Compressors with no accessible side chain filters and potential workarounds

[cashhewn]

Hi all, I’d love some help understanding something here…

I’m really confused about a response I got on another forum (a forum that is infinitely less useful than SoS in every way but is great if you care to hear subjective feelings about equipment).

I was suggesting that someone might want to think twice about getting a 33609 style compressor due to its lack of a user accessible, EQable, sidechain input. Sometimes I find my 33609 style compressor unusable for certain jobs due to its lack of a HPF in the sidechain.

Another poster responded to the effect of:

“You can use a ‘ghost plugin’ to trigger a hardware 33609. Put the 33609 as a hardware insert and a plugin afterwards with a key to the relevant track/bus, set your trigger, and have the plugin 100% dry.”

I can’t make any sense of this, can anyone advise? Regardless it seems like they’re talking about ducking a signal, not EQing the sidechain.

Also, ARE there any tricks/workarounds for compressors without accessible sidechain inputs? Seems like they would involve multing signals, treating them, and recombining them, in a parallel-like way…but I can’t get my head around it. I’ll typically just use a comp with an accessible sidechain.

Thanks all.

[Hugh Robjohns]

Yeah, that seems to be ducking the compressor output which is not the same as frequency-selective compression.

There is nothing you can do to make a compressor frequency selective without access to the side chain.

As always, use the appropriate tool for each job.

[cashhewn]

Thank you Hugh.

[Matt Houghton]

On the subject of the appropriate tool, there are 33609 recreations out there that feature a side-chain HPF. Stam Audio do one, for example. (Not recommending it, as I've not used it, but I do know of its existence!) Heritage Audio, BAE, Rupert Neve Designs... and more offer a diode-bridge compressor with a SC HPF, albeit not straight clones of the 33609.

Assuming you don't want to trade, or have your device modified, one thing you can experiment with is using pre/de-emphasis EQ. In other words, putting one EQ stage before the compressor — changing the input signal inherently changes the side-chain control signal, of course — and another after the compressor to restore the desired tonality. I don't recommend it — it's not going to sound the same as filtering the side-chain, and will likely lead to an increase in noise — but you can at least get the compressor to react differently that way and, well... nothing ventured, nothing gained!

[cashhewn]

Thanks Matt.

I hadn’t considered trying to EQ out the unwanted frequencies pre-compressor and then EQ them back in post-compressor. How unadventurous of me!

[Wonks]

Or use in a parallel compression mode with EQ only before the compressor?

[jaminem]

It would help to know what you’re trying to Do here, but since you’ve mentioned frequency dependent compression I’m gonna assume it’s some sort of ducking to stop say a baseline masking a kick drum?

If it is that, and I desperately needed to use a non frequency dependent side chaining compressor, I would use a dynamic eq with a side chain, keyed to the kick drum to duck the required frequencies before the compressor. So in my case because I use Cubase, I’d use the Frequency2 plugin to low shelf, keyed to the kick drum, so every time the kick drum fires, it ducks my selected frequency….

If it’s not that, er sorry I didn’t help….

[Hugh Robjohns]

It would help to know what you’re trying to Do here...

Explore options for making a compressor respond in a frequency-conscious way when it has no side-chain access or filter options.

The relevant context is:

I was suggesting that someone might want to think twice about getting a 33609 style compressor due to its lack of a user accessible, EQable, sidechain input.

Sometimes I find my 33609 style compressor unusable for certain jobs due to its lack of a HPF in the sidechain.

[cashhewn]

It would help to know what you’re trying to Do here...

I had a grand piano recording where I thought the upper register was poking out a bit much in certain percussive passages. I wanted to see if I could rein in/even out those peaks just a touch. I ran it through an available 33609-style compressor.

The piano was recorded in the same room as a drum kit simultaneously. The grand piano lid was completely removed and the harp was draped/covered with stand-supported sound blankets with small diaphragm condensers inside this heavy tent. This arrangement attenuated most all of the drum kit bleed surprisingly well.

However, I noticed that the kick drum was still bleeding through into the piano mics enough to trigger around four/five dB of unwanted attenuation in the piano part.

So in this instance I was lamenting that the 33609-style compressor I was using did not have an accessible side chain or even a simple sidechain HPF to have the compressor ignore the kick drum low frequency energy.

I patched in an available SSL-style compressor that had a HPF at (I believe) 60, 90, and 120 Hz. I think 90 Hz did the job I was looking for iirc.

I’m open to any and all thoughts/suggestions. I’m still relatively new at all of this. Thanks.

[Matt Houghton]

Well, the other option, if you're wedded to using a compressor with no side-chain control is to use a crossover so you can process only the upper register — feed the upper band to the compressor, and feed the low band and the compressor's output to a mixer of some sort. But you might run into phase issues on a clean, natural source like that, and it's a bit Heath Robinson... better all round just to use the right tool for the job.