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Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 34

post #991 of 9491
Quote:
Originally Posted by dstew100 View Post

Graph compatibility over multiple runs I can get on board with. However now your making my point for me. The AVR test tone REW SPL calibration approach is better in this respect. It's up to the user how careful the USB mic placement is. But AVR test tone is better approach as you don't have to get two device in identical placements between runs, nor do you have to stand there reading the SPL meter bouncing the sound around. Hold an SPL meter in one place and move around it. Where you are changes the reading. Your body can be far away for the mic with the AVR test tone. Or are you now recommending two boom stands and some binoculars too?

Actually, I _do_ have two different boom stands biggrin.gif. It's more for convenience for Audyssey Pro vs. OmniMic/UMM mic holding than anything els (before I found the interchangable mic holders worked with the stand). But it's probably not neccessary (other's MMV, though).

I draw the line at binoculars....smile.gif

Gear mentioned in this thread:

post #992 of 9491
Quote:
Originally Posted by sdrucker View Post


I draw the line at binoculars....smile.gif

HaHa A man has to have boundaries. I think we agree this is not a big deal either way, I just think people should be aware of each approach including the free one. And here I am advocating the free one when I already have the SPL meter. Now that is funny.
post #993 of 9491
Quote:
Originally Posted by mogorf View Post

Quote:
Originally Posted by kbarnes701 View Post


What I mean by 'approved' is the way the guy who wrote the software says to do it.



It seems John perhaps is not up to speed on the way Audyssey works wrt to the test tones in the AVR. As I've said three times now, the AVR test tones bypass Audyssey. So the tones will be right when Audyssey is on (for 75dB) but not for when Audyssey is off. Half the time the tones will be incorrect. Audyssey can boost by up to 9dB and cut by up to 6dB. This means that there is every chance that running the test tones with Audyssey off will NOT deliver 75dB at the MLP. This means that using the AVR test tones is not a valid way to ensure that the AVR is delivering any known value of SPL after calibration. Just use a nice cheap Ratshack meter, like John suggests, and all will be guaranteed to work as designed.

I've said more than enough on this pointless topic now, so this is going to be my last word on it.

Time to give up Keith my friend! If your peculiar logic penetrates we will all end up sooner or later thinking JohnM is another unreliable soure, next to Chris K. eh?! wink.gifwink.gifwink.gif

 

There are one or two unreliable sources around here, Feri, and John M is not one of them.

 

If John says it is OK to use the AVR test tones in the way it has been suggested he has said and he has not taken account of the fact that the test tones bypass Audyssey, what can I say? John is an expert on REW but I have no idea what he knows about Audyssey. If you know different, you can enlighten us.

 

You have been consistently incorrect in your assertion that you can set up REW in the way you described in your earlier post (the one with the screen shots). You are also incorrect in your assertion that it is sensible, or even possible, to 'calibrate' something when you have only a single instrument involved. You are also trying to convince us that you have a better understanding of how REW works than the person who wrote it. To make matters worse, when Jerry has taken the time and trouble to ask John M for clarification, instead of then accepting that you are wrong, you had a tantrum and said you were leaving the thread, possibly leaving AVS and wanted your name removed from Jerry's setup guide because he will not acquiesce to your erroneous ideas. So, do you accept you are wrong this time?  You will not convince us that you are right, so I assume you are going to make good on your promise and leave the thread? Is that right?

 

Oh, and BTW, you know very well that the AVR test tones bypass Audyssey, thus making it useless for use in the way suggested, but as that does not suit your agenda you have conveniently ignored it. Perhaps you can explain how the AVR test tones can be reliably used as a 'reference SPL', both with Audyssey on and off, when they bypass the FR adjustments (SPL) that Audyssey has made?  How can the 'reference SPL' be correct in both circumstances when it is possible, or even probable, that Audyssey has boosted some frequencies by as much as 9dB?

 

TBH, your posts for the last few weeks have been tantamount, IMO, to trolling. You introduce a ludicrous proposition, such as this one, or the one concerning 60Hz hum which is allegedly measurable but not audible, or the one saying that active and passive speakers are the same thing, or the one where you assert that clipping cannot damage speakers, and then you attempt to defend these ludicrous positions ad infinitum, derailing the threads as you go, wasting page after page of everyone's time for no purpose at all and refusing to accept that you are wrong no matter how many people tell you are, nor how many people provide sensible, reasoned arguments to show you that you are. 

post #994 of 9491

I have watched today with interest, and sometimes amusement, as various thread participants expressed their views on the burning issue of whether the REW microphone needs to be calibrated or not.  I feel compelled to add my comments.

