Hollywood Impulse Response Technical Notes

“Hollywood Impulse Responses (HIR) was inspired by the ambiences of 20 major Hollywood films released between 1977-2006. The musical scores for these films were recorded in some of the greatest recording studios, sound stages and concert halls in Hollywood and London. The sound of these films was designed to give the listener a “larger than life” listening experience, so often the actual impulses of these rooms are not accurate reproductions of actual acoustic spaces.

The source material in these film recordings often contained more bass and lower midrange power than comparable “normal” acoustic spaces, so the perceived size of the reverberant space is often much larger than these studios' physical dimensions would ever be able to create.

For an engineer to get this type of sound a pair of ambient mics would be placed a good distance from the orchestra (usually placed near the ceiling), routed to a digital reverberation unit and then EQ'ed before blending them with the dry signals into the final mix. This approach “samples” the natural acoustics of the room by capturing phase and delay differences between the direct sound and the ambient mics. When all of the dry and wet signals are mixed together, the resultant sound is huge. Capturing and making available to users the immensity and grandeur of the Hollywood film sound is the central focus of this library. Due to this additional signal processing, film ambience is more a composite reverberation impulse (CRI) which is electro-acoustic in nature.

Two Unique Features

There are two new features in HIR that are new to the word of ambience. First there is the addition of specially filtered RIs designed to adjust the timbre of the overall reverb sound when it is mixed in with the original dry signal. These filters are unique and do not exist in normal analog or digital gear. You have four variations of each RI to choose from: Dark, Warm, Flat, Clear and Bright. The Flat RIs are neutral and do not change the timbre of the source material.

The second new feature is the addition of 6 sets of RI's that are high pass filtered at points of the frequency spectrum that match the exact range of many orchestral instruments. These points are at notes C2, G2, C3, G3, C4 (middle C), and G4. These “instrument designed” RI's add much more sonic precision and clarity to existing sampled instruments and libraries. For example, RI's from the 04_G3 will exactly match the range of a solo Violin and optimize its tonal character. C3 will optimize Viola timbre and C2 will optimize the timbre of a Cello.

Three numbers are used to describe the "timbral" quality of each RI. These numbers give the user an indication of the relative length of the decay time of the bass, midrange and treble frequency bands. Every RI, regardless of the category, is referenced to the same hall with the average median of (Lo Mid Hi ) 100 100 100. For example, HIR no. 4 has a RI decay characteristic of 129 89 83 which means that the bass frequencies ring or resonate 129% more that the reference hall, 89% (or 11% less) in the midrange band and 83% (or 17% less) in the treble region. So, overall this reverb has a darker sound with more low end resonance. Remember that your source material has to have bass energy in order to hear the RI's effect on low end resonance.

Maximum Ambience for an Audio Sequencer

Once you've completed your arrangement, create several 100% wet tracks using your convolution program (Space Designer, Pristine Space or others), a dry track and the desired HIR to generate the ambience track. Make sure that there is no direct (dry) signal in the wet track. There are 5 different tones for each RI so you could have a Dark, Warm, Flat, Clear & Bright ambient tracks as well as other halls or other HIR pitches all at the same time. In the mixing stage you can use automation to mix the desired ambient track(s) in the final mix changing the levels and thus the tone of each individual instrument in the mix as well as having the tone “evolve” through the course of the mix by changing the levels of selected wet tracks.

All the reverberation impulses are digitally watermarked with a serial number so that each reverb impulse is traceable to the purchaser of this product. HIR ambience can be detected in a final audio mix.

RI File Name	Type of Hall	Location	Bass	Mid-Range	Treble
01_SmSndStg 02_SmSndStg 03_SmSndStg 04_MedSndStg 05_MedSndStg 06_MedSndStg 07_MedSndStg 08_MedSndStg 09_MedSndStg 10_LgSympHall 11_LgSympHall 12_LgSympHall 13_LgSympHall 14_LgSympHall 15_LgSndStg 16_LgSndStg 17_LgSndStg 18_HugeSympHall 19_HugeSndStg 20_HugeSndStg	Small Sound Stage Small Sound Stage Small Sound Stage Medium Sound Stage Medium Sound Stage Medium Sound Stage Medium Sound Stage Medium Sound Stage Medium Sound Stage Large Symphony Hall Large Symphony Hall Large Symphony Hall Large Symphony Hall Large Symphony Hall Large Symphony Hall Large Symphony Hall Large Symphony Hall Huge Symphony Hall Huge Sound Stage Huge Sound Stage	Toronto London London Los Angeles London London London San Francisco London Boston USA USA USA USA London Los Angeles UK Boston London London	68 77 84 129 113 95 138 112 94 87 110 114 108 139 115 129 102 183 181 154	78 80 93 89 90 102 96 102 99 120 113 123 130 107 123 132 126 133 156 197	90 93 102 83 81 119 97 127 101 128 116 117 138 125 120 124 118 135 128 200

User Guidelines (Just Suggestions!)

For Set 1 note C2 Full Range Instruments such as Doublke Bass, Cello & Tuba
For Set 2 note G2 Tympani, Trombone
For Set 3 note C3 Viola, Trumpet
For Set 4 note G3 Violin, Alto flute
For Set 5 note C4 Flute, Piccolo, Trumpet & Oboe
For Set 6 note G4 1st Violins, Percussion & Lead Instruments