Amplifire - Cab Bottom in Param EQ?

massless

Member
Messages
261
Does anyone know the exact specification of the Cab Bottom control? Can it be duplicated using the Parametric EQs?

I'm assuming its a simple EQ applied to the IR block or is it something more complex? If EQ, what kind of curve and Q is it?
 

Slapshot1977

Silver Supporting Member
Messages
751
I imagine it's an eq of some sort but why waste an EQ block on something that can be handled in the cab block?
 

Jay Mitchell

Member
Messages
5,643
Edit: As is the case with so many other Amplifire features, the general behaviors of the cab parameters are described in the manual (page 19). The following adds some detail.

I've been meaning to do this. I've just run some response tests. Here is a description of the functions of the filter parameters in the cab block.

Rolloff - 2nd order (12 dB/octave) Lowpass filter.

Peak Q - Edit: Please see my post below for a corrected explanation of this parameter.

Bottom - First order LF shelving, corner frequency approximately 250 Hz, 12 dB of boost or cut available.

Air - First order HF shelving, with corner frequency around 6.7kHz. Boost/cut operation is asymmetric, with about 9dB boost and 15dB cut.

My first suggestion would be to find IRs that sound the way you want with no tweaking, set Q to 1.1 and everything else to have no effect: rolloff at 20kHz, everything else to 0.

If you decide to make use of any of the cab parameters, bottom will be of greatest use, with rolloff possibly a close second. I would caution against ever setting Q above 4, because, even though the peaked response at almost 20k will not be audible with guitar (or with any signal through most systems), it can drive downstream devices into clipping and endanger HF transducers as a result.
 
Last edited:
Messages
238
My first suggestion would be to find IRs that sound the way you want with no tweaking, set Q to 1.1 and everything else to have no effect: rolloff at 20kHz, everything else to 0.
That is pretty interesting useful information. I have been setting my Q at 1.1 on all of my settings for awhile now, but I had no idea why other than that is where I liked it. Now I need to go and look up what exactly a 2nd order Lowpass filter is and how it works/what it does. I generally like to set the rolloff to something between 5 to 6, but I have no idea what that is actually doing? Thanks for running the tests and providing this information Jay!
 

massless

Member
Messages
261
I imagine it's an eq of some sort but why waste an EQ block on something that can be handled in the cab block?
Because I'm using both sets of outputs: one for FoH (cab IR) the other for regular guitar cabs on stage (no IR)

Ideally I'd like a separate 'filter only' to be available on one of the outputs as it's perfect for tailoring the bottom end of a guitar cab. I find AF is a bit light and middly into a SS power amp.

Thanks @Jay Mitchell, that's the info I was after.
 
Last edited:

Jay Mitchell

Member
Messages
5,643
I just did some more testing, because the apparent behavior of the Q parameter made no sense. It is the Q of the lowpass filter controlled by the rolloff parameter. Because I tested parameters individually, I had only looked at the behavior of Q with rolloff set to maximum (20kHz). With lower settings for rolloff, the parameter makes much more sense.

The setting for maximally flat is .7. This setting preserves flat response to the highest possible frequency before the rolloff begins. Settings lower than .7 cause a response that begins drooping below the rolloff frequency. Settings higher than .7 cause a peak just below the rolloff frequency. The higher the setting, the greater the magnitude of the peak, and the narrower the band of frequencies affected by the peak. For example, with rolloff set to 5kHz and Q set to 3, there is an 18-dB boost centered at 4.9kHz. This is pretty extreme, and Q may be set as high as 10. It is difficult for me to imagine any benefit from setting it higher than 2 or so.
 
Last edited:

massless

Member
Messages
261
The setting for maximally flat is .7. This setting preserves flat response to the highest possible frequency before the rolloff begins. Settings lower than .7 cause a response that begins drooping below the rolloff frequency. Settings higher than .7 cause a peak just below the rolloff frequency. The higher the setting, the greater the magnitude of the peak, and the narrower the band of frequencies affected by the peak. For example, with rolloff set to 5kHz and Q set to 3, there is an 18-dB boost centered at 4.9kHz. This is pretty extreme, and Q may be set as high as 10. It is difficult for me to imagine any benefit from setting it higher than 2 or so.
Interesting, my ears tell me that 0.7 is my preferred setting too. Now I know why.
 