 

Issue 1:  Can REW capture meaningful measurements upon which we would base decisions regarding listening room improvements without calibrating the microphone?

 

My opinion:  Yes.  The only variable affected by microphone calibration is the vertical location of the measurement line in the graph.   Within the same REW session, different measurements can be taken and compared, and the positioning on the vertical axis of the measurement lines has no bearing on being able to make valid comparisons.  Having said that, without calibration  the measurements could have vertical axis differences across different REW measuring sessions, and could make interpreting the graphs somewhat more difficult for the average user.  Bottom line:  calibrating the microphone adds a level of consistency and repeatability to REW measurement that some may find appealing.  Recommendation:  calibrate, or don’t calibrate, depending on your personal preferences, and as long as you know the impact of not calibrating.

 

Issue 2:  Is a SPL meter absolutely required to make a meaningful calibration?

 

My opinion:  No.  While a SPL meter is a more accepted method of calibrating to a known external sound level, there could be other equally acceptable methods.  Take, for example, the AVR speaker test tones.  When the test tones are invoked, a properly-calibrated system will produce a sound level of 75dB, when measured with a SPL meter at the MLP.  At least one of you claims that the test tones are at 75dB only if Audyssey is turned off.  This is not an issue—simply turn Audyssey off, calibrate the mic, and the mic stays calibrated for any subsequent measurements, whether Audyssey is off or on, DEQ is off or on, etc.  In summary, an alternative method of calibrating the microphone is to output the speaker test tones, open the REW SPL, click Calibrate, and enter 75dB for the sound level.  I tested this today, and it works just fine.  So, for those who don’t have a SPL meter, and don’t want to purchase one, this is an acceptable alternate calibration process.

 

So, who was right, and who was wrong?  It doesn’t matter.  We need to move on to more meaningful dialog around actual measurement and analysis, now that the microphones are arriving.  If anyone’s feelings have been hurt, we all need to apologize to one another and keep our thread focused and on topic. 


Edited by AustinJerry - 2/4/13 at 5:12pm
post #995 of 9491
Quote:
Originally Posted by dstew100 View Post

Quote:
Originally Posted by kbarnes701 View Post


What I mean by 'approved' is the way the guy who wrote the software says to do it.
He said using your AVR's test tone is a valid way to do it, you're welcome to ask him again, but I provided the information from the author which disagrees with what you are saying. I feel you should stop using him to support your position as you are not paraphrasing him accurately.

 

 

I will absolutely capitulate on using AVR test tones if John can confirm that the fact they bypass Audyssey has been taken into account, and then explain how the test tones can then be correct in both circumstances, 1) with Audyssey on and 2) with Audyssey off.

 

Even then, John is still saying it is important to calibrate - all that this line is showing is that he is saying that there is another way to achieve it. He is not in any way supporting Feri's way as put forward by him in his post (the one with the screen shots).

 

Quote:
Quote:
It seems John perhaps is not up to speed on the way Audyssey works wrt to the test tones in the AVR. As I've said three times now, the AVR test tones bypass Audyssey. So the tones will be right when Audyssey is on (for 75dB) but not for when Audyssey is off. Half the time the tones will be incorrect. Audyssey can boost by up to 9dB and cut by up to 6dB. This means that there is every chance that running the test tones with Audyssey off will NOT deliver 75dB at the MLP. This means that using the AVR test tones is not a valid way to ensure that the AVR is delivering any known value of SPL after calibration. Just use a nice cheap Ratshack meter, like John suggests, and all will be guaranteed to work as designed.

I've said more than enough on this pointless topic now, so this is going to be my last word on it.

Audyssey EQ is bypassed when playing the test tones, Not the trim levels. The test tone is calibrated to 75db. That's the whole point of the test tones, for levels. Really unsure where you are going with that????????????
 

