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Ilkka 08-22-2005 02:19 PM

Since HTSpot transferred this quide into section where you have to be a paid member to get in, I decided to copy it here. Hope you'll all enjoy!

TrueRTA is a nice and small RTA-program (Real Time Analyzer) made by John Murphy. The free demo of the program can be downloaded from here. Unfortunately the demo is quite limited so you can't really use it efficiently. To make the most of it, you need to purchase an upgrade. True Audio offers four different upgrade levels from 1 to 4. I definitely recommend level 4, because this way you get the full 1/24 octave resolution, which is almost a MUST, especially if you are planning to some EQ'ing with BFD or similar. Level 4 retails $99.95, but it's all worth it. If you absolutely can't make it, take level 3, it comes with 1/6 octave resolution. Here is a little proof why 1/24 is recommended.

Before anything, read the help files/topics, they are very helpful.

The program itself is very small (~1.4MB installed), but the project files are around 10MB each, so make sure you have atleast that much of free space on that drive.

1. What do we need?

-Computer/laptop equipped with a decent soundcard.
-Microphone (and preamp if needed).
-Some RCA cables between them.

Minimum System Requirements:
A 500 MHz Pentium III class PC with 64MB RAM running
Windows 98/ME/NT/ 2000/XP

Most modern soundcards will work just fine, for example almost any Soundblaster (Live, Audigy, Aydigy2 etc.) is fine. Soundcard must have line in and line-out connections. If you have some expensive soundcard, it will most probably work. Integrated soundcards like nVIDIA Soundstorm will work, but they are more difficult to calibrate, you need to set the input/output levels very carefully with them. I haven't yet seen a laptop with a decent soundcard. Most of them won't work. Use a USB or PCMCIA soundcards with laptops. For example M-Audio MobilePre USB is great. They retail around $100 - $150.

You can use the Radio Shack SPL meter as a microphone, but its accurancy is not very good. You can find few compensation charts for it, but none of them is perfect for your meter. They are just estimates. You can download the correction file from here. NOTE: Check the end of this post, more info about RS. Save it as a text file along your other correction files (in "TrueRTA/Mic calibration files" folder). Frequency response of the RS meter limits up to around 10kHz (even with correction file). With the correction file it is reasonably accurate down to 15-16Hz. I personally have the older analog model, but the newer analog will work just fine. The digital version does not need any corrections when connceted from the output jack.

Much better choice is a Behringer ECM8000 microphone and a Behringer UB802 preamp/phamtom power. It's basically very flat even without any corrections, but here is a correction file for it too. Don't use the file that comes with TrueRTA. This better file is actually property of Edward Mullen (perfect for his mic), so everyone who's using this file, remember to thank Ed!

2. Calibration

First you have to make a simple loop from line out to line-in using the normal RCA cables and proper 1/8" connectors. You can just connect the other channel (use left) or both. Before you start the program, check your soundcard settings. Enter by double-clicking the speaker icon on the lower right corner of your desktop (if you can't see this, enter through control panel). In playback side all sliders except wave/mp3 and master volume should be muted. If you can't see the line-in slider, enable it through options/properties and mute it. This is crucial if you don't want to have some nasty microphone feedback. In recording side select line-in, if you can mute the others, do it. With most soundcards you can set all slider at full. If you have the nVIDIA Soundstream, set line-in slider at about 1/4. Now you can start the program itself.

By default the program is monitoring only the left channel, normally you don't have to change this. Now enter the "Audio I/O" menu and check that both sampling frequencies are set to 48 kHz. If your soundcard doesn't support these, use something lower for example 41 kHz. Now using the same menu, start "Sound System Calibration". Follow the instructions and you should see two lines on your screen. First a line something like this.

After a second or two the line should straighten up.

If the first line is not completely straight, lower the sliders like we learned before. If there is no line at all, check the connections. If you can't have a straight line, your soundcard is propably very cheap and will not work.

Now you can load the mic calibration file. Enter the same menu and "Open a mic calibration file". Select the correct file and open it. The range will throw you out, but use the buttons on the right side to make it readable (use around 0 dB - 120 db range). Now you should see a line like this.

The absolute level (SPL's) might not be the same as in my picture. If you can't see the SPL readings, push down the SPL button. Notice that if you want to do the sound system calibration again, you have to unload the mic calibration file before doing it.

3. Connections

Unhook the loop at first.

If you have the RS meter: RS meter has an analog output using a single female RCA connector. Connect this into the line-in of your soundcard. Use proper adapter if needed. Connect both left and right channels from line out into your stereo system (usually pre/pro/amp). Use AUX/CD or similar analog inputs. Set your RS meter to C-weighting (very important, though some sources claim that output is not weighted, I will research this matter) and fast (actually fast or slow doesn't matter). Use the 80dB range. Make sure you have a fresh battery. Place the meter on a tripod or similar and point it towards the speakers. Place the tripod at the listening point (sweet spot, ear level).

If you have the ECM8000 or similar: You need an XLR cable (male/female) between the mic and the mixer. Mixer also supports 1/4" jack. Mixer output is either normal RCA or 1/4" jack. Check that microphone control knobs are near center, phantom ON, Main Mix around center. Output can be either Main Out, Ctrl Room Out or Tape Out.

4. Settings

When you have all the nessecary connections ready, we can look at some of the settings.

This is the start screen of the TrueRTA. You can use either pink noise or quick sweep (QS) for measuring. If you have a proper mic, both ways will give very similar results. With RS meter the QS can be a little bit inaccurate at the lower end of the spectrum. The pink noise is more reliable, but also much slower.

Normally you should have the "L IN", "MIC CAL" and "SPL" buttons pushed down. "RTA Resolution" as high as you have purchased. "Speed Tradeoff" 20Hz. Averages 1. "Input/output sampling frequency" should be set to 48 kHz, if your soundcard supports them. Use lower if not. "CPU speed setting" anywhere you like.

5. Measuring

Select the "Pink N" from the left (Wave). Push the green "GO" button and you should see a wavering line like this.

That is some backround noise of your room and also the noise from the whole measuring line. The lower the better. Now set averages 100 and the line should settle down. Averaging means that the program takes every 100th, or what ever number you have set, sample into account. John Murphy suggest a value over 1000, but I think it's too much. If you are using QS, averaging doesn't affect at all. Now you can push the Generator ON. Adjust the volume from your pre/pro/receiver so that the meter reads around 75 dB - 80 dB. It sounds quite loud, but it's not dangerous. Keep the noise running around 5-10 s so that the line settles down. Now you should see a line something like this.


You can adjust the range if you want a closer look. This one is also smoothed, you can find the smooth option from the utilities menu.


6. Advanced features

TrueRTA has an option to calibrate the absolute SPL level. Play for example 100Hz or higher sine wave (but below 500 Hz) and check the reading on your meter. You can play the tone using the built-in generator or you can use a cd/dvd. Have the program measuring all the time (GO button down) and enter Audio I/O / SPL Calibration menu and enter the SPL reading. Now the program is calibrated and it's showing absolute SPL's (=real). Notice that if you are playing a pink noise or similar wide band signal, you can see the real SPL level by pushing the dB button down. The line itself is at much lower level (~50 dB), but this is just because the nature of the signal. If you are measuring pure sine waves, the absolute level can be seen straight from the line itself.

Quick Sweep is a much quicker way, but I've noticed that sometimes the RS meter gives false readings especially at the lower end, since the sweep is so damn quick. You can make the sweep "slower" (actually it just sweeps narrower range) by lowering the input sampling frequency. I suggest 22.05kHz. If you set it too low (8kHz), your computer will slow down significantly. Pink noise is the "safe way".

You can also use Avia/DVE or similar disc for measuring. Find a suitable sweep (do not use single sine waves) and remember to have "PEAK HOLD" pushed down. Start the analyzator (GO) and start the sweep. Stop the analyzator (STOP) after the sweep and you should have the line on your screen.

Another cool feature is the Oscilloscope mode. You can easily check for example if your calibration signal is clipping or not. It's quite easy to use. Just have the signal running using the built-in generator and push the GO button (remember that you have to have the loop again). Adjust the range if you can't properly see the shape of the signal. Now you can set your levels very accurately. Just add the level (input/output sliders and Ampl. level) until the signal clips. Then back off by few dB until the signal doesn't clip anymore.

Here you can see a perfect waveform of a 1kHz signal.



Here you can see the same signal, but now it's clipping heavily.



7. Quick recap

-Make a loop
-Run sound system calibration (adjust levels)
-Load the mic calibration file
-Connect the cables, line out -> receiver and mic -> line-in
-Calibrate absolute SPL if needed
-Measure your FR using either pink noise or QS

Copyright Ilkka Rissanen
-------------------------------------------------------------------

I must have forgotten something or maybe you didn't understand something. Please, post questions and I will make a small Q&A list out of them.

