SPAN

Honestly, there is no reason why you shouldn't get this plugin. I know you might think you don't need it or you already have a spectrum analyzer in your DAW either as a plugin or inside one of your EQ's but SPAN is different.

I used Ableton Live's own Spectrum plugin as well as the spectral analysis in EQ Eight before, and I liked it. Used it to find annoying frequencies but also harmonics. But there were two problems in terms of that I couldn't zoom in an area I needed more in-depth visualization and to have the spectrum analyzer at a certain place on my screen.

Now with SPAN it was possible to zoom in when you hold down [ALT] and place/resize the GUI whereever/however I want since.

But I didn't know that it offers so much more.

It is possible to look individually at the Mid or the Side channel (Mid-Side Stereo mode) or Left or Right channel (Dual Mono). A heavy feature for mixing.

You also have the option to listen to a specific frequency band by holding [CTRL] or [CMD] while you dragging around the cursor, which also helps to find problematic frequencies by ear.

Then you got the Meters to the right and bottom side, which helps you take control over the volume and Mono compatibility of your mix. But you also can hide them.

As a Voxengo plugin, you furthermore can costumize the GUI visually in the settings of the plugin to you likes. Especially for an analyzer a very good feature.

If you want to take control and get a visual help, SPAN is the way to go and it's completely free.