# Newbie



## stevestudio (Jun 22, 2006)

Have the Tascam us122 soundcard. Just starting, do I need also the Radio Shack meter if I have the Berhinger 8000 mic?

Thanks
Steve


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

The SPL meter is for setting the relative level of the measurements. Typically you calibrate REW to 75 dB, by adjusting the system (or sub) volume to 75 dB on the meter. At that point, when you enter 75 dB into REW's settings, it then "knows" where 75 dB is. The program has no other way or knowing the correct SPL if you don't "tell" it. For instance, if you got the sytem level to 80 dB by mistake and entered 75 dB into REW, REW will then "think" 80 dB is 75 dB. Make sense?

That said, you _can_ use the program w/out a SPL meter. Just run the test signal up to a comfortable level and enter it as 75 dB. You can generate a meaningful graph; you'll just have to keep in mind that the dB indicators one the left side of the graph are not accurate. 

Regards,
Wayne


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## stevestudio (Jun 22, 2006)

Is there a quick guide to this?

I have the Tascam US122, Integra 40.1 setup as 5.2 from speaker arrangement. RS digital meter,Behringer 8000 mic. Do I let Integra run its setup calibration program first?

Are the steps as follows?
Calibrate the Sound card with R out to R in.
Load cal file for SPL meter.
Hook up the SPL in R in hookup loop on L out to L in.
Measure at set to 75.
This is where I'm not sure what to do? Do you actually measure some with the SPL in place or do you switch to the Behringer setup?


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

> Are the steps as follows?
> Calibrate the Sound card with R out to R in.


 Yes, calibrate the sound card with the R in and R out connection. Save the calibration file, then load it into REW under the *Settings* icon, *Soundcard* tab. 




> Load cal file for SPL meter.


You won’t need to load the SPL meter calibration file. That’s only of you’re using the SPL meter to take the frequency response measurements. Since you’re using the ECM8000 mic, load the calibration file for it instead, under the *Settings* icon, *Mic/Meter* tab. While you’re on that page, uncheck the C-weighting box - you won’t need it.




> Hook up the SPL in R in hookup loop on L out to L in.
> Measure at set to 75.


Again, no reason for you to connect the SPL meter to the sound card since you’re using the ECM. Here’s the connection scheme you should have using the Tascam:












> This is where I'm not sure what to do?


Set the mic near the listening position on a tripod or mic stand - something to keep it away from any kind of a boundary. If you’re measuring full range, point the mic at the speaker you wish to measure, angled slightly up @ 20˚. If you’re using a 90-degree calibration file for the mic, the mic should be straight up and angled slightly towards the speaker @ 70˚. If you’re measuring a subwoofer, mic orientation isn’t important. 

Once the mic is set up:

1. Prepare to run the Check Levels routine (*Settings* icon, *Soundcard* tab) selecting *Check/Set Levels with Subwoofer* in the *Levels* pull down box.

2. 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. 

3. 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.

4. Set the *Wave Volume* at 1.000 and the *Output Volume* about ~0.500. 

5. Adjust your receiver’s volume control so the SPL meter reads ~75db at the listening position. Then adjust REW *Input Volume* to end up with -18dB on the REW input VU meter.

6. Still in the *Settings* section, run the *Calibrate SPL* routine (*Mic/Meter Tab*) to match REW's SPL meter to the real SPL meter to ~75dBSPL. 

7. Close *Settings* window. Run the *Set Target Level* routine which will set the target to ~75dB. Make the Speaker Type selection for what you want to measure – subwoofer, full range, etc.

8. Run the *Measure* routine.

9. Using the *Graph Axis Limits* icon, set the vertical scale to 45dB to 105dB and the horizontal scale for subs to 15 Hz to 200 Hz or 15 Hz to 20 kHz for full-range.

10. To save the graph, select *Graph* from Menu Bar, then *Save Graph as JPG.* Use 800 size setting or smaller. 



Regards,
Wayne


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## stevestudio (Jun 22, 2006)

an not find the MANAGE ATTACHMENTS to post an attachment.


