Enhancer can be very useful!

[DLC86]

I'll report here what I wrote in the IR properties thread on TGP hoping someone else could find my idea useful:


A few days ago this thread gave me an idea on how to improve the sound of my 2x12 cab.

With that cab, depending on the relative position where I stand, I can clearly hear the comb filtering caused by the destructive interference between the two speakers.
But I think I've found a way to avoid (or at least reduce) that.

In the axe fx the modern mode of the enhancer block (and i think the stereoizer too) works by creating two complementary comb filters in the two audio channels.
Complementary in this case means that the comb filter on the L channel has the peaks where the R channel has the notches and viceversa.
Basically the output of one channel doesn't contain the frequencies that are present in the output of the other channel, but when the two are recombined (aka summed to mono) you get a flat frequency response again.

So I thought: if two nearby speakers, which normally interfere with each other, don't emit the same frequencies there can't be any phase cancellation.
Even though the sound coming from the furthest speaker will reach the listener's ears (if he's off-axis) with a slight delay, that won't cause destructive interference and he will hear the full (summed) spectrum the speakers can emit at that angle.
The cab will basically behave like a 1x12.

This seems to be proven by my unscientific listening tests, with the enhancer engaged the cab sounds bigger and its response seems more even across all the various listening positions.
This paired with the "mitchell donuts" I have in that cab seems to have improved quite a lot the dispersion pattern too.

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To make the discussion of my idea a bit more scientific I've made a simulation, within the axe fx, of what happens with the enhancer block and a 2x12 cab.
I used the synth block to generate pink noise and looked at an RTA plugin to see what happens in the various situations.

Here's the spectrum with no enhancer and no comb filtering, as you might expect it is flat:




Here is what happens when listening to a 2x12 in an off-axis position (I simulated this by adding a 1 ms delay on the right channel and then summing both channels to mono. 1 ms seems a realistic value considering the typical distance between the two speakers in a 2x12, but obviously in real world the comb filtering will be more complex than that cuz speakers are not point source emitters and there would be a volume difference between the two.. but you get an idea):




As you can see there are pretty big notches in the response, this means that those frequencies will be completely missing in that particular listening position.

Now let's see what happens when we add the enhancer block:




The big notches are gone. The response is not perfectly flat though, there's still some phasiness left.
As @yeky83 suggested me, this is caused by the fact that the comb filters created by the enhancer don't (and can't) have an infinite slope so there will still be some frequencies emitted by both speakers that can interfere, but in most listening positions they won't coincide with the nulls of the speakers' interference so they won't cancel out completely as, instead, it happens in every off-axis position without the enhancer.
IOW the sound seems to be a lot more even with the enhancer anyway.

The result also varies depending on the delay time used in the enhancer (which in the axe fx is controlled by the width knob), basically it needs to be substantially greater than the delay between the two speakers to work good enough.

I also recorded these short samples to show the audible differences between the three settings.




PS: I attached the preset I used to record the samples in case someone is interested in experimenting with that.

 

[AlGrenadine]

Yes, maybe that explains why i can't have a preset without enhancer, i'm addicted to it

 

[VidarAus]

Yes, maybe that explains why i can't have a preset without enhancer, i'm addicted to it

Me too. I often drop the enhancer at stock settings into my presets. It is amazing.

 

[Jarick]

Where is everyone putting the enhancer in the signal chain?

 

[AlGrenadine]

Where is everyone putting the enhancer in the signal chain?

At the end

 

[yek]

I'll report here what I wrote in the IR properties thread on TGP cuz someone else could find my idea useful

This definitely is something that I wouldn't do myself.
It takes the "life" out of the sound. And the posted clips seem to demonstrate this.

I use a traditional 2x12 with two different speakers on stage.
I'm not bothered by phase differences or whatever.
2x12's and 4x12's exist for a reason.
In the end, it's just sound and it's just rock'n'roll.

 

[PBGas]

I think I use the enhancer when I am using headphones and practicing. Gives it a bit of breathing room. Kind of like the Kemper has the headphone space feature......Live though, not really hearing it as nice on a high gain patch in stereo.

Again though, we all hear things differently and thus, you go with what works for you!

 

[DLC86]

Where is everyone putting the enhancer in the signal chain?

At the end usually but you can also try it before mods/delays/reverb cuz with some effects the sound changes a bit

It takes the "life" out of the sound. And the posted clips seem to demonstrate this.

Really? To my ears the third sample sounds much closer to the raw sound than the second one, I hear much more "life" with the enhancer on.

