‘True Stereo’ hardware FX used with hardware synths

[BillB]

I’m putting this in the synth section because, although it’s a question about FX, it really only relates to my synths.

I’m just arranging some synths/mixer/fx in a corner of my studio and wondering how to keep maximum sonic flexibility. Some of my hardware FX boxes are described in their manuals or other blurb as ‘true stereo’ (e.g Lexicon MPX110/500, Alesis Microverb, Digitech DL-8, SP-7, CR-7). I presume that means that the L/R Inputs are not internally summed to mono before being processed, and that the processing (say reverb or delay) responds to the stereo input signal in generating its output. It was a good while ago, but I am pretty sure I heard my Digitech Hardwire DL-8 delay repeats following the stereo input of a panned synth. Beyond that, I haven’t really played with my hardware FX to see what difference a mono/stereo input makes to certain types of processing. I like stereo panning on (some) synth patches, but also stereo chorus and phasing, so am curious about the likely interaction between these. An obviously stereo effect like ping-pong delay would do what it does irrespective of mono/stereo input, but others, like reverb, might respond differently.

The question also relates to whether to use something like a Lexicon on an aux send from a mixer (Mackie 1202). Advantage: all inputs have access to 2 Aux sends > FX units; disadvantage: the sends are mono. I have enough FX to stick something directly on the stereo output of each synth that doesn’t have FX - or decent FX, e.g. SQ80 (none), KingKorg (nice Mod FX but crap reverb), V50 (early digital FX much surpassed by even a Lexicon MPX110). So if I had a synth sound which panned L/R by envelope or LFO, would say reverb be likely to sound different if fed by either a mono (Aux send) or a stereo (direct from synth) signal.

Perhaps the answer is suck it and see, but I thought it would be helpful to ask the vast experience that is SOS what ‘true stereo’ means for hardware FX, and whether using an Aux send as a mono input might limit the potential of the FX.

Then there is the whole other question of whether the FX allows the dry signal to be fully killed, preferably with a simple wet/dry mix knob. The rack units generally do, the pedals generally don’t (I don’t have any Strymons!) Some Mod FX obviously need the dry signal killed (vibrato - others?) but I’m not sure about Chorus and Phasing - can the dry signal always be part of the FX mix, or are there some FX, such as stereo chorus/flange/phase, where only the ‘wet’ sound is heard, with no dry component? In which case, does any stereo (panning) element of the synth sound get lost? Or does that depend what ‘true stereo’ means for different devices?

Sorry for the rambling questions. It would be so much easier if I did everything in the box, but I like my chunks of metal

[Hugh Robjohns]

As you said, most effects hardware boxes, if they have dual inputs, sum them to mono before applying processing, and then combine the generated stereo FX with the dual inputs -- so any stereo effect or panning on the source remains in the dry element of the mixed output.

Mono summing for an effect like reverb is fine in most situations. If you think about someone stood in the middle of a cathedral, singing. They are a mono source generating a stereophonic reverberation field... just like a Lexicon or whatever!

However, some reverbs -- mostly the ray-tracing type, like some TCs -- claim to have 'true stereo' reverb, meaning that they genuinely process the left and right inputs separately and calculate the stereo output that would be created. This can be useful if you have a true stereo source with a wide image -- like an orchestra recording, say -- so that the generated reverb actually does take into account and provide something appropriate for the cellos on the right as opposed to the violins on the left...

Whether anyone is likely to notice such a subtle effect is open to debate... It's never bothered me! And for that reason, my Lex PCM90 and TC M-One are both fed from mono auxes... although both inputs of both units are available on the patch-bay should I decide I need to send in a stereo source one day.

[BillB]

Thanks Hugh, useful observations on reverb and, as you say, fine on a mono Aux send. So do you think ‘true stereo’ could mean either ‘true stereo processing’ as in the example you gave; or true passing the stereo input to the stereo output - depending on which manufacturer is talking about which bit of kit? Is there any well-understood definition?

