Help me learn more about REW and reading data...

ICTWoody

Junior Member
Hey guys,

Tonight I started playing around with REW and my miniDSP UMIK-1. I got a new laptop so I figured I’d give this a whirl. Previously I was just using the mic for an RTA with my iPad.

Here’s a couple of measurements overlaid. They are basically the same, but with the phase switch on my pair of REL T5i’s switched. I was playing around with adjustments earlier, as you can see from the ones turned off. But these seemed best... but I don’t know what the hell im doing. With the subs set to zero phase, there’s what seems to be a huge dip about 160hz... when the phase is inverted it seems to be lessened. All other settings were the same between these two measurements.

It should be noted that before I was measuring I just setup the subs and did a little tuning by ear per RELs instructions and they SOUNDED better to me set to 180deg phase.

I’m looking forward to being able to measure and interpret this data better in the future with your help.

- Woody


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If you are measuring "far field" in your room, below a certain frequency the standing waves from your room will affect the measurements. That is quite possibly the reason for the 160 Hz dip. The standing waves from the room could be out of phase with your sub woofers at that frequency. Try measuring at different positions around the room and see if you get different results.
 

rogerfederer

Junior Member
how are you using the miniDSP in this setup? if you use it as a 2-way crossover you can use the REW to create room corrections that you input into the crossover. there is a lot of back and forth over the merits of using a miniDSP as crossover. minus: the miniDSP does analog to digital and then back to analog conversions and its electronics are unlikely to be as good as whatever fancy DACs you have. plus: if you have difficult room you can address the room issues. If the benefit from room correction is great enough it can overwhelm the disadvantage of the AtoD and then DtoA conversions.
 

ICTWoody

Junior Member
how are you using the miniDSP in this setup? if you use it as a 2-way crossover you can use the REW to create room corrections that you input into the crossover. there is a lot of back and forth over the merits of using a miniDSP as crossover. minus: the miniDSP does analog to digital and then back to analog conversions and its electronics are unlikely to be as good as whatever fancy DACs you have. plus: if you have difficult room you can address the room issues. If the benefit from room correction is great enough it can overwhelm the disadvantage of the AtoD and then DtoA conversions.

Not using miniDSP... just a miniDSP UMIK-1 measurement mic.

I had a friend help me a few years ago measuring the room, but that was with an entirely different system. I have full range bass traps in the front corners, and open passageways out of the room in the other two corners. I didn't understand much of what he was saying then, but I want to learn now. The way he explained it to me is that the openings in the corners basically act as natural bass traps. I also have 4’x4’x4” first reflection panels set 4” off the walls which also offer absorption.

I have the mic placed approximately in the listening position. Ear height etc... I'm running out of my MacBook air into the internal USB dac in my NuPrime IDA-16. The only real tuning I can do at this point is how I implement the subs.

Here's some pics of the setup as it stands...

- Woody

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That measurement looks pretty good. I have the same 160 dip but have another one around 60Hz.

REW is a steep learning curve for me. Thanks for the inspiration to make some more measurements.
 
I agree that your measurement does look pretty good also. You could try moving the subs around a bit. Maybe directly behind the speaker stands?

Sound travels roughly 1125 feet per second. 1125 / 160 Hz ~= 7 feet. Distance between subs?? This could be a number to look for and change, if possible. It gets rather complex with all of the combinations of distances that can be added, subtracted, and multiplied.
 
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