[brucek]

The meter appears to be accurate even when the needle becomes pegged.

As John suggested above, you only need to examine the Scope to see if there is distortion from the meter.

Are you familiar with interpreting the Scope information?

brucek

 

[brucek]

interpreting the Scope information

The scope is available after each measure and is lost when you do the next measure, so you do have to look directly after a measure.

It simply gives a picture of the output and input signal.

See a typical measure below where the output is the purple signal from the soundcard and the red is the input signal once it's received by the soundcard. See I have one peak there received that is about 80% of full scale (FS). That's a good sweep signal as long as the meter itself wasn't clipping.

Hard to see anything when you look at the entire horizontal axis of the sweep, so........

Below is an expanded horizontal scale version and you can see the output and input are not clipped. If I increased the input level control so that the VU meter on the Settings page showed more than 0dBFS, then the red signal would be as large as the output signal and you would see the red signal clipping (flat top). If on the other hand, the signal from the meter was clipping, you would see a flat top or other distortion of the input signal without it being 100%FS. This is likely the case when you leave an SPL meter on a lower scale and measure high SPL readings (your case). This is one of the other advantages of a microphone over an SPL meter for measuring audio.

brucek

 

[brucek]

The RS meter is apparently only accurate down to 24 Hz

It's not particularly accurate in general, but it's fine for home use and can be used down to 10Hz with our calibration files - You are using a calibration file?

if I get a good outdoor measurement, can I then compare it to the room measurement and draw some conclusions on what the sub is doing vs. the room modes?

Certainly.

brucek

 

[brucek]

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

Do you not feel the near-field measure overwhelms the effect of the room on the reading at the mic?

Is this not the purpose of near-field measurements?

brucek

 

[brucek]

The only exception would be a quick gated reading.

For sub testing, you don't want to alter the IR gating, since the gating puts a limit on the lowest frequency and the resolution of the response. For example, if you were trying to limit reflections from surfaces 1 meter away, you would use a 6msec gate (d=(time*speed)/2), but this would limit the lowest frequency of usable response information to ~167Hz (1/gate time). Not much use in this case. The default windows are much better for low frequency testing. Gating is reserved for measuring mains.

Moving a sub to the middle of the room and taking a near-field response is a pretty good method of removing the room. One of the problems that arises is that it isn't very practical with a ported sub, since both the driver and port contribute at different frequencies, and so setting the mic to get a decent mixing point places you outside of the area you would consider near-field. In that case it's better to drag it outside.

brucek