You can use a transient/starter pistol or a sweep.
With a sweep it must be deconvolved. maybe steinberg has their own version in house, or maybe they use deconvolver?
The two versions have pros and cons. And they do SOUND different, not immensely so, but the result will be different. The sweep beeing the more analytical and precise version, but it will also be a little bit time smeared because of the process itself. At least that’s my take on the difference, but I’m no full on expert. But I have recorded a few.
With a transient/starter pistol you get the result at once.
The recording can simply be trimmed and imported into the reverb as is.
But it is dependent on a really good recording situation, any noise will be reproduced through the IR all the time, so it puts high demands on a quiet recording area. And a high SPL from the “igniter” and in populated areas, in these days, this is quite likely to be a problem.
A sweep is a specific sweep that is created by the deconvolver tool. They can be set at different lengths and there are pros and cons to that as well. The longer the higher the “fidelity” but it takes more time to do the recordings and if anything goes wrong it takes a lot longer to do it again. If the environment changes over time then a long sweep will be affected differently over the frequency spectrum as it changes.
Then there’s the issue with IRs just recording high level responses if you use a starter pistol. With a sweep you can also record at lower spls to get more of a low level response of a room, like you have when two people talk.
Setting up IR verbs to create a realistic reverberation isn’t as easy as just loading a setting and go. If you really want realism you will have to use at least two.
Look at it like sampling with multiple velocities, it’s not enough to just record a hard hit of the snare and lowering the level. It’s the same thing with IR verbs, and so far there’s really no true solution to that apart from complex setups with several reverbs and where you have dynamic range splitters (gates) ahead of the verbs to mimic splitting the levels (velocities) to the different verbs (samples).
So you can see that there are reasons for why the folks that record IR needs to be quite proficient.