# Check levels, ridiculously high SPL.



## JapanDave (Mar 29, 2010)

People have been telling that I have not setup correctly (I agree with them) so I tried to redo everything from the begining.

Ok, I think I might be doing something wrong. I calibrated the sound card tonight with the C weighted box unchecked, went through the steps to make a calibration file. I then cleared the sound card calibration file to read "none" and clicked make measurement , but instead of getting a flat response line I got a similar response to sound card calibration file , only with a higher SPL. No matter what I did, that was all I could get.

So, I proceeded to checking levels and I have to turn the volume up to about 120db's the get withing the -12db to -24db range. Whats going on? I thought that it should be around the 75db area? 

I am using Art USB dual preamp and ECM8000 mic with cal files. A galaxy 140 SPL meter was used to monitor the SPL values.


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## laser188139 (Sep 19, 2009)

JapanDave said:


> ... I calibrated the sound card tonight with the C weighted box unchecked, went through the steps to make a calibration file. I then cleared the sound card calibration file to read "none" and clicked make measurement , but instead of getting a flat response line I got a similar response to sound card calibration file , only with a higher SPL. No matter what I did, that was all I could get. ...


If you cleared the sound card calibration file to read none and then took a measurement, it should indeed read similar to the soundcard, only at a higher level instead of being adjusted to ~0. If you want to perform the verification step, you need to leave the soundcard file loaded, and then take a loopback measurement. If the soundcard is loaded and you then measure the loopback connection, the resulting measurement should appear flat. 



JapanDave said:


> ... So, I proceeded to checking levels and I have to turn the volume up to about 120db's the get withing the -12db to -24db range. Whats going on? I thought that it should be around the 75db area? ...


The CheckLevels step verifies that the output level and input levels are in the -12dB to -24dB range relative to the maximum digital levels of the soundcard. It does not set or change the value reported in the measurement. The calibration of that value is set through the CalibrateSPL step. (Use the SPL meter icon at the top and then press calibrate in the SPL meter dialog.) Only by doing the Calibrate SPL step does REW know what number to display when it hears a particular level signal. You need to do this at least at the start of each session, because the signal level to the soundcard depends on the gain controls in the preamp, in the operating system or REW, and the master volume setting of the receiver. 

Regards,
Bill


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## JapanDave (Mar 29, 2010)

laser188139 said:


> If you cleared the sound card calibration file to read none and then took a measurement, it should indeed read similar to the soundcard, only at a higher level instead of being adjusted to ~0. If you want to perform the verification step, you need to leave the soundcard file loaded, and then take a loopback measurement. If the soundcard is loaded and you then measure the loopback connection, the resulting measurement should appear flat.


I feel quite silly now. :whistling: Thanks for the help.






laser188139 said:


> The CheckLevels step verifies that the output level and input levels are in the -12dB to -24dB range relative to the maximum digital levels of the soundcard. It does not set or change the value reported in the measurement. The calibration of that value is set through the CalibrateSPL step. (Use the SPL meter icon at the top and then press calibrate in the SPL meter dialog.) Only by doing the Calibrate SPL step does REW know what number to display when it hears a particular level signal. You need to do this at least at the start of each session, because the signal level to the soundcard depends on the gain controls in the preamp, in the operating system or REW, and the master volume setting of the receiver.
> 
> Regards,
> Bill


This is a quote from the "Check Levels" on line help, which you obviously would know. But I need some understanding if that is ok.

_"Press the Check Levels... button and follow the instructions on screen. The test signal defaults to an RMS Level of -12dB FS. If connected to an AV processor, start with the volume fairly low and increase it until the meter is reading around 75dB. The exact level is not critical. If connecting directly to an equaliser such as the BFD, use the Sweep Level control to change the level of the generated signal. In either case, the final Sweep Level will be used for subsequent measurements - *remember to use the same AV processor volume setting whenever measurements are made.*"_

It says to use the same AV processor volume when making measurements? If I did that I will have to run the speakers at about 120-130db's when making a measurement(as measured on my SPL meter). As it is now I am using ear protection just to check levels. Any thoughts would be appreciated.