Second question is back to the Mod effects. Can stereo chorus (etc) be driven from a mono Aux send without messing with the stereo imaging from a synth (e.g. panning)? I suppose I am wondering how much of the dry signal is output with a Mod FX, such that if you add say a chorus effect back to a mix, would a summed mono component affect stereo positioning?

Alternatively, put the Mod fx between the synths and the mixer?

[Hugh Robjohns]

... do you think ‘true stereo’ could mean either ‘true stereo processing’ as in the example you gave; or true passing the stereo input to the stereo output - depending on which manufacturer is talking about which bit of kit? Is there any well-understood definition?

In my experience 'true stereo' means genuine stereo processing of a stereo input source -- which is relatively rare in hardware processors. Passing the dry stereo input to mix with the stereo effects processor output is just a stereo pass through, and everyone does that.

Can stereo chorus (etc) be driven from a mono Aux send without messing with the stereo imaging from a synth (e.g. panning)?

Stereo chorus intentionally blurs and widens the stereo image. If panning is important you might be better to apply chorus to the mono synth and then pan the (stereo) chorus output. The alternative is to have a panned mono synth sound swimming about within a stereo chorus effect.

[James Perrett]

In my experience most budget gear will sum the channels but some gear will behave differently depending on which algorithm you use. I've found that on some kit reverb settings will sum the inputs while delay settings will be true stereo. You really have to read the manual to know for sure. Once you get up to the more expensive kit it will be true stereo all the way.

If you want to use true stereo on the auxes you are going to have to devote 2 sends to each effects unit - that's why 6 or 8 aux sends were common on larger analogue mixing desks.

[BillB]

You really have to read the manual to know for sure. Once you get up to the more expensive kit it will be true stereo all the way.

If you want to use true stereo on the auxes you are going to have to devote 2 sends to each effects unit - that's why 6 or 8 aux sends were common on larger analogue mixing desks.

Apart from throwing around phrases like ‘true stereo’ in the intro, I find that manuals don’t give much clarity on these points, but then I am using budget gear.
I have options to play with stereo sends (e.g. Alt3/4 on the Mackie) but will mostly stick to putting the Mod pedals before the mixer and the reverb on Aux sends.
Thank you for your thoughts, much appreciated

[Ben Asaro]

I would say it depends on what you are trying to achieve with using stereo effects.

If you are trying to widen out a sound, I would use a mid-side processor; it will work with a mono source and mono effect.

One way to get (pseudo?) stereo using a Mackie is to feed the aux out to an effect but bring the effect into unused channels and pan them however; I find this works well with delay and modulation effects, not necessarily reverb. That is, if you have available channels. Another alternative, if your Mackie has this ability, is to use the direct out from a channel, mult it, and bring it back into two unused channels panned left and right.

Dunno if you will find any of this helpful. I have a WORNG LRMSMSLR, which is a brilliant mid-side processor and works wonders for widening out sounds in a mix. It is, however, a eurorack module which means it runs VERY loud compared to line level sources; so you would need to plan accordingly.

https://www.worngelectronics.com/

[BillB]

Thanks Ben, mid-side is something I have read about over the years in SOS, but never tried - must get around to it! What interests me as regards stereo chorus is the way it can alter a sound as well as increasing stereo spread. I was really impressed with the examples here, taking nice but simple DX7 sounds and processing each one in turn:
Pads: https://www.youtube.com/watch?v=j1KTAkoAj38
Lead and Bass: https://www.youtube.com/watch?v=EbCwPemMQQ4

I appreciate it isn't something you want to do with *every* sound, but in places it is fabulous. Works particular wonders with otherwise cool FM sounds, and I have an SY77 and V50 in mind when thinking about this. Both have inbuilt FX, but they are not the greatest. However, they are both blessed with an "Effects off" button on the front panel.

The DX7 has a single output so in these instances acts as a 'mono' source. The V50 is 'sort of' stereo (fixed panning) and the SY77 has amazing stereo panning capabilities. So my above questions were around retaining the stereo movement, esp of the SY77, whilst being able to create a stereo chorussy overlay.

