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Discussion Starter #1
Last weekend, I had REW working fine. :smile: This evening, I cannot do a measurement - I have tried about 10 times but I always get the error msg shown in the first attachment. The window I get before the error msg shows up, is given in attachment #2.

But the external soundcard is producing the sweep - I can hear it quite loudly through the speakers! :frown:

Can anyone tell me how to get past this problem?


Thanks,
Andrew
 

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The problem is with the input, not the output, as the message says. How are your REW soundcard preferences set?
 

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The problem is with the input, not the output, as the message says. How are your REW soundcard preferences set?
I have no idea, John. But what I do know is that it was set exactly the same as when I closed it down last weekend - I hadn't made any changes.

Andy
 

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Can you not post a screenshot of them?
Thanks, John. I will do that when I figure out how to (do that) ... but REW is now working perfectly!!?? :grin2:

All I did was take the USB plug out of the computer ... and then plugged it back in.

Which leads onto another problem which perhaps you can advise on. I put the mic back into what I thought was the place I had it when I did the measurements last weekend - however the 1/3rd smoothing graph which REW is now showing has quite a bit of difference to the one I ended up with after EQing, last weekend. My final one last weekend was quite smooth ... this latest one is not! :crying2: At worst, I would say the mic is no more than 5cm of where it was last weekend.

So my question is ... if a slightly different mic position produces a non-smooth curve ... what's the point in playing around with PEQs - as the result will only be relevant to that exact mic position?

Andy
 

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Depends which frequency range you are talking about, above the bass range response changes a lot with position. Also best make sure you are actually looking at a graph with smoothing applied and that your system is configured correctly. For the latter could post the mdat file for one of your measurements. As it sounds like this is new territory best spend a little time getting comfortable with how measurements look as you change mic posn, speaker posn or contents of the room.
 

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As it sounds like this is new territory best spend a little time getting comfortable with how measurements look as you change mic posn, speaker posn or contents of the room.
Thanks John,

Speaker positions, furniture positions do not change in this room - the only thing that can change from one measurement session to the other (on another weekend) is the mic position, as I have have to clear the room between sessions. Hence my question about what's the point of going to the EQ trouble, if different mic positions give quite different results? Each time I set the mic up, I am trying to put it between where my ears would be, in the 'sweet spot' - so the various mic positions are all close to each other - and the mic is aimed at the centre, between the Maggie panels.

Depends which frequency range you are talking about, above the bass range response changes a lot with position. Also best make sure you are actually looking at a graph with smoothing applied and that your system is configured correctly. For the latter could post the mdat file for one of your measurements.
I have attached 2 mdat files - last Sat and just now. The differences are noticable from around 200hz up.


Regards,
Andy
 

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I wasn't suggesting things were moving, more that you should experiment with moving them to see what effect that has. The measurements posted look entirely normal and variation is well within expectations, the overlay below is without smoothing to show the level of agreement over the first 500 Hz (I offset the Feb 18 result to align with those from Feb 11). You'll find more on what EQ can and can't do in the limits of EQ help topic. Bass looks very well controlled in the room, by the way. As an aside, if you play both speakers at the same time when measuring (which looks like it might be the case in those measurements) you will see more comb filtering at high frequencies due to the slight path length differences from the mic to each speaker.

overlay.jpg
 

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JohnM;1554074 said:
I wasn't suggesting things were moving, more that you should experiment with moving them to see what effect that has. The measurements posted look entirely normal and variation is well within expectations, the overlay below is without smoothing to show the level of agreement over the first 500 Hz (I offset the Feb 18 result to align with those from Feb 11). You'll find more on what EQ can and can't do in the limits of EQ help topic. Bass looks very well controlled in the room, by the way. As an aside, if you play both speakers at the same time when measuring (which looks like it might be the case in those measurements) you will see more comb filtering at high frequencies due to the slight path length differences from the mic to each speaker.

View attachment 136634
Thanks, John,

So you loaded both of my mdat files onto the same graph? And you took out smoothing up to 100hz?

But yes, my room seems well-behaved at LFs - I'm presuming this is because the room dimensions were planned with the THX room-calc program. :smile:

But if you look at the higher frequencies - say, 500hz and higher - and put the 1/3rd smoothing back on, to my way of thinking there are major differences in the FRs? 11 Feb is tilted ... but very smooth; 18 Feb is tilted the same but has peaks & troughs which are not there on the 11 Feb graph (I'm assuming because the mic is in a slightly different position)? So all the PEQs I put in for 11 Feb are null and void? So what are "correct" PEQs to use?

Regards,
Andy
 

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If you do apply EQ above the bass range it should only be broad filters (low Q values) to shape the response, it is futile aiming EQ at any narrow feature above a couple of hundred Hz because of the variation in response with position.
 

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If you do apply EQ above the bass range it should only be broad filters (low Q values) to shape the response, it is futile aiming EQ at any narrow feature above a couple of hundred Hz because of the variation in response with position.
Aah, OK - understood. Thanks John.

Back to the drawing board!


Regards,
Andy
 
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