# very Low "Ref In" level



## Oblivion (Dec 5, 2011)

Hello, and thank you for the great software and the supporting forum...

i just got an ECM8000 mic. and i'm trying to calibrate my m-audio profire 610, using REW 5.01 beta in windows XP sp2.

i have 2 RTS, and 1 XLR cable.

to create a loop, i have connected one end of a RTS's into input 3 and the other end into output 1.
and the other RTS, is connected from output of left monitor into input 2 of profire 610.
the XLR is connected to my ECM8000 as well.

so first question: am i going wrong in any of steps above to make a correct loop?

second question: is microphone position important in calibrating the soundcard? of course, closer the mic gets to speaker, the higher the "In Level" goes... but i wanted to know where should i put my microphone at this stage?

third question is: i get very low "Ref In" when 1 khz tone is played (at default -12 db)
i did set my microphone gain level at around 2 O'clock, so that when i turn up the main gain on the soundcard, the "In" level goes up synced with "Ref In" level. *BUT * i get a very low "Ref In" level... i can turn it up to get to -12db but then i'll have to turn the main gain all the way up! and you can't stand in the room!
the only way that being in the room is tolerable, is to set the sweep level to -40 db, which i guess shouldn't be good at all...
this is a snapshot of the levels and my settings:

[URL="file has been deleted[/URL]

so along side with the 2 questions above, how can i set my "Ref In" level to -12db without having to turn the knob all the way up...

*thank you in advance*


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## Oblivion (Dec 5, 2011)

anybody?...


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## Samoth (Oct 18, 2007)

Oblivion said:


> Hello, and thank you for the great software and the supporting forum...
> 
> i just got an ECM8000 mic. and i'm trying to calibrate my m-audio profire 610, using REW 5.01 beta in windows XP sp2.
> 
> ...


Yes, I suspect you are going wrong in creating a correct loop. You don't need a microphone connected at all to do the loopback to make a soundcard calibration. What you probably want to do is just connect a single TRS cable from output 1 to input 1 on the device, and then follow the instructions for making a soundcard calibration in the instructions. Once you've done that you can remove the loopback and plug the microphone into input 1, and then follow the instructions for checking levels.

You *can* use another loopback after that for a timing reference, but that's not essential for measurements, so we can come back to that once you've got this bit working.



> second question: is microphone position important in calibrating the soundcard? of course, closer the mic gets to speaker, the higher the "In Level" goes... but i wanted to know where should i put my microphone at this stage?


You shouldn't have a microphone connected at all to calibrate the sound card.



> third question is: i get very low "Ref In" when 1 khz tone is played (at default -12 db)
> i did set my microphone gain level at around 2 O'clock, so that when i turn up the main gain on the soundcard, the "In" level goes up synced with "Ref In" level. *BUT * i get a very low "Ref In" level... i can turn it up to get to -12db but then i'll have to turn the main gain all the way up! and you can't stand in the room!
> the only way that being in the room is tolerable, is to set the sweep level to -40 db, which i guess shouldn't be good at all...
> this is a snapshot of the levels and my settings:
> ...


I think what you're trying to do with the reference level there is related to having the wrong connections on the loopback for the soundcard calibration. You shouldn't have any sound coming out in the room for the calibration, it's just a loopback out and back into the device.

The only things that should be connected to do a loopback for calibration should be output 1 to input 1.


