Can i use motu 828mk2 with REW?

[jf1]

Hi,

It's my first post here so please forgive any stupid questions!!

I'm intending to use REW to test the frequency response of my small home studio room..i've already made some rockwool bass traps & wall panels for it & they've made a massive difference already. I'd still like to test the room though to see if i could use some more room treatment & where might be best to put it.

I've got a couple of questions :

can i use the motu 828mk2 with REW, and will the direct monitoring on the 828 cause any issues?

would a nuemann or groove tubes mic be suitable for performing the test? I'm pretty sure i've got a frequency response chart for both these mics so could i use this data to help in achieving a more acurate test?

will i need an spl meter as well if using a mic to do the testing?

any advice or help with this would be really appreciated

thanks!

[brucek]

can i use the motu 828mk2 with REW, and will the direct monitoring on the 828 cause any issues?

I think it would be fine. With REW, less is more when it comes to soundcards, so people with simple twenty dollar stereo cards have a lot less trouble than those with the complicated ones. In the world of complicated, I would say the motu wins a prize. This means you need to identify a simple analog line-out and line-in with no monitoring and no effects.

If monitoring is turned on, the output will be internally looped back to the input. This is a no-no with REW.

Sometimes it's easier to use an old XP PC with a crummy soundcard and do your measuring. It's a thought anyway if you run into roadblocks..

would a nuemann or groove tubes mic be suitable for performing the test? I'm pretty sure i've got a frequency response chart for both these mics so could i use this data to help in achieving a more acurate test?

If you have calibration files or calibration graphs for a microphone, you can create your own calibration file for REW. It isn't difficult to do. We can help if you run into any snags..

will i need an spl meter as well if using a mic to do the testing?

Well, an SPL meter is used in the initial calibration of REW before switching to the microphone to do the actual measuring, but you can get away without the SPL meter if you accept a relative, rather than absolute measure.

brucek

[Wayne A. Pflughaupt]

(EDIT: brucek beat me to the punch while I was out running an errand!)

I’m going to say “it’s possible, but it may be a challenge.”

As you probably know, any room-measuring platform is only as accurate as the components involved. The beauty of REW is that it is able to compensate and calibrate itself for run-of-the-mill stuff like cheap soundcards and the mics in SPL meters.

In order for REW to calibrate the soundcard, it has to have line inputs and outputs. You should be covered there, but the mics you want to use may be a problem. I’m not sure if REW will work with a mic input for self-calibrating.

Then there is the issue of the mic itself. No mic has perfect response, so you would have to create a calibration file for it that you could load into REW.

You’ll still need an SPL meter, because you have to set the level of your sound system before running REW. Since you have to have one anyway, you could just plug it into one of the Moto’s non-mic inputs. The Radio Shack meter with a calibration file you can download here is pretty accurate up to ~5-7 kHz, which should be adequate for what you want to do. If you need accuracy out to 20 kHz, then you might want to get a Galaxy 140 meter instead.

Regards,
Wayne

[jf1]

Thanks so much for the replies

I'll give it a try with the motu first, the main thing i'm a bit worried about is the direct monitoring because as far as i know, the only way to turn off direct monitoring is via the control panel in a daw. Maybe using an app like rewire to link the ins & outs of the motu (with direct off) via the daw to the in & out of REW would work? I'll have to look into this further!

I have got an xp laptop with in-built sound, but it may be a bit too crappy to use..there's only mic in (not a mic pre-amp) & speaker out on it. I've no problems with grabbing a soundblaster or whatever if needs be though.

In terms of mic calibration would this be a case of inputting the frequency response data of the mic into a text file or somthing that REW can read? I would like to be able to take acurate readings up to 20k if possible so it may well be worth getting the spl meter you mentioned for this, plus it sounds like it'd be better for setting levels.

I'll have a mess around with the motu today & let you know how i get on..

Thanks again!

[brucek]

In terms of mic calibration would this be a case of inputting the frequency response data of the mic into a text file or somthing that REW can read? I would like to be able to take acurate readings up to 20k if possible so it may well be worth getting the spl meter you mentioned for this, plus it sounds like it'd be better for setting levels.

Yeah, go to the download page and drop one of the cal files (like the Galaxy cal file ) into notepad and you'll see the txt format. You can create it with notepad and then save as a .cal file. It's quite free form in the spacing between frequency readings also. REW will simply 'connect the dots'. At the limits of the file REW will continue out with the last value.

I don't know if the Galaxy is accurate out to 20K or not. Perhaps you can use one of your full range mics and run it through the motu preamp and then send the (required) line level signal into the XP PC soundcards line-in (if you can find one with line-in). If your mics aren't full range, then I guess the Galaxy is your next best bet. Sometimes studio mics aren't great measurement mics as they may be oriented toward voice range responses. You would know that though, since you have the graphs of them.

I have got an xp laptop with in-built sound, but it may be a bit too crappy to use..there's only mic in (not a mic pre-amp) & speaker out on it. I've no problems with grabbing a soundblaster or whatever if needs be though.

Laptops typically only have mic in and that is indeed not really suitable. Most people who use a laptop for REW use the simple and inexpensive USB soundcards..... that's your best bet.

brucek