When making an Impulse Response recording, ideally you will have:
One speaker for each (speaker) location required by the chosen format, if you are going to be generating sine wave sweeps. As examples: If you are recording a true stereo impulse response, you will need two speakers; if you are recording a six channel surround impulse response, you will need six speakers, and so on. If you are not generating sine wave sweeps, you don’t need speakers to play them back (the sound is generated by the starter pistol).
Note: In many cases, it is sufficient to record one speaker position (but all microphone positions required by the chosen impulse response format), and create a mono/omni discrete impulse response. This will result in a less CPU-intensive impulse response in the required format. See Recording a Mono to Omni 5 Channel Impulse Response.
One or more microphones to record the resulting audio from each speaker (or your starter pistol) combined with its echo reflections. The number of microphones you will need depends on the chosen impulse response format. As examples; if you are recording a six channel surround impulse response, there are six microphone positions, so ideally you would have six microphones; if you are recording a six channel B-Format encoded impulse response—where only one microphone position and four tracks are required—you would need fewer microphones, and so on. See B-Format Surround Encoding for more information.
An audio interface that offers enough outputs to send a broadband audio sine sweep into each speaker (if using sine sweeps), and enough inputs to record the resulting audio from each position.
Note: You may also need additional microphone pre-amplifiers if you find that your microphones can’t capture a strong enough signal, or your audio interface doesn’t offer enough mic pre-amp inputs.