Trouble getting started...

[brucek]

Can you help me understand the difference between the flat line at 110.1dB and the corrected and target curves down at 75dB ?

The flat line at 110db is excellent and tells you that you have a calibrated signal. The only "mistake" you made was to not run the Calibrate SPL routine when you measured the cable and set it to 75dB. This aligns REW's SPL meter with the real world normally, but when running the loopback measure simply tells REW that the level is 75dB and to place it on the graph at 75dB..... no big deal, it doesn't matter that REW placed it at 110dB (it had no reference as to where it should place it). The important thing is that it is flat, which is what you would expect a cable to measure from 0Hz to 20KHz if you had a perfect soundcard (which you now have with the cal file in place).

Anyway, as I said before...you now will set your vertical scale to 45dB-105dB for all future measurements.

The target curve is what you want your sub only measure to track to, as long as you match the crossover frequency in REW to your receivers crossover frequency. It's a guide, that REW will use to evaluate the response of a sub and recommend filters for an equalizer.

When you are ready to measure, start with the mains in your system shut off and your receiver in stereo mode and the crossover set, so you will only have the sub playing.
Use a horizontal scale of 15hz-200hz for REW.

brucek

intelonetwo wrote:

At any rate, tickertape, now that your setup, and ready to go, what is your goal? What are you trying to achieve by using REW, and BFD.

I still haven't figured out what BFD is, but I ultimately plan on calibrating my home studio, and my home theater. And since I have an on-location mobil studio, I'll probably calibrate and do some limited room treatment to various performance venues now and then.

What is BFD ? ...lots of acronyms out there ! ...reminds me of the military.

[brucek]

It's an inexpensive parametric equalizer that a lot of people here use to equalize their subwoofers.

REW will recommend filters to enter directly into a BFD. In fact you can connect a midi /USB cable from your PC and download the REW recommended filters into the BFD (or you can enter them by hand).

BFD stands for Behringer Feedback Destroyer. No-one uses the feedback destroyer function of the BFD (which eliminates microphone feedback on a stage for musicians), but we use the two channels of 12 parametric filters that happen to also be a feature of this unit.

REW will create suggested filters for several equalizer types besides the BFD. The filters are what that target line is all about that you questioned....

We have a BFD Guide to get you started...

Not everyone requires an equalizer, as speaker placement and treatment are the first order, but if you have a large resonant peak at sub frequencies, it's hard to beat a cheap BFD.

First you have to take measurements of your sub from the listening position......... that's what the goal of this journey is all about.......

brucek

Brucek,
Thanks for that explanation (about BFD).

Everything seems to be working correctly now, thanks to all your help.

Now, is there anything I should know about transitioning from SPL measurements to measuring with a reference microphone ? (I do have a calibration file for the microphone) The "Making Measurements" section of the help file seems to discuss taking measurements only with the SPL meter.

[brucek]

Now, is there anything I should know about transitioning from SPL measurements to measuring with a reference microphone ? (I do have a calibration file for the microphone) The "Making Measurements" section of the help file seems to discuss taking measurements only with the SPL meter.

Yeah, you'll still require the SPL meter for a one time hand held refernce during the Check Levels routine, when you use a microphone.

Here's the deal...

You connect the microphone (and its preamp, or connected directly to a mic input of soundcard with built-in preamp). Then you connect the line-out to your receiver (always in stereo mode with all soundfields and effects off) and the crossover set to the normal one you use (i.e. 80Hz).

Be sure the soundcard cal and the microphone cal file is loaded into REW.

Run the Check Levels routine and set the output sweep level of REW to -12db, and then adjust your receiver volume so the level at the listening position is 75dBSPL. This where you hold the Radio Shack SPL meter near your hooked up microphone so you're able to set that 75dB level (kinda hard without it). Once that's done, put away the SPL meter.

Now set the REW line-input level until it's at ~-12dB. The levels are now setup - finish....

Then run the Calibrate SPL routine in REW and set it to 75dB (now the REW meter knows what 75dB actually is).

Now run the Measure routine.....

brucek

[playitbyearmusic]

I'm having the same problem. I can't get the output to match the input. I read somewhere in this forum that REW is not compatible with the MAC that I have because the input is not supported (733MHz). Is this true? I cannot get the program to calibrate my soundcard (MOTU 828). I'm now looking for any demo software that allows me to take the measurements. Also, when they say to use an RTA, is that what the particular program is called or can I use an FFT analyzer, spectrum analyzer, oscilliscope, etc?

[brucek]

playitbyearmusic, it would be best to start a new thread with your questions.

brucek

brucek wrote:

Be sure the soundcard cal and the microphone cal file is loaded into REW.

Not sure how to load the microphone cal file...do you load it by browsing to it from the Settings/Mic/Meter window ?

[brucek]

Not sure how to load the microphone cal file...do you load it by browsing to it from the Settings/Mic/Meter window ?

Yep. Just download the file from our download page and store it anywhere you like in your computer and browse to it and click...... (I am assuming you're using an ECM8000. If you're using some other mic and you have the cal file for it, be sure it's in the correct format for REW).

brucek

[JohnM]

tickertape wrote:

I think I found the problem.

