I-Mount

A proprietary tweeter mounting system used to simplify flush mount installation of tweeter in vehicles. This technology is found on JBL Reference and Kappa Tweeters.

Imaging

The effect of reproducing a sound stage faithful to that of an original recording. Represented, for instance, in the listener's ability to place a particular instrument at a single point, rather than to hear it as if spread throughout the sound field. Good imaging is often described in terms of channel separation of openness.

IMG

Injection Molded Graphite cones material used in JBL Beta Series Drivers. This material injects carbon fiber in the cone in a special radial pattern improving cone stiffness.

Impedance-Audio

A measurement of the resistance to the audio current by the voice coil of the speaker.

Impedance is a measure of electrical resistance specified in ohms. Speakers are commonly listed as 4 or 8 ohms but speakers are reactive devices and a nominal 8 ohm speaker might measure from below 4 ohms to 60 or more ohms over its frequency range. This varying impedance curve is different for each speaker model and makes it impossible to design a really effective "generic" speaker level high-pass filter. Active devices like amplifiers typically have an input impedance between about 10,000-100,000 ohms and the impedance is the same regardless of frequency.

Impedance-Electrical

The total opposition offered by a device or circuit to the flow of alternative current.

IMQ2

Cone material made up of a blend of Polypropylene and graphite for stiffness, with a quartz silicate added for damping of unwanted resonance.

In-Line Fuse

A fuse and holder incorporated into a length of supply wire .

Inductance

The capability of a coil to store energy in a magnetic field surrounding it. It produces an impedance to an ac current. Inductors are commonly used in audio as low pass crossovers.

Inductive Coupling

Radiated noise that is transmitted through a magnetic field to surrounding lines.This frequently occurs in long runs wire where power and signal cables are in too close proximity. This is a frequent source of noise and interference.

Inductor

An electrical component in which impedance increases as the frequency of the AC decreases. Also known as coils that are used in passive crossovers. Inductors are rated in Hennes.

Infinite Baffle

A loudspeaker baffle of infinite space that has no openings for the passage of sound from the front to the back of the speaker. Also, a sealed enclosure where the internal volume is greater than the Vas of the driver.

Infrasonic Subsonic Filter

A filter designed to remove extremely low frequency (25Hz or lower) noise from the audio signal. Useful for Ported box designs.

Input-Audio

The high level (speaker) or line level (RCA) signal connections that run into one component from another system component.

Input Sensitivity

is the SPL (Sound Pressure Level) a speaker will produce given one watt of power as measured from one meter away given a typical input frequency (usually 1kHz unless otherwise noted on the speaker). Typical sensitivities for car audio speakers are around 90dB/Wm. Some subwoofers and piezo horns claim over 100dB/Wm. However, some manufacturers do not use true 1W tests, especially on low impedance subwoofers. Rather, they use a constant voltage test which produces more impressive sensitivity ratings.

Input Voltage

The power voltage provided to an amplifier. While most cars can be expect to reliably produce 12 volts, amplifiers are sometimes measured at higher voltages; up to 15 volts. In this way, higher power can be developed, albeit at the expense of longevity. It is a practice that allows higher power figures to be claimed.

Insertion Loss

The loss of voltage (or power), as measured in dB, resulting from placing a resistor (or some other power absorbing network or component) between a voltage or power source (amp) and its load impedance (speaker.) It is the ratio of the voltage (or power) absorbed in the load without the resistor (or network) to that when the network is inserted. For example, if the voltage across a load is 2 volts without a network and 1 volt with the network, then the insertion loss is stated as 6 dB.

Instant Trigger

The term used to describe any trigger input on a security system that is designed to cause the system to respond instantly when triggered.

Insulation

A non-conductive protective covering for electrically active parts and wire that prevents short circuits and other unwanted interference.

Integrity

The expected durability of a component or connection.

Interconnects

Cables that are used to connect components at a low signal level. Examples include CD player to receiver, pre-amplifier to amplifier, etc. Most interconnects use a shielded construction to prevent interference. Most audio interconnects use RCA connections although balanced interconnects use XLR connections.

Intercooling-Audio

A design feature of JBL's GTi subwoofers that draws cooling air into the motor structure and vents out heated air.

Intermodulation Distortion

Distortion created by a device that is not harmonic with the original signal. Since it is not harmonics of the original signal, intermodulation distortion is often described as ""harsh and grating,"" and tends to be more noticeable than harmonic distortion. Intermodulation distortion is often the result of poor amplifier design or the use of excessive amounts of negative feedback in the circuit. Systems that are fatiguing to listen to often have high rates of intermodulation distortion.

Intermount

A speaker mounting system JBL has developed where a mounting ring is first fastened to the car and the speaker is fastened to the mounting bracket. This method not only allows for easier installation, but in the case of Intermount II, allows for the use of a larger cone in the speaker, creating added efficiency and bass response.

Intermount II

Is a mounting system that allows a single 6-1/2" speaker to fit into all four 6" hole standards. This is found on all JBL 6" models.

Internal Loss

The ability of a material to absorb unnecessary vibration or resonance. If unchecked, this resonance produces distortion.

Inverter

Takes the input signal and applies a 180º phase shift.

IR Filter

Infinite Impulse Response Filter - A digital filter employing a single stage, through which the signal is passed repeatedly to achieve the desired processing effect. Offers simplicity of design and lower cost than the FIR type.

ISO-DIN Mounting

Refers to a mounting system in which the headunit is mounted behind the dash panel with side brackets, employing factory installed trim panels.

ISO-DIN Mounting

Refers to a receiver mounting system in which the headunit is mounted behind the dash panel with side brackets, employing factory installed trim panels.

Isobaric

The mounting of two speakers in a way that will couple their output. This can be done by mounting the drivers in a back-to-front, or front-to-front (clamshell) arrangement with the drivers mounted out of phase with each other. This method of box construction allows the use of a smaller than normal box.

Isolation

Electrical or acoustical separation to prevent the spread of noise and the effect on the signal of unwanted elements produced by internal or external devices.