If you're like me you were overwhelmed by the REW "guide" on home theater shack. So here is a more thorough step-by-step of how to get REW working. I like to think once you have everything hooked up this guide will get you measuring in about 10-20 minutes.
First things first lets go over the equipment needed
- Tascam US-122 MK2 audio interface/pre-amp
- Dayton EMM-6 Mic (only $5 shipping through amazon.com, vs $12 on parts express)
- Onstage mic stand
- SPL meter
- TRS to TRS OR XLR->RCA for calibrating the external soundcard (OPTIONAL)
- XLR female to male for connecting the mic
- RCA cables to amp/receiver (everyone should have some of these)
The cheapest good audio interface for the purpose of measuring is the tascam US122 MK2.
It has decent DACs as well and functions as a decent 2 channel device.
I have studio monitors on my desk setup and if i were to do it again i would buy an m-audio mobilepre audio interface because it has balanced outputs. The tascam's knobs also feel a bit cheap and the m-audio might feel better built.
For those wanting cheaper, i dont know of anything. If you have a capable pci soundcard you can skip the tascam and buy a behringer xenyx 502 for phantom power (to power the emm-6) but it gets a lot more complicated AND it's not portable. So i would recommend buying an actual audio interface like the m-audio or tascam that has phantom power built in.
(Note: for this guide I'm using my tascam US144 MK2, thats why it looks slightly different)
I have the aperion meter and I'm pretty sure its the same as the radioshack meter, it's just $29 with free shipping, making it a GREAT deal. For some reason it's still a fairly well kept secret. It's pretty accurate too which cant be said for a lot of the cheaper mics on places like amazon
Issues with Monoprice.com
Some of you are probably wondering why I've recommended cheap looking cables when monoprice has "nice" ones for cheap. The problem with monoprice is they had a bad batch of RCA->XLR cables over the course of several months. I ordered cables in november, RMA'ed them almost a month later, then they shipped me even more defective cables. I dont trust them to wire RCA->XLR cables anymore, so i can't recommend them. The "cheaper" looking cables work for me fine. Youre free to order from monoprice, just realize if you dont have a multimeter and know the pin guide its hard to establish if a cable is broken or something else is.
The Dayton emm-6 comes with a calibration .txt file (this will makes sense later in the guide) from 20hz to 20khz, if you think you have a serious subwoofer setup and have a lot of output below 20hz you may want to buy a mic that is calibrated from cross spectrum labs. The Basic+ is $75 + $9 shipping. This will result in 5hz to 20khz calibration. Apparently its also recommended for car audio measurments (probably because it offers 90 degree angle of incidences if youre facing the mic "up" at the position of your head in a car, best guess).
Alright, now onto the instructions:
- Install the USB drivers for your audio interface, heres the tascam drivers
- Install Room EQ Wizard v5.07 beta
Before opening up REW make sure your windows levels are up all the way on the tascam (if its not shown, right click on the volume icon and go to "Volume control options" to enable it)
Once REW is open click on preferences
This guide uses V5.07 beta. v5.07 uses "ASIO." Doesnt change much I just recommend using it, in the program you can change the output on the tascam from left to right in case you want to test two different subs without unplugging and plugging the cable. Make it look like the image below
Tascams and most audio interfaces in the $100+ price range measure very flat from the factory, so you could get by without calibrating it all! If you are curious or still want to do it, please click HERE to read my page on calibrating a soundcard/audio interface in REW
Now go to the mic/meter tab
Go to dayton audio for your calibration file, input your serial number that is on your dayton emm-6, and save the .txt mic calibration file on your computer
Now press on browse and navigate to the file, then press okay.
Exit out of preferences...
Now take your tascam, unplug the TRS to TRS cable, and plug in an RCA cable from the left LINE OUT and plug one end into whatever channel of your receive that you want to start measuring. If youre measuring a subwoofer you can plug it directly into the amp if you want. Turn PHANTOM to On.
Plug your xlr cable into the tascams MIC IN L, and plug the other end into the emm-6
For the purpose of measuring a subwoofer i put the mic facing down at the listening position at my couch.
Before we can do frequency response sweeps time to take out an SPL meter
Make sure the SPL meter is set to C weighted, and Slow response (highlighted below)
Now, if you ran the built in calibration on your receiver then the volume at "0" should be reference at listening position. Basically means 85db where your mic is. Feel free to turn the receiver to "0" then adjust the LINE OUT on the tascam accordingly. Getting the SPL # accurate isn't extremely important if all youre doing is getting an idea of how your room behaves with low frequencies, as nulls and peaks will show up anyways. The program will still work exactly the same, its SPL numbers will just be completely off.
Back to REW, press the SPL button
Depending on what youre doing select subwoofer cal or speaker cal, for our purposes we're doing subwoofer right now
If your receiver is on the right input and REW is configured correctly you should have white noise blasting out of the subwoofer. You might want to keep the receiver volume low so that way you can turn it up with the remote to a "comfortable" level while you hold the spl meter near the mic. Aim for around 85db, take it louder if you want just realize depending on how big the room is and what type of subwoofer that even 85db can strain it.
Enter the number on the spl meter into the window, press ok, and close the SPL meter. Now its time to click on the Measure icon
Change the start freq and end freq to 20 to 125hz, for most people that should cover the entire range of bass that can be "fixed," feel free to start the freq earlier if you know what you're doing. Set sweeps to 2 or 4 because it finds anomalies in the signal (truck driving by vibrating the floor, vent turning on or off, etc) and eliminates them.
I dont know enough about the other feature of REW to write a guide about them, red spade audio does a pretty good job though here and the rest of the blog is very useful as well