I use a traditional 2x12 with two different speakers on stage.
I'm not bothered by phase differences or whatever.
2x12's and 4x12's exist for a reason.
In the end, it's just sound and it's just rock'n'roll

I guess each one has his own preferences, for some those phase cancellations are an imprescindible part of the sound of 2x12s and 4x12s.
Additionally I don't know how it would work with two different speakers, but mind you my samples are just a "simulation".
I will repeat the measurements and recordings with a mic and my real 2x12 as soon as I have a bit of time and access to our rehearsal space.

If you already use a stereo power amp though, it's pretty easy to add the enhancer in a patch and judge for yourself if you like the result IRL.

 

[DLC86]

I think I use the enhancer when I am using headphones and practicing. Gives it a bit of breathing room. Kind of like the Kemper has the headphone space feature......Live though, not really hearing it as nice on a high gain patch in stereo.

Again though, we all hear things differently and thus, you go with what works for you!

If live you mean thru a stereo PA system I can see a few issues arising, especially with extreme settings.
In that situation all those which are not in a central listening position would hear one side louder than the other and it will sound a lot "phasy".
That simply can't happen in a 2x12 (with identical speakers) though cuz the two speakers are too close to have any appreciable volume difference, regardless of the listener's position.

 

[unFILTERed]

Did you put a mic in your position and record the real cab in your demo files? If not, what about the rooms impact on all those peaks and dibs caused by bouncing waves which would change for every stage/room/sutio etc. And also, most important part probably: We don't hear/listen with 1 ear like a Mic captures and i don't think you can demonstrate smth like this in the box.


I never heard a phase cancelation in studio, on stage...like your demo files (in the room/with my ears/from the cab). Yes, it can happen with a mic/recorded sound, but you also never put a mic at your listening/playing position . My 2cents

 

[DLC86]

Did you put a mic in your position and record the real cab in your demo files? If not, what about the rooms impact on all those peaks and dibs caused by bouncing waves which would change for every stage/room/sutio etc.

As I said earlier and as should be evident from the post/graphs that's just a simulation of what happens by listening to a 2x12 cab from a random off-axis position.
Obviously that simulation doesn't include ambience reflections, but even in real world if you want to take a significative measurement of a phenomenon you should try to isolate it by removing all other variables, otherwise it's a pointless exercise.
To do the same in real world I would need an anechoic chamber or a place large enough to capture reflection-free IRs but unfortunately I don't have any of those available.

Having said that, as soon as I have the opportunity I'll take real measurements with a mic too cuz, even though those peaks and dips will be somewhat masked by reflections, I expect a significative and measurable difference anyway, because I hear it.

And also, most important part probably: We don't hear/listen with 1 ear like a Mic captures

Yes that's true, but all that happens with two ears/mics, being them a at a slightly different angle and distance relative to the speakers, is that they will hear two slightly different comb filters, each with its own peaks and dips.

I never heard a phase cancelation in studio, on stage...like your demo files (in the room/with my ears/from the cab). Yes, it can happen with a mic/recorded sound, but you also never put a mic at your listening/playing position . My 2cents

I'm pretty sure you've heard it (probably slightly masked by ambience reflections) but you didn't know it was due to phase cancellations.
Ever compared the sound of a 2x12 and a 1x12? Ever noticed that the 2x12 sounds more "scooped"? Ever noticed that cabs with more than one speaker tend to be more beamy than 1x12s? All those things are caused by interference between the speakers and all I'm trying to do is reduce those "defects".

 

[Mutha Goose]

2x12's and 4x12's exist for a reason.
In the end, it's just sound and it's just rock'n'roll.

Just a side note, and useless (but interesting) trivia:

James Marshall has talked about how the 4x12 format came to be in a few interviews. It had NOTHING to do with acoustics, and everything to do with his own self-protection. As he tells it, his cabinet design came from John Entwhistle and Peter Townsend battling to have the loudest and biggest stage rig. This eventually led to an 8x12 cab. It was HEAVY! The roadies threatened to come after James if he didn't lighten the load. So he cut the cab in half. Then he angled the top one simply because he thought it looked better with the head on top.

And the rest, as they say, is history

 

[unFILTERed]

My experience is, i have a wider sweet spot if i use 2x12 instead of 1x12. Yes there is an inteference between the speakers but no where close to the in the box demonstration recording you posted. Still thx for sharing your thoughts, experiments...i just don't feel/hear like it adds smth and takes away actually...but as always, these things are subjective.

note: when i use 2x12 its actually 2 1x12 cabinets, side by side...i don't know how much this would impact, soon my 2x12 is coming, loaded with pulsonic greenbacks. Maybe i will agree with you once i play that.(chances are slim in my opinion) But that will also have 2 slighty different speakers. 1 is a 55hz green back 25 watt the other one is 75hz 20watt...