I also wondered how much difference a 'true stereo' processor might make, but from what Hugh said, very little in respect of reverb. The slight issue that leaves is that the Lex MPX's have really nice (if subtle) stereo mod FX, so might be better on a stereo signal than a mono Aux send. I think the Mackie has enough connections to let me play with options and find out how they sound, but this was just about hearing what the very experienced SOS-ers thought - for which I am most grateful

[Ben Asaro]

I will do some experimenting with my TX7 and mid-side chorus and reverb and post the results. (The TX7 has a mono out as well.) This will be fun!

[Ben Asaro]

Edit: You know, have you ever considered using a TC Electronic MIMIQ? It may yield some interesting results with various effects.

...

Okay, I just pulled my MIMIQ from my pedal case and will add it to tonight’s experimentation!

[BillB]

Didn't know MIMIQ existed - it looks interesting. The TC info is focussed on guitars, but as you suggest, it could be good with synths too

https://www.soundonsound.com/reviews/tc ... iq-doubler

[Hugh Robjohns]

If you are trying to widen out a sound, I would use a mid-side processor; it will work with a mono source and mono effect.

Just for clarity, a mid-sides processor won't do anything on its own with just a mono source.

You need to generate a 'fake' Sides signal of some sort -- which has to be significantly different in some way from the Mid signal -- to get any kind of stereo widening effect. So the original mono source has to be processed (by a mono effect) to create a fake Sides signal which can then be decoded with the original mono source as the Mid signal, to create a pseudo-stereo effect... I think that's what Ben is suggesting, but thought it might be helpful to spell it out for anyone less familiar with the idea.

The simplest technique aims to replicate the natural effect of a point-source (mono) sound being generated in a reflective room. If you imagine a vocalist in a chamber in front of an MS mic, a simplistic view is that the Mid mic captures the direct vocal sound, while the Sides mic only captures the vocal after it has bounced off the wall, and is thus delayed...

So to achieve something similar, simply split a mono source signal into two, passing one part directly to the Mid channel of an MS decoder.

The other part should be high-pass filtered (to avoid the low-end appearing only on the decoded left output), and then fed into a short delay -- anything from 10-100ms depending on the effect you're after. This signal becomes the fake Sides signal, and can be fed into the MS decoder's Sides input.

The MS decoder's left-right output will then have a sense of stereo width, the character and scale of which depends on the delay value and the relative level of Mid and Sides signals.

Other effects can be substituted for the delay -- mono reverb being an obvious upgrade! Mono-compatibility is always guaranteed, of course, which can be helpful, although the entire effect will also be completely lost to a mono listener, which might not be!

H

[Ben Asaro]

^ Yup, all of that is very true. Mid side is great for headphone listening, less great over speakers or in mono. I should have gone into greater detail, but was going to save that for when I have audio examples.

[MOF]

Mid side is great for headphone listening, less great over speakers

Why isn’t it great over speakers, are you confusing MS with binaural?

[Ben Asaro]

Mid side is great for headphone listening, less great over speakers

Why isn’t it great over speakers, are you confusing MS with binaural?

It's not as pronounced as some other stereo effects, imo.

[Drew Stephenson]

Hmmm. I might have to take issue with this. M/S isn't an effect, it's just a way of encoding a stereo signal. In itself it's no different to L/R - just different ways of doing the maths.

[Hugh Robjohns]

Quite so. Mid-Sides is just an alternative formatting of Left-Right with mathematical equivalence.

Probably, the reason its use as an stereo effect is 'not as pronounced' as some other types of effect is that, by definition, the stereo effect is created only by level differences between the two channels, whereas many stereo effects -- like stereo chorus, for example -- typically involve intentional time differences (as well as level differences) between the two channels.

H

[MOF]

Quite so. Mid-Sides is just an alternative formatting of Left-Right with mathematical equivalence.

