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Discussion Starter · #1 ·
Hi All

I am a complete REW noob and just managed to produce my first measure. I followed the tutorial on the GIK Acoustics website. I'm not sure that it looks "right" or like the example i the tutorial.

Please could someone take a look at the file and let me know if it is a satisfactory file or not? If it is satisfactory, what do the results show?

Many thanks in advance

http://imgur.com/vv6PXgm,z3cmi7F,vk8Bod1
http://imgur.com/vv6PXgm,z3cmi7F,vk8Bod1#1
http://imgur.com/vv6PXgm,z3cmi7F,vk8Bod1#2
 

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Discussion Starter · #3 ·
No problem, thanks for letting me know - I've just realised this thread may have been better in the REW sub-forum swell - my apologies.
 

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There they are.

It is a little bit difficult to read a plot with such a wide-range dB scale. We usually try to limit the vertical scale on a frequency response plot to a 60 dB total range. Some smoothing will help, also.

The measurements appear valid.

What they show appears fairly flat above 500 Hz, interesting peaks between 50 and 200 Hz, and maybe need a sub below 50 Hz.
 

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Discussion Starter · #6 ·
I really appreciate you checking as I was messing around with it for a good couple of hours trying to get a valid sound card calibration and then an actual measurement. I know what you mean about the sub area - I have alexis m1 active monitors, does the graph show a peak at about 50hz or a null between 100hz and 60hz?
 

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Peak at 50 Hz. Could be because they are right against a wall. Are they? Or sometimes a peak like that is designed in to make the bass seem deeper. Looks like another peak at 120 Hz, also possibly by design.

There is probably nothing below 48 Hz, what you see is most likely LF noise.

The highs really look pretty flat.

Again, all indications are that the measurements are valid, will be able to tell better when zoomed in and with some smoothing (1/6 oct).
 

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Discussion Starter · #9 ·
AudiocRaver you are right they are right up against my front wall but given how narrow my room is, they are very close to walls swell. I have ordered materials from GIK and this was my before measurement. I'm hoping I can smooth some of that low end out with some bass traps.
 

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Not sure which version you have of the M-1. Are the ports on the front or back? Are there tone controls?

If tone controls, be sure they are set for flat, like willlis7469 suggested, possibly even for some rolloff to help control that LF peak. If against the wall, experiment with locating them even a few inches to a foot away to control that peak.

Frequency response plots online seem to indicate that the natural bass response for the M1 is pretty flat down to 50 Hz. So a combination of proper setting and some space from the wall should help control that peak. The treatments you have ordered can help, too. All are factors, hopefully some combination will help you get there.
 

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Discussion Starter · #11 ·
AudiocRaver the ports are at the front, in the manual it does advise having them horizontally so I will change to that and try to get them into a better position to flatten the peak. Thanks a lot for your help.
 

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AudiocRaver the ports are at the front, in the manual it does advise having them horizontally so I will change to that and try to get them into a better position to flatten the peak. Thanks a lot for your help.
Doubt if the horizontal orientation will change frequency response by much, easy to try though. Probably not as good for imaging.
 

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Discussion Starter · #13 ·
Yeah good point, I'm sure I will just need to keep tweaking their placement to get the best spot for them. My room is only 200cm wide so I'm bit limited in where they can actually go.
 

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There we go, you are definitely getting legit measurements.

Frequency response match between L & R is very good.

I know the conventional wisdom is point tweeters straight at LP for best freq response, but that rarely gives good soundstage & imaging (SS&I), imo. Try (along with reflection matching, below) angling speakers out past shoulder tips or beyond, see if it gets sharper. Small FR sacrifice can give BIG SS&I benefits. If you are mixing, though, FR might be more important.

Look at Overlays > Impulse > %FS (upper left corner) > -0.001 to 0.020 horizontal scale > L & R plots only. Symmetrical placement, distances from walls & LP, treatments, etc, should give matching major reflections.
  • Your L plot has a set of reflections from 5 to 6.6 mS, same set on R plot is 4.5 to 6.1 mS.
  • L reflection at 11.6 mS vs 11.2 mS on R.
  • More of the same farther out.
Basic rule, make them match to 100 uS (50 uS is better), you will be amazed at the SS&I improvement. The ones that do not pair up or cannot be made to match because of room weirdness should be eliminated via treatment, in your case absorption because your RT60 is high (0.5 sec). Reflections are not bad if they pair up and match closely.

HF response still looks pretty good, the plots should match even closer with above reflection matching & treatment.

LF peaks at 56 and 128 will probably need EQ. Notch at 240 HZ is from reflection off the front wall cancelling at front of speaker, should get better with absorption behind the speakers.

Hope that helps.
 
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