-------------------------------------------------------------------
Radio Shack SPL meter info:

Today I got my professionally calibrated microphone. Even without any correction files, it's only 0.5 dB off at 10 Hz. Pretty impressive. It was calibrated against B&K 4133 microphone.

I have now measured it against my analog RS meter. As I have said, the RCA output jack is weighted (C or A). But as Ethan showed, it appears that the output of the RCA jack of the digital RS meter is unweighted when set to C-weighting, when set to A, it's A-weighted. When set to C, it has a flat FR atleast down to 20 Hz.

Here is a TrueRTA screen of my results.



As you can see, even with those general CFs, the RS meter is still below the true FR. It tracks the mic down to 40 Hz, but below that it's off. You need to compensate even more than for example 7.5 dB @ 20 Hz. Around 11.5 dB seems to be more closer. Of course every RS is different, so this might not apply to your RS. Although me and my friends have measured total of three RS meters (analog) and they all give pretty similar FR.

http://personal.inet.fi/private/ilkka/RS_calibrated.txt

Here is a calibration file which turns my RS into calibrated measurement microphone. When using this file its FR is within 1 dB (10 Hz - 200 Hz) from my calibrated microphone. It may not be as perfect with your RS, but much better than the general CFs. Notice that general CFs are way off below 15 Hz.

Analog version:
Use atleast general CFs or this file when measuring with the TrueRTA or smilar. Same thing if you are measuring manually (looking at the needle). You can use the rough corrections below, if you don't want to check the file (if you are measuring manually, add those corrections, do not subtract them).

Frequency / Correction
10 Hz +5 dB
12 Hz +6 dB
16 Hz +14.8 dB
20 Hz +11.5 dB
25 Hz +7.8 dB
30 Hz +5 dB
40 Hz +3.2 dB
50 Hz +2 dB
80 Hz +1 dB
100 Hz +1.2 dB

Digital:
Do not use any correction files when measuring with TrueRTA or similar. The output of the RCA jack is unweighted when set to C-weighting. When measuring manually, add corrections shown above to the readings.

Ilkka 08-22-2005 02:43 PM

Pictures of the connections (text/pictures property of Floyd Pierce) Thanks Floyd!

Note that I'm using a laptop so the Mic symbol would equate to line in with a normal sound card and the headphone symbol would equate to line out.

The loop connection for sound system calibration: (loop is just a stereo mini straight through)

[IMG]http://www.***************.com/html/spotadmin/uploads/loop.jpg[/IMG]

Radio Shack SPL Meter as Microphone:

[IMG]http://www.***************.com/html/spotadmin/uploads/RS_SPL_as_mic.jpg[/IMG]

Both hookups:

[IMG]http://www.***************.com/html/spotadmin/uploads/hookups.jpg[/IMG]

The more elaborate setup with a Behringer Mic and Mixing Console (provides phantom power to the Mic):

[IMG]http://www.***************.com/html/spotadmin/uploads/w-mic_and_pre-amp.jpg[/IMG]

The 2 following pics are a Closer look at Mixing Console connections:

[IMG]http://www.***************.com/html/spotadmin/uploads/mic_preamp.jpg[/IMG]

[IMG]http://www.***************.com/html/spotadmin/uploads/ub802.jpg[/IMG]

BradJudy 08-23-2005 12:21 PM

Excellent primer. Thanks for the work. Perhaps I'll add a bit on using ETF in a similar manner when I get the chance.

sholei 08-24-2005 10:24 AM

Thanks for the post, that is very helpful...
I think I am going to get the same software as you..

Brucemck2 08-28-2005 11:47 AM

On rec's from Forum members I've purchased TrueRTA and and an M-Audio FastTrack USB for the mic interface

http://www.m-audio.com/products/en_u...kUSB-main.html )

I'm still a bit unclear about how to set up the initial calibration loop for TrueRTA ...

I'll be using an outboard M-Audio FastTrack for the mic preamp and USB functionality.

FastTrack has mic input (XLR) and 1/4" input (for guitar or other line in.)

FastTrack has USB output and RCA stereo left and right outputs.

Laptop has USB port, mic input (tiny jack) and headphone output (tiny jack).

Two questions:

(1) in normal use (once all is calibrated) the proper setup is (a) mic into XLR input of FastTrack and (b) FastTrack into laptop via the USB port and (c) laptop headphone out into receiver's line in (for sending the pink noise, etc, signal to the speakers.)????

(2) in calibration loop/setup (a) headphone out from laptop into line in for the FastTrack and (b) USB from the FastTrack into the laptop via the USB port?????

Thanks!!!

Ilkka 08-29-2005 06:57 AM

Quote:
Originally Posted by Brucemck2 View Post

On rec's from Forum members I've purchased TrueRTA and and an M-Audio FastTrack USB for the mic interface

http://www.m-audio.com/products/en_u...kUSB-main.html )

I'm still a bit unclear about how to set up the initial calibration loop for TrueRTA ...

I'll be using an outboard M-Audio FastTrack for the mic preamp and USB functionality.

FastTrack has mic input (XLR) and 1/4" input (for guitar or other line in.)

FastTrack has USB output and RCA stereo left and right outputs.

Laptop has USB port, mic input (tiny jack) and headphone output (tiny jack).

Two questions:

(1) in normal use (once all is calibrated) the proper setup is (a) mic into XLR input of FastTrack and (b) FastTrack into laptop via the USB port and (c) laptop headphone out into receiver's line in (for sending the pink noise, etc, signal to the speakers.)????

(2) in calibration loop/setup (a) headphone out from laptop into line in for the FastTrack and (b) USB from the FastTrack into the laptop via the USB port?????

Thanks!!!

Which microphone do you have?

To your questions: You have to forget the internal soundcard of the laptop.

(1) In normal use (once all is calibrated) the proper setup is (a) mic into XLR input or into line-in (1/4") of FastTrack and (b) FastTrack into laptop via the USB port and (c) Fastrack headphone out or Fastrack stereo RCA output into receiver's line-in (for sending the pink noise, etc, signal to the speakers.).

(2) In calibration loop/setup (a) from headphone out or stereo RCA output of Fastrack into XLR input or line-in (1/4") for the FastTrack and (b) USB from the FastTrack into the laptop via the USB port.

sholei 08-29-2005 08:44 AM

Hi,

I just purchased the TRUE RTA, and I have download it to my lap top. I need to get a mic now. I have the Radio shack analog SPL meter, but I want to get a better one. If I decided to get the Behringer Mic do I need to get the Mixing Console?
Can I just use the Mic only and plug it direct to the laptop?
may be I will get an adapter that will convert the XLR to RCA.
Or can I get a simpler mixer?

The mixing amp looks complicated, I don't even know what's all the button for.
is there a smaller version without all the buttons.
I want everything to be simple

thanks

Mario

BradJudy 08-29-2005 09:13 AM

You need a mic pre-amp with phantom power for the Behringer ECM8000. Your options include the mixing console shown above (there are a few different models) or a simple mic pre-amp like the Art MicroMix, Rolls (I forget the model number), etc. A basic mic pre-amp will run you about $50 and the mixing panel would run a bit more, but not much.

BradJudy 08-29-2005 09:16 AM

BTW: It also requires a soundcard that has a real stereo line-in which many notebooks lack.

noah katz 08-29-2005 10:34 AM

Can't he just use the RS meter's output jack and published calibration curves?

BradJudy 08-29-2005 11:55 AM

Yes, but since he asked about getting another one I gave him the important points. The RS meter could be used with the published calibration info and it would be reasonably accurate.

Brucemck2 08-29-2005 12:09 PM

Ikka ... Thanks!!! Your user guide was very helpful.

To answer your mic question: I'm using a five year old calibrated mic that came with my GoldLine 1/12th (low) 1/3rd (elsewhere) RTA

Had to replace the M-Audio FastTrack with a MobilePre. Salesman that pitched the FastTrack said they were "identical, except FastTrack was single channel rather than two channel". He was right, IF you ignore the phantom power differences!

Ilkka 08-29-2005 02:30 PM

Quote:
Originally Posted by Brucemck2 View Post

Ikka ... Thanks!!! Your user guide was very helpful.

To answer your mic question: I'm using a five year old calibrated mic that came with my GoldLine 1/12th (low) 1/3rd (elsewhere) RTA

Had to replace the M-Audio FastTrack with a MobilePre. Salesman that pitched the FastTrack said they were "identical, except FastTrack was single channel rather than two channel". He was right, IF you ignore the phantom power differences!

Yep, Fast Track doesn't have a phantom power, so you can't use it for example with the ECM8000 (w/o an external power).

I think your mic is pretty good. Although calibration should be done every year, but it is still much better than say the RS meter.

