General SPL Plotting Question

[G29]

Can anyone explain what is causing the limits/oscillations in the following SPL plots of these 64-bit float, 256K tap linear phase XO slopes.

There appears to be 3 different floors (presumably the limit of 32-bit and/or plotting API). 1 between -140 and -150 dB, another after -150 dB and another pushing -170 dB.

The sub's first (steepest) 4:7 sub trailing edges start oscillating on descent and then tilt/knee ( starting @ -70 dB and lower ) to the right before descending into the floor. The last (shallowest) 3:7 do not have the bend/knee to right before going into the floor.

Specifically, I would like to understand:

1. Why are there 3 different floors / what causes them ?
2. What causes the bend/knee to the right of the steepest 4:7 sub trailing edges before the floor ?
3. What causes the falling oscillations before the floor or specifically what do they represent ? Adding more taps does not appear to change these oscillations.

Thanks much !!!

 

[John Mulcahy]

You would need to attach or link to the mdat files or the xover WAV files.

 

[G29]

Here is an MDAT with the 64-bit wav files added. They may have been reduced on load.

Hmm, mdat isn't loaded, must be too big.

Trying again with one of the wav files.

 

[G29]

Trying again with a smaller mdat.

 

[G29]

Here is what the steepest XO looks like in rePhase.

It contains:

• 96dB linear phase high pass
• 96dB linear phase low pass
• linear phase 6dB/octave low shelf filter
• 256K taps
• mono 64-bit float format

Pictured scale is 10dB to -400dB
Left limit is @ -160 dB
Right limit is @ -250 dB

 

[G29]

Here is the same XO in 32-bit in rePhase.

Pictured scale is 10dB to -400dB
Left limit is @ -160 dB
Right limit is @ -170 dB

 

[John Mulcahy]

You need to increase the left window so that the full impulse response is covered, so 743 ms each side.

 

[G29]

Thanks for the quick response. I thought they were already set to 743ms in preferences.

Do I need to set them anywhere else ?

 

[John Mulcahy]

IR import only uses the right side default width. I'll fix that for the next build, use the IR windows dialog to set the left width you need after import.

 

[G29]

FWIW, I have been using the drag-n-drop for the XO .wav files.

Changing the windowing algo got rid of the oscillations, but still have the knee kicking out to the right.

Will search for the other settings window under the new version. Still finding my way around the new layouts.

Thanks for the updates.

Also, thanks for adding the auto "L", "R", "LR" to the sweep measurement namings.

 

[G29]

Drag-n-drop behaves differently than imports.

 

[John Mulcahy]

It's the button labelled IR windows, to the left of the SPL meter button.

 

[G29]

It's the button labelled IR windows, to the left of the SPL meter button.

Thanks !!!

 

[John Mulcahy]

Drag-n-drop behaves differently than imports

It doesn't, it runs exactly the same code.

 

[G29]

Thanks, have it working with the "IR windows" option. It appears much more as expected for 32-bit.

The only variance remaining are the 3 different floors which is the least of my concerns.

Plot using 1/48th octave smoothing to get rid of the hash.

 

[G29]

IR import only uses the right side default width. I'll fix that for the next build, use the IR windows dialog to set the left width you need after import.

Thanks much !!!

Left side import works now with default values.