*Racks* : Sweepable Crossover

ethios4 · Post by **ethios4** » Mon Oct 02, 2006 5:10 pm

EDIT : Here's the file for the Sweepable Crossover Rack. Assign a knob to "X-Over Freq" (Macro 1) of the top level rack to sweep.

Hey,

For my first project with racks I am working on building a multi-band crossover with just 2 bands to start out with. I am working on using 2 EQ8's in parallel to accomplish this, but I am having trouble setting the frequency and resonance for each the LP and HP filters I am using. I am wanting to use a Macro knob to sweep the crossover point if possible, so I suspect I will also have to make adjustments to the Max/Min values of the frequency of each filter.

Any tips on setting the correct frequency/resonance?

Once this is complete I will post the appropriate file so that this basic building block will be available to all!!

Thanks

(PS - For testing purposes I have been working with a white noise file)

melocoton · Post by **melocoton** » Mon Oct 02, 2006 5:35 pm

I didn't buy 6 yet and my beta just timed out but I got it working in 5. The crossover sounds pretty transparent if you have the Q of both filters set to 1 and the frequencies spread out by a few hundred Hz. In other words, if you set the high and lowpass to the same frequency cutoff you get a weird frequency boost where they overlap but if you spread them out a bit this dissapears. I have them spread out by 365Hz but that's just arbitrary. I tuned them by ear until the overlap went away. Hope this helps.

In this particular case I have the highpass set to 948 and the lowpass set to 583 and when I toggle it on and off there is little to no difference in sound.

ethios4 · Post by **ethios4** » Mon Oct 02, 2006 9:54 pm

hmm....I'm thinking I may have to lose the sweepable-crossover idea. The problem is that the only way to keep the frequencies apart by whatever amount is to set different ranges for the macro knob, which makes the scale of each frequency parameter different, and therefore the difference in frequencies will change as the sweep happens.

I'll keep tinkering with it and post the final product when it's ready, sweepable or not.

The reason for this project : I want to be able to have multi-band side-cahin compressors for DJ mixing, and be able to have an auto-pan generated gate effect on tap for mids and highs only. Little things like these...

melocoton · Post by **melocoton** » Mon Oct 02, 2006 11:27 pm

ethios4 wrote:The problem is that the only way to keep the frequencies apart by whatever amount is to set different ranges for the macro knob, which makes the scale of each frequency parameter different, and therefore the difference in frequencies will change as the sweep happens.

That sucks. If nothing else maybe you can figure out a way to make it switchable. EQ8 allows any band to be a high or lowpass right? So you could essentially make set 8 highpass filters at different frequencies and toggle different bands on and off. Maybe. I'm not really sure if that would work and I guess it would be a little too clumsy for live use.

ethios4 · Post by **ethios4** » Tue Oct 03, 2006 12:44 am

Interesting solution...that sounds like a pretty good workaround if I can't get the sweepable thing to work.

I'm leaving on our honeymoon tomorrow morning so I won't be working on this for a week, but when I come back....

melocoton · Post by **melocoton** » Tue Oct 03, 2006 7:10 am

The easiest way is of course to use 3 EQ Threes on three different chains of the effects rack. Each instance has just one of the bands turned on. The Low Cutoffs of all three are mapped to macro 1 and the high cutoffs to Macro 2. It works well enough. If you need more bands you can probably set a maximum high range for the high freq macro control and then add another triple set of EQ3 plugins with a constraint on the low range. Have a great honeymoon!

ethios4 · Post by **ethios4** » Thu Oct 12, 2006 4:10 am

That is such a great idea!!

I tried it out, and it works more transparently than I was able to achieve using EQ8s, but there is still some notch filtering. It is especially evident using the white noise test file. I am guessing that this is the "coloration" that some people dislike about the EQ3?

I will continue work on this until a usable version is found. At this point I am thinking of abandoning the sweepable crossover, and just have a fixed crossover at some usefull frequency(ies).

Thanks melocoton!!!

Robert Henke · Post by **Robert Henke** » Thu Oct 12, 2006 10:13 am

Tip:

If you want a totally flat frequency response, do this:

Take a lowpass filter, like one band of EQ-8, with a Q of 0.7.
The output of this one is your Low Out. Now take the output and subtract it from the original signal by adding it with inverted phase to the original. To invert the phase use the Utility device. This gives you the High Out. By cascading more of these you can create a 3 or 4 band crossover with moderate seperation but perfect flat frequency response and almost no coloration of the signal at the crossover points.
If i find the time I will post a Rack doing this...

Robert

Johnisfaster · Post by **Johnisfaster** » Thu Oct 12, 2006 10:24 am

jesus christ robert, you really are a mad scientist...

ethios4 · Post by **ethios4** » Thu Oct 12, 2006 3:52 pm

That is a beautiful solution!!

Thank you Robert!!

ethios4 · Post by **ethios4** » Thu Oct 12, 2006 4:53 pm

Here's the file for the Sweepable Crossover Rack

I used nested racks to achieve Robert's tip, which may not be the most elegant implementation of such an elegant crossover build, but it works with perfect transparency!! Yay!!!

So, to use this rack, assign a MIDI knob to "X-Over Freq" (Macro 1) of the top level rack. As you turn this knob you will be sweeping the crossover frequency.

To add an effect to just the high-pass part of the signal, add the effect at the end of the "High Pass" signal chain.
To add an effect to just the low-pass part of the signal, add the effect at the end of the "Low Pass" signal chain.

Have fun!!

longjohns · Post by **longjohns** » Fri Oct 13, 2006 1:22 am

thanks for posting the rack

ethios4 · Post by **ethios4** » Fri Oct 13, 2006 7:00 pm

bump!
I swear this is a useful building block!

Meef Chaloin · Post by **Meef Chaloin** » Sat Oct 14, 2006 12:42 pm

im not really sure what this is/what its for.
is it just so that you can add fx to high/low end seperately?

ethios4 · Post by **ethios4** » Sat Oct 14, 2006 5:41 pm

I use it for adding FX to highs or lows in a way that is very convenient for live performance. Most importantly, the crossover point can be moved at will, which makes it usable as a more interesting wet/dry knob. I use it for mangling the top end while the bottom end still kicks...fun on-the-fly remix technique.

Racks : Sweepable Crossover

Racks : Sweepable Crossover