Thanks Hugh.

[Ben Asaro]

Bill, here's my humble attempt at various stereo schemes using the TX7.

I used a total of three effects: two Lexicon Alex units, the TC Electronic Mimiq, and the WORNG LRMSMSLR.

Here's the audio, https://soundcloud.com/asfollowswriting/tx7-stereo-test

Here's a description of what I did:
(1) is the mono output of the TX7; (2) is the mono output from the TX7, multed, and put into each Alex on the same Chorus algorithm but set with slightly different regeneration times; (3) is the multed output into the TC Mimiq set for 1 dub and then into the Lexicons; (4) is the same, but with the Mimiq set to 2 dubs; (5) is the same but with the Mimiq set for 3 dubs; (6) is the TX7 going mono straight into the LRMSMSLR with a single chorus going through the mid-side processing; (7) is the TX7 going mono straight into the LRMSMSLR, but the mid-side is going from the chorus into a hall reverb.

Now, I know people were poo-poo'ing the idea of mid-side processing being an effect; and I agree, it's a process, not really an effect -- but I'll be damned if you can't hear it on these examples; it definitely creates a really interesting sound: it has stereo width but also a really strong center image with lots of low frequency girth. Adding the reverb makes it suuuuuper wide, however.

Anyway, I hope you find this useful.

[Drew Stephenson]

Just to clarify, i wasn't knocking the benefits of using m/s processing (preserving mono compatibility is one), just saying that the principle itself is just one of maths.

[Hugh Robjohns]

Now, I know people were poo-poo'ing the idea of mid-side processing being an effect; and I agree, it's a process, not really an effect -- but I'll be damned if you can't hear it on these examples; it definitely creates a really interesting sound: it has stereo width but also a really strong center image with lots of low frequency girth. Adding the reverb makes it suuuuuper wide, however.

Sorry... I'm still at a loss as to exactly what your processing chain is and what's feeding the inputs of the MS decoder...

But MS isn't an 'effect' or a 'process', it's a format conversion, plain and simple. The more you put into the Sides channel, the wider the image gets.

H

[BillB]

Ben, just to say thanks, I’ll give the demo a good listen.

[Ben Asaro]

Sorry... I'm still at a loss as to exactly what your processing chain is and what's feeding the inputs of the MS decoder...
H

Sorry, Hugh -- see a more granular breakdown below:

TX7 MONO OUT > LRMSMSLR LEFT IN
LRMSMSLR SIDE OUT > Lexicon Alex [chorus effect] MONO IN
Lexicon Alex [chorus effect] MONO OUT > LRMSMSLR SIDE IN
LRMSMSLR LEFT OUT > 18i20 INPUT #1
LRMSMSLR RIGHT OUT > 18i20 INPUT #2

^ That's the penultimate round in the loop. On the final loop, it's the same but with a second effects processor added with reverb:

TX7 MONO OUT > LRMSMSLR LEFT IN
LRMSMSLR SIDE OUT > Lexicon Alex MONO IN
Lexicon Alex #1 [chorus effect] MONO OUT > Lexicon Alex #2 [reverb effect] MONO IN
Lexicon Alex #2 [reverb effect] MONO OUT > LRMSMSLR SIDE IN
LRMSMSLR LEFT OUT > 18i20 INPUT #1
LRMSMSLR RIGHT OUT > 18i20 INPUT #2

[BillB]

And the Mimiq?

[Ben Asaro]

And the Mimiq?

When I used the Mimiq:

TX7 MONO OUT > MULT
MULT Out #1 > Mimiq MONO IN
MULT Out #2 > Mimiq STEREO IN
Mimiq MONO OUT > Lexicon Alex #1 [chorus effect] MONO IN
Mimiq STEREO OUT > Lexicon Alex #2 [chorus effect] MONO IN
Lexicon Alex #1 [chorus effect] MONO OUT > 18i20 INPUT #1
Lexicon Alex #2 [chorus effect] MONO OUT > 18i20 INPUT #2