Ilkka 08-29-2005 02:33 PM

Quote:
Originally Posted by sholei View Post

Hi,

I just purchased the TRUE RTA, and I have download it to my lap top. I need to get a mic now. I have the Radio shack analog SPL meter, but I want to get a better one. If I decided to get the Behringer Mic do I need to get the Mixing Console?
Can I just use the Mic only and plug it direct to the laptop?
may be I will get an adapter that will convert the XLR to RCA.
Or can I get a simpler mixer?

The mixing amp looks complicated, I don't even know what's all the button for.
is there a smaller version without all the buttons.
I want everything to be simple

thanks

Mario

If you have a laptop, then I would recommend getting a M-Audio MobilePre USB soundcard (external). It has also phantom power for the ECM8000 mic. Very easy to use and not too many buttons, unlike the UB802 shown above.

MikeTz 08-30-2005 05:07 PM

Ilkka:

Thanks for the primer! When will you follow up with ETF for Dummies?

MT

Ilkka 08-31-2005 02:39 PM

Quote:
Originally Posted by MikeTz View Post

Ilkka:

Thanks for the primer! When will you follow up with ETF for Dummies?

MT

Didn't BradJudy promised to do that one?

BradJudy 08-31-2005 03:11 PM

Quote:
Originally Posted by Ilkka View Post

Didn't BradJudy promised to do that one?

I'll work on it once I have my mic back. I now have to different setups (one with a MobilePre and one with a separate mic pre-amp) so I can show two different connection setups. If I'm really feeling motivated, maybe I'll also work on one for the new R+D.

Grandarf 09-01-2005 09:37 PM

Nice thread! I didn't know you could connect the RS meter straight to a laptop!

Quote:


I haven't yet seen a laptop with a decent soundcard. Most of them won't work. Use a USB or PCMCIA soundcards with laptops. For example M-Audio MobilePre USB is great. They retail around $100 - $150.

In the pics, you seem to be using your laptop, didn't you say that laptop soundcards are horrific and don't work very well?

Quote:


I just purchased the TRUE RTA, and I have download it to my lap top. I need to get a mic now. I have the Radio shack analog SPL meter, but I want to get a better one. If I decided to get the Behringer Mic do I need to get the Mixing Console?

Quote:


Yes, but since he asked about getting another one I gave him the important points. The RS meter could be used with the published calibration info and it would be reasonably accurate.

Quote:


BTW: It also requires a soundcard that has a real stereo line-in which many notebooks lack.

why would you need a stereo input if you're using one mic?

Ok, so I'm a bit confused now.. Laptop + RS meter, does this actually work? Or it depends on the stereo line in? (how can you know if it is?) And if it actually works, it works? No need for an external soundcard? (good quality?)

sholei 09-04-2005 08:27 AM

For the RS meter, doe it made a difference to use the digital or analog meter for the RTA software?
Will the reading be more accurate, if using the digital meter?

thanks

Ilkka 09-04-2005 10:17 AM

Quote:
Originally Posted by sholei View Post

For the RS meter, doe it made a difference to use the digital or analog meter for the RTA software?
Will the reading be more accurate, if using the digital meter?

thanks

Check the end of my post. Some new info.

Ilkka 09-04-2005 10:29 AM

Quote:
Originally Posted by Grandarf View Post

Nice thread! I didn't know you could connect the RS meter straight to a laptop!

In the pics, you seem to be using your laptop, didn't you say that laptop soundcards are horrific and don't work very well?

As I said, those are not my pics or my laptop. I just linked them.

I don't suggest using built-in soundcards (laptop or home PC). Usually they are crap. Use external soundcard, that is my adwise.

Quote:


why would you need a stereo input if you're using one mic?

They are always stereo inputs.
Quote:


Ok, so I'm a bit confused now.. Laptop + RS meter, does this actually work? Or it depends on the stereo line in? (how can you know if it is?) And if it actually works, it works? No need for an external soundcard? (good quality?)

It may work or it might not work. If it has a real line-in and line out connections, you have a chance. Make a loop and run a sound system calibration. If the first line is almost flat and the second (after calibration) is totally flat, it's working.

http://audio.rightmark.org/download.shtml

This is a good program (RMAA 5.5) which shows if your soundcard has a flat FR. It shows also THD, IMD, etc.

Jesse S 09-07-2005 10:00 PM

I get a large, narrow peak at 60hz using the rat shack meter to a soundblaster Live. Is this a ground loop? I never get ground loops from HTPC or dvd player on this system so I dunno why it's there. Not to mention the outlet there is only 2 prong (no ground, old house).

sethwas 09-08-2005 08:18 AM

Where was this months ago when I had to wing it to figure out how to use RTA
The pics are especially helpful.

Seth

Kenrosencpa 09-12-2005 10:33 AM

The sound card on my Dell 700m didn't work so I picked up a Soundblaster Live USB and it worked fine.

I'm thinking about buying an ECM8000, I think the RS 4db correction discrepancy at 20hz is way too much and above 1k it looks almost useless. I have an older RS meter (probably more than 10 years old), it could even be further off. Has anyone used the Rolls MP13 microphone preamp? I wonder how it compares the the UB802.

Thanks

Kenrosencpa 09-12-2005 10:36 AM

Ilkka, What are the two sets of correction numbers starting at 515.625hz on you correction table?
thanks

BradJudy 09-12-2005 11:50 AM

Ken,

I haven't tried the Rolls, but I do have an ART MicroMix which is a single-channel mic pre-amp with phantom power and runs ~$50 from Sweetwater music. It works well. It isn't as flexible as a UB802, but it's very simple to use.

Ilkka 09-13-2005 10:34 AM

Quote:
Originally Posted by Kenrosencpa View Post

Ilkka, What are the two sets of correction numbers starting at 515.625hz on you correction table?
thanks

That second set is phase correction numbers for the RS. Numbers up from there are from the file which is available on the ETF site.

That ETF file doesn't have any corrections below that frequency, which is bad if your meters output is C-weighted or more (like mine). Digital version and some older analog versions output a flat signal, so for those the ETF file is pretty good.

Otherwise use my file.

Brucemck2 09-23-2005 03:00 PM

Does TrueRTA apply "C weighting" to the displayed data?

Reason for asking is that Room EQ Wizzard asks whether to correct for measurement devices's C weighting (when transferring data from TrueRTA to RoomEQwizzard.)

Thanks!

Ilkka 09-24-2005 05:13 PM

Quote:
Originally Posted by Brucemck2 View Post

Does TrueRTA apply "C weighting" to the displayed data?

Of course it doesn't.

Quote:


Reason for asking is that Room EQ Wizzard asks whether to correct for measurement devices's C weighting (when transferring data from TrueRTA to RoomEQwizzard.)

Thanks!

I wouldn't use this option unless you have a good C-weighted SPL meter. Radio Shack doesn't follow C-weighting. I would use the same correction file as in TrueRTA also in Room EQ Wizard.

But if you are transferring TrueRTA files, you don't need to apply any corrections, since TrueRTA has already corrected them once (don't do double).

Grandarf 09-25-2005 07:45 PM

Hey guys, i didn't get to try my lappy sound output to see if it worked, but there's a little gadget which might fix that problem:



I'm having a hard time finding it in Canada so I might have to order it directly from the site... Anyhow, I'll use it with optical to the Behringer DEQ Digital EQ, so the sound quality from the laptop will finally be top notch. (also ordered ECM-8000 mic) The USB 'sound adaptor' is only 30$, I think it should be superior to the laptop integrated soundcards...

Anyhow, I'll give an update if I find one, but it looks like it could be a very good solution if your laptop has a bad sound output. I know mine isn't very good, lot of interference from hardisk, its integrated DVDRom, etc.. its very noisy, I guess even with the analog from USB you wouldn't get any of that interference...



[edit] I just got it. Its really not very good with analog (noisy, moreso than my integrated laptop AC97!), and I can't get the digital output to work with my DEQ 2496

donovanhebard 10-04-2005 06:12 PM

hi all,

just been playing with True RTA for a week or so, and this thread has been very helpful so far, so let me begin by thanking everyone for the great information.

i have a question, though. i am using an IBM ThankPad A30 laptop for the RTA, and was able to get the proper flattening second line on the RTA during the Sound System Calibration - however, if i run RTA with nothing plugged in to the sound card's ins or outs, i still get quite a bit of response on the SPL meter when i initiate the analyzer with "GO" button. there is also more "noise" present on the meter when using a mic than i would think is normal. is this indicative of power supply / hard disc noise? or perhaps of an inferior internal card?

i'm currently debating on whether to purchase an external sound card Soundblaster Live? or even maybe the M-Audio Duo USB or MobliePre USB (i am using the Behringer ECM800 mic).

i am using the RTA right now primarily to tune an automotive sound system with a 1/3 octave EQ - with mixed results so far.

thank you in advance for any thoughts, information, or advice, it is much appreciated.

