How to use TrueRTA

[yromj]

We don't have a sticky thread for this and I think we should.

Let's start w/ what is required:

Hardware:

Good sound card. (M-Audio USB Mobile Pre)
Calibration quality microphone: (Behringer EMC-800)
1/4" or 1/8" Male-Male cable (for calibration)
PC (preferably laptop for portability)

Software:

TrueRTA (www.trueaudio.com)

John

[yromj]

Going through the calibration process (Audio I/O | Sound System Calibration) has typically given me something like this:



I was able to get this once:



This is where I get confused. I didn't change any wiring or anything between those two runs. I did adjust the volume on the front of the Mobile Pre so the "Clipping light would turn off.

After several retrials, I kept getting the very rough graph. I went back through the Windows settings and found that Windows had reverted the recording device back to my original sound card. After correcting this, I got the correct calibration graph.

So, it appears that now i'm calibrated.

John

[topper]

Originally Posted by yromj

We don't have a sticky thread for this and I think we should.

Let's start w/ what is required:

Hardware:

Good sound card. (M-Audio USB Mobile Pre)
Calibration quality microphone: (Behringer EMC-800)
1/4" or 1/8" Male-Male cable (for calibration)
PC (preferably laptop for portability)

Software:

TrueRTA (www.trueaudio.com)

John

Good suggestion. Yromj.

Personally, reference level volume is known as 'where 99% of my favorite music (vieo too),
sounds its very best.'


Only kidding. (Not!)


.

[GoldTeethII]

Originally Posted by yromj

We don't have a sticky thread for this and I think we should.

Let's start w/ what is required:

Hardware:

Good sound card. (M-Audio USB Mobile Pre)
Calibration quality microphone: (Behringer EMC-800)
1/4" or 1/8" Male-Male cable (for calibration)
PC (preferably laptop for portability)

Software:

TrueRTA (www.trueaudio.com)

John

Do we REALLY need a good sound card? I'd rather just use the sound card that came with my wife's laptop.

[IrritateGuy]

Originally Posted by GoldTeethII

Do we REALLY need a good sound card? I'd rather just use the sound card that came with my wife's laptop.

And I'd rather every speaker ever made sound good no matter what the price.

Notebook PCs are notorius for not providing decent sound cards. Also, aside from the Altec DIY calibration mic, all the good measurement microphones require a microphone preamp with phantom power. If you are going to spend $100 on a mic preamp, why not spend $130 for a sound card with a built in mic preamp?

There are a few really neat single channel mic to USB sound input devices which could be used with a measurement mic for less money, then you would need to use the built in sound card's output to drive the test signals, but even then the performance would not be nearly as accurate and effective as getting a proper audio interface.

This tool could become more valuable than any other accesory you buy. I know I use mine in my HT no fewer than four times a year when NOTHING changes in my system.

[yromj]

Here is the current calibration screenshot w/ the vertical scale corrected:



John

[IrritateGuy]

A long time ago I posted charts demonstrating the difference in performance between three different sound cards using TrueRTA:

Here's the noise floor of three sound cards, the built-in Dell Latitude sound card, the M-Audio Transit, and the M-Audio MobilePre:



Note how high the noise is on the Latitude notebook's internal card.

Here's the uncalibrated frequency response of the same cards:

I offset the levels in order to see the difference.

After running the TrueRTA calibration tools, here are the same cards' responses:




Clearly, the internal sound card is marginal for his sort of application.

[Towen7]

Originally Posted by IrritateGuy

Also, aside from the Altec DIY calibration mic, all the good measurement microphones require a microphone preamp with phantom power.

Have you had the opportunity to compare one of those DIY mics to store-bought mics?

I built one just for fun but could not get rid of a spike at 60Hz. I may try another one with a shielded 2-conductor cable instead of using the shield to carry the mic signal.

[Yesfan70]

I guess out of those three, the M-Audio transit is the best?

....er...

Ok, maybe let's say "out of those two", since the Dell card pretty much speaks for itself on those graphs.

[Altec]

Originally Posted by Towen7

Have you had the opportunity to compare one of those DIY mics to store-bought mics?

I built one just for fun but could not get rid of a spike at 60Hz. I may try another one with a shielded 2-conductor cable instead of using the shield to carry the mic signal.

That's a grounding issue which is unrelated to the quality of the microphone capsule. For what it's worth, I have a 60Hz spike even with my $3000 Bruel & Kjaer instrumentation microphone. It will not effect your measurements as long as it is at least 30dB or so below full scale.