Cabs and IRs
What an impulse response actually is, how one gets onto the Helix Stadium Floor, and why someone else's preset can load perfectly and still sound like the wrong cabinet.
What an IR is
An impulse response is a recording of what a mic'd speaker cabinet does to a sound. Someone plays a frequency sweep through a real cab, records it, and mathematically removes the sweep — what is left is the cabinet's fingerprint, which can then be applied to anything. It is the same idea as a convolution reverb, with a much shorter decay. In practice: it is a photograph of a specific speaker, in a specific room, with a specific mic in a specific place.
Cab block or IR block?
A Cab block holds two slots, and each can be a Guitar Cab, a Bass Cab, or a Cab IR — so "cab versus IR" is not really a choice here, it is a per-slot decision, and you can blend one of each. Adding an Amp block adds a matching Cab automatically, which is right into a full-range system and wrong into a real guitar cab. Turn that behaviour off from the Amp's sidebar if your rig always ends in a real speaker.
Helix Stadium Owner's Manual 1.3.2 · HX Edit Pilot's Guide 3.80Deleting an IR breaks the presets that used it
This is the Stadium's version of the problem, and it handles it far better than the numbered-slot approach: delete an IR that a saved preset references and that preset's Cab tab reads UNRESOLVED rather than silently loading the wrong cab. You get told. Tap the UNRESOLVED tab, choose a new IR or Cab model, and save the preset to keep the change.
Loading an IR
The Stadium holds up to 2,048 IRs and, unlike the rest of the family, keeps them as a named library rather than a numbered rack of slots.
- 1
Import through the Helix Stadium application
Free for macOS and Windows. The library lives on the device; the app is how files get there.
- 2
WAV only, and it normalises everything
Whatever the source file's length, sample rate, bit depth or channel count, it is processed internally as a 2048-sample, 48 kHz, 32-bit float, mono file.
- 3
Then pick it from the Model List
Tap Cab IR in the sidebar to jump to the bottom of the list, then 2048 IR, and your User Cab IRs folder shows everything you have imported by name.
A big import makes the next boot slow, once
Import several hundred IRs in one session and the next power-on takes a few extra minutes while the library indexes. It is not a fault and it does not happen again on subsequent starts.
Old Hybrid Cabs get converted
The Stadium does not include the Hybrid Cab models from pre-3.50 Helix firmware. Import a Helix or HX preset containing one and it is converted to a new Cab automatically — Line 6's own note says it may well sound better, and will certainly sound different.
A Clone does not add a cab for you
Amp Clone blocks do not offer the automatic Add Cab Block behaviour. If you captured an amp without a speaker sim or IR in the signal, you have to add the Cab block after the Clone yourself, or you are hearing an amp with no speaker.
IRs are in the backup
A microSD backup takes all your user data, IRs included. Restoring one overwrites what is on the unit, so the library goes back exactly as it was rather than needing a separate import.