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## laser188139 (Sep 19, 2009)

JapanDave said:


> ...
> _"Press the Check Levels... button and follow the instructions on screen. The test signal defaults to an RMS Level of -12dB FS. If connected to an AV processor, start with the volume fairly low and increase it until the meter is reading around 75dB. The exact level is not critical. If connecting directly to an equaliser such as the BFD, use the Sweep Level control to change the level of the generated signal. In either case, the final Sweep Level will be used for subsequent measurements - *remember to use the same AV processor volume setting whenever measurements are made.*"_
> 
> It says to use the same AV processor volume when making measurements? If I did that I will have to run the speakers at about 120-130db's when making a measurement(as measured on my SPL meter). As it is now I am using ear protection just to check levels. Any thoughts would be appreciated.


If you are adjusting the volume on the AVR to the point where the *external* meter is reading around 75dB, then I don't see how your speakers are at ~120dB. It sounds to me as if you are adjusting to where the *internal* meter is reading 75dB, which makes no sense as you have not yet calibrated the internal meter levels. There is no built-in calibrated accurate SPL meter -- that is why you use an external SPL meter to calibrate the level. The internal, built-in meter is just a tool that reads back to you a number based on how you have calibrated it, see below. 

After you have adjusted the volume to where the external meter is reading 75dB, or whatever is comfortable, you can adjust the volume gain on the preamp or soundcard input to ensure the digitized input level is between -12dB and -24dB. 

You can then use the CalibrateSPL step to calibrate the internal SPL meter to read correctly, i.e., to read the same value as is given by the external SPL meter for the test signal. (If you did not have an external meter, you would just calibrate the level to read back 75dB.) 

The comment about using the same master volume setting on the AVR is a reminder that, if you change the master volume setting, your signals will now no longer be at 75dB. To obtain the normal measurement readings, nominally 75dB, you would need to do the Calibrate SPL again. Basically, changing the output level at the computer, the AVR master volume setting, or the position of the microphone, changes the actual sound level at the microphone. Anything you do to change the preamp gain, or the soundcard input gain, changes the accuracy, i.e., the calibration, of the internal SPL meter relative to the external SPL meter. 

I hope this helps,
Bill


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## JapanDave (Mar 29, 2010)

I am using the external SPL meter. My problem lies that when I set the speaker level at 75db's on the AV, I then turn the gain level knobs on the preamp and the speaker volume increases, way past 75db's. BTW I am aiming for a -18db FS, even at -24db's the volume is very loud.


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## laser188139 (Sep 19, 2009)

JapanDave said:


> I am using the external SPL meter. My problem lies that when I set the speaker level at 75db's on the AV, I then turn the gain level knobs on the preamp and the speaker volume increases, way past 75db's. BTW I am aiming for a -18db FS, even at -24db's the volume is very loud.


If you are turning the gain knobs on the preamp and the sound from the speakers changes, there is something wrong with the process. In my case, with the EMM-6 calibrated mic and an external Xenix 802 preamp, changing the preamp gain affects the signal coming back into the computer, but has no effect on the sound from the speakers. 

If yours is having an effect on the speakers, either there is feedback (and you should hear this and recognize it) or you are in fact changing the output gain control, on the signal going from the computer to the AVR. I have no hands on experience with external USB amps, so I am just guessing here from the manual. To adjust the gain on the signal from the mic, you are adjusting the Left or Right channel gain on the Front? If this is affecting the output, too, it sounds as if you do have a feedback loop. For the output side, on the back of the box, you would need to turn the Mix knob all the way clockwise to Computer. Otherwise some of the incoming preamp signal will be mixed back into the output. If the Mix knob is all the way clockwise, then the Level knob on the back should affect only the output signal, and the Left Gain/Right Gain knobs on the front should affect only the input. At least, that's my best take from reading the manual. 

