[Wayne A. Pflughaupt]

My cheap mic is on a tripod pointing horizontally right behind where your head would be.

What "cheap mic" are you using? Do you have a calibration file for it? If not, none of your measurements are valid.

Regards,
Wayne

 

[Wayne A. Pflughaupt]

Looks like you are compressing on your highest level measurements. Either the sw itself or otherwise.

That was the first thing that crossed my mind. But then it came to me that the peak is acoustic, not electronic. IOW, the amp does not "know" that there is a peak at 45 Hz and therefore would not be trying to flatten it at higher volumes.

I admit I had to Google subwoofer compression. I read about thermal compression and power compression. They seem to have the similar definitions. I'm not familiar with this so bear with me. My understanding is power compression occurs when the voice coil heats up, the impedance goes up. So as the power goes up the coil heats up, impedance rises, and less power is delivered to the driver. But my plots show compression at lower levels. Is my understanding of this correct?

That's a different issue. What Ricci is talking about, some subs have a limiting feature that restricts their output at a pre-determined level in order to prevent damage. It's most noticeable in that at a certain point, the sub just won't put out any more volume, irrespective on how high you crank the receiver's volume control.

Regards,
Wayne

 

[Wayne A. Pflughaupt]

Does this method minimize room gain?

If you asking if it will minimize the effects of the room, the answer is no.

Regards,
Wayne

 

[Wayne A. Pflughaupt]

Sorry, my response was admittedly a bit hair-triggered. Sure, close-micing will get you a different response reading than what you'd get at the listening position, but it's not going to totally eliminate the effect of the room. This will be obviously apparent once he performs his outside measurements.

The only exception would be a quick gated reading. I seem to recall some discussion as to whether or not REW could do this, but I don't recall the details...

Regards,
Wayne

 

[Wayne A. Pflughaupt]

Moving a sub to the middle of the room and taking a near-field response is a pretty good method of removing the room.

I had forgotten about the graph Brian showed us in post #21, which pretty well supports your contention; I can’t imagine an outside measurement showing anything different other than less extension (which would be from a lack of room gain). Sorry to sidetrack the thread.

Regards,
Wayne