-d

noah katz 10-18-2005 05:49 PM

Just noticed this:

The digital version does not need any corrections when connceted from the output jack."

That's great if true (I have one), but why would that be so?

Isn't the digital aspect just a different way of displaying the level from the same microphone?

Thanks

Ilkka 10-20-2005 03:47 PM

Quote:
Originally Posted by noah katz View Post

Just noticed this:

The digital version does not need any corrections when connceted from the output jack."

That's great if true (I have one), but why would that be so?

Isn't the digital aspect just a different way of displaying the level from the same microphone?

Thanks

I don't know the reason, but I know atleast two occasions where a digital RS meter was compared to a Behringer ECM8000 mic and RS provided the exact FR without any CFs.

Ilkka 10-20-2005 03:51 PM

Quote:
Originally Posted by donovanhebard View Post

hi all,

just been playing with True RTA for a week or so, and this thread has been very helpful so far, so let me begin by thanking everyone for the great information.

i have a question, though. i am using an IBM ThankPad A30 laptop for the RTA, and was able to get the proper flattening second line on the RTA during the Sound System Calibration - however, if i run RTA with nothing plugged in to the sound card's ins or outs, i still get quite a bit of response on the SPL meter when i initiate the analyzer with "GO" button. there is also more "noise" present on the meter when using a mic than i would think is normal. is this indicative of power supply / hard disc noise? or perhaps of an inferior internal card?

i'm currently debating on whether to purchase an external sound card Soundblaster Live? or even maybe the M-Audio Duo USB or MobliePre USB (i am using the Behringer ECM800 mic).

i am using the RTA right now primarily to tune an automotive sound system with a 1/3 octave EQ - with mixed results so far.

thank you in advance for any thoughts, information, or advice, it is much appreciated.

-d

I would suggest you to buy a better, external sound card.

Have you checked your sound settings? Are you sure you are recording line-in? And have muted all except master and wave from the play side (including line-in)? Laptops usually have built-in mics which can mess things up. You should disable/mute them if you get an external sound card.

catapult 10-22-2005 10:44 AM

Quote:


I don't know the reason, but I know atleast two occasions where a digital RS meter was compared to a Behringer ECM8000 mic and RS provided the exact FR without any CFs.

I'd take that with a grain of salt. There have been a number of similar but different RS meters sold. The schematics of all the meters on Eric Wallin's mod page, two analog and one digital, all show the output jack tapping off after the A and C weighting filters. One easy way to tell would be to flip between the A and C settings on the meter with TrueRTA running. If the curve changes shape, the filters are being applied and you need a correction file.

Eric's page seems to be gone but here's the archive on the wayback machine.

http://web.archive.org/web/200411200...in/rsmeter.htm

noah katz 10-22-2005 12:10 PM

Thanks, catapult.

Much to my shock, I read that I had sent Eric my very own RS meter!

So I guess I'm good to go

jplacson 12-07-2005 04:53 AM

I'm planning to purchase the Level 4 version of TrueRTA... does it come with more mic calibration files?

I'm using an M-Audio Firewire 410 w/ any of the following mics (so how do I calibrate any of them?)

Shure PG81
Shure SM94
Shure KSM 109

AKG CK98
AKG CK93

I live in the Philippines and I don't know anyone here who can calibrate microphones... so does anyone have cal files for any of these mics? Thanks!

Thomas-W 12-07-2005 10:59 AM

Those are all really nice general purpose recording mics, not test mics with flat FR. The Shure KSM 109 has reasonably flat response and goes lower than the rest.

Given your location it's going to cost you more money to get it calibrated, than it will to buy either the ECM-8000 or it's twin the Nady CM100.

J_Palmer_Cass 12-07-2005 11:40 AM

Quote:
Originally Posted by catapult View Post

I'd take that with a grain of salt. There have been a number of similar but different RS meters sold. The schematics of all the meters on Eric Wallin's mod page, two analog and one digital, all show the output jack tapping off after the A and C weighting filters. One easy way to tell would be to flip between the A and C settings on the meter with TrueRTA running. If the curve changes shape, the filters are being applied and you need a correction file.

Eric's page seems to be gone but here's the archive on the wayback machine.

http://web.archive.org/web/200411200...in/rsmeter.htm



I bought my RS Digital meter late last year, and the A and C scale does indeed change the shape of the curve with True RTA running.

The filters are being applied to my meter's output jack!

churchboy 12-09-2005 09:49 AM

Hi everyone, I am new here, what a great resource.
I just downloaded the trail version of Trueaudio RTA last night and I have a question. I conected a external sine wave generater (Rain Gain - 400hz @ 0dBu) into a channel on a Behringer UB802 mixer and ran the main out into the line-in on my internal sound card (Realtek AC97). I am trying to get familiar with the program and maybe I had something hooked up wrong. I wanted to measure the actual clipping point of the amplifier verses the indicaters on the mixer. The problem was the scope in RTA would show the signal clipping with the channel gain set almost to 0 and the faders at unity gain. Help?

jameswayneanders 03-10-2006 06:59 PM

I have downloaded the demo and when I start the software, I don't get any input response from the mic I am using. It is a condenser mic plugged into the M-Box which is plugged into the USB port. The input driver is RealTek AC97 Audio.

The Windows Sounds and Audio Devices properties only has one input driver and that is the RealTek driver.

Will this work? Or is there something else I need to do to get the software to recognize the audio input?

Thanks

Daniel.N 04-02-2006 09:48 AM

Interesting guide, thank you! I've been playing with this a little but can't get decent results; my S/N ratio is ~25dB at best, maybe that's why. The reason I can't get better S/N is that I check input signal from the SPL meter with the 'scope functionality to check for clipping.

Is that a reasonable thought, that if measuring a sine wave it should sort'a look like sine wave even after passing through the speakers and the mic? And also that if measuring pink noise, the scope should show no full amplitude samples? Or will measuring work even if the SPL meter seems to be outputting a square wave?

Thanks in advance!

DeCapo 04-17-2006 06:36 PM

Hi All,

I am considering using TrueRTA in conjunction with a laptop. However, I don't plan on using a mic. I would just like to use the line in/out's to take some frequency response measurements of some amplifier circuits I'm designing.

I was considering the SoundBlaster Extigy or the M-Audio MobilePre USB. Does anyone have any comments on either?

I noticed that some external soundcards seem to have a headphone output, but not a 'line out'. Can they be used interchangeably?

Are there any special features I should look for (or stay away from)?

Thanks!
-Dan

Nexus1 09-30-2006 05:23 PM

OK, I've tried three different external USB sound cards and none will give me a flat line when conducting a Sound System Calibration.

I broke down today and bought the Sound Blaster Live! 24-bit USB external sounds card thinking this would resolve the issue. Unfortunately, it didn't. Everything is muted except for Wave out. What else could it be?

Kenrosencpa 09-30-2006 05:28 PM

Quote:
Originally Posted by Nexus1 View Post

OK, I've tried three different external USB sound cards and none will give me a flat line when conducting a Sound System Calibration.

I broke down today and bought the Sound Blaster Live! 24-bit USB external sounds card thinking this would resolve the issue. Unfortunately, it didn't. Everything is muted except for Wave out. What else could it be?

I had the same problem, can't remember exactly how I fixed it but it was fixed with adjustments in the sound card's software driver.

Nexus1 10-01-2006 12:48 PM

Ken,

Thanks for the tip. I lowered the main volume and mic level to half and that did the trick.

Kenrosencpa 10-01-2006 12:52 PM

Quote:
Originally Posted by Nexus1 View Post

Ken,

Thanks for the tip. I lowered the main volume and mic level to half and that did the trick.

Hope you didn't buy those three sound cards

philip miller 11-14-2006 09:01 AM

I have completed purchase and installed Level 4 of RTA and, using a Behringer 8000 microphone along with a Soundblaster Live USB card on my pc, I began taking measurements of my room. The response graph that I end up with has various steep vertical spikes, for want of a better term, throughout the range. What am I likely to be doing wrong. Thanks in advance for your help. Phil Miller

tlparker 11-30-2006 12:44 PM

Don't know if anyone was aware of it or not, but "duhouse" on Ebay it trying to sell "valuable information", a big chunk of which is simply a URL that points to this thread.

I'm mentioning and including it here because all he's trying to do is make a fast buck off of public information posted on this site as well as public domain information (he doesn't even have the brains/cajones to copyright the two page word doc he sends you) and it made me sick.

I would question the legality of his trying to SELL a link to a thread on this site as something he has the rights to and can make money off of. If it isn't illegal, it's certainly wrong. He takes the "I have 25 years of experience in the field and this is valuable information that the average consumer should know about." If the "average consumer" can't find the info via a simple web search engine, then they're far too stupid to manipulate the parametric EQ settings in a Denon receiver. Good grief.

