Need help with "Target Level"

[Pete7874]

Hello,

Please don't shoot the newbie...

Can someone explain to me in simple terms at what level I should set my target level in REW? I read the help file, but still don't quite understand the process.

When I use REW to come up with a target level on its own (Set Target Level...), I end up with 69.2. But then when I try to "Find Peaks", REW gives me a warning message: "Target level may be set incorrectly (too low)".



So, what should I set my Target Level to? Obviously this is going to greatly affect the filters and the amount of overall bass output, so I don't want to screw it up.

And a second question about the RadioShack SPL meter (the old analog one): Does it matter whether it's set to 'slow' or 'fast' response? I guess that setting only affects the actual display on the SPL meter itself and probably does not affect its line output, but I wanted to make sure.

Lastly, the frequency response of my sub seems awefully peaky. Can it really be this bad or am doing something wrong in my measurements?

The sub is SVS PCi 25-31 hooked up to a Denon AVR-2801. I am running it in 'dolby pro logic' mode while performing the measurements so that the receiver's crossover is properly engaged. The soundcard I'm using is Behringer UCA202. I have the SPL meter on a tripod, sitting upright with the MIC pointing straight up - is this the correct placement?

Thanks for all the help.

Cheers,
Pete

[Wayne A. Pflughaupt]

Traditionally we’ve recommended setting the target level for 75 dB. That’s a good start, but I think it’s better to move it after you’ve procured a measurement, if need be, to a good midway point between your worst peaks and dips. If you don’t REW is going to try to equalize down to the target level, generating a lot of filters that wouldn’t be needed with a more realistic target.

Judging from your picture, ~78 dB looks like a good place to start with the target level. Also, limit the “find peaks” to ~60 Hz, since any equalizing up close to the crossover point will likely be blown out when you add the mains. Of course, this should be double-checked by subs only, mains only, and mains w/ subs graphs.

REW is not going to recommend any filters to boost the wide depression in the 35 Hz region once you set the target level above it, but you can create your own filters and tweak them on-screen, in the Filter panel.

Set the SPL meter for slow, set your receiver to 2-channel stereo (as long as that allows your sub to operate), and turn off the mains during measurement. Mic positioning isn’t terribly critical for bass frequencies – just put in near the primary listening position. Your peaky response is very common.

Regards,
Wayne

[Pete7874]

Thanks so much! I'm going to give it another go taking your recommendations into account.

I was basically trying to see if a BFD 1124p would be useful in my setup. It looks like it may have a job to do.

[brucek]

When I use REW to come up with a target level on its own (Set Target Level...), I end up with 69.2.

I don't see how that is possible.

You set the level at the listening position to 75dBSPL with the Radio Shack SPL meter - (using the Check/Set Levels with Subwoofer pull down).

Then you run the Meter Calibrate routine and it sets the internal REW SPL meter to match that 75dB - (using Use REW subwoofer cal pink noise pulldown).

Then you run the Set Target Level routine and it sets the target level to ~75dB........

It simply can't set it to 69dB if you did all that.

brucek

[PeteD]

I have also experienced REW "setting a target level" lower than the calibrated SPL reading.

It doesn't seem that unusual to me because I believe you are calibrating with pink noise from 30 to 80Hz to get 75 dB SPL overall (during the check levels step), but then REW adjusts the target line to fit a certain way through the response line (which includes lower frequencies). I know I had REW pick a target level of about 72 dB, after I had "checked levels" and "calibrated the SPL" to 75 dB with pink noise.

Brucek, it sounds like you are setting target level only before taking a measurement in your example above. Are we not supposed to "set target level" after taking a measurement?

I am still playing around with measurements on REW and not sure exactly how it all is supposed to work. To me, it seems best to adjust the target level manually to achieve desired cuts and boost (if needed for sufficient line level output from the BFD), depending on the shape of the frequency response curve, as Wayne suggested above.

Pete

[zilbenz]

So are we supposed to Set Target Level before taking a measurement or after as the Help File states? Thanks.

Chris

[brucek]

You should set it before creating any filters............... You can manually set it after taking a measurement if you want to modify the filter results, or you can simply let REW decide by using the Set Target Level routine.

brucek