Multiband compression is a normal tool in most producers’ audio toolkits that allow you to bring out each instrument’s unique qualities, but is also used by podcasters and broadcasters to give the impressive amount of body in the announcer’s voice.

I’m still studying the different effects of the various bands to mixing and mastering, so I’m probably going to leave the beginner explanation of these different bands to later.  However, for those who have read the book “The Mixing Engineer’s Handbook,” by Bobby Owinsky, they will have come across the descriptions of seven different bands of frequencies used to bring out the best in instruments.

1. Sub-Bass (20-60 Hz)
2. Bass (60-250 Hz)
3. Low Midrange (250-500 Hz)
4. Midrange (500-2000 Hz)
5. High Midrange (2-4 KHz)
6. Presence (4-6 KHz)
7. Brilliance (6-20 KHz)

A little more detail on the frequencies can be found here.

Jack has the benefit of being extremely flexible.  It has the ability to combine the multiple-instance capabilities of software with the advanced routing features of analog gear, and with the help of Jack Rack, the LADSPA plugin tool, we can actually jury rig a multi-band equalizer/compressor using three plugins.  In fact, why stop there?  With this setup, you can actually apply any plugin adjustments individually to these bands as you wish!

One thing to note: This will require a bit of work to get set up, and it’s not the easiest thing to use.  However, like hammers and screwdrivers, what this lacks in visual stimulation and easy settings, it makes up for greatly in sheer flexibility of control; each band will have its own compressor, amp, and anything else you care to add.

Creating the Multiband Compressor Project in Ladish

Upon creating a room for the compressor in Ladish, create a project for this.  Name it as you wish.

Creating Jack Rack Instances

Now, we want to create seven instances of Jack Rack.  To make each one’s settings persistent, we need to give each of those instances their own preset names, so we’ll need to make sure we use the command line setup.  In Claudia, you will need to use the “Custom” entry instead of the normal “Add Application” item.

In the “command” line, type “jack-rack” followed by the preset name you want to give the channel; avoid spaces, using a dash or underline as needed.  For the name, it may be best to keep it the name of the band we’re setting up.  Make sure you record the preset name, as you’ll need it again when you finally save the new preset.

Since Jack-Rack supports the LASH session protocol, I like to keep it set to that.

Now, you’ll notice that it will give you an error when it starts up.  This is normal; you have not saved the band preset yet.  This is fine, it won’t hurt anything, just go ahead and accept the warning.

The Plugins

Now, our first instance will handle the sub-bass frequencies, spanning from 20 Hz to 60 Hz.  In order to filter only these frequencies, we need to set up a bandpass filter, which will only allow those specified frequencies to pass.

There are only three bandpass filters available for LADSPA that are not tied to the top or bottom of the spectrum, and the best one is the Glame Bandpass Filter, found in “Add,” “Frequency,” “Filters,” and “Bandpass.”

Like all LADSPA plugins, it’s pretty ugly, but it gets the job done.

Now the Glame Bandpass Filter is in, but turned off.  Before we turn it on, let’s set the values.  You’ll notice that it does not show the start or end frequency, but instead shows “center frequency” and “bandwidth” options.  This took a little calculation, but here are the values you’ll need to know:

1. Sub-Bass – Center Frequency is 40 Hz, Bandwidth is 40 Hz.
2. Bass – Center Frequency is 155 Hz, Bandwidth is 190 Hz.
3. Low-Midrange – Center Frequency is 375 Hz, Bandwidth is 250 Hz.
4. Midrange – Center Frequency is 1250 Hz, Bandwidth is 1500 Hz.
5. Upper-Midrange – Center Frequency is 3000 Hz, Bandwidth is 2000 Hz.
6. Presence – Center Frequency is 5000 Hz, Bandwidth is 2000 Hz.
7. Brilliance – Center Frequency is 13000 Hz, Bandwidth is 14000 Hz.

I’m not sure exactly how the stages work, except that the more poles you have, the steeper the dropoffs are for the edges of the band.  I’ll just leave it at the default for now, until I know more… I’m satisfied with the result as it stands.  Once the settings are set, go ahead and enable the plugin.

Next, let’s save the preset; after this, this instance of Jack Rack will automatically load all plugins you have assigned to this band.  Simply click “Save,” navigate to the project directory you chose originally, and use the name we chose when creating the instance (such as my example of “Sub-Bass”).

Next, I add the other plugins I intend to use for this.  What you use is up to you from this point; keep in mind that Jack Rack only supports LADSPA plugins, and I’ve not seen another independent plugin host that can contain all the plugins you open in them (lv2rack is not very organized, and Carla isn’t self-contained right now; it won’t even start inside the project room).  An alternative is to use a DAW like Ardour or QTractor to hold the plugins in their own buses… I’ll leave that as an exercise to those who are interested.

To simplify matters for those who want to know what to use, I tend to prefer the Harris’s “Simple Amplifier” plugin, and the “Invada Mono Compressor” plugin.  The amplifier allows the band to act like an equalizer, while the compressor compresses the dynamic range of the band’s frequencies.

At this point, you save the preset, and move on to create the other instances of Jack-Rack using the above steps each time (changing the bandpass parameters and preset name).

Wiring

Now that the individual Jack Rack instances are set up, we now reach the point where the magic happens: wiring these individual instances together to make a 7-band whatever.

What you see in the above image is that the different bands are wired in parallel, meaning that the signal is split in seven ways for each channel, and rerouted to every one of the bands separately.  This means that all seven bands receive the exact same signals.  Once the signal is in each instance of Jack Rack, it uses the bandpass filter to throw out all bands that it has nothing to do with, and just works on its slice.  Once all seven bands are done with their slices, the signal is remerged at the other end by recombining the wiring into the output node, in this case, “Playback.”

Warning

This works, for the most part, but it is computationally intensive; you will want to limit this to mixing and mastering, so you can boost the Jack delay buffer.  Otherwise, you might get a burst of static at maximum amplitude, a particularly painful experience if you happen to be wearing headphones.

Conclusion

Even if you never use the multiband idea, this article has hopefully shown you just how you can make advanced audio routing in the Jack platform work for you.  Now, go forth and make something good!