To top it off, in addition to mentioning download TrueRTA (I can't disagree there, I own the 1/24th octave version myself), he also includes the following Denon "tweaks":


AVR-3806 Secret' Installer Modes



IR (Infrared remote) Disable Mode

*
1) IR Disable Mode Setup is available only from the Front Panel (not by remote)

2) Enter into System Setup, select 6. Option Menu', press ENTER'

3)* Scroll down to Exit' (of Option Menu), then press and hold (for 3sec.) the cursor left button' when the cursor points*to "Exit"*of #6 Option Menu.

4) Remote Lock setup mode will be activated. Select*on/off by cursor left and right button

-In Off' Mode FL Display shows as following *Remote Lock*On / Off* : < Off

* -In On' Mode FL Display shows as following**Remote Lock On / Off* : > On

5) Press ENTER' button to exit this mode.

6) When this mode is On', and an IR*command is received, AVR will show "Remote Lock On" on the FL Display

*This caution also appears for the power on sequence and in status*mode*
check on the FL Display

7) Even if IR Lock mode is on, AVR will continue to accept serial 232 commands



Front Panel LockOut Mode


Two Different Lockout Modes are available:

All Controls (Buttons and Knobs) on the Front Panel

a. Start with unit in Standby' Mode

b. From the Front Panel, press and hold,*STANDARD' and INPUT MODE' buttons and turn the Master AC power on

All Controls (Button and Knobs) on the Front Panel, EXCEPT Master Volume

c. Start with unit in Standby' Mode

d. From the Front Panel, press and hold, STANDARD' and EXT.IN' buttons and turn the Master AC power on
*
How to Defeat these modes:

From the Front Panel, press and hold* STANDARD' and ANALOG' buttons and turn the Master AC power on


When*each mode is On', and any button is pressed, AVR will show Panel Lock On' on the FL Display
*
*This caution also appears for the power on sequence and in status
mode*check on the FL Display

Even if Front Panel Lockout mode is on, AVR will continue to accept serial 232 protocol commands


**IR Disable and Panel Lockout Modes can be set*simultaneously or independently**




AVR-4306 Secret' Installer Modes


IR (Infrared remote) Disable Mode

*
1) IR Disable Mode Setup is available only from the Front Panel (not by remote)

2) Enter into system setup, select 6. Option Menu', press Enter'

3)* Scroll down to Exit' (of Option Menu), then press and hold (for 3sec.) the cursor left button' when the cursor points*to "Exit"*of #6 Option Menu.

4) Remote Lock setup mode will be activated. Select*on/off by cursor left and right button

-In Off' Mode FL Display shows as following *Remote Lock*On / Off* : < Off

* -In On' Mode FL Display shows as following**Remote Lock On / Off* : > On

5) Press Enter' button to exit this mode.

6) When this mode is On', and an IR*command is received, AVR will show "Remote Lock On" on the FL Display

*This caution also appears for the power on sequence and in status
mode*check on the FL Display

7) Even if IR Lock mode is on, AVR will continue to accept serial 232 commands




Front Panel LockOut Mode


Two Different Lockout Modes are available:

All Controls (Buttons and Knobs) on the Front Panel

e. From the Front Panel, press and hold,*DIRECT/STEREO' and INPUT MODE' buttons and turn the Master AC power on

All Controls on the Front Panel, except Master Volume

f. From the Front Panel, press and hold, DIRECT/STEREO' and EXT.IN' buttons and turn the Master AC power on
*
How to Defeat these modes

From the Front Panel, press and hold* DIRECT/STEREO' and Analog' buttons and turn the Master AC power on

When*each mode is On', and any button is pressed, AVR will show Panel Lock On' on the FL Display
*
*This caution also appears for the power on sequence and in status
mode*check on the FL Display

Even if Front Panel Lockout mode is on, AVR will continue to accept serial 232 commands


**IR Disable and Panel Lockout Modes can be set*simultaneously or independently**

CSEmoses 11-30-2006 11:08 PM

OK, i downloaded and installed the demo of TrueRTA... i've a problem, simple i'm sure:

to quote:
"By default the program is monitoring only the left channel, normally you don't have to change this. Now enter the "Audio I/O" menu and check that both sampling frequencies are set to 48 kHz. If your soundcard doesn't support these, use something lower for example 41 kHz. Now using the same menu, start "Sound System Calibration". Follow the instructions and you should see two lines on your screen. First a line something like this."

OK, first of all... my soundcard input/output sampling frequencies can go up to 96khz, should i use that? or stick with the mentioned 48khz?
Second: where it says to use the same menu to start "sound system calibration" i do not have that in this menu. I've got "Line Input Calibration" and "line output calibration" only. Are these what is being referred to? When i click either of these, it is wanting me to get out a volt meter... which I so don't have. And hey, it doesn't include that in the list of 'what you need' in this guide for dummies either so uh... that's where i'm stuck, for now. Do i need a volt meter? *confused* or am i looking in the wrong place?

FYI: My soundcard is an SB Audigy, i'm connecting an RS Analog Meter (33-4050) with an Stereo 1/8 to RCA-Y cable to the same jack on the back of the Audigy as my headset mic (unplugged while messing with TrueRTA of course, no splitter there).
... I'm short on cables. Going to hit radio shack (source by circuit city here in canada) and buy some tomorrow, so i can actually get some measurements done.

Thanks a TON for any help you can provide, as i'm REALLY new at using this software, and audio 'tweaking' in general. ... Though i'm not a computer newbie, not at all, so that should help in the learning curve with this really thorough looking application!

Red GTI VR6 12-15-2006 12:23 PM

Here's a screen shot of the menu as it should be and where the Sound System Calibration is listed. Hope it helps!
LL

Red GTI VR6 12-15-2006 12:55 PM

One quick question, when doing the first part of the calibration, should the graph be in relative mode?

When I'm calibrating, if I don't have it set to relative mode, I don't get the flat line. If I have relative mode turned on, I get the flat line. In my case, at a 69.5 dB.

Is this correct?

Otherwise, it's really jaggid.

Also, should I be using a mono cable, or a stereo cable to link the two? Does it make a difference?

This is all on this card: http://www.auzentech.com/site/products/x-meridian.php

With Burr Brown opamps.

Thanks!

tlparker 12-15-2006 06:01 PM

Quote:
Originally Posted by Red GTI VR6 View Post

One quick question, when doing the first part of the calibration, should the graph be in relative mode?

When I'm calibrating, if I don't have it set to relative mode, I don't get the flat line. If I have relative mode turned on, I get the flat line. In my case, at a 69.5 dB.

Is this correct?

Otherwise, it's really jaggid.

Also, should I be using a mono cable, or a stereo cable to link the two? Does it make a difference?

This is all on this card: http://www.auzentech.com/site/products/x-meridian.php

With Burr Brown opamps.

Thanks!

I'd be curious as to anyone's impressions or experiences with this card, in particular as it compares to the m-audio Revolution 7.1 and/or Audiophile 192 (both of which I have). I've got mixed feelings about both of my m-audio cards. When the 7.1 card is working, everything sounds fantastic, but then there are moments when it takes up so much cpu (I have a 2.4ghz p5) that during some heavy disk access times it can choke or stutter during playback of files. I also don't care for the 7.1's connectors (one coax digital I/O, which is great as optical stinks), but all the rest are mini jacks that you use mini to 2-rca cables for connections, and that really stinks. The audiophile 192 is a fantastic card, particularly for bringing in analog audio at the very highest quality (with XLR connections, monitor connections, etc., via a small extension multi-connector), but that's about it. I'd like to find one card that does both, I'm wondering if this is the card??

Red GTI VR6 12-16-2006 06:58 AM

Quote:
Originally Posted by tlparker View Post

I'd be curious as to anyone's impressions or experiences with this card, in particular as it compares to the m-audio Revolution 7.1 and/or Audiophile 192 (both of which I have).

I cannot help you there, sorry. I've not listened to either of those cards. In fact, I haven't even listened to this card yet...lol I'm still in the process of making a bunch of modifications.

Quote:
mini jacks that you use mini to 2-rca cables for connections, and that really stinks.

I agree, I really wish these cards would come with RCA outputs. Because of that, I'm modifying my card: http://www.mp3car.com/vbulletin/showthread.php?p=979552

Quote:
I'd like to find one card that does both, I'm wondering if this is the card??

I cannot comment on the 7.1 features of this card as I'm not interested in using them. I'm using this card in my car for stereo play back. If for some reason, this set-up doesn't work, I'll be throwing this card in the home theater PC/system that we are starting to build and go with something like Mark Of The Unicorn UltraLite (http://www.motu.com/products/motuaudio/ultralite/)

Istari1 12-18-2006 02:38 PM

Good stuff. . .I sense myself going out and buying a new mic, meter, and TrueRTA. . . damn you all

Vidfreaky 12-19-2006 06:49 PM

Hey guys, I've got the 1/3 octave version of True RTA (just thought I'd try it with more than just the 1 octave version before upgrading) and I'm using the Edirol UA-25 as a soundcard for my laptop.