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## Oblivion (Dec 5, 2011)

Samoth said:


> Yes, I suspect you are going wrong in creating a correct loop. You don't need a microphone connected at all to do the loopback to make a soundcard calibration. What you probably want to do is just connect a single TRS cable from output 1 to input 1 on the device, and then follow the instructions for making a soundcard calibration in the instructions. Once you've done that you can remove the loopback and plug the microphone into input 1, and then follow the instructions for checking levels.
> 
> You *can* use another loopback after that for a timing reference, but that's not essential for measurements, so we can come back to that once you've got this bit working.



thank you so much Samoth... i did as you said and it worked...
i guess video tutorials i've been watching were a bit misleading; because for calibrating the soundcard in those videos you could hear the 1kh noise and also the swip sound...
so i did as you said and this is the result for calibrating the soundcard:
[URL="file has been deleted[/URL]
would you plaese do me the favor of telling me how to do the check levels?
i mean, for this purpose what should be connected to what... does it involve the microphone and sound in the room? if yes, where should microphone be placed?
that would be great too if you tell me how to do another loopback for the timing reference...
thank you


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## Samoth (Oct 18, 2007)

Oblivion said:


> thank you so much Samoth... i did as you said and it worked...
> i guess video tutorials i've been watching were a bit misleading; because for calibrating the soundcard in those videos you could hear the 1kh noise and also the swip sound...
> so i did as you said and this is the result for calibrating the soundcard:
> http://s1.picofile.com/file/7662467632/calibration_loopback.jpg
> ...


The calibration trace looks good although I'm a little surprised it doesn't fall off at the bottom of the frequency range, but anyhow, that looks right enough.

To do the 'check levels' part, you want to disconnect the loopback cable, connect the microphone to input 1, and then output 1 should be connected to your home theatre receiver. You should place the microphone in your usual listening position, so about where your head would be if you were sat there.

You then start the check levels, which will play a sound through your speakers, adjust the volume on your receiver until the noise from the speakers is around 75dB (if you have a separate SPL meter to check with, or just 'loud but not painful' if you don't).

You can then adjust the input gain on your input 1 mic channel until REW reports around -18dB on the Input meter. The Ref meter will not read anything at the moment because there's no loopback.

Finally, if you want the timing loopback, you would connect your TRS from output 2 to input 2, and make sure the appropriate tickbox is selected in the Analysis preferences.

You should be ready to measure then. Hope that helps.


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## mc_lover (Aug 25, 2012)

This is how I connected. Hope it helps.


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## Oblivion (Dec 5, 2011)

Samoth said:


> The calibration trace looks good although I'm a little surprised it doesn't fall off at the bottom of the frequency range, but anyhow, that looks right enough.


this is what i suspected. and as our friend "mc_lover" has shown, apparently there should be an XLR to TRS cable to soundcard calibration loopback...
i used a TRS cable. i put one end into "TRS input" of the back of the panel. and the other end into TRS output...
so i did it wrong?
i guess i should look for an TRS to XLR adapter?

PS: thanks for hints on doing the check Level. i'll do that as soon as i get the soundcard calibration right...


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## Samoth (Oct 18, 2007)

Oblivion said:


> this is what i suspected. and as our friend "mc_lover" has shown, apparently there should be an XLR to TRS cable to soundcard calibration loopback...
> i used a TRS cable. i put one end into "TRS input" of the back of the panel. and the other end into TRS output...
> so i did it wrong?
> i guess i should look for an TRS to XLR adapter?
> ...


On your particular soundcard you have a lot of different connector types to choose from as you have multiple inputs/outputs. You don't need an XLR cable to do a loopback on your card. mc_lover is using a different card with different connectors.

According to the manual, the two front panel inputs marked 'Mic/Inst' are designed to take Microphone or Instrument (guitar etc) level inputs on XLR or TRS connectors. The two rear panel inputs are for line level TRS.

If you have a TRS cable, you can do a line level to line level loopback on the back panel of your soundcard. Connect the cable from Line Input 3 on the back, to Line Output 3 on the back. Then in the REW preferences panel set the Output Device to your Profire, Output 3, and the input device to your Profire, Input 3. Then attempt the loopback again, and see if you get the same results as before.

When you want to perform actual measurements, you will want to use the microphone connected to input 1 on the front, and change the REW preferences back to Output 1 and Input 1.


