Abbey Road Reverb Trick - Filter Placement Myth

It's commonly held that the filters in the Abbey Road reverb trick have to be before the reverb. This isn't true. See how the results with the filters pre or post reverb null to silence unless the reverb features modulation.
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[@hambone148]

HOWEVER, when the EMI engineers came up with this, whether they were using the chambers or plates, it would have been a tube amp driving the speakers in the chamber or the driver on the plate. If the low frequencies saturated, they'd create harmonics ABOVE the high pass filter, muddying things up. Placing the filters before that system would fix it. Placing them after the system wouldn't. At least that's my thinking.

[@rickhbrown]

I was literally just wondering about this today and discovered your video. Many thanks!

[@dikrek]

Not sure why this video was even made. The essence of the “trick” is to prevent reverberation of certain frequencies. Whether you do that before or after the reverb isn’t the point and I don’t think there was ever any huge debate about this. I use reverbs that have this functionality built-in, so I don’t even need to worry about this. I just tell the reverb to not process below and above certain frequencies. Where exactly that happens inside the reverb itself - I don’t know or care, the important part is taken care of. And let’s say most people EQ before. If it’s the same, why not keep doing it before anyway? Nobody has to change their templates. From a purely logical standpoint though, it does make a little more sense to not even send some frequencies to the reverb. That way you absolutely know what went into it, so no matter what the internal reverb tech is, you know it won’t even try with some frequencies because there’s simply nothing there. This may be more a factor with some reverbs than others, so why not just leave it like that?

[@silvansky]

The original trick was made for analog gear where the room itself could add resonances for some frequences. In digital world there is no difference because the simulation is too perfect. At least with no modulation. ;)

[@musician1971a]

I love it when audio engineering myths get busted!! This is one video to add to my links when the subject comes up in one of the many audio groups!

[@LanewoodStudios]

I made a recent video about this trick and also had assumed that it did make a difference putting the EQ before or after. Funny that it doesn't, except for with modulated reverbs. Great test!

[@moskva-kassiopeya]

I would say there is absolutely no difference even if there are some type of modulation because modulation just adds unpredictability hence it doesn’t null BUT our ears are unable to distinguish it from two different takes anyway.

[@tomw1970]

You saved me from commenting the same observation.

[@Pinkybum]

I just commented a similar thing. I think the unpredictability is the way the developer starts the cycle of the modulation. If it perfectly lined up between takes I think they would null.

[@jadedsean]

What i never understiood about this trick is, you always hear that paralell filters create phasing issues on a send but this doesn't? Why? I suppose it depends also on the steepness of those filters though, right? What am i missing here?

[@leesparey3595]

I think Dan Worrall did something similar on Linear and Non Linear plugins. As is mentioned below, if you are using a physical space, spring or plate the results might well be different.

[@Pinkybum]

I don't think it matters if you have modulation either. What is probably happening is the modulation has to have a cyclical starting point which will differ between takes. The different starting point will make it so that the reverb is slightly different however, this difference will not be noticeable for any particular single take. I'm not sure how you would test this out because it will depend on how the developer created the modulation algorithm.

[@josephmerrill2686]

Perhaps you busted the myth and didn't reveal all the nitpicky tests to prove the hypothesis about "modulation" but what I saw showed that it doesn't matter with plates and convolutions but it matters with halls. You manage to not rebuke your hypothesis with those tests but not quite a controlled experiment isolating "modulation". Two skepticisms: my ear always told me it mattered which doesn't trump null tests per se, but the issue here is my imperfect ears test does not necessarily get trumped by an imperfectly designed null test; reverb tends to get compressed to sound good and its hard to imagine low frequencies not affecting a compression detector. I just searched if any frequencies are created in the reverberation process and looks like no new frequencies are created by reverberation and that supports that idea that it does not matter as much as we may think. Uncompressed reverbs sound explosive and so its very common to have compression built into reverb presets.

[@user-sl4vo6mt5z]

Eq3 is bypassed during test

[@ProductionExpert]

It isn't. Bypassed plugins show as blue in Pro Tools.