I've connected the L RCA out to the L 1/4" in. Everything's set at 48KHz. The output pot is cranked and the input pot is at 12 o'clock on the edirol. I can't use the "sound system calibration" as it is greyed out on the menu so I can't click on it. I see it, it's there, just not active. How do I activate it?

cacin 12-23-2006 08:52 AM

How would you do your setup if you're using the software with laptop in a car? Where do you connect the line in and line out from the soundcard?

208 12-26-2006 04:16 PM

The sound system calibration is grey'd out on mine also. Do I need to upgrade to a higher level in order to activate it, or am I missing something?

208 01-02-2007 09:04 AM

OK, I answered my own question. Just upgraded to level 4 and every function is now available. Just goes to show you that you get what you pay for!

mpsmps 01-08-2007 08:12 PM

I'm not able to get a reasonable calibration on my Dell 300m laptopwith either my PCMCIA Audigy 2 ZS (even following the Audigy instructions mentioned in the TrueRTA FAQ) or with the integrated audio. What soundcards have people used successfully with their laptops?

Thanks,

Mike

mpsmps 01-09-2007 01:49 PM

Quote:
Originally Posted by philip miller View Post

I have completed purchase and installed Level 4 of RTA and, using a Behringer 8000 microphone along with a Soundblaster Live USB card on my pc, I began taking measurements of my room. The response graph that I end up with has various steep vertical spikes, for want of a better term, throughout the range. What am I likely to be doing wrong. Thanks in advance for your help. Phil Miller

Hi Philip,
Creative automatically maps the line-out into the line-in for game effects. If you go to the FAQ on the TruRTA website, you'll see a question about calibrating with the Audigy containing directions on how to fix that problem.

Mike

wiz561 01-17-2007 11:06 AM

Quick Question... TrueRTA looks like something I am looking for. But once you get done running all of the tests as outlined in the first post, what do you do next?

As you can tell, I'm just trying to learn about this. I'm guessing that you want to adjust your equalizer so that dB SPL is 'flat' across all frequencies when it does the sweep. By flat, I mean as flat as possible. At this point, everything is correctly adjusted.

Am I on the right path or WAY OUT in left field?

Thanks!

josh1233 01-17-2007 12:33 PM

I've been thinking about getting the TrueRTA for a while (I have an old Audio Control RTA and a Coustic RTA). I am wondering what cables I would need if I am going to use the M-Audio MobilePre USB Portable Audio Interface and the Behringer ECM8000 Microphone with TrueRTA and a laptop?

- I guess I would need a XLR (1 male end/1 female end) to run from the mic to the preamp.
- USB cable to run from the laptop to the preamp.
- mini headphone jack on both ends to run from the stereo mic input to the stereo line output on the MobilePre for calibration?
- and what cables to run out of the MobilePre to the amp (dual RCA and the other end 1/4" jack?)

help would be greatly appreciated,
Josh

josh1233 01-17-2007 01:10 PM

donovanhebard, did you get your issues worked out?

When setting up the audio system in a car, you should EQ each side of the car separately (provided your EQ has separate adjustments for right and left and you are trying to get the car to sound good from both the driver and passenger side). After the initial setup of each channel, check both together (stereo). Do not boost any frequencies when adjusting both channels together, only cut frequencies. Try using both correlated and uncorrelated pink noise when EQing each channel separately and together. Set the EQ at an average between the 2. Do a lot of listening to well recorded audio tracks between EQing (like something from Sheffield Labs). And don't try to go for a flat (straight line) curve. Just get rid of peeks and dips. To do this properly, it will take a lot of time over the course of a week or two, depending on how flexible your processors are.

Before you do any of this you should set your gains from each piece so that the signal does not clip, then when you get to the amp(s), set the max amp gain to a 3:1. In other words, set the amp gain to just below clipping, read the voltage, then multiply that by three and set the amp gain to that, then cut the gains from amp to amp to balance the sound. Also, the xover points and slopes should be set before EQing to get the car sounding as good as possible. The EQ is only used to smooth thing out.

Also, make sure that, if you have time delays, they are turned off before EQing the car (they should be the last thing set). You will probably end up with a small dip at 250hz-400hz that can not be entirely corrected (if you are running speakers in the doors).
*Kick panels would be better to eliminate cancellation, would widen the sound stage, and decrease the path length differences of the right and left channel.

Another trick that may help, before eqing. If your sound stage is low, try reversing the polarity of one channels tweeter and the other channels mid. I know it sound wrong, but it usually bumps the image up about a foot. And with the amount of reflection points in the car audio environment, it will most likely focus the image better and you should not notice any loss in the mid-mid bass range that one would expect from doing this. Also, it should help the center image from both the right and left seating positions.

WSLam 01-30-2007 01:24 PM

Does anyone know how to create a 'loop' for the Apogee Mini DAC and Mini ME? I am using an ECM8000 and have the Apogee combo, but I can't figure out how to get it to work! Can anyone help? Thanks.

tsound 01-31-2007 09:59 PM

I have a problem with TrueRTA when used with a Soundblaster Live! 24 USB. The program crashes after pushing the "Stop" button. It starts fine, the tone generator works fine, but as soon as "Stop" is pressed the program crashes. Anyone seen this before?

tsound

jaegertc 02-20-2007 12:31 PM

Quote:
Originally Posted by tsound View Post

I have a problem with TrueRTA when used with a Soundblaster Live! 24 USB. The program crashes after pushing the "Stop" button. It starts fine, the tone generator works fine, but as soon as "Stop" is pressed the program crashes. Anyone seen this before?

tsound

If you haven't, try the REW/BFD forums at HomeTheaterShack.com. They have several threads dedicated to REW (and RTA?) and at least one to getting room eq software to work nicely with that soundcard.

audiozealot 03-19-2007 11:44 AM

Is there a way to splice together 2 graphs in TrueRTA? I am trying to splice together a near field measurement of the woofer with a far field measurement for a better representation of the frequency response of a speaker. I see how to shift the curves but is there a way to delete the unwanted pieces of the curves at let's say 300Hz? Please don't make me go into Paintbrush and delete pixels

Thomas-W 03-20-2007 05:20 PM

You can't splice but if you save each one to a different memory setting, you'll see the two plots combined.

andybdjuk 03-22-2007 01:39 PM

Hi guy's I have read all the post and hope I have not missed the answer to my question. I have an M-Audio USB Portable Audio Interface and the Behringer ECM8000 Microphone with TrueRTA and a laptop?

I set it up last night in my club to monitor the SPL across the spectrum of a band that was playing.

I have cal'ed the interface flat but later noticed that the clip light was coming on. Turning down the input gain obviously changes the SPL graph. Could somebody give me any pointers and what I am doing wrong? And how I set it up correctly

Thanks in anticipation

Andy

karos 04-22-2007 06:21 AM

how is trueRTA different from RoomEQ? Isnt it the same author?

sorry-I just notice that one is John Murphy the other is John Mulcahy. But how are these apps different?

jonleelk 04-23-2007 04:48 AM

Just set up TrueRTA on my acer laptop equipped with onboard Realtek HD audio. The FR for the realtek is quite bad, started to slop down from 100Hz downwards. However, TrueRTA was able to equalised to a almost flat line when using calibrating sound card option.

Is this result accurate enough to use, or should I add an external PCMCIA Sound Blaster® Audigy® 2 ZS Notebook which is supposed to have a Frequency Response (+/-3dB, 24-bit/96kHz input) = <10Hz to 46kHz (2V Rated Output)hae a FR of +1 3dB

taiguy 04-25-2007 11:03 PM

I've got a Behringer ECM8000 microphone running to a Mackie 1202-VLZ mixer/preamp to Audigy 2 ZS notebook. I tried following the directions in the pdf file off of TrueRTA's website but they're for an older version of the creative software and I can't find the same options available. It shows in my sound system calibration test. Can anybody please explain in detail how they got their Audigy 2 ZS card to work properly with TrueRTA? Thanks.

mitchlampert 04-26-2007 10:09 AM

Will True RTA run on Windows Vista?

catapult 04-26-2007 10:56 AM

Quote:
Originally Posted by taiguy View Post

I've got a Behringer ECM8000 microphone running to a Mackie 1202-VLZ mixer/preamp to Audigy 2 ZS notebook. I tried following the directions in the pdf file off of TrueRTA's website but they're for an older version of the creative software and I can't find the same options available. It shows in my sound system calibration test. Can anybody please explain in detail how they got their Audigy 2 ZS card to work properly with TrueRTA? Thanks.