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## Oblivion (Dec 5, 2011)

Samoth said:


> On your particular soundcard you have a lot of different connector types to choose from as you have multiple inputs/outputs. You don't need an XLR cable to do a loopback on your card. mc_lover is using a different card with different connectors.
> 
> According to the manual, the two front panel inputs marked 'Mic/Inst' are designed to take Microphone or Instrument (guitar etc) level inputs on XLR or TRS connectors. The two rear panel inputs are for line level TRS.
> 
> ...


this couldn't be explained better... thank you so much.
ok here's the result:










the purple one is my soundcard response and the pink one is the "phase" (which i don't quiet know what phase is in here...)
i guess that should look good and normal...
i'll run the check level right now


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## Samoth (Oct 18, 2007)

Yup, that looks like the kind of soundcard response I would expect, with a gradual roll-off at the bottom end and a sharp one at the top.

If you've saved that and used it as your soundcard calibration you're good to go with the check levels now


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## Oblivion (Dec 5, 2011)

Samoth said:


> To do the 'check levels' part, you want to disconnect the loopback cable, connect the microphone to input 1, and then output 1 should be connected to your home theatre receiver.


so basically this test is done by using only one speaker?



Samoth said:


> You should place the microphone in your usual listening position, so about where your head would be if you were sat there.


if it's one speaker, so should i point the microphone directly forward, or point to to the said speaker?



Samoth said:


> You then start the check levels, which will play a sound through your speakers, adjust the volume on your receiver until the noise from the speakers is around 75dB (if you have a separate SPL meter to check with, or just 'loud but not painful' if you don't).


unfortunately i don't have access to a SPL meter. and if i want to get it exactly around 75dB, isn't there another way to determine it?



Samoth said:


> You can then adjust the input gain on your input 1 mic channel until REW reports around -18dB on the Input meter.


so basically at this point, "Out" level and "in" level in REW prefrences don't need to be in the same level?

ps: i'm having 11 bass traps on my first reflection points and on the floor, they don't interfere with sound level check, right?


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## Samoth (Oct 18, 2007)

Oblivion said:


> so basically this test is done by using only one speaker?


Yes, you test only one speaker at a time for most purposes with REW.



> if it's one speaker, so should i point the microphone directly forward, or point to to the said speaker?


If you're just testing in the bass frequencies (below say 400Hz) it really shouldn't make a lot of difference. A lot of people test with the microphone pointed directly upwards for the low frequency tests. For full range tests, it's in theory more correct to point the microphone directly at the speaker. It's probably more important to make sure that the microphone remains in the same position for repeated tests.



> unfortunately i don't have access to a SPL meter. and if i want to get it exactly around 75dB, isn't there another way to determine it?


No, there isn't really a way to determine it without an SPL meter. You can get valid frequency response measurements at any reasonable volume, so you can set the level by ear, at 'quite loud' but not 'painfully loud'. Best to aim a little quieter at first until after you've heard the first measurement sweep to make sure you're not going to deafen yourself!

You're probably going to want an SPL meter at some point, to match the levels between your speakers, so you might want to pick up a cheap one at some point.



> so basically at this point, "Out" level and "in" level in REW prefrences don't need to be in the same level?


Yes, for this, you set the "in" level a bit lower, to allow some headroom for the peaks in the in-room response that you're measuring, as some frequencies will be much louder than others in most rooms.



> ps: i'm having 11 bass traps on my first reflection points and on the floor, they don't interfere with sound level check, right?


The bass traps won't affect your sound level check.


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## Oblivion (Dec 5, 2011)

thank you 
this is a snapshot of sound check. i hope it seems right.










about the timing loopback, you mentioned i should connect my TRS from input 2 to output 2... my input 2 is XLR, so it's ok that i connect it to input 4 (TRS input) just like what i did for calibrating the soundcard (only now different inputs and outputs)
(sorry if the question sounds dumb)

after that and setting my time preference options, i should press calibrate again and do the same things as i was doing for calibrating the soundcard?
plus i'll be thankful if you tell me that with my settings, which checkbox should i select now? (too many questions i know. hehe i'm just very new with this)


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## Samoth (Oct 18, 2007)

Oblivion said:


> thank you
> this is a snapshot of sound check. i hope it seems right.


