RS SPL Meter - clipping problem

[spdracer22]

I'm having a problem with clipping when running REW with my RS SPL meter. This happens mostly with my laptop's internal card, but my desktop has also shown very little headroom...

When I set the levels in REW, the lowest I can get is -12 dB with the RS meter range set at 70 dB, and -14 db with the range set at 80 dB. This is with a reference level of 75 dB (pink noise through REW), set according to the RS meter. The problem, I think, is something with the laptop's audio driver...even with the input volume setting at 0.001 in REW, it sits at -12 or -14 dB.

What I was wondering is if I could set the reference level to 75 dB with the RS meter range at either 70 or 80, then change the range to 100 or 110 and reset the input level and SPL calibration in REW before taking a measurement. This would give me the additional headroom I need, but will the results be accurate??

[brucek]

The problem, I think, is something with the laptop's audio driver...even with the input volume setting at 0.001 in REW, it sits at -12 or -14 dB.

Most laptops internal soundcard don't offer a line-in. They usually only offer a mic-in. Hopefully you're not using that (which is a no-no)...... ?

brucek

[spdracer22]

brucek wrote:

Most laptops internal soundcard don't offer a line-in. They usually only offer a mic-in. Hopefully you're not using that (which is a no-no)...... ?

brucek

I am...and no, it doesn't have a line-in... I use the line in on my X-fi in my desktop, but I was at a buddy's trying to help him with his setup...

Now I'm curious as to why using the mic port is a no-no...all I read in the REW help files is that "it's not suitable and shouldn't be used."

[brucek]

all I read in the REW help files is that "it's not suitable and shouldn't be used."

hehehe, that should have been the clue for you not to use it.

You've already figured out one of the reasons.... because the mic input will offer too much gain since actual mic signals are quite low in relation to line level signal (such as the SPL meter outputs).

This extra gain at the mic inputs front end usually results in increased noise.

In addition, mic inputs usually enjoy a very limited bandwidth that is designed to comply with a narrow voice frequency range that a cheap microphone would supply.

Most members that use laptops for REW purchase an external USB soundcard. They are quite inexpensive and offer line-in and line-out suitable for REW.

brucek

[spdracer22]

I know, I know

Your explanation makes complete sense. And, it sounds vaguely familiar...I wouldn't be surprised if I read something like that on here in the past and just forgot about it...

Thanks again, brucek.