I am expecting that the closer the XO gets to the SWs null around 115 Hz less SPL reinforcement and EQ ability there will be in the XO range. If we compare 60 to 80 Hz alignments above there is not much difference in overall SPL, but there is less SPL reinforcement across the XO range using the 80 Hz XO.Also, how are you analysing to not recommend 90 or 100hz XO from my data?
It appears a difference in mic location between the measurements used for targeting vs those now used for verification may be responsible.- The first recommendation (SWs delayed by an additional 5.5 ms) (called _a_ in file) for XO80 did not align with the simulation. I took new measurement with _a_ settings and did tried to get the sum to align your suggestion, measurement 13-15. I used the alignement tool and got quite good match (16 Aligned sum_c_) with delay -1,37ms. Verified with 17 and 18.
(open first "...file 1 of 2" and then "...file 2 of 2 " to get measurements number in correct order.
I used the "Align phase at cursor" ad the new line match you blue quite good. Maybe this is all wrong, but I was playing around at tried this feature.You indicated a delay of -1.37 ms. I don't understand how that relates to all this this data.
Anyway, I´m quite sure the 80-a are vary sensitive to mic location since its no more then +-1cm from when I took the original measurements. AND the verification for all other are in same mic location as for 80-a. So maybe I should go with your suggestion for setting 80-a instead of my 80-cIt's very possible that the 80-a alignment SPL is more sensitive to small mic positional changes than the 80-b setup and that is why there was no SPL problem with 80-b.
There is no expected detriment to group delay when applying PEQ. There may be improvements.When adding EQ to the subs, should there be an increase in group delay?
Web browse for 'audibility of group delay'. You will find some studies and a raft of opinions. Test results vary widely depending on the conditions chosen. Most of the arguments don't deal with all the interactions that occur in a SW setup situation.And what is acceptable GD below 100Hz?
So what we measure here is the combined sound during all 500 ms, okey. Is our hearing also working in same way, that we sum the direct and up to 500 ms late sound? I´m fooling myself with a nice looking graph or what?I summed the L and R channels; with and without EQ.
- The first chart is the GD without FDW applied so we are looking at the apparent GD using the entire window for all frequencies. This allows the room to influence the result for the entire 500 ms window. These late arriving room reflections and modes cause comb filtering of sound and thus chaotic phase changes. Since GD is the slope of the phase at any given frequency it also appear chaotic. This chart is not representative of the direct sound.
The spikes you are referring to; is it both positive and negative? 32hz neg, 100hz and ~200hz pos.
- The second GD chart has a 3 cycle FDW applied. This trace includes the first 3 cycles at each frequency so the later arriving room effects are filtered out. Note that there are still some strong room effects, but we can now easily see the trend of the direct sound. The large spikes in the GD trace indicate where room effects create nonminimum-phase conditions. EQ in these areas is very inefficient and not normally recommended. I find some EQ there to help the surrounding frequencies helps so long as it is done sparingly. Direct sound nulls cannot be removed, but some late arriving sound at those frequencies can be helpful to smooth the SPL. The spectrogram can show this better.
Would it be wise to increase the subs overall volume and then negative eq all above the target for minor boost in the 32 hz region? or what is the correct action in your opinion to handle the dip at 32-33 hz and spike at 43 hz? also spike at ~100 hz?
- The third GD chart has a 1 cycle FDW applied. In this case it shows the GD of the first cycle of each frequency. Because this is a very tight window it can sometime under estimate the phase rotation and thus GD a little. It is probably better to use a 3 or 4 cycle FDW and ignore any frequencies where there are spikes.
The conclusion then is that the GD of the direct sound was not significantly impacted by the addition of the EQ. The EQ boost filter at about 32 Hz removed the large dip with later arriving sound that was reflected around the room. We can point out that this is GD as it is late arriving sound so the first chart is indeed correct in that sense. Our choice is little or no SPL in those areas or more reasonable SPL albeit late arriving. We are much more sensitive to SPL irregularity than we are to group delay, but too much boost or too narrow filters can also cause sound quality problems also. I suggest moderation with EQ, but it is an individual preference.