Trying REW for the first time, Problem

**tonyvdb** · **07-09-09, 04:37 PM**

This is my first time using REW and I feel real dumb for asking this but I cant find the answer in the help files.
I have all the cables hooked up according to the diagram and when I select "check levels" and I raise the volume to start seeing a level on the left and right meters I also get feedback in my speakers/sub.

What am I doing wrong?

I am using a Galaxy CM140 and have the proper calibration file loaded into REW.
EDIT: I should also add that I am going the "loopback route" but my understanding is that I need to get the levels correct before proceeding with the loopback calibration.

**brucek** · **07-09-09, 05:57 PM**

Quote:

I have all the cables hooked up according to the diagram and when I select "check levels" and I raise the volume to start seeing a level on the left and right meters I also get feedback in my speakers/sub.

I advice against using the "Left Channel as Calibration Reference".

Disconnect all cables and install a single loopback cable on the right channel line-out to line-in and run the soundcard calibration routine, and create a soundcard calibration file.

Be sure your soundcard is in the stereo only mode, with all soundfields and effects turned off, and be sure the monitor mode is disabled.

Let me know how that goes...... post a pic of the cal file.

bruce

**tonyvdb** · **07-09-09, 07:00 PM**

Ok Here is my calibrationfile for the sound card. Does this look right? Its an older Creative Soundblaster PCI card

**brucek** · **07-09-09, 07:30 PM**

You're getting a bit of oscillation above 1Khz. Below that it's fine.

Try and play with the sweep level and see if you clear up the signal. Adjust it and then run the soundcard calibration file, then repeat until you have the best result.

Then when you like it, before you remove the loopback, save it and run a Measure from 0-20000Hz of the loopback cable itself (with the meter cal cleared) and the soundcard cal file loaded to see if the result is a flat line.

You must run the Check Levels routine and the Calibrate routine (set to 75dB) before running the measure.

Tell me how that goes....

brucek

**tonyvdb** · **07-09-09, 08:09 PM**

Ok, Got it, I got a nice flat line after running measure. Thanks Bruce

Now what is next?

**brucek** · **07-09-09, 09:04 PM**

Quote:

Now what is next?

Remove the loopback and use that (right) calibrated channel for the SPL meter and connection to your receiver. The left channel is not used.

Hook up the SPL meter to the line-in (be sure to load the meter calibration file).

Hook up the receiver from the line-out. Use the AUX or CD input on the receiver with a Y-splitter so you can check both left and right speakers and sub.

Run Check Levels routine at 75dB (with the meter at the listening position).

Run Calibrate routine.

Measure.

brucek

**tonyvdb** · **07-09-09, 10:05 PM**

Sigh, Ive about given up for today. I cant find any reason that it wont work and I've already spend almost 5 hours on this so I'm done for today.

**brucek** · **07-09-09, 10:51 PM**

Quote:

I cant find any reason that it wont work

If the soundcard calibration worked fine, then you're almost all the way there.

What specifically is not working when you go through the steps I outlined?

brucek

**tonyvdb** · **07-09-09, 11:01 PM**

I get this graph when I run Measure for my sub...It is obviously not correct?

Thanks for your help again Bruce

**brucek** · **07-10-09, 07:47 AM**

Quote:

It is obviously not correct?

That measure is an inverse plot of the meter calibration file, so it means you are either measuring a loopback cable with the meter cal file loaded, or you have the soundcards monitor mode turned on - turn it off.

brucek

**tonyvdb** · **07-10-09, 02:14 PM**

Ok, I finaly got tired of using an older PC and dug out my main PC and reinstalled REW on it.
Below is my graph I get when running the test.
Blue is the sub alone and the green is mains and sub. What do you think?

Why do I see so much below 10Hz on the graph? should it not fall off?

**tonyvdb** · **07-10-09, 02:37 PM**

Here is a graph with my mains crossover set to 80Hz

**brucek** · **07-10-09, 02:43 PM**

Quote:

Below is my graph

Change the graph axis to the standard we use here at HTS.

For subwoofers, always use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - 200Hz) using the Graph Limits button in the top right corner of REW. Use a measurement start frequency of 0Hz and an end frequency of 200Hz.

For full range, use the standard Vertical graph axis of (45dB - 105dB) and the Horizontal graph axis of (15Hz - upper limits you desire, i.e. 1KHz -20KHz).
For full range only, enable smoothing to eliminate the comb filtering. Use a 1/3 octave smoothing.

Always set a measurement target of 75dBSPL. To accomplish this, you use a level of 75dB when running the Check Levels routine, then followed by running the Calibrate routine.

That's an extremely noisy soundcard cal file. See if you clean it up a bit by altering the sweep level and input level in the soundcard cal routine.

brucek

**tonyvdb** · **07-10-09, 04:04 PM**

Ok I think I've got it. Does this look better?
Blue is the mains Green is the sub

The crossover is set to 80Hz

Here is the mains and sub together in Purple

**tonyvdb** · **07-10-09, 05:17 PM**

I did a test graph and was surprised by the results as I did not know how good the A/D/S ms3u sub that I had before was.
Below is the A/D/S in Green and in yellow is both subs together.

**brucek** · **07-10-09, 06:01 PM**

Looks pretty good now..................

brucek

**tonyvdb** · **07-10-09, 06:07 PM**

Do you think I should change anything or does it look good enough to just leave alone. There are two dips one at just above 70Hz and the other at around 120Hz?

**brucek** · **07-10-09, 06:10 PM**

I would probably leave it alone..............

brucek

**tonyvdb** · **07-10-09, 06:17 PM**

Fantastic

I knew I had it sounding fairly good.
One more question is it ok for me to use both my subs at the same time given the graph above or is it really not helping as they are not matching subs but seem to be very close with regards to response.

Thanks for all your help with this.

**brucek** · **07-10-09, 06:30 PM**

If they're co-located and with the same response, they'll simply give you extra headroom. But if you don't co-locate them, it's a new ball game. You would have to measure them together from the listening position and move them around until you got a good response.

brucek

**tonyvdb** · **07-10-09, 06:35 PM**

They are located in the same spot. The measurements were all taken at the listening position.

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