By trial and error mostly, I set the latency of the Tascam soundcard to the highest setting. The clicks/dropouts don't stop completely, but they're now down to about one every twenty seconds or so. Anyway, good enough to finally get a 'clean' soundcard cal measurement...I think !

The laptop I'm using is not all that old - 3 years - I think it should be fine for this application, especially now that I've turned off all unnecessary background applications.

You can also increase the replay and record buffer sizes in REW on the soundcard settings tab and see if that helps.

brucek wrote:

Yep. Just download the file from our download page and store it anywhere you like in your computer and browse to it and click...... (I am assuming you're using an ECM8000. If you're using some other mic and you have the cal file for it, be sure it's in the correct format for REW).

brucek

I'm using a DPA 4006 as my calibration mic, and was successful loading it's .cal file.
Here is the 0 - 200 Hz room measurement I'm getting so far:

[brucek]

Change your vertical scale to 45dB-105dB. (use the Graph Limits Icon and enter 45dB-105B for bottom/top and enter 15Hz-200Hz for left/right. Hit Apply Settings).

brucek

Moved the sub closer to room center, changed plot axis scaling...





Is there a way in REW to overlay multiple measurement plots ?

[brucek]

Yep, use the Measured tab. You can select any or all your measurements with checkboxes.....
It's really the best way to compare plots..

Your response is getting quite good, although it would be nice to have a bit lower bottom end. Perhaps a new sub is in the future.................

brucek

brucek wrote:

... it would be nice to have a bit lower bottom end. Perhaps a new sub is in the future.................

brucek

Yes, I agree. I'm currently using a Canadian-built Mirage Omni S8 (with an 8" driver). It does have a very nice sound though, especially for a $350 speaker !

Hoping to upgrade soon to a Dynaudio BM9S (10" driver), to go with my Dynaudio BM5As.

REW had been working great on my XP system, but that particular laptop is noisy. So I tried moving it all over to my Vista laptop (much quiter) but can't seem to get it working after installing REW, soundcard, drivers and duplicating all XP settings.

Are there any configuration differences I should know about for Vista ?

[brucek]

Yeah, Vista is a bit different, in that you usually have to control the levels in REW from the Vista Playback and Recording Devices screens. They are accessed by right clicking on the speaker icon in your desktop System Tray.

Read through this thread with regard to the setting of levels while using Vista Recording and Playback screens and their respective Levels tabs. Also be sure to have the Output Volume mixer (left click speaker icon in System Tray) full up. It is a proxy for Wave in Xp world.

If you don't get anywhere with that information, we'll look into it further.

I trust you loaded the Tascam Vista driver.

brucek

brucek,
I read over your USB soundcard thread. The Tascam drivers were loaded, and they do show up in device manager.



The sound card also shows up and is selected in the Vista playback and recording screens.
As far as I know, the Tascam doesn't have any control panel settings other than the few shown on the window above. All the I/O level settings are on the unit itself.




Here is the configuration on my settings window.



When I try to check levels in REW, there is no meter level shown in the Peak output meter, nor is there any output from the Tascam soundcard to the speakers.
Additionally, I don't get any level setting windows in the Vista recording and playback screens like those you showed in your thread.

[JohnM]

Try setting REW to 44.1kHz. If that doesn't help look in the REW log files (the location is shown in the About... dialog) to see if any error messages are being logged.

[brucek]

I'm assuming that the left click on the speaker icon in the System Tray has the master volume up full......

Other than that, it all sure looks correct.

brucek

I switched the REW settings window sample rate to 44.1kHz, but it made no change...still no level.

Also checked the speaker icon in the System Tray, and the level is at max.

Setting the REW soundcard to 44.1 gives the following error message on REW startup, and the REW logs seem to indicate a java-related problem loading some dll files.

[JohnM]

The warning message can be stopped by clearing the current cal file you have loaded, which was measurd with a 48k sample rate. that is not appropriate when running the card at 44.1k, and it is best to run the card at that rate to avoid software resampling from the card's 44.1k to 48k.

The dll message happens because Vista doesn't allow REW to write the dll into the java bin directory. The dll is only required for RS232 comms, you can ignore it.

The problem is the "timed out" message, which indicates that REW is having problems sending audio data to the card. Try setting the REW output device and input device to default.

After setting the REW output device and input device to default, there is still no output. I generated a debug file which indicates no devices or inputs selected.

[JohnM]

I see from your image of the settings tab the output volume and input volume both show 0.000. Check that when you right click the volume icon and select Open volume Mixer (with REW running) the volume level for REW is at 100. It may be labelled as "Java SE binary" or, if you have the REW settings tab open, "Settings". It would usually be the right-most volume slider.

Also select the Tascam speakers entry in the Windows Sound Playback tab, click Properties and see if there is a levels tab on the properties dialog, if so make sure the level is at 100. Select the Tascam Line In on the recording tab and do the same. Even devices that have no volume controls in their own drivers usually have level control from the Vista playback/recording properties entries.