More > JRiver Media Center 27 for Windows
Feature Request: Equalizer Improvements
Foggyroad:
--- Quote from: mattkhan on January 04, 2021, 04:52:49 pm ---I measured the effect of Q on high/low pass filters in MC and can say that jriver Q = actual Q / sqrt(2)
i.e.
jriver Q= 0.707 is a conventional Q=0.5
jriver Q = 1 is a conventional Q = 0.707
jriver Q = 1.414 is a conventional Q = 1
jriver Q = 2 is a conventional Q = 1.414
and so on
conventional in this case being the RBJ audio cookbook implementation of a variable Q high or low pass filter (assorted references online, one copy can be found at https://github.com/libaudioverse/libaudioverse/blob/master/audio%20eq%20cookbook.txt)
--- Code: --- omega = 2*PI*frequency/sampleRate
cos = cos(omega)
sin = sin(omega)
alpha = sin/(2*Q)
LPF: H(s) = 1 / (s^2 + s/Q + 1)
b0 = (1 - cos)/2
b1 = 1 - cos
b2 = (1 - cos)/2
a0 = 1 + alpha
a1 = -2*cos
a2 = 1 - alpha
HPF: H(s) = s^2 / (s^2 + s/Q + 1)
b0 = (1 + cos)/2
b1 = -(1 + cos)
b2 = (1 + cos)/2
a0 = 1 + alpha
a1 = -2*cos
a2 = 1 - alpha
--- End code ---
I do not know how this is implemented in jriver but it's definitely not going to give the results that anyone expects when using an external filter design tool unless they know to scale Q accordingly.
--- End quote ---
Yes, you are spot on, here.
Just to illustrate how the lack of a graphical representation of input to the PEQ can lead to large errors here are a couple of LR4 crossovers @120Hz. Both are constructed of two cascaded BW 12dB/oct. One (purple and red) has Q=1 and the other (green and blue) has Q=0.707 (actually 0.71 as JRiver will only allow 2 digits).
As @mattKhan has pointed out Q=1 is actually 0.707 and Q=0.707 is actually 0.5.
The difference between the two is not small.
wer:
Thanks Matt for adjusting the GEQ frequencies!
I'm hoping that will be the beginning not the end of some much needed improvements... :)
samtheman57:
I was very happy with the built in Graphic EQ, but just downloaded and tried this parametric plug in instead, HUGE difference, and easy to figure out. You do need to keep your volume low enough while adjusting.You need the 32 bit version of MC 27 for this to work as a plug in. http://www.rs-met.com/freebies.html
samtheman57:
Nevermind. It kept crashing the program. ::)
Foggyroad:
--- Quote from: wer on January 07, 2021, 01:37:59 am ---Thanks Matt for adjusting the GEQ frequencies!
I'm hoping that will be the beginning not the end of some much needed improvements... :)
--- End quote ---
+1 :D
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