes the mke2 would be better for that application in terms of polar pattern. OH, and another cool audio program that is nice to have is nch tone generator. search for it and you should find it.

[audioslavematt]

http://www.redrocksaudio.es/impulse.html

http://www.pensa.fr/freqresplot/index.htm

You want to use the FFT. An RTA is fine to hunt down feedback, but it doesn't take time into account. I'll come back and edit this with a better explanation after rehearsal.

[Schniapereli]

Okay, maybe I'll back away from the idea.

The reason I am trying to do this, is that I am still fairly new to tech, and don't trust my ears as much (or jerry-rigging and RTA for that matter). Plus, I just heard that it was some pretty weird numbers, and the guy who originally analyzed the place couldn't remember them, and couldn't really figure it out by ear.

But, I am mainly just trying to explore. It also helps me get a little better at understanding all of the high end equipment, if I can scrap together a pathetic similar one. I'm kinda a hands-on learning person sometimes. I also have no idea how our current state compares to how it could be.

I'm also always looking for any other way possible to make the best of our pathetic equipment that we have at school. While I focus a lot on developing my talent, and the talent of the crew, I like to find new toys. I especially love any free audio program. (I tried TrueRTA, but it doesn't load on my home PC because of my dad's wacko administrator set up that never works...)

Anyways, thanks for the input and advice. Your soapboxes are my favorite part of this site, so keep them coming whenever.

I guess I'll probably just play around with listening some more, or maybe just try to work with a higher expert, who has actually heard in our auditorium. Maybe its not as bad as I think.

[stantonsound]

I am sure that you have a favorite song, a song in which you know every beat and every note. It may not be something popular, just something that you listen to on your ipod or when you are alone driving in your car and can not help but to sing along. (For me....Wagon Wheel by Olde Crow Medicine Show, Paradise City by GNR, and Brr...Stick Em by Beastie Boys.)

Just pop the CD into the system and listen to it. It will sound pretty bad if the eq is off as far as you have said. Then play with the eq and make it sound better....and then a little better...and soon it will sound perfect.

Different songs have different strengths, if you will. Some are high and mid, some are the low end. Go through a few songs and soon you will get something that you like. That is the easiest way to dial in a system.

Also, if your speakers are biamp, it is possible that the crossover might be part of the problem, so take a quick look at that first.

[Hughesie]

here's an idea, im currently working with it

it's a program called simple feedback trainer
the makers of the software, their site isn't always active so you can get a version of it off my website

www.alexhughes.bravehost.com then go to files and it is called simple feedback trainer

use that for a while, thought it might drive you crazy but it should help