Re-Sounding

Recording & Mangling IRs

Back in March, on my last day at Blue Frog, my colleague Ishan Naik and I decided to record an impulse response of the studio lobby – a large space with a wonderful reverb. We had the choice to either use Apple’s IR utility (ships with Logic) or Altiverb’s own sweep generator and IR pre-processor. We chose Altiverb.

GEAR:

Preamps: SSL AWS900+
AD/DA: Prism ADA8XR
Microphones (near & far stereo config): Pair of Earthworks TC25 and AKG C414
Monitors (playback of the sweep): Dynaudio AIR 15 (stereo setup)

SPEAKER & MICROPHONE SETUP:

The first stereo microphone pair (C414) was placed about 5 metres away form the speakers (in line with the tweeter – AB stereo config). The second pair (TC25) were placed about 5 metres from the C414 pair.

Speaker/Microphone placement. Not the best photograph - clicked with my phone!

RECORDING:

We used a 10 second long sweep with 7 seconds of silence at 96KHz. The monitors were set at a comfortable level with no audible distortion and the preamps were set at a level that allowed for a few dBs of headroom.

RESULT:

Before playing back and recording the sweep, we recorded an apple loop played back in the space – so we would have something to compare our results with. Below is a comparison of the loop recorded in the space versus the loop processed with the impulse response for both configurations (C414 and TC25).

IR Comparison on SoundCloud

IR MANGLING:

It would be wrong to only stop at recording the IR! I decided to have some fun and imported the recorded sweep into Pro Tools and processed it with a variety of plugins. I then ran these processed files through Altiverb’s Pre-Processor to create presets. Additionally, I also processed a clean sweep (straight from the sweep generator) with a few plugins (Audiosuite and as automated inserts) to see what I ended up with. Some of the sounds surprised me and most of them would work well in creating abstract sounds and textures.

I used a sample from Tim Prebble’s awesome Seal library and from Frank Bry’s Bear Trap library:

Seal Convolved on SoundCloud

Bear Trap Convolved on SoundCloud

The processed IRs (about 23 of them) can be downloaded here:

Download Effected-IRs.zip (19.1MB)

Place them in your Altiverb IR folder and have fun! If you try making your own IRs or end up creating cool sounds with these do share them!

UPDATE: Now that I’ve figured out a way to translate sweeps to other plugins (new post), I’ll release a universal format for download soon.

Additional reading:

Altiverb Documentation
SOS: Using Logic’s IR Utility
JED’s Impulse Response AB Test on Sonic-Terrain

Tags | Altiverb, Impulse Response, IR, Sound Design