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weverb 08-22-08 11:13 AM

REW Noob
 

1 Attachment(s)
I am trying to start using REW. Can you please help point me in the right direction on measurments. This is the graph I am getting. What am I missing? :huh:

brucek 08-22-08 12:45 PM

Re: REW Noob
 

Quote:

What am I missing?
You're taking a measurement of your loopback cable to test your soundcard cal file, and have the SPL meter calibration file loaded. It should not be loaded when you do this test, as the result will be a perfect inversion of the SPL meter cal file....

brucek

weverb 08-22-08 03:03 PM

Re: REW Noob
 

2 Attachment(s)
Thanks for the help. Just had the loop back connected backwards. I feel like a .... :duh: Here are the plots. The first is just subs and the second is with the mains on.

brucek 08-22-08 03:12 PM

Re: REW Noob
 

Change your graph axis to the standard of:

Vertical = 45dB-105dB
Horizontal = 15Hz-200hz.

Anyway, it doesn't look like the first graph is a sub only through the receiver, with the crossover set, and mains disconnected (in fact, both graphs look identical). The usual starting point is to do the sub only and position it for the best response. Then add the mains and get the best crossover response.

brucek

weverb 08-22-08 03:19 PM

Re: REW Noob
 

2 Attachment(s)
Sorry for the graphs. This should be correct. I turned of my external amp for the first so my mains would not receive anything. Do I have to go into the receiver and tell it there are no main speakers?

brucek 08-22-08 04:38 PM

Re: REW Noob
 

Quote:

I turned of my external amp for the first so my mains would not receive anything. Do I have to go into the receiver and tell it there are no main speakers?
Well, I think you can see that the "sub only" graph is simply not tracking the standard target crossover.

You simply need to turn off the mains. But, you certainly have to have the mains set at small in your receiver and the crossover set at the normal crossover you use (i.e. 80Hz).

BTW, set the measurement level at 75dBSPL. You're a bit high.

brucek

weverb 08-22-08 07:40 PM

Re: REW Noob
 

1 Attachment(s)
brucek

Thanks for your help. The speakers are currently set to small and the crossover is set to 80Hz. When I manual get a reading playing the test tones on the HSU disk, I get a graph that looks like this (with mains on).

brucek 08-22-08 07:51 PM

Re: REW Noob
 

That graph also doesn't really make sense. How can the signal after 80Hz continue to produce ~75dBSPL all the way up to 250Hz. The crossover is suppose to continue to reduce the signal above the crossover frequency.... The signal should act like the target REW shows. This is a bit confusing.

I would suggest to use REW to check out the receivers crossover. Feed the soundcard line-out to the CD or AUX input of the receiver and then feed the receivers sub out signal to the soundcard line-in and do a Check Levels setup and a measure up to 200Hz and see what the graph looks like. It should track the REW ideal target....

brucek

weverb 08-23-08 08:52 AM

Re: REW Noob
 

The above graph was with the mains on. That is why it continued to produce 75dB. What gets me is the major dip at 80Hz with REW versus the manual reading of 75dB at 80Hz when playing that specific tone. :huh:

I will try your recommendation of testing the crossover. I can say, when I play those different frequencies manually, you can verify that at 80Hz the mains start to play.

weverb 08-23-08 12:03 PM

Re: REW Noob
 

1 Attachment(s)
Found something interesting. My MBM xo has been "out" during all my first testing and that's what all the previous graphs show. I just switched it to "in" and....


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