A few (hopefully simple) questions

[Ryan_M]

I've read quite a bit of the material in the sticky and am at the point of playing with REW to familiarize myself with it. I'm primarily interested in setting my system up for music if it matters.

1.) I'm wondering how important the SPL Calibration is. I don't have an SPL meter, I'm using an ECM8000 for measurements. I've set the volume of the system at normal listening levels and adjust the target curve up or down to it overlays well with the measured response. Any disadvantage to doing this?

2.) I've read the bits about house curves and the hard knee curve, but I haven't seen how those levels relate to the level of the mains or what the combined response of the mains+sub should look like. Should I set the sub response to match the house curve and then just use the gain on the sub-amp until it sounds right?

3.) I am using an H/K AVR-235 to handle signal processing. AFAIK the slopes should be 4th order low pass and 2nd order high pass so it combines with the natural roll off of the mains to make a 4th order acoustic roll off. I've measured the mains by them selves and the sub by itself and playing with the cross over settings at the left side of the REW screen my response matches a 12db/octave roll off pretty well at 120HZ which is what I have the receiver set at. Could there be something I'm missing or doing wrong? since I expected to see 24db/octave for each.

Thanks for any help,
Ryan

[Anthony]

Not having an SPL meter shouldn't be too big of a hinderance. What it will do is keep you from having repeatable measurements from time to time, since you won't have a consistent baseline.

That being said, for a quick adjustment or just seeing how good your room is, the ECM8k will be just fine.

I haven't done much with house curves other than to keep the system a little bass heavy to compensate. Others here are much more well versed on that subject.

As for the last question, your speakers might play lower than 120Hz and not start their drop, which is why you'd only see the crossover roll-off during the measurement. Your best bet would be some sort of bypass mode to see how the speakers measure with no crossover in the loop.

Hope this helps,
Anthony

[brucek]

1.) I'm wondering how important the SPL Calibration is. I don't have an SPL meter, I'm using an ECM8000 for measurements. I've set the volume of the system at normal listening levels and adjust the target curve up or down to it overlays well with the measured response. Any disadvantage to doing this?

Yeah, don't do it that way. If you don't have an SPL meter, then set the listening position to a reasonable level and then run the Calibrate routine and set the level to 75dBSPL. This fools the REW internal SPL meter, so you won't have to make any further trace adjustments.

2.) I've read the bits about house curves and the hard knee curve, but I haven't seen how those levels relate to the level of the mains or what the combined response of the mains+sub should look like. Should I set the sub response to match the house curve and then just use the gain on the sub-amp until it sounds right?

No, first use the receivers test tones to set all your speakers and sub levels.

Then run REW (with a house curve loaded) and apply your EQ. A house curve generally won't affect the levels at the crossover, since the level in the house curve file at the crossover should be 0.
An example of a typical house curve.
30 8.0
80 0.0
If you feel after you've applied your EQ that the sub is too low, then yeah, adjust its own volume knob.

my response matches a 12db/octave roll off pretty well at 120HZ which is what I have the receiver set at. Could there be something I'm missing or doing wrong? since I expected to see 24db/octave for each.

Yeah, the room is working against you and messing up the slope a bit. If you're convinced your sub output of the receiver isn't 24dB/oct, then simply take an REW measure of the receiver, just as you would a loopback cable. Be sure to clear the mic calibration file, and you have to fuss with the levels a bit in the Check Levels routine, but it's easy to see the response of your receiver. You'll be surprised how perfect it is - just like an REW target.

brucek