# Total newbie, first REW result



## carlob (Mar 15, 2016)

Hi,

I am a total newbie at this, just got an Umik and after a quick reading of REW manual I tried to measure my speakers for the first time. My setup is for hi-fi listening, not home theatre. I have two bookshelf Harbeths on stands in a room roughly 5X7 meters. Speakers are on the short side, I measured with the mic straight in between at my listening position (couch) which is at about 2.2 meters from the speakers (spaced about 2.2 meters). Basically is a triangle.
I put the mic at ear's height which is same height of the tweeters. I have a glass coffee table on a rug between the couch and the speakers (I suppose is a bad thing).

Can you help me to understand the results and what I should do to improve?

Thanks!


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## carlob (Mar 15, 2016)

Graphs


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## tonyvdb (Sep 5, 2007)

By looking at your first graph its actually not that bad. The area between 2K and 100Hz is a little hot compared to the higher 2k-10k range but still remains quite flat. The dip at 800Hz could be boosted slightly but again over all not that bad. Your speakers do seem to fall off quite rapidly above 10k do you have them angled towards the listening position?


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## carlob (Mar 15, 2016)

tonyvdb said:


> By looking at your first graph its actually not that bad. The area between 2K and 100Hz is a little hot compared to the higher 2k-10k range but still remains quite flat. The dip at 800Hz could be boosted slightly but again over all not that bad. Your speakers do seem to fall off quite rapidly above 10k do you have them angled towards the listening position?


Thank you for the reply. Yes, I measured them toed in just a little but even if I move them I don't see much of a difference in the graph. If I point them towards the listening point it does boost the graph a bit above 10Khz but my feeling is that the scene becomes very narrow and the measured difference is small. Was starting to think that something is wrong with my tweeters... Or maybe the glass table reflections? Or the UMIK?


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## tonyvdb (Sep 5, 2007)

natural fall of of the highs is normal as if you had a flat response your ears would be bleeding but it is a little more than a gradual fall off so the room is effecting it somehow. do yo have any EQ applied to the speakers?


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## jtalden (Mar 12, 2009)

carlob,
Did your measure both speakers together? There is often a HF falloff like this if the mic is not exactly centered. We normally suggest measuring the speakers separately to avoid this problem.


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## carlob (Mar 15, 2016)

tonyvdb said:


> natural fall of of the highs is normal as if you had a flat response your ears would be bleeding but it is a little more than a gradual fall off so the room is effecting it somehow. do yo have any EQ applied to the speakers?


No EQ applied at all.


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## carlob (Mar 15, 2016)

jtalden said:


> carlob,
> Did your measure both speakers together? There is often a HF falloff like this if the mic is not exactly centered. We normally suggest measuring the speakers separately to avoid this problem.


Yes, I did measure both speakers together. I read that you should measure one at the time but I listen to both obviously so even if the curve is perfect for one speaker alone what's important to me is what happens when I listen to the music...I think. I'm a little bit confused and maybe I'm wrong.

Even my head is not perfectly centered at times, I mean I seat on the couch roughly at the center but not taking measurements every time


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## jtalden (Mar 12, 2009)

The mic is very small (6mm diameter) and in one position. Any deviation from equal distances from the 2 speakers will result in high frequency (HF) destructive interference due to phase differences. We have 2 ears each picking up the sound from each speaker. The brain processes the sound more like an average of mic positions would. 

We have several options as how we measure, but a single positon off ideal center with 2 or more speakers active is not a useful one for HF.

The easiest way is to measure each speaker individually. We can average the 2 measurements to get an idea of how we will perceive them when a phantom center (mono) sound is played.

Also, for HF measurements be sure to point the mic at the speaker or at least forward between them if using a 0° calibration file. We should point the mic vertically if using a 90° calibration file. If there is no cal file then the HF response is not to be trusted.


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## dgmartin (Oct 29, 2011)

carlob said:


> Yes, I did measure both speakers together. I read that you should measure one at the time but I listen to both obviously so even if the curve is perfect for one speaker alone what's important to me is what happens when I listen to the music...I think. I'm a little bit confused and maybe I'm wrong.
> 
> Even my head is not perfectly centered at times, I mean I seat on the couch roughly at the center but not taking measurements every time


Yes normally you measure each separately. You listen with both ears but then they are not at the same location so even the sound from one speaker will arrive to each ear at different time (your brain deals with it and it helps you localize sounds). Another benefit is to see if a particular problem originates from a speaker or its positioning. The unsmoothed response might not be as rough as with two speakers.

Try removing the smoothing, you can see if the dip at 800Hz is really deep (cancellation from reflection or not) 

By default REW will measure the steady state response (speaker +room). You can make abstraction of the room response by using gated measurements with the "IR Windows" to avoid including the reflection(s). However this will limit your ability to measure anything below, say, 250Hz. So you are better off positioning the speaker in the middle of the room and be left only with the floor bounce (remove the table for that one ). You can calculate the time value (typically a few ms) or look at the impulse response to see the effect of the windowing. Some explanations here:
https://www.minidsp.com/application...s/loudspeaker-measurements#gated-measurements


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## carlob (Mar 15, 2016)

Thanks, seems I need to study. In the meantime I'll measure them separately and try to post the results.


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