These instructions for running the 2 ZS with Praxis are over a year old but maybe they will help.

http://www.libinst.com/Audigy%202%20...h%20PRAXIS.htm

scotland60bwork 05-17-2007 01:21 PM

Hi all -

I have TrueRTA full, ECM8000 mic, MobilePre USB, and the digital RS SPL meter. I've downloaded all cal files from this site. I perform the sound card cal with a loop from the line out 1/8" jack to the ch1/line 1/4" jack with adapter. I am able to get a flat line and do not appear to get any clipping. In the MobilePre audio control panel in Windows, I have the USB Record and Output sliders maxed and the monitor slider muted. Additionally, I keep the knobs on the front of the MobilePre at midposition.

After sound card cal, I hook up the SPL meter to ch1/Line and perform the absolute SPL cal, with the RS SPL meter cal file in use. This appears to work well. However, when I then proceed to hook up my ECM8000 and change the cal file to the ECM8000 file I got from this site, the SPLs appear to be pretty far off, usually about 5-10 dB difference.

I also set up the SPL meter on ch1 and the ECM8000 on ch2 and I have the same problem, even if I change the cal files. I find it hard to believe the cal files would be so far off.

Is there something that I'm missing?

Please help!

Cheers
Scot

Richard Mayer 05-21-2007 04:57 PM

Quote:
Originally Posted by scotland60bwork View Post

Hi all -

I have TrueRTA full, ECM8000 mic, MobilePre USB, and the digital RS SPL meter. I've downloaded all cal files from this site. I perform the sound card cal with a loop from the line out 1/8" jack to the ch1/line 1/4" jack with adapter. I am able to get a flat line and do not appear to get any clipping. In the MobilePre audio control panel in Windows, I have the USB Record and Output sliders maxed and the monitor slider muted. Additionally, I keep the knobs on the front of the MobilePre at midposition.

After sound card cal, I hook up the SPL meter to ch1/Line and perform the absolute SPL cal, with the RS SPL meter cal file in use. This appears to work well. However, when I then proceed to hook up my ECM8000 and change the cal file to the ECM8000 file I got from this site, the SPLs appear to be pretty far off, usually about 5-10 dB difference.

I also set up the SPL meter on ch1 and the ECM8000 on ch2 and I have the same problem, even if I change the cal files. I find it hard to believe the cal files would be so far off.

Is there something that I'm missing?

Please help!

Cheers
Scot

That's because the RS SPL meter and ECM8000 have different output voltages. You can't calibrate the absolute SPL with another and then simply switch to another.

Instead you should hook up the ECM8000 and monitor the SPL with the RS SPL meter. By monitor meaning holding the SPL meter right next to the ECM8000 and checking the SPL it shows. Then enter that SPL into TrueRTA.

scotland60bwork 05-22-2007 12:39 AM

Thanks Richard!

I was able to calibrate the SPL by holding the RS meter right next to the ECM8k. I just didn't know whether this was a valid method of calibrating it or not, and wondered what the reason was for the difference. I guess this is the only way I can do it then. Thanks for the help!

JimP 06-06-2007 09:03 AM

Quote:
Originally Posted by mitchlampert View Post

Will True RTA run on Windows Vista?

Does anyone know??

DrFeelgood 06-14-2007 09:39 AM

Hi there - newbie to all this very technical stuff, and come from the world of ICE

Could someone hold my hand, and walk me through the most simple setup of TrueRTA? At present, I'm only using it for spectrum analysis in a car for the purposes of equalisation/crossover setting. I thought I'd better get that confession out of the way first :redface: I promise to learn more of its features later! The kit seems to be the standard recommended stuff from reading this thread - ie laptop, M-audio mobile pre and a Behringer ECM8000. I got lost when you reached the word loop...

Many thanks!

Richard

eugovector 06-14-2007 10:07 AM

Quote:
Originally Posted by DrFeelgood View Post

Hi there - newbie to all this very technical stuff, and come from the world of ICE

Could someone hold my hand, and walk me through the most simple setup of TrueRTA? At present, I'm only using it for spectrum analysis in a car for the purposes of equalisation/crossover setting. I thought I'd better get that confession out of the way first :redface: I promise to learn more of its features later! The kit seems to be the standard recommended stuff from reading this thread - ie laptop, M-audio mobile pre and a Behringer ECM8000. I got lost when you reached the word loop...

Many thanks!

Richard

If you're completely new, Room EQ wizard might be a better place to start. Great help file, and free.

mitchlampert 06-14-2007 10:35 AM

Quote:
Originally Posted by mitchlampert View Post

Will True RTA run on Windows Vista?


Yes it will but the drivers for the M-Audio will not. So I had to use an older laptop to get it running.

mitchlampert 06-14-2007 10:39 AM

One more question. Can I use the pink noise generator in my processor for the tone or do I have to use the tone generator in the RTA program?

freythman 06-22-2007 09:00 PM

Has anyone had experience with the Alesis MultiMix 8USB Mixer? It's the same price as the M-Audio MobilePre, except its an 8 channel mixer with 4 XLR inputs, each with phantom power. It just seems like I'd be getting more bang for my buck...

Here's what I'm considering for my RTA techie package:

TrueRTA Level 4 (no brainer)
Behringer ECM8000
Either: MobilePre OR Alesis Multimix

Calvary 07-14-2007 08:16 AM

Good Day All,

I have read all the replies on this thread and have found it quite interesting. I will admit that I am brand spanking new to this so I apolozige if my questions seem to waste your time.

My church santcuary is in an industrial warehousing unit that is a 50'W x 50'L x 24'H. We have flat surfaces all over the place (all of the walls are drywalled with no insulation, the roof is corrugated metal with trusses, the floor is concrete covered with industrial carpet)
The dimensions and physical properties of the room make it a real challenge to get "proper" sound. I am investigating several methods of sound treatment, however I would also like to tune the room.

Question: Will TrueRTA work for a room this large? I am looking to purchase the M-Audio Mobilepre and the Behringer ECM8000 along with a Radio Shack SPL meter. ---> are these compenents suitable for tuning and profiling my santuary? Would I the church mixer in this setup?

Thanks in advance.

Rayjr 07-21-2007 08:45 AM

Hello all
I was wondering if TrueRTA can do energy time graphs.

Thanks
RayJr

DrFeelgood 07-25-2007 11:33 AM

Evening! I'm still struggling....:shake:

I've connected the MobilePre USB each and every way I can trying to setup the loop, but can't get a proper trace. Could someone take pity on me and walk me through it? tia!

Kal Rubinson 07-25-2007 12:06 PM

Quote:
Originally Posted by Rayjr View Post

Hello all
I was wondering if TrueRTA can do energy time graphs.

Thanks
RayJr

Not that I've seen. You need different software for that.

Rayjr 08-08-2007 07:09 PM

Quote:
Originally Posted by Kal Rubinson View Post

Not that I've seen. You need different software for that.

Kal
What software do you recommend for doing Energy time graphs......I have been useing a borrowed Sencore sp295..but would like to know what else is out there?

RayJr

Kal Rubinson 08-08-2007 07:13 PM

Room EQ Wizard, ETF, TEF in order of sophistication, complexity and cost. There are others but these are the 3 I know.

SierraMikeBravo 08-11-2007 05:38 PM

32 Attachment(s)
Hey all!

Well, just got done using the true rta fir the first time. I have one question. For some reason, I could not get the pink noise graph to get to 70 dB or higher. My entire graph was hovering around 50-60 dB no matter how much how much I increased the gain on my Denon 4306. As a comparison, I used a SPL to see if I was in the ballpark. The SPL showed 80-90 dB while the true rta showed only 50-60. Is this normal? However, when I used a since wave tone of 200 Hz, it spiked up to around 80 dB on the true rta with no increase in gain on the receiver. I used that as the reference, but is it in the nature of the pink noise signal to display that low on the rta? Doesn't make sense. The loop was fine and flat lined around 105 dB. Anyone know what may be the issue? I am using a ECM 8000 mike with the calibration file from tru rta. Also, and M-Audio PreUSB. I had the "R in" button pressed for the RTA as I using right input and outputs. I

Thanks a bunch!
Shawn

IncraTL 08-22-2007 05:35 PM

Hi:
Thanks for the RTA info . It's well written and detailed and will be quite helpful to me.
Just a quick question, if you don't mind -
I tried to download the free Level 1 RTA and was told I couldn't because my Dell has a Vista operating system. O.K. On 4 December 2006, my father-in-law purchased a level 4 RTA disk, (Version 3), as a Christmas present for me.
Question: Could I use this Level 4 disk on my Dell, (w/ Vista)?

Thanks for your time with this,

George

tonyptony 09-01-2007 05:18 AM

I just ordered TrueRTA via credit card for direct download. How long does it take for the process to complete? That is, once I order, how long till I get it?

