Looking for REW Setup Help for Church Sound Consultant

[pajohnso58]

I recently retired from corporate IT and am looking to start a business/ministry helping churches with their sound systems. In 2010 I had a copy of Smaart that I used to tune a system I designed for a church. I am trying to keep my cost down, so I can deliver my service free or at a very low cost, and came across REW. I quickly downloaded a copy and have started "playing" with it. I have an older generation Scarlett 2i2 and I just bought a Rational Acoustic RTA-420 mic with a cal file. I've also been reading (and rereading) Bob McCarthy's Sound System Design and Optimization book to get me prepared to provide the service.

I'm looking for someone to help me get everything setup and running properly on REW. I need to know that my rig is configured properly and that my measurements are accurate and valid. I also need to be proficient with REW and have a game plan for analysing a church sound system and room. It's really important that I get this right upfront, as I can't afford to do a lot of trial and error and on the job training in front of clients. I am willing to pay, but, again, I am trying to keep my costs down.

 

[Wayne A. Pflughaupt]

I suggest getting your feet wet by using REW with your home stereo system or other audio playback system.

Cheers,
Wayne

 

[pajohnso58]

Thanks, Wayne. I’ve already started doing that but feel I need more guidance.

 

[Wayne A. Pflughaupt]

What are you having trouble with?

Regards,
Wayne

 

[pajohnso58]

Largely initial set up: asio vs java drivers, creating a sound card cal file, making sure I’m using the best cal file for my mic, possibly creating a cal file for my backup mic, getting initial spl settings right, setting levels for measurements, etc. Then I need an effective and repeatable process for taking, saving and evaluating measurements, including which graphs to use for which purposes. I ultimately want to use the power of REW, but simplify things so I have a consistent process for use in the field.

Thanks, Paul

 

[Wayne A. Pflughaupt]

initial set up: asio vs java drivers,

I’m not big on ASIO, but AFAIK it’s utilized with USB measurement mics in conjunction with a multi-channel home theater system. Since you have a standard mic and USB interface, that will be feeding a mono signal to a mixing console, it doesn’t apply to your equipment and situation.

As far as Java goes, if you already have REW up and running, nothing else is needed.

creating a sound card cal file

The great majority of interfaces these days come with ruler-flat response out of the box. So your Scarlett will not need a calibration file. It’s plug-and-play.

making sure I’m using the best cal file for my mic,

The best calibration file for the mic is the one it came with, or that you had a lab custom-generate for you.

possibly creating a cal file for my backup mic,

Unless you have sophisticated laboratory equipment to measure the mic’s frequency response characteristics, you can’t create an accurate calibration file for it yourself. You could create something if you had a frequency response plot for the mic supplied by the manufacturer, but it wouldn’t be as accurate as one created by a lab like Cross Spectrum.

getting initial spl settings right, setting levels for measurements, etc.

Standard stuff covered in the REW Help Files.

Since you don’t have a USB mic, you need a SPL meter of some kind. But even that isn’t necessary. You can simply play the test signal through your system at a comfortable volume and “tell” REW it’s 75 dB. 75 dB on the graphs you generate won’t be an actual 75 dB, but the graph’s dB scaling will still be accurate, ans therefore your measurements will be accurate.

Then I need an effective and repeatable process for taking, saving and evaluating measurements, including which graphs to use for which purposes.

This comes with practice and experience. In addition to using REW with your home system, you could practice on the system at your church, or a friend’s church.

Frankly, most issues I see with (especially) small churches is stuff that REW can’t help with: Poor installations performed by volunteers (exposed cables or worse), problems with stage cables that have cheap XLRs, cheap wireless mics, subs not set up properly (too loud), individual console channels not EQ’d properly (i.e. boomy, bass-heavy vocals, muddy bass), ground loops due to inadequate electrical provisions (stage and FOH equipment on different phase or [even worse] panels), etc.

Regards,
Wayne

 

[pajohnso58]

Thanks, Wayne. All good advice I will take to heart, especially all the other problems small churches have that have noting to do with REW.

I would still like someone to help walk me through the setup process to make sure I have everything right. I'm going to re-watch the 2 videos on the REW website and also re-read the help files. I'm 70% confident things are setup properly, but I would like to get that up into the 90s if possible.

 

[Wayne A. Pflughaupt]

The folllowing is based on an older version of REW, but should pretty close to the current version.

1. Connect your audio interface to the laptop, and the measurement mic to the interface, and open REW.
2. From the computer’s "Speakers" menu, select the interface as the recording and playback devices.
3. Open the REW “Preferences” tab. Select “Mic/Meter,” then select the “Mic or Z-weighted SPL Meter” option. Browse and open a calibration file for the mic that you have saved to the laptop.
4. In the “Soundcard” Tab:
5. (A) Select the interface as the Input and Output devices, and select if the input you will be using, i.e. the Right or Left channel. The channel you select will be the one the measurement mic is plugged into. In this window you can also browse and open the interface calibration file (typically not needed).
6. (B) In the “Levels” section, select in the dropdown box the preferred test signal: A bass signal for subwoofers, or a full-range signal for main speakers.
7. Click “Check Levels” and follow the directions provided in the box.
8. Close the “Preferences” window and open the “Measure” window. Select the frequencies you want the sweep to start and end with. Click “Start Measuring.” After the measurement sweep, a frequency response graph will appear on the screen. You can find an icon to adjust the graph’s axis limits, both horizontal (frequency range) and vertical (dB range). For the latter, typically a scale of 45-105 dB is recommended.
9. At this point you may want to re-adjust the system level for subsequent sweeps if you felt the sweep level was too high or too low, either via REW’s Measurement box, or with the sound system’s master volume control.

Upon subsequent uses,the program will remember your settings (e.g. calibration files), so you can typically go straight to the "Measurement" window. There is an icon there for checking levels beforehand. As mentioned, a SPL meter is helpful, but not a hard requirement. It will at least insure your initial sweep is in a good and usuable range (read level).

Hope this helps.

Regards,
Wayne

 

[pajohnso58]

Thanks, Wayne. I have done a lot of this but I'll double check to make sure I got it right.