 

 

Yes, the EQ is bypassed. That is the point. If Audyssey needs to boost several areas of the FR by as much as 9dB in order to hit the target curve and set a level of 75dB, then clearly if you turn Audyssey OFF (which is what happens when you listen to the AVR test tones) then the SPL once Audyssey is inactive will be different from when it is active, with the SPL boosts it made in order to meet the target curve. Does that explain it for you?  To adjust the FR Audyssey applies SPL boosts which means the measured SPL is correct with Audyssey engaged. It does not follow that it remains correct with Audyssey disengaged.

 

 

Quote:
The ratshack meter confirms this approach is valid. If you want to waste the time and money acquiring one to verify what is true (and multiple people are telling you which have tested it), go for it. But if you are going to make recommendations to other people, it should not be to go buy an SPL meter for this purpose.
 

 

 

John M says you need the meter to perform the calibration required (unless you have the UMIK-1 mic). That is all the information I need. I am not sure who these "multiple people" you mention are - TTBOMK only Feri is supporting the notion that there is no need for this step.

 

Quote:
I'm still not hearing a technical reason why the simple, no extra hardware/money approach does not work.


I hope I'm not coming off argumentative as some of the posts on this topic are, just trying to get accurate info out there.
 

Not at all argumentative AFAIAC. Not sure why you are persisting with it though. The Setup Guide says to use the SPL meter, John M says to use it (unless you have the UMIK-1 mic). And as Stuart says in his eloquent post on the topic, there can be no downside to using the meter so what is all the fuss about?  I remind you, a meter costs 20 or 30 bucks. Most of us have owned meters for years anyway.

post #996 of 9491
Quote:
Originally Posted by AustinJerry View Post

So, who was right, and who was wrong?  It doesn’t matter.  We need to move on to more meaningful dialog around actual measurement and analysis, now that the microphones are arriving.  If anyone’s feeling have been hurt, we all need to apologize to one another and keep our thread focused and on topic. 

Absolutely. The entire topic is virtually pointless IMO.

post #997 of 9491
Quote:
Originally Posted by mogorf View Post


Oh my dear Jerry, if you have the MV on your AVR set to -14 dB you should not get 80 dB SLP at the MLP!!! Altough you did not specify what the input level is in this case! biggrin.gif

0 dB MV setting means you should get a 75 dB SPL at the MLP with a test tone at -30 dBfs. Now, turn it down to -14 dB and you get an SPL at the MLP at 75 -14 = 61 dB, right?
 

 

Feri, I have been meaning to get back to you for clarification regarding measuring 80dB at the MLP. 

 

I have a properly-calibrated system, and each of my speakers produces a sound level of ~75dB when measured with a SPL meter placed at ear level in the MLP.  With this same SPL located in the same spot, I launch the REW microphone calibration test tone.  Since I want to conduct my measurements at an 80dB level, which provides 40dB above my noise threshold of 40dB, I gradually adjust the AVR master volume until the SPL meter reads 80dB, and then enter 80dB in the SPL Calibration Input box.  This occurs (on my system) at an MV setting of -14.  Kindly explain where the flaw in my procedure is.

 

Thanks.

post #998 of 9491

As we begin to generate measurements with the USB mics, I think it is important that we all generate a standard "set" of measurements that can be shared.  I have drafted a measurement guidelines document.  Please review and tell me what needs to be added/corrected.

 

 


Edited by AustinJerry - 2/4/13 at 5:43pm
post #999 of 9491

If anyone is interested in helping JohnM in qualifying the UMM-6 for plug-and-play use in REW, read post #7 in this HTS thread:  http://www.hometheatershack.com/forums/rew-forum/65260-using-usb-mics-hdmi-several-questions.html#post588064

post #1000 of 9491
Quote:
Originally Posted by AustinJerry View Post

As we begin to generate measurements with the USB mics, I think it is important that we all generate a standard "set" of measurements that can be shared.  I have drafted a measurement guidelines document.  Please review and tell me what needs to be added/corrected.

 

 

 

This is excellent work again, Jerry. It is precisely what is needed IMO so that we are all on the same page. Only query I have is that those of us with HDMI don't need to use PLII to use the centre channel do we? Do we not simply select the centre channel in REW?

 

Should this document be included as an addendum in the Guide?

post #1001 of 9491
Quote:
Originally Posted by AustinJerry View Post

If anyone is interested in helping JohnM in qualifying the UMM-6 for plug-and-play use in REW, read post #7 in this HTS thread:  http://www.hometheatershack.com/forums/rew-forum/65260-using-usb-mics-hdmi-several-questions.html#post588064

 

Too computer-geeky for me. One for Jason I think. I see Amirm has offered to do it over at HTS. I will absolutely continue to calibrate the mic in the usual way using my SPL meter.

post #1002 of 9491
Quote:
Originally Posted by AustinJerry View Post

Feri, I have been meaning to get back to you for clarification regarding measuring 80dB at the MLP. 

I have a properly-calibrated system, and each of my speakers produces a sound level of ~75dB when measured with a SPL meter placed at ear level in the MLP.  With this same SPL located in the same spot, I launch the REW microphone calibration test tone.  Since I want to conduct my measurements at an 80dB level, which provides 40dB above my noise threshold of 40dB, I gradually adjust the AVR master volume until the SPL meter reads 80dB, and then enter 80dB in the SPL Calibration Input box.  This occurs (on my system) at an MV setting of -14.  Kindly explain where the flaw in my procedure is.

Thanks.

Hi Jerry, good question. Please try this. Go to Soundcard Preferences, there you will see Sweep Level set by REW to a default value of -12 dB. If you set this to -30 dB you will get the "gold standard" measurement of 75 dB at the MLP, but you can skip this point. Since you'd like to measure at 80 dB SPL (which is 5 dB higher) set this value to -25dB. Recalibtare REW SPL Meter and make sure your MV on the AVR stays set to 0 dB.

Report back please. smile.gif
Edited by mogorf - 2/5/13 at 2:43am
post #1003 of 9491
Quote:
Originally Posted by kbarnes701 View Post

 

This is excellent work again, Jerry. It is precisely what is needed IMO so that we are all on the same page. Only query I have is that those of us with HDMI don't need to use PLII to use the centre channel do we? Do we not simply select the centre channel in REW?

 

Should this document be included as an addendum in the Guide?

 

Keith, yes, you are correct regarding not needing to run in PLII Cinema for HDMI users with full 8-channel support, or non-HDMI users.  A corrected document is attached below.  And yes, once we have general agreement, and the "TBD" sections are completed, the guidelines should by merged with the guide.  Thanks for the feedback.

 

post #1004 of 9491
Quote:
Originally Posted by AustinJerry View Post

Keith, yes, you are correct regarding not needing to run in PLII Cinema for HDMI users with full 8-channel support, or non-HDMI users.  A corrected document is attached below.  And yes, once we have general agreement, and the "TBD" sections are completed, the guidelines should by merged with the guide.  Thanks for the feedback.



Great work, Jerry! One question on the list of measurements: Sub1 and Sub2 separately, but not together? I can see the.value of individual sub testing for placement purposes, but wouldn't a test of the total (subwoofer only) response be essential before moving on to evaluating speaker(s)+sub(s)? biggrin.gif
post #1005 of 9491
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by kbarnes701 View Post

 

This is excellent work again, Jerry. It is precisely what is needed IMO so that we are all on the same page. Only query I have is that those of us with HDMI don't need to use PLII to use the centre channel do we? Do we not simply select the centre channel in REW?

 

Should this document be included as an addendum in the Guide?

 

Keith, yes, you are correct regarding not needing to run in PLII Cinema for HDMI users with full 8-channel support, or non-HDMI users.  A corrected document is attached below.  And yes, once we have general agreement, and the "TBD" sections are completed, the guidelines should by merged with the guide.  Thanks for the feedback.

 

 

Great stuff Jerry. Thanks for doing this - it will be immensely useful.

post #1006 of 9491
Quote:
Originally Posted by sdrucker View Post


Great work, Jerry! One question on the list of measurements: Sub1 and Sub2 separately, but not together? I can see the.value of individual sub testing for placement purposes, but wouldn't a test of the total (subwoofer only) response be essential before moving on to evaluating speaker(s)+sub(s)? biggrin.gif

 

Stuart, of course, we should have a Sub1+Sub2 measurement as well.  Thanks for pointing out this omission.  Here is an updated version:

 

post #1007 of 9491

OK, now to solicit suggestions regarding several areas on my frequency response graph that I would like to address.  In the graph below, which shows Left+Right+Subs (1/6 smoothing), with Audyssey on, I want to focus first on understanding and correcting the dip in the 330-370Hz range.  This range is right in the middle of the fundamental frequencies of the human voice, so it's an important range.  I'm familiar with using the Room Mode calculator to identify how room modes affect the lower frequencies, but I don't now how to identify what is causing the dip centered at ~360Hz.  Anyone have any guidance?

 

BTW, I looked at Left only and Right only measurements, and both show this same dip.

 

 

post #1008 of 9491
Does anybody have a calibration file for an Audyssey microphone shipped with Denon ARV-xx08 and similar AVRs?

As much as I know, these AVRs have a generic calibration for this microphone in their firmware which is not unique for that particular AVR+mic which were boxed together, but it's for that type of Audussey microphone in general.
So, I guess it could be useful if somebody who has the necessary equipment could create a calibration file for "the Donon kind of Audyssey mic". This would theoretically be closer to the result I would get if I were able to extract the mic calibration from the AVRs firmware.

Could somebody possibly do this? I know it's a laboratory job, but who knows if there are people who have access for a lab (may be collage students to start with...). smile.gif


By the way, I finally managed to set up REW with the AISOforAll driver after reading the first few posts in this topic. smile.gif
Edited by janos666 - 2/5/13 at 9:28am
post #1009 of 9491
Quote:
Originally Posted by janos666 View Post

Does anybody have a calibration file for an Audyssey microphone shipped with Denon ARV-xx08 and similar AVRs?

As much as I know, these AVRs have a generic calibration for this microphone in their firmware which is not unique for that particular AVR+mic which were boxed together, but it's for that type of Audussey microphone in general.
So, I guess it could be useful if somebody who has the necessary equipment could create a calibration file for "the Donon kind of Audyssey mic". This would theoretically be closer to the result I would get if I were able to extract the mic calibration from the AVRs firmware.

Could somebody possibly do this? I know it's a laboratory job, but who knows if there are people who have access for a lab (may be collage students to start with...). smile.gif


By the way, I finally managed to set up REW with the AISOforAll driver after reading the first few posts in this topic. smile.gif

 

I am not aware of any published calibration file.

 

So, you read the first couple of posts, but you didn't read the step-by-step guide? 

post #1010 of 9491
Quote:
Originally Posted by AustinJerry View Post

I am not aware of any published calibration file.

It would be nice if my AVR would allow me to put my own calibration file in, then I could see actually bothering to send the audyssey mic out for calibration at CSL.

Of course, it would be REALLY keen if my AVR would allow me to use its front USB port as the microphone port for Audyssey setup, so I could just use the new UMM6 for the job.
post #1011 of 9491
Quote:
Originally Posted by JD in NJ View Post


It would be nice if my AVR would allow me to put my own calibration file in, then I could see actually bothering to send the audyssey mic out for calibration at CSL.

Of course, it would be REALLY keen if my AVR would allow me to use its front USB port as the microphone port for Audyssey setup, so I could just use the new UMM6 for the job.

In the techology relationship between Audyssey and the AVR manufacturer, this is already taken care of.  Audyssey provides a calibration file that the AVR manufacturer loads into their firmware for when the Audyssey mic is used.  Why do you think a UMM-6 with a CSL calibration file would be any more accurate than the Audyssey mic with its calibration file?

post #1012 of 9491
Quote:
Originally Posted by mogorf View Post


Hi Jerry, good question. Please try this. Go to Soundcard Preferences, there you will see Sweep Level set by REW to a default value of -12 dB. If you set this to -30 dB you will get the "gold standard" measurement of 75 dB at the MLP, but you can skip this point. Since you'd like to measure at 80 dB SPL (which is 5 dB higher) set this value to -25dB. Recalibtare REW SPL Meter and make sure your MV on the AVR stays set to 0 dB.

Report back please. smile.gif

 

Feri, as long as the microphone has been properly calibrated, then setting the Sweep Level to -25dB with the AVR MV set to zero is the same thing as leaving the Sweep Level at -12dB and setting the AVR MV to -13dB.  Both result in a reading of 80dB at the MLP, measured on the UMM-6 or on the RS SPL.   We are in agreement here, which is why I asked you to clarify your original post.

post #1013 of 9491
Quote:
Originally Posted by AustinJerry View Post

In the techology relationship between Audyssey and the AVR manufacturer, this is already taken care of.  Audyssey provides a calibration file that the AVR manufacturer loads into their firmware for when the Audyssey mic is used.  Why do you think a UMM-6 with a CSL calibration file would be any more accurate than the Audyssey mic with its calibration file?

