What is an Exciter?
An exciter (also called a harmonic exciter or aural exciter) is an audio signal processing technique used to enhance a signal by dynamic equalization, phase manipulation, harmonic synthesis of (usually) high-frequency signals. It also adds subtle harmonic distortion. Dynamic equalization involves a variation of the equalizer characteristics in the time domain as a function of the input. Due to the varying nature, it reduces more noise compares to static equalizers.
Harmonic synthesis involves the creation of higher-order harmonics from the fundamental frequency signals present in the recording. As noise is usually more prevalent at higher frequencies, the harmonics are derived from a purer frequency band. This results in clearer highs. Exciters can also synthesize harmonics of low-frequency signals to simulate deep bass in smaller speakers.
Treating master tapes
Although enhancers are often used during mixing and recording in order to treat individual tracks or sub-mixes, they are used as well during mastering process or post-production. A common practical example would be to treat master tapes. High-frequency enhancement can help to compensate for the loss of clarity inherent in mass cassette duplication. To a lesser extent, this process can add life to a poorly mixed master tape. Additionally, it can treat an analog tape master that has suffered a loss of high frequencies loss because of repeated playing, aging or minor head- alignment during the recording process.
Producers use Harmonic enhancement to make the lead vocal more intimate. However, it’s necessary to avoid sibilance as any form of high-frequency enhancement. Conventional EQ`s tends to exacerbate sibilance problems. Harmonic enhancers also work well on poorly defined drum sounds, electric pianos, and acoustic guitar. However, it is always better to use them to augment an already good recording then to rely on them to fix up poor recordings.
Harmonic enhancer history
When it comes to the history of harmonic enhancers, one of the first successful commercially available units was Aphex Aural Exciter first presented back in 1970`s. Aphex Electronics developed this effect in the mid-1970s. The Aural Exciter adds phase shift and musically related synthesized harmonics to audio signals. The first Aural Exciter units were available in the mid-1970s, exclusively on the rental basis. In the 1970s, certain recording artists, including Jackson Browne, The Four Seasons, Linda Ronstadt and James Taylor recorded their albums using the Aphex Aural Exciter.
Aphex started selling the professional units and introduced two low-cost models: Type B and Type C. Today, a growing list of manufacturers, including Yamaha, MacKenzie, Gentner, E-mu Systems, and Bogen are building the Aural Exciter circuit. The original Aphex Aural Exciter did not have the Big Bottom circuit. It was added in1992. Later revisions of the Aphex Aural Exciter included the Model 104 Type C and Type C2 units. Aphex released in 2001 the Model 204 Aural Exciter and Optical Big Bottom, yet another refinement of the original unit. According to Aphex, the Model 204 updates the Aural Exciter and Big Bottom processor blocks with improved circuitry. It also includes an optical gain-control element for the Big Bottom compressor.
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