Can someone with hands-on experience with one of these confirm my understanding?

There could also be some monitoring enabled in Windows that might cause the input signal to affect the level of the output. 

Bill


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## JapanDave (Mar 29, 2010)

laser188139 said:


> If you are turning the gain knobs on the preamp and the sound from the speakers changes, there is something wrong with the process. In my case, with the EMM-6 calibrated mic and an external Xenix 802 preamp, changing the preamp gain affects the signal coming back into the computer, but has no effect on the sound from the speakers.
> 
> If yours is having an effect on the speakers, either there is feedback (and you should hear this and recognize it) or you are in fact changing the output gain control, on the signal going from the computer to the AVR. I have no hands on experience with external USB amps, so I am just guessing here from the manual. To adjust the gain on the signal from the mic, you are adjusting the Left or Right channel gain on the Front? If this is affecting the output, too, it sounds as if you do have a feedback loop. For the output side, on the back of the box, you would need to turn the Mix knob all the way clockwise to Computer. Otherwise some of the incoming preamp signal will be mixed back into the output. If the Mix knob is all the way clockwise, then *the Level knob on the back should affect only the output signal*, and the Left Gain/Right Gain knobs on the front should affect only the input. At least, that's my best take from reading the manual.
> 
> ...


My problem in bold. I was adjusting both the levels and the gain which was why I was getting incredible SPL. I just went and redid the check levels again and you are absolutely correct. It was all my fault. :sweat:

Thanks so much for all the help Bill.


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## laser188139 (Sep 19, 2009)

You're welcome, Dave. I'm glad to have guessed right.


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## JapanDave (Mar 29, 2010)

Sorry for another question, but I need to make some nearfeild measurements of about 1m away from each of the LCR's. What mode in the AVR should I be using to get correct measurements. I used Dolby PLII movie mode and only connected each speaker individually so I would not get any singals from other speakers. This is what I came up with , but there seems to be something a miss. Any help would be greatly appreciated.

The graphs.

First things first, this is the measurement of the lower Catalysts woofer at 1/2" set in Dolby PLII/Movie.








The center at 1m with 1/12th smoothing (Dolby PLII/Movie).








The Left at 1m with 1/12th smoothing (Dolby PLII/Movie).








The Right at 1m with 1/12th smoothing (Dolby PLII/Movie).


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## JapanDave (Mar 29, 2010)

Ok, so I have been told I need to connect to the Integra DHC80.1 multichannel inputs and use direct mode. How do I do this using an external USB preamp connected to an ECM 8000? 

I am using these (in the pic below) ATM to connect to the AUX inputs, but it will only play the left and right channels when testing and I need to test all the mains individually. Do I just connect one and leave the other unconnected when using the milti-channel inputs?


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## laser188139 (Sep 19, 2009)

JapanDave said:


> ... I used Dolby PLII movie mode and only connected each speaker individually so I would not get any singals from other speakers. ...
> 
> The center at 1m with 1/12th smoothing (Dolby PLII/Movie). ...


Dolby PLII mode is the clever solution to driving the center speaker with REW without re-cabling, as the identical left/right channel content is recognized and dropped into the center. 



JapanDave said:


> ... The Left at 1m with 1/12th smoothing (Dolby PLII/Movie).
> The Right at 1m with 1/12th smoothing (Dolby PLII/Movie). ...


I'm not sure why you see such an upward slope at the high end. It would be nice to rule out that the AVR is introducing it through some option, by using Direct or Stereo mode instead Dolby. 



JapanDave said:


> Ok, so I have been told I need to connect to the Integra DHC80.1 multichannel inputs and use direct mode. How do I do this using an external USB preamp connected to an ECM 8000?
> 
> I am using these (in the pic below) ATM to connect to the AUX inputs, but it will only play the left and right channels when testing and I need to test all the mains individually. Do I just connect one and leave the other unconnected when using the milti-channel inputs? ...


