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Getting Started With REW

12K views 31 replies 9 participants last post by  Justin Zazzi  
#1 ·
Hey guys so I am trying really hard to get a grasp of how to properly tune a system and I was thinking REW would help me a lot for level matching my system.

I was wanting to use my auto eq mic that came with my deh-80prs, would there be any problems with doing that?

I also assume that I will need to get an spl meter to calibrate it, but when I looked spl meters up briefly they were like $300... is there any inexpensive SPL meters that will still function accurately enough to get the job done?

Is there anything else I need that I do not know of?

Thanks guys
 
#2 ·
You will not be able to use the microphone that came with the 80prs for a few reasons, the most important being you don't know the frequency response of that microphone.

You'll need a microphone that comes with a calibration file, like the ones that are sold from cross-spectrum labs. You'll also want an external sound card to interface with the microphone and the car. All in all, expect about $200 worth of gear or maybe less if you can find some used gear.

I'm working on a set of how-to videos for this and will PM you links to the rough drafts I started. Hopefully they can steer you in the right direction.
 
#3 · (Edited)
I'm working on trying to use the mic that came with my Alpine PXE-H660 DSP

http://www.diymobileaudio.com/forum....com/forum/technical-advanced-car-audio-discussion/248585-rew-audyssey-mic.html

REW help file has instructions to calibrate your internal sound card.

Now I'm completely new at this and have had several hold ups with time and my laptop.

I'm not challenging Jazzi's knowledge of REW at all just sharing information I have found.
I agree with him about getting the correct mic with a calibration file, but I also like to play with what I can within my limited budget. LOL
 
#5 ·
Damn, I too am short on cash at the moment :p I was really hoping I could just get by with using this microphone. I guess I knew less about rew then I thought :p

I didn't see that huge help folder in REW, when it says sound card what is that talking about? like the physical card for processing audio on my computer? or is it something different? is that necessary to get an external one?

I think it would probably be better to get some sound barrier before I get stuff $200-300 more of equipment :p if only the price of the CAD dollar wasn't so low...
 
#7 ·
Those of you using USB microphones, how do you feed the test signal to the car? Do you use the on-board sound card on your laptop? Do you use a CD? What do you do?
 
#8 ·
I have the Dayton umm6. I use the REW generator with a connection from the microphone jack on my laptop into my hu. I have the Pioneer 80prs and there is an input on the front which is nice. You can also use a cd or music/pink noise stored on a thumb drive to usb. Lots of ways to do it. There is no loopback this way though and really wish I could do that.
 
#10 ·
That's what I thought. The downside of using a USB powered microphone is two-fold: 1) you can't calibrate the sound output from your laptop using a loopback cable so it may be influencing your frequency response, and 2) you can't use a loopback cable in your 2nd channel to get timing references when doing a sweep (your impulse response measurements become much less useful). Further, if you're using pink noise on a CD you completely miss all the awesome features that REW has to offer from using the measure (sweep) function such as phase plots, group delay, waterfall plots, and averaging of multiple points of measurement.

But if it works for you, then keep doing it I guess.
 
#13 ·
Further, if you're using pink noise on a CD you completely miss all the awesome features that REW has to offer from using the measure (sweep) function such as phase plots, group delay, waterfall plots, and averaging of multiple points of measurement.

But if it works for you, then keep doing it I guess.
Maybe a silly question, but how does using a separate pink noise source prevent you from averaging?


I've had good results using a USB umik-1 from minidsp with calibration file. Initially I was using Behringer UCA202 usb dac with a stereo rca to 3.5mm into my head units aux in, but now I use a cheap $9 usb to spdif DAC that goes straight into my DSP.

If $s are a big issue then a usb mic should run you less than $100cad
 
#12 ·
Jazzi I completely agree and wish I would've done more research before I got the umm6 usb mic. I do the best I can with it for now and it might explain why I don't enjoy tuning as much as others. At some point I'll upgrade so can get more accurate results.

I've been out tuning today trying a few different things from Andys handbook. I luckily saved it off before the removed the link. I still have quite a ways to go and taking a break. Back on dad duty until tonight.
 
#15 ·
Ah right, I've been using my mic on a tripod in the drivers seat and taking sweeps and moving it slightly each time, in a few minutes I've got 9 to 12 sweeps to average and the results are quite repeatable.

On the Mrs car I skipped the dac and just used rew to create a pink noise and pink PN .wav file to play from her head unit
 
#16 ·
Thank you everyone. I'm very interested in this subject, still a little stumped though.

