Other ADA Gear > ADA Cabinet Simulaters
Favorite vintage ADA cabinet simulator
Casey_Butt:
I don't know how old this thread is because the board is not showing me the date, so forgive me if this is severely necro...
I like the MicroCabs because they can be modded to be more cab-like. On their own, none of the ADA cab emulators that I know of (I don't know about the new GCS's) are really that accurate to any actual cab responses I've seen. You could make the argument that the Ampulator has the closest and most sophisticated response (though it's very similar to the MicroCabs), but its notch filters are still a bit too extreme (as are the MicroCabs).
In practice, it doesn't matter too much though... because all of them still sound good and your ears really aren't that sensitive to the areas where they're 'weak' anyway.
But some simple mods can make the MicroCabs more cab-like. Another simple low-pass filter on the output increases its high-end rolloff to much more like an actual cab. And a simple resistor in series with the wire that goes to the cab selection buttons (one resistor for each channel) can adjust the frequency notches to more like a real cab.
There are lots more other things you can do to make the MicroCabs almost identical to a real cab frequency response (at least close enough that your ears couldn't detect the difference) but some of them get more involved and provide additional control 'options' rather than improve the ones that are already there. Just the simple additions mentioned above put the MicroCab responses closer than practically any of the analog cab sims available.
Here's a modded MicroCab with a slew of 'additions'...
That one has a switch for guitar or open-back (or bass) cab, a knob to adjust the cab resonance point from 125Hz to 240Hz (like a 4x12 to open 2x12), switches to tweak the mic types (bright, flat, mild to mimic the presence boosts some mics have), a mid-shift button to mimic Marshall style vs. American or German cabs, depth knobs that mimic the distance the mic is from the cab or the effect of multiple mics, and speaker baffle switches to mimic the effect of floating vs fixed baffles.
El Chiguete:
Rob get working on this!!!
MarshallJMP:
That sounds interesting.Can you give some more details?
Casey_Butt:
Sure. I took the frequency responses of the MicroCabs and compared them to dozens of actual cab frequency responses that I either took myself or collected from a host of sources (other people's cabs, the FFTs of cab impulses, Axe FX models, etc). Then I went about mimicking the responses of the cabs I wanted to emulate by tweaking the filters in the MicroCab and also adjusting some of its behaviours to be more accurate to the real things. The "extra" features, like the resonance adjust, baffle type, depth, etc, were put in to mimic cabs that the existing circuit couldn't do without affecting some of it's other cab settings... so adjustment ranges were needed and pots and switches added for that.
I also added another circuit board in the MicroCab that adds more frequency notches to the existing response. In stock form, the MicroCab has four major notches in the 4x12 settings. A real cab has many notches - four major notches are sufficient, but there are also other, smaller, notches that characterise the response. So I added 3 extra notch filters on an extra circuit board to match the cabs I was emulating.
But, the first thing that jumps out about the MicroCab is that its frequency notches (at points determined by the circuit) are too extreme. The Ampulator is the same; the MP-2 cab emulation is different. In practice, that doesn't matter a huge amount because the notches are very narrow at their peaks and only affect a narrow range of frequencies. But it's an easy "fix" (add a resistor), so why not do it? The next thing is that the MicroCab only has a 2nd order low-pass filter on the high-end roll-off. Cabs roll-off more aggressively than that. Some emulators have 5th order roll-offs but, from the real cab responses I have, that's too aggressive. Most cabs roll-off more like a 3rd or 4th-order LPF, and that's easy to achieve in the MicroCab by simply adding one cap in the right place (and forming a 1st-order LPF in series with the existing filter = 3rd-order).
I wanted to better emulate open-backed cabs (or large and ported cabs) so I could use it with bass and get a more authentic Fender response. So I added the cab type switch, which lets more bass through and attenuates the big resonance point that closed 4x12's have. 2x12's also resonate at higher frequencies than 4x12's (or, more accurately, they don't have a strong resonance point below ~240Hz), so I put in the pot to dial the resonance from 125 Hz (like a Marshall 1960B or big slant cab) to 240 Hz (like a typical 2x12).
The Mic switches are to account for the presence peak that some mics have (like the Shure SM-57), but others don't (like many condensers), and some are in the middle (like the original Sennheiser MD421).
Most closed-back cabs will have a major frequency notch at 500-625 Hz. The mid-shift button accounts for that by shifting the major notch in that region around by ~125 Hz. For instance, some Engl and Peavey cabs seem to notch lower, but Marshall and Mesa cabs usually mid-notch in the 600-620Hz range.
A single mic, up close to a 4x12 cab, will produce many deep frequency notches as the proximity of the speakers to the mic cause phase cancellations. But as the mic is moved away from the cab the response will smooth out. The summed response of multiple mics will also smooth out the response. So the "Depth" controls dial the depth of the frequency notches up and down to mimic mic distance and/or multiple mics.
Floating baffle cabs don't have a pronounced notch in the mid-frequency range. This is a large part of the reason why vintage cabs tend to be middier and honkier than modern cabs. Plywood baffle boards don't have as strong a notch there as MDF boards, either. So the "SPKR BAFFLE" switches control the depth of that notch to either be characteristic of a modern 4x12, a vintage style floating baffle board, or a plywood board 2x12/4x10.
I know that might all sound vague and arbitrary when laid out like that, so I'll try to post some example frequency responses.
Casey_Butt:
This is the response of a Peavey JSX 4x12 cab with four UK Celestion G12M-25 Greenbacks with an SM57 on-axis in the centre of the cap...
This is the response of a stock MicroCab...
This is the response of a modded MicroCab with the extra board added to produce the "mini notches". (All the "extra features" controls are set to neutral so they aren't affecting the response)...
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