The levels look just right there, and the rest of your settings look good.



> about the timing loopback, you mentioned i should connect my TRS from input 2 to output 2... my input 2 is XLR, so it's ok that i connect it to input 4 (TRS input) just like what i did for calibrating the soundcard (only now different inputs and outputs)
> (sorry if the question sounds dumb)


The timing loopback settings you have in the preference pane there look correct for output 2 to input 4, so that's fine. Do you have a loopback cable connected during that test though? If you do, I'd expect to see a signal level on the 'Ref In' meter as well. You may need to adjust the input gain on that channel (which I think you have to do in the soundcard's control panel as there isn't a physical knob for that channel). Or it may be that you've just not enabled the timing reference yet in the Analysis preference pane.

Bear in mind that you don't *need* the timing loopback reference to do frequency response tests really, it's mostly useful if you're going to start doing the more advanced examination of impulse responses/group delay/phase etc.



> after that and setting my time preference options, i should press calibrate again and do the same things as i was doing for calibrating the soundcard?
> plus i'll be thankful if you tell me that with my settings, which checkbox should i select now? (too many questions i know. hehe i'm just very new with this)


You don't need to do any more calibrations after this. You are ready to measure now. If you want to make sure the loopback for timing is enabled, that's the 'Use Loopback as Timing Reference' checkbox in the Analysis preference pane : http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/analysis.html

You should be in a position to make a measurement with what you have set up now though.


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## Oblivion (Dec 5, 2011)

Samoth said:


> Do you have a loopback cable connected during that test though? If you do, I'd expect to see a signal level on the 'Ref In' meter as well.


actually no. i pulled it out. i put them back in again, in previous Ins and Outs to have a Ref In level.



Samoth said:


> Or it may be that you've just not enabled the timing reference yet in the Analysis preference pane.


oh no i had not enabled that. will do now 



Samoth said:


> Bear in mind that you don't *need* the timing loopback reference to do frequency response tests really, it's mostly useful if you're going to start doing the more advanced examination of impulse responses/group delay/phase etc.


actually i have a friend who is going to help me do the advanced examinations. so i'll be needing the timing loopback.




Samoth said:


> You don't need to do any more calibrations after this. You are ready to measure now. If you want to make sure the loopback for timing is enabled, that's the 'Use Loopback as Timing Reference' checkbox in the Analysis preference pane


thanks. is this 'Use Loopback as Timing Reference' has to be checked during the measurements as well? also for the rest of the measurements the timing loopback cable should be connected. right?

so i connected the timing loopback and the highest levels i could get was this:










i set the mic input knob in a way that the "In" level and "Ref In" level go up in a same level, otherwise i could get In level higher. but i couldn't get Ref In any higher because the level you see in the picture is actually the threshold of being painful!
i tried my audio interface mixer channels and turned up the In 4 and Out 2 levels in there, but no changes...


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## Samoth (Oct 18, 2007)

You don't need the ref in to go to a high level. You should set the mic in level independently, so that you can get -18 on the the In meter. If the ref meter is down at -30 it'll still work fine I reckon, all it needs to do is be able to tell when the audio arrives on that channel.

The Ref in should be entirely affected by the output level on Out 2, and the Input level on in 4 - it shouldn't make any difference how loud the output through the speakers is, as there's no microphone on that channel, just a loopback cable.

So, get the audio out of a speaker to a sensible level, make sure the In meter reads -18, and that there's *something* coming through on the Ref meter, and you should be good to go.


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## Oblivion (Dec 5, 2011)

Thank you Samoth for your time.
you were a great help:T


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