A distorted preamp by itself is usually bright, thin and fizzy. Real guitar speakers are not full-range hi-fi speakers; their limited response is a major part of the familiar guitar tone.
Digital rigs use cabinet models or impulse responses, often called IRs, to reproduce that filtering. Cabinet simulation reproduces the strong frequency shaping of a guitar speaker, cabinet and often a microphone. It is a fundamental part of direct guitar tone, not a decorative effect added after the amplifier.
Speaker character
Different speakers emphasise different mids, bass and upper-frequency roll-off.
Cabinet size
A small open-back cabinet feels different from a closed 4×12 because resonance and low-frequency behaviour change.
Microphone position
A virtual mic near the speaker centre sounds brighter; moving toward the edge usually sounds darker.
Impulse responses capture a fixed response
An impulse response, or IR, records how a specific cabinet, speaker, microphone and position affect the signal. It is highly realistic for that captured setup, but it does not model every nonlinear behaviour of a moving speaker.
Guitar speakers are intentionally limited
They do not reproduce the full frequency range of studio monitors. Their roll-off, resonances and breakup remove harsh upper frequencies and shape the midrange that makes distorted guitar sound familiar.
Build the sound in stages
- Keep cabinet simulation on for direct headphones or recording.
- Change one cabinet variable at a time.
- Match output volume between cabinets.
- Do not run two cabinet simulations accidentally unless you want that filtered effect.
- Compare the same amp tone with cabinet simulation on and off at low volume.
- Try a brighter and darker cabinet while leaving every other control unchanged.
When the tone is not working yet
The direct tone is fizzy and painfully bright
Confirm that a cabinet or speaker simulation is active after the amp or distortion stage. A raw preamp signal is rarely intended to go directly to full-range headphones or monitors.
The tone is too dark
Try a brighter speaker, move the virtual mic toward the centre or reduce duplicate cabinet filtering.