Help a newbie with some filters?

wingfeather · Jul 31, 2003, 03:41 PM

I've just started messing with EQ and filters to try and optimise my system for surround. Having just downloaded the ufx pack, I can say I like the parametric EQ, although the fancy graphics don't do it for me. Anyway, on to the problem...

I don't seem to be able to get the results I want from the EQ HighPass filter. Essentially what I'm trying to do is cut off everything below about 40Hz because I know my sub can't deliver it. The parameters of the HighPass filter are confusing - what does the parameter 'Width' mean? The number of octaves over which the response goes from -inifinity to 0dB? That sounds logical to me but it doesn't appear to behave that way.

All of the crossover/filter notation I've ever come across uses the crossover point (-3db point?) and x dB/octave for the slope steepness. Would it not be more logical to have filters using these parameters? I mentioned the ufx pack before - I've tried creating a high pass with this, but cannot get the slope steepness needed to cut off sharply (it seems to be limited to first-order or 6 dB/octave for the highpass type and 12dB/octave for the Low-S Shelf type).
In terms of filters, ideally I'd like a central EQ component for each channel with a frequency response curve in it, and the ability to add any number of EQ components such as EQ HighPass or EQ Notch. These components would then directly affect the response curve and it would be a lot easier to see what all those EQ components are actually doing.

Another thing I'd like to say is that I've been using Wave Generator 2.0 to listen to my altered response curves and it's next to useless for this purpose. Dragging the freq slider with the mouse gives a fast clicking sound over the top of the actual wave being generated so that it isn't even audible. Also, the frequency increments in more than 200Hz jumps, which is making things difficult. Instead of single frequency notes being generated, could it also be set to linearly/sinusoidally sweep the audio band over and over at various speeds?

Of course, I'm unable to program this stuff myself and am hardly in a position to criticise the excellent work the developers are all doing. This set of drivers is most certainly on a different level to anything Creative will let their paying customers have. From the rate at which things are moving now, eventually it will outperform, in terms of ease-of-use and features, many pro cards up to the limit of the kX DSPs. A wonderful achievement.

Sorry for the long post, and thanks to any who reply!

Wingfeather

Max M. · Jul 31, 2003, 06:36 PM

>I mentioned the ufx pack before - I've tried creating a high pass
>with this, but cannot get the slope steepness needed to cut off
>sharply (it seems to be limited to first-order or 6 dB/octave for the >highpass type and 12dB/octave for the Low-S Shelf type).

All filter types in EQP5 are 12db/oct... You may construct filter with higher slope just by setting several bands to same high-pass type with same cut frequency... (See for example "Brickwall - 22K" preset - there's about 60db/oct cutoff)

wingfeather · Jul 31, 2003, 10:29 PM

Cheers Max, a stroke of genius

The EQ P5 requires so few registers that you can have several running at once on the A2 without any problems.

Wingfeather

Lex Nahumury · Aug 9, 2003, 05:49 PM

Quote:

Originally posted by wingfeather
Another thing I'd like to say is that I've been using Wave Generator 2.0 to listen to my altered response curves and it's next to useless for this purpose. Dragging the freq slider with the mouse gives a fast clicking sound over the top of the actual wave being generated so that it isn't even audible. Also, the frequency increments in more than 200Hz jumps, which is making things difficult. Instead of single frequency notes being generated, could it also be set to linearly/sinusoidally sweep the audio band over and over at various speeds?

In regard to Wavegenerator2.0;
It's not that hard to code a freq. sweep or an exponential scale slider.
EYagos is the author of Wave gen2.0 . You could request him to implement such features.

In the mean time try; Rightmark Audio Analyzer.
Its free, has buid in sweep gen. and more.
You can make a quite nice freq.response plot with it.

/LeMury

Jul 31, 2003, 03:41 PM	#1
wingfeather DriverHeaven Newbie Join Date: Jul 2003 Location: UK Posts: 18 Rep Power: 0	Help a newbie with some filters? I've just started messing with EQ and filters to try and optimise my system for surround. Having just downloaded the ufx pack, I can say I like the parametric EQ, although the fancy graphics don't do it for me. Anyway, on to the problem... I don't seem to be able to get the results I want from the EQ HighPass filter. Essentially what I'm trying to do is cut off everything below about 40Hz because I know my sub can't deliver it. The parameters of the HighPass filter are confusing - what does the parameter 'Width' mean? The number of octaves over which the response goes from -inifinity to 0dB? That sounds logical to me but it doesn't appear to behave that way. All of the crossover/filter notation I've ever come across uses the crossover point (-3db point?) and x dB/octave for the slope steepness. Would it not be more logical to have filters using these parameters? I mentioned the ufx pack before - I've tried creating a high pass with this, but cannot get the slope steepness needed to cut off sharply (it seems to be limited to first-order or 6 dB/octave for the highpass type and 12dB/octave for the Low-S Shelf type). In terms of filters, ideally I'd like a central EQ component for each channel with a frequency response curve in it, and the ability to add any number of EQ components such as EQ HighPass or EQ Notch. These components would then directly affect the response curve and it would be a lot easier to see what all those EQ components are actually doing. Another thing I'd like to say is that I've been using Wave Generator 2.0 to listen to my altered response curves and it's next to useless for this purpose. Dragging the freq slider with the mouse gives a fast clicking sound over the top of the actual wave being generated so that it isn't even audible. Also, the frequency increments in more than 200Hz jumps, which is making things difficult. Instead of single frequency notes being generated, could it also be set to linearly/sinusoidally sweep the audio band over and over at various speeds? Of course, I'm unable to program this stuff myself and am hardly in a position to criticise the excellent work the developers are all doing. This set of drivers is most certainly on a different level to anything Creative will let their paying customers have. From the rate at which things are moving now, eventually it will outperform, in terms of ease-of-use and features, many pro cards up to the limit of the kX DSPs. A wonderful achievement. Sorry for the long post, and thanks to any who reply! Wingfeather

Jul 31, 2003, 06:36 PM	#2
Max M. h/h member-shmember Join Date: Dec 2002 Location: Evil Empire Posts: 2,606 Rep Power: 66	>I mentioned the ufx pack before - I've tried creating a high pass >with this, but cannot get the slope steepness needed to cut off >sharply (it seems to be limited to first-order or 6 dB/octave for the >highpass type and 12dB/octave for the Low-S Shelf type). All filter types in EQP5 are 12db/oct... You may construct filter with higher slope just by setting several bands to same high-pass type with same cut frequency... (See for example "Brickwall - 22K" preset - there's about 60db/oct cutoff) __________________

Jul 31, 2003, 10:29 PM	Thread Starter #3
wingfeather DriverHeaven Newbie Join Date: Jul 2003 Location: UK Posts: 18 Rep Power: 0	Cheers Max, a stroke of genius The EQ P5 requires so few registers that you can have several running at once on the A2 without any problems. Wingfeather