JiveTurkey

Trumpets and Tants
Silver Supporting Member
Messages
19,711
Checking back in after finally tweaking the cab block settings to Jay's suggestions. I don't know if it is some sort of placebo effect or whatever; but I changed all my go to preset cab blocks to match. Before rolloff was @ 8.9 and Q was @.5. I changed rolloff to 20 and Q to .7 and I felt (and heard) the presets open up just a bit. Maybe I'm crazy :crazyguybut I like what I am hearing; even after that minor adjustment. I dig it :rockin
 
  • Like
Reactions: RGB

jaybird71

Member
Messages
81
Checking back in after finally tweaking the cab block settings to Jay's suggestions. I don't know if it is some sort of placebo effect or whatever; but I changed all my go to preset cab blocks to match. Before rolloff was @ 8.9 and Q was @.5. I changed rolloff to 20 and Q to .7 and I felt (and heard) the presets open up just a bit. Maybe I'm crazy :crazyguybut I like what I am hearing; even after that minor adjustment. I dig it :rockin
I was / am using .5 and moved the Q up to .7 today. It does "open things up" but after tweaking down the high end on a high gain patch to accommodate for this change I wasn't digging the sound. Tried .6 and ended up back at .5. I will definitely experiment with it on other sounds in the future, but for what I was doing and taming the brightness of the Amplifier using FRFR speakers it wasn't doing it for me. My 2 cents.
 

JiveTurkey

Trumpets and Tants
Silver Supporting Member
Messages
19,711
I was / am using .5 and moved the Q up to .7 today. It does "open things up" but after tweaking down the high end on a high gain patch to accommodate for this change I wasn't digging the sound. Tried .6 and ended up back at .5. I will definitely experiment with it on other sounds in the future, but for what I was doing and taming the brightness of the Amplifier using FRFR speakers it wasn't doing it for me. My 2 cents.
I actually forgot about tweaking it that way until after I had all my gear put away. I didn't get to crank it up as loud as I would have liked. I have some time this weekend and I am going to put it through it's paces; so I'll know how it flies at gig volumes after that.
 

Jay Mitchell

Member
Messages
5,643
I was / am using .5 and moved the Q up to .7 today.
Where have you set the cutoff frequency?

It does "open things up" but
Unless you've got the cutoff set to ~8kHz or below, you will not be able to hear the difference between a Q of .5 and .7.

but for what I was doing and taming the brightness of the Amplifier using FRFR speakers
The Ampifire is not intrinsically "bright." If a preset sounds too bright when played through a quality monitor, it's being caused by a combination of amp settings and choice of cab IR. It may occasionally be possible to alter the sound of a too-bright IR to your liking, but IME that is more effectively done (when it can be done at all) with PEQ than with parameters in the cab block.
 

jaybird71

Member
Messages
81
Where have you set the cutoff frequency?

Unless you've got the cutoff set to ~8kHz or below, you will not be able to hear the difference between a Q of .5 and .7.

The Ampifire is not intrinsically "bright." If a preset sounds too bright when played through a quality monitor, it's being caused by a combination of amp settings and choice of cab IR. It may occasionally be possible to alter the sound of a too-bright IR to your liking, but IME that is more effectively done (when it can be done at all) with PEQ than with parameters in the cab block.
I have been varying the cutoff between 7-8 kHz.
 

iam_krash

Silver Supporting Member
Messages
662
Jay...very valuable information.
I do have a question...some guidance would be appreciated.
Playing through a tube amp and real speakers presents a different challenge.
When attempting to roll off a bit of shrillness and top end...I find until I set the low pass to below 6k it has little effect...if I I set it below 5k it does finally tame the high end...but tone looses its realism and depth...my speakers are pretty neutral...thoughts?
advise?
 

Jay Mitchell

Member
Messages
5,643
Playing through a tube amp and real speakers presents a different challenge.
If, by "real speakers," you mean a guitar cab, you are correct. Since you really should turn off cab sims with a rig like this - there is no such thing as a "neutral" guitar speaker - the cab parameters aren't particularly relevant to your circumstances. You may want to try turning off power amp modeling as well.
 

iam_krash

Silver Supporting Member
Messages
662
If, by "real speakers," you mean a guitar cab, you are correct. Since you really should turn off cab sims with a rig like this - there is no such thing as a "neutral" guitar speaker - the cab parameters aren't particularly relevant to your circumstances. You may want to try turning off power amp modeling as well.
I've been playing with my presets and turning everything(cab ir/power amp ir)and playing with the PEQ in post...seems to work pretty well...
 




Trending Topics

Top