Comparison Pioneer GM-D8704 vs Pioneer GM-D8604

Rated power output by the amplifier per channel when a load (speakers) with a nominal impedance of 1 ohm is connected to it (for more details, see "Maximum impedance"). By rated power, conscientious manufacturers most often mean the so-called RMS (Rated Maximum Sinusoidal) — the highest output power at which the amplifier is guaranteed to work for an hour without damage; it is much less than the maximum value (see below for more details).

In general, the higher the rated power, the higher the sound volume that the amplifier can produce (ceteris paribus, including the characteristics of the connected acoustics). This indicator also determines compatibility with car audio: the speakers connected to each of the channels should ideally have the same rated power (in fact, a deviation of 10-15% is allowed).

Rated power output by the amplifier per channel when a load (speakers) is connected to it with a nominal impedance of 2 ohms. For details, see "Nom. channel power (at 1 Ohm)”.

The highest nominal load impedance (speaker) that the amplifier can handle.

Rated impedance (the term “impedance” is also used in acoustics) is one of the most important characteristics for the normal compatibility of acoustics and an amplifier: according to this characteristic, they must match. If the acoustic impedance is higher than the calculated one, the sound volume will be very low even if all other parameters match; if on the contrary, the sound will be distorted, and in the worst case, even the speaker may fail.

For a number of reasons, for car amplifiers, the maximum load resistance is traditionally indicated, that is, the maximum at which the device is still able to provide full sound volume. Standard values in car audio are 1, 2, 4 and 8 ohms. If the amplifier design does not provide resistance adjustment (see above), then the indicated maximum resistance is also the only permissible one. If there is such an adjustment, then the amplifier will be able to provide at least operation with the “neighboring” impedance value: for example, at a maximum resistance of 4 ohms, two-ohm speakers will also be normally supported. The specific “degree of freedom” in the adjustments for different models is different, this point should be clarified according to the official documentation.

The rating of the fuse installed in the amplifier is the current strength, at which the fuse operates, opening the circuit and de-energizing the device in order to avoid unpleasant consequences (see "Protection — Short circuit protection"). In some models, several fuses can be installed — in this case, this is usually directly indicated in the characteristics, and the current required to operate the protection corresponds to the sum of the ratings. For example, the rating marked "4x25 A" corresponds to four fuses that operate at a current strength of more than 100 A.

This parameter determines, first of all, the features of the power connection: it is desirable that the fuse in the corresponding section of the on-board network of the car be of a higher rating than in the amplifier, otherwise it may burn out at a current that is quite normal for the device. In addition, the fuse rating is related to the power rating of the amplifier and can be useful if you have doubts about the reliability of the data specified by the manufacturer. There are special formulas that allow you to calculate the maximum possible rated power depending on the fuse rating and device class (see above).