Difference between cab lo cut and amp speaker tab tone adjustments?

GazzaBloom

GazzaBloom

Inspired
could someone help explain what the difference is between adjusting the tone, hi/lo cut in a cab and making adjustments to the speaker tab settings in the amp models to roll off hi and lo end?

Also, what's the difference between adjusting the amp speaker tone setting and just using the amp GEQ?

What with most effects have the ability to tweak tone as well ther are so many ways to tweak bass mid treble!
 
My simple thought about is:
- hi/lo cut are pass-filters, so the cutted-out frequencies are no more in the signal.
- the EQs are a kind of frequencies mixers, the frequecies are there and you can mix them.
- the difference between EQs (from the tone controls of the amp, to the amp EQ, to - say - an EQ block) are mostly in the range of the spectrum and in the portion of the signal dipending of the location of the signal chain (pre/post inside the amp; the whole tone for a EQ block at the end of the chain or the tone of the guitar signal at teh star of the chain)
- then we have tone controls (EQs) inside single FX blocks (like say... reverbs, delays etc). That EQs works for the tone of that FX (i.e. if you have a good floating phaser or - say - a wha, but you think that those fxs are pushing the highs to much you can EQ those fxs, and only the fxs tone)
 
I've always assumed it was location, location, location. The speaker low/high cut are just more tone type controls, but in a different place in the signal chain, so presumably they will have a different impact on the overall sound.

I don't know what the technical difference would be, but I'd be willing to bet that the answer will boil down to something like, "Try the adjustments in both places, and see which you like better".
 
PacoCasanovas said:
The Speaker Tab adjustments were for the impedance curve of your speaker and the way the amplifier will react to it - this is not similar to regular tone controls. ;)
Click to expand...

OK I don't pretend to know what that really means but I do like a tweak so will explore further....
 
This means that depending on the real cab connected to a real amp the power amp will behave and therefore sound differently because it "sees" the connected cab. Since a cab block in the Axe is not a "real" cab this must be simulated, which is done in the speaker tab of the amp block. Ideally the adjustments there should be based on the real cab your IR was made of and your chosen amp model in the Axe. Typically you only need to adjust the low frequency value, because some power amps change their behavior more, some less depending on the connected speaker, which is already set by Cliff as default, which at least I never touch.
Unfortunately most commercial cab packs don't deliver such data, except those of cabir.eu. That's the only way to correctly simulate the interaction of a power amp and cab in the Axe!
 
GazzaBloom said:
could someone help explain what the difference is between adjusting the tone, hi/lo cut in a cab and making adjustments to the speaker tab settings in the amp models to roll off hi and lo end?

Also, what's the difference between adjusting the amp speaker tone setting and just using the amp GEQ?

What with most effects have the ability to tweak tone as well ther are so many ways to tweak bass mid treble!
Click to expand...


I'll give this a shot, but I must provide fair warning by saying that I'm no expert here.


Hi/Lo cuts in cab block: these are effectively hi and low-pass filters. Since these cuts happen after the mic simulation and cab simulation -- and therefore, after the amp sim too -- they affect the overall sound of what comes before. I use these to narrow the bandwidth of my tones, to remove unwanted hi and low frequencies that interfere or do not contribute positively to my final sound. There is no real analogy to using a "real" amplifier. These kinds of cuts would have traditionally been accomplished using hi and low pass filters in the studio after the amp was mic'd. These hi/low cuts affect the final tone, but don't have an affect on the virtual power amp or other aspects of the virtual amp.

The speaker tab is a way to model how a power amp reacts to the load of a speaker. There are lots of non-linear responses here. Out here in meatspace, we can compare two speakers and hear that they sound different, and most guitarists say "this has a different frequency response than the other one, that's why they sound different." And yes, that's true. But it's also true that the speaker makes the power amp respond differently.

There are some fascinating entries in the Tech Notes section, regarding speaker interaction. Here are two links, but you should know that there are several more threads concerning this topic that are worth reading.

http://forum.fractalaudio.com/tech-notes/78003-about-speaker-lf-resonance.html
http://forum.fractalaudio.com/tech-notes/81121-about-hf-resonance.html


Regarding the "eq" of the amp itself. That's a really broad subject, and of course, it gets even broader when you start looking at the differences in how amps are designed, and specifically what the designer did to the EQ section of the preamp, and where the EQ controls are located.

For me, I tend to think of the bass-middle-treble controls of a standard amp as gain-reducers set to a specific frequency. When I say "gain" here, I mean gain as an engineer understands it -- level, roughly. Not "gain" as in what guitar players normally think --- gain = dirt.

Think of a simple amp, one that has passive bass-mid-treble knobs. The knobs are connected to potentiometers whose jobs are simply to reduce the level of gain centered on a specific frequency and Q as set by the amps designer. With the knobs on "10" -- that is, full up -- they are allowing the maximum level for that frequency to pass. As you turn the knob down, the pot reduces the amount of gain centered around that frequency.

Because there are other things downstream -- other preamp tubes and/or diodes, the power inverter, the power amp and it's components -- the level of these controls not only affects the EQ, but the overall quality of the sound. For instance, it's well known that in several common amp circuits (many Mesa Boogies, for example) if you crank the treble controls on the preamp, that extra level cascades downstream and creates even more distortion and/or saturation. It's like an additional "dirt" knob, as well as a treble knob. IIRC, it even says as much in several of the Mesa Boogie manuals (which, totally off topic, are usually very well written, and often fun to read.)

So as you can see, turning up the "treble" control on a guitar amplifier may have much more of an affect on the sound than simply "adding high end". It's fascinating really. But it's also way more complicated than most guitarists want to consider, and amps work differently. Some have their B-M-T controls located in different parts of the circuit as compared to other amps, so these controls work in a fundamentally different way.
 
I will talk about low frequencies...
Did you ever play with EQ before the gain stage? If yes you will probably know that cutting bass before the gain stage is way different than cutting it after the gain stage. Why? Because if you use cut or boost bass before gain stage, you alter how much or less the bass is saturated/overdriven. I am talking about the gain stage because it is the most obvious place where EQ is so obvious.
The same can apply to the other EQ. Maybe you want to saturate the power section/OT of the amp with bass and than reduce it after it is captured at the speaker. It is different than starving the power amp from bass and add it later. Location is important becase we have non linear stages in our chain of sound. Each stage reacts different to EQ hence the abundent choice of EQ places.
I hope it makes sense...
 
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