First REW plot, before doing anything

[Mr X]

Hi to all,

I've a few questions / comments after my intiial experience with REW.

1. REW, sensational piece of work, thanks John

2. I read many threads to determine which USB soundcard to use with my laptop (HP6730 with XP)
Finally settled on the Behringer UCA202, cheap and line in, line out only so no worry about selecting inputs. Worked first time. control panel->audio will allow you to set volumes easily.

3. The guides on the site are fantastic, they need to be read several times and then again.

4. My initial sweep shows response al the way down to <10Hz, not sure if I believe this. Subwoofer is 2 x Adire Tempest with 350W plate amp in IB config.

5. Amp is HK AVR635 with Eq already set for mains.

6. I'm not ready to equalise just yet, only trying to understand what I am seeing.

7. In the upload file the black circled area looks roughly like the inverse of the mic cal curve.

8. In the file the red circled area in the "flat" response of the HK EQ

9. Does the house curve only apply to the sub and then greater than say 100hz (xover) goes flat with the AVR?

10. Is it advisable to sweep the sub with the mains disconnected first?



thanks

Murray (Melbourne, Australia)

[brucek]

4. My initial sweep shows response al the way down to <10Hz, not sure if I believe this.

See the dip at about 15Hz? Below that your actual signal is falling into the noise. The meter calibration file is lifting the noise and making it appear to be signal. It's not, it's simply noise. You are correct in your #7 observation. The solution (and the standard here) is to use a horizontal graph axis of 15Hz-(upper limit you choose) and a vertical axis of 45dB-105dB.

9. Does the house curve only apply to the sub

The house curve applies to the target line that REW uses to determine filters.

10. Is it advisable to sweep the sub with the mains disconnected first?

Yes, that way you can see what it offers to the response without the influence of the mains. Generally, you'll measure the sub alone from 0-200Hz (with a graph axis from 15Hz-200Hz). Then you can move the sub around for the best overall response and add any EQ if you have it while remeasuring. Then you add the mains (using the same 0-200Hz) and observe the crossover region. If there's a problem, adjust the subs phase to smooth it out.

brucek

[Mr X]

Bruce,

thanks for the info.

I understand the 15hz up part now.

Next graphs (when I can get the laptop off my wife will adhere to the standard)

I only wanted to get the big picture at this stage.

Yes and good point of the individual contribution of the mains vs sub.

thanks

Murray