One for RBJ if he's back from his hols :) or anyone kind enough to answer of
course...
Is there a way to modify the bandpass coefficient equations in the cookbook
(the one from the analogue prototype H(s) = s / (s^2 + s/Q + 1)) such that the
gain of the stopband may be specified? I want to be
On 4/01/2013 4:05 AM, Thomas Young wrote:
Is there a way to modify the bandpass coefficient equations in the
cookbook (the one from the analogue prototype H(s) = s / (s^2 + s/Q +
1)) such that the gain of the stopband may be specified? I want to be
able
I'm pretty sure that the BLT bandpass
The zeros are at DC and Nyquist because the numerator is s…Basically, you
need to adjust the zeros based on the pole positions (both angle and Q) and the
desired stop band spec. I'm not 100% sure what Thomas is after, but I suspect
it's just an inversion of band reject (swap the poles and
Thomas—it's a matter of manipulating the A and Q relationships in the numerator
and denominator of the peaking EQ analog prototypes. I'm not as good in
thinking in the s domain as the z, so I'd have to plot it out and think—too
busy right now, though it's pretty trivial. But just doing the gain
Thanks Nigel - I have just been playing around with the pole/zero plotter (very
helpful app for visualising the problem) and thinking about it. You guys are
probably right the simplest approach is just to scale the output and using the
peaking filter.
Additional optional mumblings:
I think
OK, I had (well, took) time to think:
You need to divide the numerator by the gain (A), and multiple the denominator
by the gain (aka multiply the numerator by A^2). That will keep the peak at
unity. Swap the numerator and denominator if you want the EQ to be symmetric
for cut and boost. If
Well, you're already working with rbj's equations, so just multiple the
numerator coefficients by A^2...
On Jan 3, 2013, at 1:05 PM, Nigel Redmon earle...@earlevel.com wrote:
OK, I had (well, took) time to think:
You need to divide the numerator by the gain (A), and multiple the
Glad I read this again—brain thought one thing, and fingers typed
another—multiply the denominator by A^2, not numerator.
Oh, and for cut…it depends on if you want symmetrical response or not, but if
you do, just swap a and b coefficients (yes, after multiplying by the A^2
factor so it ends up
sigh…hopefully my last post on this…
Sorry, I looked at rbi's peak spec and it is symmetrical—I was thinking of his
shelving filters, which need to be inverted for symmetry. So just multiply the
denominator coefficients by A^2 and you're done.
On Jan 3, 2013, at 2:02 PM, Nigel Redmon
Hi Thomas,
Replying to both of your messages at once...
On 4/01/2013 4:34 AM, Thomas Young wrote:
However I was hoping to avoid scaling the output since if I have to
do that then I might as well just change the wet/dry mix with the
original signal for essentially the same effect and less
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