Yes, you can connect to each input individually. On my Denon AVR, I connect to just the left AUX input or just the right to test the front speakers individually. 

I expect that using the multichannel inputs will force Direct mode, and will bypass Audyssey and other features. For measuring the sound at your listening position, you will want to go back to the AUX inputs if you use Audyssey. 

Bill


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## JapanDave (Mar 29, 2010)

Thanks Bill,

I connected the center to the right channel XLR input to get a signal in direct mode.(In dirrect mode the center channel won't register as connected, in other is is) If that is not going to give correct results , feel free to chime in. But it is the most consistent of all my measurements yet.

Center in direct mode 1/12th smoothing at 1m. (this signal was run through the right channel with the center connected to the right channels XLR input on the AVR)










Left in direct mode 1/12th smoothing at 1m.










Right in direct mode 1/12th smoothing at 1m.










Sub in direct mode 1/12th smoothing.










I am still being told that the graphs don't look right and that these speakers should not have this kind of response. 

I ran a check levels and changed the default of -12db fs to -18db fs and aligned the soundcards levels to the -18db fs on the test signal. I then calibrated the SPL and ran measurements. I really don't know what else I can do and I am getting desperate here, have I set things up correctly? 

I am using the 0 degree narrow band cal file of the ECM 8000 and I have it pointed straight at the speakers. The soundcard's calibration and test signal file is as follows. 










If I am doing something wrong , please help.


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## laser188139 (Sep 19, 2009)

JapanDave said:


> ...
> Center in direct mode 1/12th smoothing at 1m.
> 
> Left in direct mode 1/12th smoothing at 1m.
> ...


I'm not sure what you think might be wrong in any of these recent graphs. They all look reasonable flat, in direct mode. I'm sure they would look smoother with more smoothing, but the levels are essentially in the same range, a little higher at the low end. These are similar to what I saw when I took near field measures at ~0.75 meters. You might see more even measures if you had a real anechoic chamber, or if you took the speakers outside and raised them on a ladder so they would be away from all surfaces -- but I don't see anything that doesn't look right about them. 

The interesting question, I think, is that you took these trying direct mode, left and right alone. Your earlier graphs were taken in Dolby PLII Movie mode, and showed the raised levels at the high end. Now this should not be an effect of Dolby PLII mode itself, so something else is different between the two graphs. 

I assume that your normal listening position is not 1m from the speakers -- that would seem a small room even for Japan -- so these measures were not taken from your normal listening position. One hypothesis, then, is that your speakers themselves are flat, near field, but that you have more rolloff at the high end at your normal listening position. In Dolby PLII Movie mode, you may have had Audyssey enabled, and Audyssey might be adjusting the high end upwards to flatten out the response at your listening position, undoing the room rolloff of the high frequencies. 

If I look back at your earlier thread, I did not see a lot wrong with that picture either, if we make the assumption that you have either an Audyssey or THX mode enabled. There you showed both mains together. Below 80Hz there was a gradual upward trend, that might have been DynEQ enabled under Audyssey. In the typical sub range, below 80Hz, the level might be a little higher, which results from the two channels being combined into a single signal at the one sub and thus not interfering with each other. The troughs around 200Hz, 400Hz are typical of room reflections. Above 1kHz, there are troughs that might be the comb filtering interference between two front speakers being fed identical signals. Above 8kHz, there is no rolloff typical of the Audyssey reference curve, which makes me think the receiver had a THX mode enabled. As I understand it, on the Integras, enabling THX is how the Audyssey Flat curve is enabled. 

What makes you think there is anything wrong here? If you used more smoothing, 1/6 octave or 1/3 octave, that would give you a response that is closer to what the ear hears. If you are comparing your curves to other people who run Audyssey Pro, you need to remember that Audyssey Pro averages the results across multiple positions, so its graphs are much smoother than you will see when you measure a single point with REW. You will see a smoother graph with REW if you measure at the same eight points you use for the Audyssey microphone, and ask REW to generate the average response. 

Regards,
Bill


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