UMIK-1 is the first microphone recommended by REW in the help file under equipment needed.

I guess I'm still not understanding the limitations of a USB mic.
Why can't you just use the USB mic while still using the signal from REW from your internal sound card fed to your Aux on the head unit.
I would guess its critical to calibrate your sound card as well.

:confused: but still learning.... :)
 
#18 ·
Thank you everyone. I'm very interested in this subject, still a little stumped though.

UMIK-1 is the first microphone recommended by REW in the help file under equipment needed.

I guess I'm still not understanding the limitations of a USB mic

:confused: but still learning.... :)
Currently you can't directly measure impulse response which helps with setting time alignment, although there are other ways to set time alignment. However this may change very soon with the next beta of rew to come out.

But currently you would need a real mic (like with an XLR plug) with preamp and external sound card. You run say the left output to your sound system being measured, and the measuring mic to the left input on the sound card. In addition you connect the right output to the right input and the software measures how long the signal takes to come back on the right input vs how long the sound takes to travel thru the air to the mic and then into the sound card.
 
#17 ·
What is a good setup for mic and external soundcard. Dayton emm6? I searched for thru the threads and saw you recommend an m audio fast track pro but that was a while ago.

I used to use sweeps but then switched to pink noise because it was much faster. I sit in the vehicle and the sweeps drive me nuts! In rta, the preferences tab, change the mode to RTA 1/48 and averages Forever. Also select the Adjust RTA levels. With these settings I just sweep the mic and my head with pink noise until the graph basically quits moving which doesn't take long. I honestly don't know how accurate this is compared to sweeps but it somewhat works for me. I still have a lot to learn.
 
#21 ·
What is a good setup for mic and external soundcard. Dayton emm6? I searched for thru the threads and saw you recommend an m audio fast track pro but that was a while ago.
Check this thread out, and look for Gazoink's post near the top. He goes into detail about what you need from an external sound card (though I disagree with the requirement of 24/96) and he summarizes many of the inexpensive solutions on the market:

REW Sound Card Database - Page 11 - Home Theater Forum and Systems - HomeTheaterShack.com

I used to use sweeps but then switched to pink noise because it was much faster. I sit in the vehicle and the sweeps drive me nuts! In rta, the preferences tab, change the mode to RTA 1/48 and averages Forever. Also select the Adjust RTA levels. With these settings I just sweep the mic and my head with pink noise until the graph basically quits moving which doesn't take long. I honestly don't know how accurate this is compared to sweeps but it somewhat works for me. I still have a lot to learn.
This method is called spatial averaging and is valid for making measurements.
 
#27 ·
I see you quoted my thoughts from earlier this year. Since then I have changed my recommendations some. I think the USB microphones like the UMIK-1 and the Dayton UMM-6 are a better route to go for most people instead of getting a regular microphone and an external sound card. Although the mic/card combo has the potential to make better measurements, there are so many variables to consider and it requires more care to setup properly than just plugging in a USB microphone and going for it. I think the extra hassle and potential problems of a mic/card combo are not worth the potential small increase in performance.

But is making the jump from using the IMM6 with your custom cable to using a UMIK-1 going to be worthwhile? I'm not sure. I don't have experience with the IMM6 so it's really hard to say. You will loose the laptop sound card calibration file, but it seems like the sound card in your laptop is capable enough to make measurements so long as you don't rely too heavily on information below 30hz or so (I assume you're still going to be using it to generate sweeps).

At the end of the day all that matters is you have a measurement system that is reliable and predictable *enough* that you can get the results that you want. Even if that system has flaws, so long as you know about them you can still use it pretty effectively. For example I used to have an older computer monitor that was darker than it should have been, but I knew about it. So when I was preparing photographs to be printed, I was able to keep that in mind and compensate. My tool was flawed, but I was still able to get the results I wanted from the printer in the end. Ironically, the sales of the photographs I printed using that old monitor helped me save up to buy a new one :)
 
#28 ·
Thanks Jazzi, I appreciate it.

Like you said, there are always going to be small variables. Think about the analog input to the deck too, that is (in theory) going to have a response that isn't perfectly flat.


In the end, probably shouldn't have splurged on the new mic... but I'll play with it then maybe post it up for less than $100 in the classifieds.

Gotta work on the tendency to rush into things i think (at the time) are great ideas... :rolleyes: