# first measurements



## BK_856er (Oct 23, 2009)

I finally took my first measurements! Setup is E-MU Tracker Pre USB + EMM6 calibrated mic + RS SPL meter. Measuring sub + mains crossed at 60Hz. Mic was 9ft from mains and pointed up. First few attempts I forgot to turn on the external sound card - doh! REW also later complained about low levels, so I did some mic input level fiddling until it seemed happy. I need to dive into the REW documentation, but anything jump out to the trained eye, apart from the low level??

BK


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Looks good, except for the low level. A waterfall at that level is fairly useless.

Regards,
Wayne


----------



## BK_856er (Oct 23, 2009)

I ran Audyssey for the first time, then collected another series of full-range REW measurements. This time I just ignored the message about low levels, and I think I ended up at about the right levels despite the message. For the two runs below, the top one is with the AVR in its now default "Dynamic EQ" mode and the lower one is in "Direct" mode which among other things shuts off output to the sub.

Am I on the right track with this stuff?

Is it normal for the REW "SPL meter display" to indicate ~58-60db even if a measurement is not underway?

As always, I'm hugely appreciative of any input! :T

BK










And just for fun, here is the smoothed full response from both mains + sub:


----------



## JohnM (Apr 11, 2006)

BK_856er said:


> Is it normal for the REW "SPL meter display" to indicate ~58-60db even if a measurement is not underway?


That would be very high for a reading with the room quiet, but it is probably due to not running Calibrate on the SPL meter panel after settling on your mic gain, unless you made those plots with very loud sweeps. Try doing the meter Calibrate.


----------



## BK_856er (Oct 23, 2009)

JohnM said:


> That would be very high for a reading with the room quiet, but it is probably due to not running Calibrate on the SPL meter panel after settling on your mic gain, unless you made those plots with very loud sweeps. Try doing the meter Calibrate.


The displayed ~58-60db is not real and I get the same reading with the soundcard off.

The sweeps were pretty loud - got my windows rattling at the low frequency! I'm measuring with a calibrated EMM6 mic and a custom CSL cal file loaded. I use a new RS SPL meter to set the 75db level with REW main speaker output signal.

I think I might be missing a step in the measurements. When I did the (USB external) soundcard calibration a few weeks ago with a loopback cable, I remember adjusting the mic input level knob to get the correct level per the screen instructions. For the room measurements shown above I just left the mic level at the "unity" setting and maybe that was wrong.

These were my general steps:

1) Make connections, power-on USB soundcard and activate 48V power with slider switch.
2) Start REW.
3) "Calibrate" SPL with the main page icon/button, set AVR volume so RS meter reads 75db with mains output, click the button.
4) "Measure" and respond to the dialog boxes, ignoring the low levels...

I remember messing with the "check levels" part for some measurements, but I don't remember getting meaningful values/changes in the display. I think I need to step through the whole process again and make sure everything responds correctly.

FWIW, I have an image of my EMU Tracker soundcard response curve towards the top of the soundcard subforum.

BK


----------



## laser188139 (Sep 19, 2009)

BK_856er said:


> ... For the two runs below, the top one is with the AVR in its now default "Dynamic EQ" mode and the lower one is in "Direct" mode which among other things shuts off output to the sub. ...


DynamicEQ raises the levels at the bass and high end, to compensate for the volume level being lower than reference. So to obtain useful measurements, and to avoid the test tones rattling the house too much, I always turn it and Dynamic Volume off and run Audyssey MultEQ alone. That way you can see how evenly it is setting the level at the low end. You can always take another run later with DynEQ on if you want to see what its effect alone is.

Bill


----------



## BK_856er (Oct 23, 2009)

laser188139 said:


> DynamicEQ raises the levels at the bass and high end, to compensate for the volume level being lower than reference. So to obtain useful measurements, and to avoid the test tones rattling the house too much, I always turn it and Dynamic Volume off and run Audyssey MultEQ alone. That way you can see how evenly it is setting the level at the low end. You can always take another run when you are done with DynEQ on if you want to see what its effect alone is.
> 
> Bill


That makes perfect sense - will do! :T

BK


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

BK_856er said:


> These were my general steps:
> 
> 1) Make connections, power-on USB soundcard and activate 48V power with slider switch.
> 2) Start REW.
> ...


Okay, I think I see the problem. What you’re calling the “Calibrate SPL” routine is actually the _Check Levels_ routine. It’s done on the “Soundcard” tab of Settings. The SPL Calibration routine is done after the Check Levels routine, under the “Mic/Meter” tab. This is the step that tells REW “where” 75 dB actually is.

Regards,
Wayne


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

If it helps, here's a "quick step-through" brucek wrote up some time back.

1. Prepare to run the Check Levels routine (*Settings* icon, *Soundcard* tab) selecting *Check/Set Levels with Subwoofer* in the *Levels* pull down box, with the SPL meter at the listening position and the dial of the meter at *80dB* position. 

Change *Input Device Input* and *Output Device Output* from *Default* to *USB Audio*, or the name of the soundcard, if that option is available, and *Speaker* for output, and *Line In* for input. 

Begin the Check Levels routine. Ensure the *REW output VU meter* is at -12db and the *Sweep Level* at -12dB. If those fields are blank, check the two *Control Mixer Volume* boxes.

Set the *Wave Volume* at 1.000 and the *Output Volume* about ~0.500. (If those fields are blank,). 

Adjust your receivers volume control so the actual standalone Radio Shack SPL meter reads ~75db at the listening position.

Then adjust REW Input Volume to end up with -18dB on the REW input VU meter.

2. Still in the *Settings* section, run the *Calibrate SPL* routine (in the *Meter Tab*) to match REW's SPL meter to the real SPL meter to ~75dBSPL. Make sure the “C Weighted SPL meter is checked.

3. Close *Settings* window. Run the *Set Target Level* routine (Target Settings icon to left of screen), which will set the target to ~75dB. Also, set the *Cutoff*, which is the crossover frequency you’re using

4. Run the *Measure* routine and set the End Frequency to 200Hz for subwoofers.


Regards,
Wayne


----------



## Lordoftherings (Feb 8, 2009)

Hi Wayne,

Just want to say how much I appreciate your inputs here at the Shack and elsewhere.
You have more to give than simply your knowledge.
And this, is a blessing indeed, and a great privilege to read you.

Best regards,
Bob


----------



## BK_856er (Oct 23, 2009)

+1 on props to Wayne!!

Session two after disabling the MultiEQ and sorting out the levels thing I think....no more REW complaints about low levels, etc....

Audyssey had my mains crossed at 40Hz. Below are stacked traces with the mains crossed at 80, 70 and 60Hz:










I chose the 70Hz crossover to play with some more (red trace above). Turned on the "PEQ" on my sub and set out to boost the dip at 84Hz. I have options for +/-7.5db, bandwidth and 20-80Hz range. Below is the best result with/without PEQ, green trace being the final outcome:










How is my logic on this stuff so far?

Would it be better to go after the dip at 57Hz or the one at 84Hz??

BK


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Thanks for the kind words, gentlemen. :T



> Would it be better to go after the dip at 57Hz or the one at 84Hz??


I'd go after both. Has it been mentioned what kind of sub you have? Equalizing requires headroom...

Regards,
Wayne


----------



## BK_856er (Oct 23, 2009)

Wayne A. Pflughaupt said:


> Thanks for the kind words, gentlemen. :T
> 
> I'd go after both. Has it been mentioned what kind of sub you have? Equalizing requires headroom...
> 
> ...


System consists of the following:

- Onkyo TX-NR807 AVR (a new 2009 model)
- Ascend Acoustics Sierra R/L mains
- Rythmik D15SE Sub

Some info on the 15" sub can be found below. 



















And just for completeness, this is the FR of the mains (looks the same as the actual test sheet that came with the speakers):










BK


----------



## BK_856er (Oct 23, 2009)

I think I'm getting a better grasp on this stuff. I updated my EMU drivers and firmware, created a new soundcard calibration file, recalibrated the levels and SPL and explored my sub some more. Somehow Audyssey was giving me some grief initially...no sub output...double-checked all the settings...cleared itself up after about an hour of trial and error???

Anyway, this is pretty much where I ended up (mains + sub, SPL calibrated with mains, 70hz x-over, Audyssey DEQ on, sub PEQ set to the 54hz dip):










And this is what happened when I moved the mic back ~3ft:










The 54hz dip became a peak, exaggerated by the PEQ! This is with the PEQ off:










As a next steps I think I need to work on the level and focus on just the sub, and take the mic location more into consideration before I go too crazy.

BK


----------



## brucek (Apr 11, 2006)

> and take the mic location more into consideration


Equalization is only effective at (and closely around) the point of measurement. A few feet away and a filter can cause the exact opposite effect. The idea is to only have the mic at the listening position. That becomes the sweet spot. The filters only mask the problems for the measurement position.

Now, if you have other listening positions you have to consider, then you must take multiple measurements and average them to create a set of filters for the larger area. The result is that everyone then gets an acceptable response.

Some people have a set of filters that is a sweet spot, and a set of filters for a larger seating capacity.

brucek


----------



## BK_856er (Oct 23, 2009)

brucek said:


> Equalization is only effective at (and closely around) the point of measurement. A few feet away and a filter can cause the exact opposite effect. The idea is to only have the mic at the listening position. That becomes the sweet spot. The filters only mask the problems for the measurement position.
> 
> Now, if you have other listening positions you have to consider, then you must take multiple measurements and average them to create a set of filters for the larger area. The result is that everyone then gets an acceptable response.
> 
> ...


Excellent info, brucek. Both the mic placements were in listening positions, so I averaged the the two curves to get the one below. Looks pretty reasonable to my untrained eye. I like the idea of multiple filter sets, with at least one optimized for MY listening position, so maybe Santa will bring me a BFD to play with...

BK


----------



## BK_856er (Oct 23, 2009)

Wayne A. Pflughaupt said:


> If it helps, here's a "quick step-through" brucek wrote up some time back.
> 
> 1. Prepare to run the Check Levels routine (*Settings* icon, *Soundcard* tab) selecting *Check/Set Levels with Subwoofer* in the *Levels* pull down box, with the SPL meter at the listening position and the dial of the meter at *80dB* position.
> 
> ...


I have a question on #2 above. I use a standalone RS SPL meter for REW SPL calibration, but I use an EMM6 mic (with calibration file from CSL) for measurements. I also use the REW speaker cal signal as opposed to the sub cal signal. My understanding is that for my scenario I should have the EMM6 cal file loaded, the "C weighted SPL meter" box should be unchecked, and I shoot for 75dB on the RS meter. Is this correct?

BK


----------



## laser188139 (Sep 19, 2009)

BK_856er said:


> I have a question on #2 above. I use a standalone RS SPL meter for REW SPL calibration, but I use an EMM6 mic (with calibration file from CSL) for measurements. I also use the REW speaker cal signal as opposed to the sub cal signal. My understanding is that for my scenario I should have the EMM6 cal file loaded, the "C weighted SPL meter" box should be unchecked, and I shoot for 75dB on the RS meter. Is this correct?
> 
> BK


If you are using an EMM6 calibration file, it really doesn't matter if you check or uncheck the C weighted SPL meter box. The helpfile indicates that the box tells REW what to do over the region not covered by the calibration file. But if you look at it, you will see that the EMM6 calibration file is very complete, it covers the entire range I expect you are measuring. In fact, almost by definition, any region beyond the calibration file, you should not be measuring. 

Of course, you can always try it both ways and see that it doesn't make any difference. 

Cheers,
Bill


----------



## BK_856er (Oct 23, 2009)

Thanks for that :T

I think my adsorption of information is only about 80% when I read/scroll things in windows. I should probably print out the entire help file, study it up and keep it in a handy binder. Looking forward to getting the basics all squared away.

BK


----------



## brucek (Apr 11, 2006)

> I also use the REW speaker cal signal as opposed to the sub cal signal.


You should use the cal signal that is appropriate for the frequency range you are measuring. If you're measuring from 0-200Hz you would use the sub cal signal.



> My understanding is that for my scenario I should have the EMM6 cal file loaded, the "C weighted SPL meter" box should be unchecked, and I shoot for 75dB on the RS meter. Is this correct?


As noted, the C-Weight box is only effective outside the calibration files bandwidth, so for full range mics with a full range cal file, the C-Weight box is meaningless.

brucek


----------



## Moonfly (Aug 1, 2008)

brucek said:


> As noted, the C-Weight box is only effective outside the calibration files bandwidth, so for full range mics with a full range cal file, the C-Weight box is meaningless.
> 
> brucek


As a side note, it doesnt really matter if it is checked either does it, and you can leave it checked whether using the cal file or not if it suits your peace of mind.


----------



## BK_856er (Oct 23, 2009)

BK_856er said:


> Thanks for that :T
> 
> I think my adsorption of information is only about 80% when I read/scroll things in windows. I should probably print out the entire help file, study it up and keep it in a handy binder. Looking forward to getting the basics all squared away.
> 
> BK


I put my "money where my mouth is" and made a single pdf document that contains all the current REW help files. 4+MB and 118 pages total - it'll make a nice reference binder. I'm happy to share the file if it's ok with the author.

BK


----------



## brucek (Apr 11, 2006)

> contains all the current REW help files


The only problem is that REW Version 5 is in Beta testing right now, and quite a bit has changed, and so the Help Files will be different fairly soon.

brucek


----------



## BK_856er (Oct 23, 2009)

brucek said:


> The only problem is that REW Version 5 is in Beta testing right now, and quite a bit has changed, and so the Help Files will be different fairly soon.
> 
> brucek


Cool! I was not aware that a new version was in the works. Any chance we can hear about the key changes? If there's already a post on the topic I totally missed it.

BK


----------



## brucek (Apr 11, 2006)

> If there's already a post on the topic I totally missed it.


No announcements have been posted yet.

brucek


----------



## Guiria (Jun 15, 2008)

BK_856er said:


> +1 on props to Wayne!!
> 
> Session two after disabling the MultiEQ and sorting out the levels thing I think....no more REW complaints about low levels, etc....
> 
> ...


Big dips like this are typically room related and cannot be fixed with EQ. Have you tried moving your subwoofer to a different position and retesting the sweep? Maybe the crawling for bass method would help you find a sub location that does not have those two dips??

Worth a shot IMO...


----------

