Program SPL Weighting

Professional Installed
1

Hello,

When using the “Program SPL” tool in Modeler, what weighting is used in that calculation?
Changing the weighting in the SPL window by right-clicking and selecting Flat, A, B or C does not change the number.
I did go to the Help menu and all it says is;

"When working with the System SPL tab additional SPL weighting scales, (A, B, C, and Flat) are available. In addition a total SPL with program material display is available – which predicts the total system SPL based upon an IEC shaped Pink Noise input source.

NOTE: All SPL predictions within the Modeler program assume an input noise source with a 6 dB Crest Factor.

It does not signify the weighting used. If this could be made to change with the selection of different weighting curves, it would be groovy!

Best Regards,

Bruce

2

Hello Again,

Phil Nelson sent me a message that indicated that since it was “shaped” IEC Pink Noise, then it applies it’s own “weighting” curve which makes sense.

I do wish we would supply a graph showing the IEC curve in our help file so you could use it as a reference when talking to others about our predictions. I clipped this one from a web site for an example.

You may now return to your regularly scheduled workload…

Bruce

3

I concur with you here Bruce - also a little more information on the SPL readout generally would also be good in the Modeler hepl file.
Regards
Ray

4

Hi all,

here a few more remarks and a warning regarding Program SPL.

Please note that you need to distinguish between the ‘input spectrum’ to the system and any frequency weighting. In principle, both are independent from each other and actually, the application of both of them is valid as well.

So what are the differences ? For all its SPL predictions, Modeler assumes an input signal to the system with a pink frequency spectrum. The resulting output spectrum may then be summed to yield a total SPL and this summation can be done with or without any frequency weighting. This is really like using an SPL meter: You feed any kind of signal into a system and measure the output SPL. The meter does not know (nor does it need to know) what kind of signal you are feeding in.

Whenever the input signal is changed (e.g. by selecting ‘Program SPL’ or simply by adjusting the equalizer), you alter the way the energy is distributed versus frequency. And in case you have multi-driver speakers and/or subwoofers in your design, then changing energy vs. frequency will also change the power that is fed into the various drivers. Since IEC program material spectrum has more energy in the low end and less energy at HF, more power will go into subs and MF drivers and less power into HF drivers, compared to pink noise. So, depending on where in frequency your system has some headroom left, the System SPL will be different from the pink noise SPL.

Note that currently, there’s a bug in Modeler that may yield wrong ‘Program SPL’ for all speakers with multiple drivers, i.e. RoomMatch and LT. So for the time being, we recommend to not use Program SPL. Should you desperately need to predict that number, you will have to work-around it by altering the EQ to the system: You will need to ADD the relative IEC spectrum to the EQ you have currently dialed in.

Hope this helps. Let us know in case you have any additional questions.

Best rgds,

Thomas

5

Hello team,

Has the SPL issue noted above by Thomas been fixed in the 6.8 version of Modeler?

Thanks,

Bruce

6

Hi Bruce,

the answer is YES, this bug has been fixed in 6.8.

Let us know in case you encounter anything unusual.

Best rgds,

Thomas