Kenrosencpa 09-01-2007 07:53 AM

Their website say's up to 12 hours. This is a holiday weekend maybe more or less

AAR 09-26-2007 03:34 PM

I am a relatively new user of TrueRTA.

The program indicates that the impulse wave is used for "delay testing", yet I cannot find any documentation in the help file as to how to do this. I want to time align (as best possible) the two drivers in a two-way system. Is there a way to derive the step response??

TIA

AAR

bgavin 11-11-2007 08:56 AM

I have found a show-stopper bug in TrueRTA at v3.3.3.

During bass horn testing, I was having data anomalies. As it turns out, TrueRTA is broken. Very repeatably broken.

1 - The program SPL meter does not agree with the captured data points

We measured a Tuba 36S at 1w/1m, and expected 105 SPL. The RTA meter display read 106+, and the peak data point read 105. At first we figured the programm was summing all the data under the curve, not just the peak value.

Bug.

2 - The data export function is entirely corrupt and useless.

I was having erratic results using the Workbench to export data. We use this function to sample 100 Hz as a reference point. We then sample Pink noise and export the data. The Pink data points are increased where 100 Hz matches the sine wave sample. The data are wrong.

Every time I export data, the .TXT file data points change by approximately 2dB. Reimporting the same data points into Workbench raises the graph 2dB. Exporting the same data raises it again, reimporting raises it yet again.

Bug. The exported data points are entirely useless.

I have notified TrueRTA this is a show stopper bug.

bgavin 11-14-2007 08:42 AM

I called TrueAudio this morning and spoke with Sharon. My email to Support from 11/11 was still sitting in queue, unread. She forwarded the mail to John Murphy along with screen shots and bug attachments. I asked for a confirmation of receipt, so I know he got it.

As usual, she was in denial about there being a bug. As a 35 year veteran of software development, I expected this. I won't accept it, but denial was expected. What is more important is what John Murphy has to say about the bug, and how soon he fixes it.

I build bass horns and pro sound cabs, and the TrueRTA bug has invalidated my measurements. The curve shapes are correct, but the SPL values are all corrupt. Many days of accumulated measurement data are worthless.

John L. Murphy 11-16-2007 08:31 AM

Hello TrueRTA users!

bgavin reports 2 bugs which I would like to address:


My Summary:

Bug 1: appears to not be a bug at all but just a normal measurement difference.

Bug 2: appears to be valid but is limited to affecting only imported .txt data.



Let me explain:

Bug 1
bgavin reports:
<< 1 - The program SPL meter does not agree with the captured data points

We measured a Tuba 36S at 1w/1m, and expected 105 SPL. The RTA meter display read 106+, and the peak data point read 105. At first we figured the programm was summing all the data under the curve, not just the peak value. >>


This is not a bug, just perhaps an unexpected result. TrueRTA is giving correct readings for both the broadband dB level and the individual narrow-band dB level because these are actually two different measurements. Look at it this way; the narrow-band dB reading will always be lower than the broadband dB level because only the level of one individual frequency "bin" is represented by an individual bar's cursor readout (or exported data point). The broadband dB level (the bar at the far left) represents the energy present in the full frequency spectrum which includes the frequency bin of interest along with all the other frequency bins. Even if the one bin is at, say 105 dB SPL, and the other bins are all at some lower (noise floor or distortion) level the broadband dB SPL reading (as indicated by the large bar at the far left of the plot area and by the on screen numeric display at the top left) will measure at some higher level due to the broadband background noise. This is normal for these types of measurements. Only in the theoretical case where the distortion and noise were infinitely low would the two measurements be the same. For real world measurements there will always be a difference.



Bug 2
bgavin reports:
<< 2 - The data export function is entirely corrupt and useless.
...Every time I export data, the .TXT file data points change by approximately 2dB. Reimporting the same data points into Workbench raises the graph 2dB. Exporting the same data raises it again, reimporting raises it yet again. >>


The data export function actually works just fine. If you have 240 bars of onscreen data you will get 240 data points when you export the data to a .txt file. If you inspect the file you will see that the data points precisely match the individual on-screen bar levels. Your exported data is fine.

However, I have confirmed a problem with data import from .txt files that would explain the reported error. While the exported data precisely matches the on-screen bar readouts, some types of data can be shifted as much as a couple of dB upon import. This shift is most likely related to the way imported .txt data is interpolated into the (much larger) internal data buffers. While a response is represented by about 240 data points on-screen or as an exported .txt file the full data set actually consists of about 32,000 data points. When you save your files in project files (.rta) or single sweep files (.rt1) you are saving and restoring the full 32,000 data points. When data is imported from .txt files it has to be interpolated into the 32,000 data points. Some loss of resolution is to be expected but I think it can be improved. Smooth, broad responses seem to be minimally affected while narrow band measurements (such as single tones) are affected the most.

The screen shot below shows the difference between measured data and the same data data exported/imported to/from a .txt file:





I will investigate this .txt data import anomaly and address it in the next release of TrueRTA. In the mean time it is fortunate that most users do not normally export and import their data. As long as you are storing your data in the normal TrueRTA project file format (filename.rta) or even exporting to single memory files (filename.rt1) you should not be affected by this bug. Again, only data imported from .txt files appears to be affected.

Regards,

John

bgavin 11-18-2007 02:39 PM

Quote:
Originally Posted by John L. Murphy View Post

This is not a bug, just perhaps an unexpected result.

I am a 33+ years professional programmer, and the corollary to this is a feature is a bug with useful side effects. This is the sort of denial one expects from Microsoft. It does nothing to correct the problem, so let's please stay focused on the bug.

Here's the first problem restated:
1) TRTA geneartes a 100 Hz sine wave
2) Separate SPL meter reads 105 SPL
3) TRTA on-screen meter reads 106 SPL
4) TRTA on-screen data point reads 105 SPL
5) Export to TXT shows 100 Hz at 105 SPL

This is a point measurement, not broad band. The sine wave is 40dB higher than background. If TRTA is accumulating across the entire spectrum, it is still hearing 100 Hz at 40dB higher intensity than background.

I always calibrate TRTA to the SPL meter.
Do I calibrate TRTA to the Screen data point, or Screen Meter value?
Question: one is wrong, one is correct. Which one?

I calibrate TRTA to the SPL meter with the screen data point. I do this because the exported TXT data point agrees with the SPL meter. I treat the Screen Meter as wrong, because it does not agree with the data points.

The meter issue is mildly annoying but certainly not a show stopper.


*************

Here is the show stopper bug:


Quote:
Originally Posted by John L. Murphy View Post

However, I have confirmed a problem with data import from .txt files that would explain the reported error. While the exported data precisely matches the on-screen bar readouts, some types of data can be shifted as much as a couple of dB upon import.

This is the entire crux of my bug report.
This effect is cumulative, and completely invalidates my test data.
Each export/import of the same data changes the TXT file and the screen data points.

I require ACCURATE data in the import/export function, so shifted as much as a couple of dB upon import is not at all acceptable for my needs.

All of my measurement work centers around the TXT data points.

Quote:
Originally Posted by John L. Murphy View Post

When data is imported from .txt files it has to be interpolated into the 32,000 data points. Some loss of resolution is to be expected but I think it can be improved.

Any loss of resolution for the known TXT data points is not acceptable.

Here is the bug fix: Interpolate the intermediary points between the known TXT data points. After interpolation, verify the results with the TXT points to insure there is no change to the known values.

I would be happy to be your early tester for the resolution of this bug. I cannot wait a year, or whatever, for the next release. If my schedule does not fit yours, I will contact you for a refund, and find a different measuring tool.

bgavin 11-23-2007 06:30 PM

I have found a critical data error bug in the Level 4 TrueRTA v3.3.3 RTA Octave Resolution display.

The on-screen and exported data points are invalid for all resolutions lower than 1/24 octave.

The user takes a measurement which is present in the Workbench.
When the user selects different RTA Resolution, i.e. 1/3 Octave, 1/6 Octave, the data values change.

The measurement has not changed. TrueRTA is changing the data point SPL values as it changes octave resolution.

This is dead wrong.

The bug is demonstrated by using 80 Hz as the sample frequency because 80 Hz is present in all octave resolutions except for 1 Octave.

In this example, a 100 Hz sine wave measurement was taken at 1/24 octave resolution.
Below are the results at 80 Hz.


1/24 Octave: 35.22 dB
1/12 Octave: 38.11 dB
1/06 Octave: 40.66 dB
1/03 Octave: 43.95 dB
1/01 Octave: 50.47 dB


Exporting the Workbench verifies the onscreen dB values match the text file data.
The 1-octave resolution does not export 80 Hz, so only the screen point was used.

Every SPL data point on both on-screen and exported values are corrupt at all resolutions lower than 1/24.


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