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Discussion Starter · #1 ·
Hi all!:wave: I'm glad to be here and I'm reading and learning a lot. I have downloaded John M.'s REW and its manual and I've read it in order to manage to improve my HT sound. Thanks a lot for your great program JohnM!!:clap::clap::clap::clap:
I'm using a basic RS SPL meter Model 33-2050 and a Behringer UCA202 USB soundcard and a normal win7 Dell laptop. My AV pre is a TagMcLaren AV32R DP, and I've got the Tagtronic cable in order to apply the filters with ease, as JohnM did consider this pre.

I've calibrated the soundcard without issues (well only without issues after verifying how important was to turn my Dlink wireless router OFF as it affected hugely the final result!, hope this helps someone!!)

However I'm having problems with my RS meter, the first step is easy: adjust the 'aux input' I set in AV32 at my normal listening level, read the RS metering and calibrate it. But then after finishing this initial adjustment I find it strange that without any noise in the room the REW SPL meter is reading about 72dB without any sound. OK, I know that this is the moment to 'check levels' and adjust my soundcard input level, but even at 100 I don't get to the recommended -24 to -12dB. I have to boost the output level to almost 100 also in order to get in that range. So:
1) I don't think it's normal that without 'sound in the room' or 'output from the RS meter' the REW SPL is around 71 or 72dBs.
2) I cannot get a normal input range when checking levels.

So, maybe the analog output from my RS SPL meter is broken?? Or I'm doing something really wrong!?
I have to say that the analog VUmeter from the RS meter seems to be working fine.

Thanks in advance for your help, and thank you again to John M. and all the great people in this forum.
 

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Discussion Starter · #3 · (Edited)
Thanks John, I've gone through this step as I've been following your manual, and it worked well. I mean, after doing so, both the physical RS SPL meter and REW SPL are displaying 75dB. But, the weird thing is that when I stop the sound and the room remains quiet, the REW SPL meter is still around 71 or 72dB while the RS analog VUmeter obviously doesn't move (at that 80 scale or even at the 60dB scale, as it should BTW being the room quiet).
And moreover, as I said, I have problems getting an adequate input level during the 'check levels' step so I guess there's a problem with the RS SPL meter analog output but maybe I'm doing something wrong?!.
I know you have to be very patient with all of us newbies but at least I promise I've read and followed the manual and my computer and electrical skills are not that bad but, somehow I'm not getting the expected results!. :crying::help:
 

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Hmmm. Might be the UCA202, some have an odd rise in level at low frequencies when connected to the RS meter - if you switch to the RTA view you might see that. Does the laptop have a mic/line input? If it does, try connecting the meter directly to that.
 

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Discussion Starter · #6 · (Edited)
Hi again John, you hit the nail on the head!! :hail::clap: I've used the line in from the laptop (thanks I had a spare 'mini' connector to try) and I had no problems adjusting the input level and calibrating the REW SPL meter. And now when I left the room quiet the REW SPL meter is displaying around 60dB that I guess it's good enough, isn't it? But now what I should do, I mean:

1- I had previously calibrated my UCA202, should I try to get a new one and expect it to work well or it really doesn't matter and I'll be OK using the UCA202 for the output and my laptop soundcard line in for the input?? Maybe trying to make a proper calibration between the UCA202 output and the laptop line in??
2- and...regarding the SPL meter I've read some threads where it is recommended to use the SPL meter without a calibration file but ticking the 'C weighting SPL meter' option: I've noticed that using the forum calibration file to read a SPL of 75dB I have to turn the volume a little more up than using just a 'C curve'. Is this normal?? How should I proceed??

Thanks again!!
 

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If your laptop also has a headphone out you can use that for output and forget the UCA202. You can calibrate your desktop in the same way as an external soundcard, just connect the headphone out to the line in.

SPL meters vary, the cal file is a reasonable average but it won't be quite right for any particular meter - using C weighting correction alone won't be quite right either as the meter doesn't perfectly follow the C weighting curve. The differences aren't huge either way over the main frequencies of interest and not really worth worrying about. Just remember the SPL meter can't be trusted above a few kHz, it has a big peak in its response around 5k and rolls off very fast higher up.
 

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Discussion Starter · #8 ·
OK, thanks, I'll use the internal soundcard and calibrate it. I will also take into account your advice about the RS SPL and especially as I won't consider its measures above 2-3kHz.
Now I'm going to read and get all info I can from this forum and stop asking (at least for a bit), as I believe our questions should be quite repetitive as we're all trying achieving the same goal! Thanks again John!
 
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