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## JohnM (Apr 11, 2006)

Click "Go Advanced" below the quick reply box.


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## stevestudio (Jun 22, 2006)

Not sure what this is?
All spreakers unpluged except sub.


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## laser188139 (Sep 19, 2009)

It looks like a sub curve, 2Hz-200Hz. If it confuses you, you can uncheck the phase display so you see just the SPL. You can also play with the ranges or use the scroll bars so the Phase is displayed on, say, the upper half and the SPL is displayed in the lower half. 

Bill


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

Also, your Target should be 75 dB not 47. And the vertical scale of your graph should be 45-105 dB. For subs, you can limit the horizontal scale to 15-200 Hz. Use the "Graph Axis" icon.

Regards,
Wayne


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## stevestudio (Jun 22, 2006)

Thanks guys,
Now what? Sorry to bother.


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## stevestudio (Jun 22, 2006)

This is as loud as I can go without clipping.


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## laser188139 (Sep 19, 2009)

Wayne A. Pflughaupt said:


> ... Also, your Target should be 75 dB not 47. ...


Wayne, with REW v5, that's not the target line, but just an indicator of the value on the left and right axis of where the cursor line is set. You can move the line up/down or left/right and read off the two axes the value corresponding to whatever point you have chosen. With v4, the cursor line was only vertical, reading frequency, but with v5 it shows the values against both the horizontal and vertical axes. 

For the target line, one now must open the EQ dialog to see a target line. The target line and the cursor line are both blue, but the cursor is a very thin blue and the target is a thick blue line. 

Bill


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## laser188139 (Sep 19, 2009)

stevestudio said:


> This is as loud as I can go without clipping.


What do you mean by that? Without hearing clipping in the sub itself? Or without seeing clipping on the VU meters during the measurement sweep? 

If you are concerned about clipping at the soundcard during the measurement sweep, you adjust the input level downward, recalibrate the SPL to 75dB, and rerun the sweep. 

Are you trying to run the sub loud, louder than 75dB, to see if the curve changes at high volumes? That's a little trickier to do. 

Bill


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## stevestudio (Jun 22, 2006)

I get the clipping notice if I turn up the knob on my amp. The subs really rattle at the present volume.


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## laser188139 (Sep 19, 2009)

If you were able to reach 75dB and complete the SPL calibration, you are good to go, as long as you don't see the clipping indication during the sweep. With the exception of the very highest volumes, the frequency response is the same, regardless of level. The reason 75dB is chosen as the target, is that it is a comfortable level well enough above the normal noise level for the mic to be measuring primarily the speakers. 

If you are seeing clipping before you reach 75dB, you can attempt to adjust downward the input level or the mic volume on the soundcard. Your goal is to have the amplification after the speakers, in front of REW, low enough that you don't see clipping during a measurement. 

If you have problems getting the clipping not to happen, you can always reduce the volume of the receiver slightly and then tell REW its 75dB, even if it is lower, 70dB, 65dB, etc. The response curve will be the same, just the noise floor will be a little higher, which you might see later on the waterfall chart. 

Good luck,
Bill


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## stevestudio (Jun 22, 2006)

I have 2 subs, should I turn one off and try to move the other one around in the room. I initally placed 1 of the subs in my chair where I sit and found where in the room the bass seemed to resonate from and moved the sub to that location. What do I do about the dips in the graph? Should I always test with both on?


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## laser188139 (Sep 19, 2009)

With both subs on, you can try switch the phase/polarity on one of them to see if one sub is interfering with the other. 

With two subs, you are right, it makes sense to also measure the curves separately. That will tell you if both subs show the same dips in the middle. You would like to position them, if possible, so they energize the modes differently and don't reinforce each other. 

It is fairly common to see the frequency dip in the middle, ~50Hz. For example, if the mic position is centered between two walls 22' apart, 11' from each, it should see a null at 51Hz. 

Bill


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## eurovybez (Jun 2, 2012)

useful


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