First, I never actually said it would be any more accurate, just that it would be 'really keen', because I don't like to have two tools when one can do the job. Besides, the case the UMM6 comes in is a heck of a lot sexier than the white paperboard box for the Audyssey mic.
That being said, I have to ask if the calibration file for the Audyssey microphone is actually based on calibrating each individual mic? I had assumed it was not, and is therefore not as accurate as the calibration on the UMM6 as delivered by Cross Spectrum. Indeed, I will continue to assume it is not until I'm shown otherwise because I just don't see that happening. So long as this is the case, the calibration file as installed on AVR can at best be 'good, not great' and would be imperfectly matched to the hardware being used to test the system.
Edited by JD in NJ - 2/5/13 at 10:30am
post #1014 of 9491
Quote:
Originally Posted by JD in NJ View Post


First, I never actually said it would be any more accurate, just that it would be 'really keen', because I don't like to have two tools when one can do the job.
That being said, I have to ask if the calibration file for the Audyssey microphone is actually based on calibrating each individual mic? I had assumed it was not, and is therefore not as accurate as the calibration on the UMM6 as delivered by Cross Spectrum. Indeed, I will continue to assume it is not until I'm shown otherwise because I just don't see that happening. So long as this is the case, the calibration file as installed on AVR can at best be 'good, not great' and would be imperfectly matched to the hardware being used to test the system.

No, the calibration for the Audyssey mic is a generic one for all Audyssey mics of a particular model number.  If you want a custom mic calibration, purchase the Audyssey Pro kit ($550 plus $150 for the AVR license).  That's the only way you are going to get better than the standard Audyssey mic.

post #1015 of 9491
Quote:
Originally Posted by AustinJerry View Post

No, the calibration for the Audyssey mic is a generic one for all Audyssey mics of a particular model number.  If you want a custom mic calibration, purchase the Audyssey Pro kit ($550 plus $150 for the AVR license).  That's the only way you are going to get better than the standard Audyssey mic.

Yeah, I don't want it THAT bad. biggrin.gif
post #1016 of 9491
Quote:
Originally Posted by AustinJerry View Post

Feri, as long as the microphone has been properly calibrated, then setting the Sweep Level to -25dB with the AVR MV set to zero is the same thing as leaving the Sweep Level at -12dB and setting the AVR MV to -13dB.  Both result in a reading of 80dB at the MLP, measured on the UMM-6 or on the RS SPL.   We are in agreement here, which is why I asked you to clarify your original post.

Jerry, I don't have my measuring gear pulled out right now, but if you have your's setup could you please check what REW will tell you for both cases as regards the available headroom for measurement? I have a feeling there will be a difference. Thanks.

P. S. Your above reply appeared on my screen with black letters on a black background. First I thought you didn't write anything but I had to highlight it to read it. LOL
post #1017 of 9491
Quote:
Originally Posted by JD in NJ View Post


Yeah, I don't want it THAT bad. biggrin.gif

 

I can certainly understand.  However, you should not feel that just because th Audyssey mic has a generic calibration file that you can't get excellent results from a calibration. 

post #1018 of 9491
Quote:
Originally Posted by AustinJerry View Post

I can certainly understand.  However, you should not feel that just because th Audyssey mic has a generic calibration file that you can't get excellent results from a calibration. 

I really don't think I suggested otherwise, although I have to say that once I have some time with an empty house, discovering the differences between using Audyssey and not using it will be one of my first measurement tasks.
post #1019 of 9491

Ok, I was scratching my head when I saw this:

 

 

Then I remembered discussing the effects of text color with the various AVS skins and after highlighting saw this:

 

 

I know I should just switch to the default skin but I use so many portable devices and white backgrounds are killer on battery life!

post #1020 of 9491
Quote:
Originally Posted by mogorf View Post


Jerry, I don't have my measuring gear pulled out right now, but if you have your's setup could you please check what REW will tell you for both cases as regards the available headroom for measurement? I have a feeling there will be a difference. Thanks.

P. S. Your above reply appeared on my screen with black letters on a black background. First I thought you didn't write anything but I had to highlight it to read it. LOL

The headroom in both cases is -16.5dB.  The frequency response curve is also identical in both cases.  What are we trying to show with this exercise?

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