Sound level and SPL Question

[BSS]

Hi,

I have some question about configuring the "out" "in" "ref in" and the SPL in REW. This is a bit difficult to explain but let me break it down into few part:

1) In the Preferences, i will see 3 indicator "out", "in" and "Pref in". For my understand, this should be cap at the same level where the noise signal generated by the REW (whcih is represent by the OUT indicator), should be similar to what i am getting from the microphone (which present by the IN indicator). Am i right about this?

2) So after adjust the volume at my amplifier to match the IN and OUT level, then turn on the "SPL METER" so check if i am getting a 75db volume level. I am not too sure why it should be 75db, but i just follow the standard where everyone is talking about it. But anyway, at this part i have to lower down the "SWEEP LEVEL" to -18.0 dBFS to get the 75db volume level. At this part am i doing it right?

3) After that, i assume everything should be good to go, so i open up the "measure" panel and hit measure. But i am getting error message that i am having sound clipping. I am not too sure why as i think i didnt over volume the entire thing. But to solve this issue, the direct way is to lower than the "INPUT VOLUME" from 1.00 to 0.6. But the issue is if i am lowering down the "INPUT VOLUME", then i would not be able to get all the 3 indicator bar at the same level (OUT, IN, REF indicator).

4) So after decrease the INPUT VOLUME to 0.6, i crank up the amplifier volume so that the 3 indicator would get the same level. But at this point the sound level is too loud and is more than 90db. So i lower down the "SWEEP LEVEL" to -40dBFS. By doing this, i notice that i am increasing too much volume on the amplifer (volume at +1.0) and i hear some noise from the speaker, obviously my system is not a high end system where i can get dead silent on high volume. This is not a big issue, as i just move on with the measure and get the curve right. But i am not too sure if i am doing the entire right. It look so wierd as i need to decrease the SWEEP LEVEL to -40, where most ppl in youtube is adjusting around -18.

By the way my system setup is

UMIK-1 ------ PC-------DAC ------- Integrated-AMPlifier ----- Speaker

 

[John Mulcahy]

Matching input and output levels is only relevant when measuring with soundcard line interfaces (even then it only needs to be roughly similar). With a USB mic the input would usually be 30 or 40 dB below the output when the mic is set for unity gain, which on Win10 (for example) is an input volume setting of 0.53. Input volume of 1.0 applies 24 dB of gain in the mic, which makes it more likely to clip when measuring.

75 dB is used to make sure the test signal isn't too loud or too quiet.

 

[BSS]

how about the "SWEEP LEVEL", what number is good? should i increase the "SWEEP LEVEL" to meet 75 db OR should i be adjusting the integrated amplfier volume ?

 

[John Mulcahy]

Put the amplifier volume at the level you normally have it for listening and adjust the sweep level to get around 75 dB.

 

[BSS]

After setting as suggsted, this is how the level in and out indicator looks like. will this be a problem where the input level is only -41.82. By the way for the output, should i be using Left channel only or both L+R? i feel like L+R is the way to go because i am setting the EQ at the EPO for all, and i didnt do it independently for both speaker, as i feel that its not a hige different whether i do it at a single speaker or both at once. what do u think?

 

[John Mulcahy]

Levels look fine. Generally best to measure L and R separately, when both are playing it causes comb filtering unless the mic is exactly (to the mm) the same distance from each speaker.

 

[BSS]

Thanks for the help. Finally did another calibration again, and this time the sound is much better. By the way, would like to seek your advice, for a stereo 2.1 setup. How would you tune the system to the best sounding? Since my system cannot adjust the freq response purely for the subwoofer. I can only adjust the bass freq response to left or right.

1) Calibrate the speaker only, and then turn on the subwoofer and manually adjust the volume and the crossover at the subwoofer to my liking

OR

2) Calibrate the speaker together with the subwoofer turn on together.

Why am i asking this question, because at first i am using method 2, but i cant get it to sound natural. i prefer natural warm sounding. And always i am getting it sound very thin or not natural anymore. i guess i dont know how to adjust the filter right. i tried multiple times with different kind of combination but just cant get it right. As you can see in picture 1 [raw measurement result], the issue is that my bass is always very boomy due to the freq bump at 115.6-hz. When the subwoofer is turn on, that particular freq from my sub will cause it to go even higher. hence even more boomy. Freq from 30 to 80 just get covered up.

So i decided to use method 1, first adjust the filter for the speaker only, on the bass region. Picture 2 show the filter setting. i dont know whether i did it right or not, but the idea is to get rid off the freq at 115.6-hz. But maintain the vocal warm sounding by preserving the original freq from 160hz to 500hz. Then i turn on my REL subwoofer and then manually adjust the crossover and volume to get the desire bass. And the filter look so wierd, i am not too sure i get this right or not, but the equaliser just look wierd (picture 3) . up and down as you can see, i normally see V curve equaliser. Anyway, it does sound better. at least it preserve the natural warm sound, and at the same time have some textile bass.

So what do you think? which part am i doing it wrong?

 

[John Mulcahy]

I would use 2), but I would also only allow much lower overall max boost, not more than 6 dB (I would more often use 0), and lower individual max boost, not more than 12 dB. To have a warmer sound use the room curve settings to add some LF rise to the target.