Comparison Pioneer GM-D8704 vs Pioneer GM-D9701

The number of audio channels that the amplifier can handle. The smallest number is 1 channel(the so-called monoblocks); in the case of car amplifiers, these models are mainly used to connect subwoofers. At the same time, it is considered that the use of a monoblock is fully justified only at low-resistance loads (up to 4 Ohms), for higher resistances, you can consider connecting via a bridge circuit to a multi-channel amplifier (if the design allows it; see "Bridge connection").

Multi-channel models usually have an even number of channels — two or four(up to 8, but such options are rather the exception). However, there are devices with an odd number — most often this means that one of the channels is designed to connect a subwoofer.

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)”.

Rated power output by the amplifier per channel when a load (speakers) with a nominal impedance of 4 ohms is connected to it. For details, see "Nom. channel power (at 1 Ohm)”.

Rated power delivered by the amplifier to a load connected in a bridge circuit. For more information about the rated power, see "Nom. channel power (at 1 Ohm)”.

With a bridged connection, the speaker is connected not to one channel, but to two at the same time — the “positive” connector of one channel and the “negative” connector of the other are used. If the amplifier has a similar format of operation, then such a pair of channels operates in antiphase, due to which the power is summed up. This allows you to connect speakers to the amplifier, the power of which is twice the nominal power of the device: for example, at 150 watts per channel, 300 watts of acoustics can be bridged. If there are 4 or more channels, it becomes possible to use several speakers according to the "bridge" scheme. This is usually directly indicated in the specifications — for example, the entry "2x300 W" in the "Bridge connection" item means the ability to work with two speakers, each with 300 W.

The requirements for load resistance when connecting with a bridge are the same as for conventional; see "Maximum Resistance" for details.

The highest output power provided by the amplifier. It is worth noting that this indicator is not standardized, and different manufacturers may mean different values \u200b\u200bfor it — for example, the highest power of short-term, in a fraction of a second, peaks (power surges), the highest power that the amplifier can transfer for several seconds, or even the power at which the device will fail. Therefore, it makes no sense to compare different models with each other in terms of maximum power. But when choosing acoustics for an amplifier (or vice versa), this parameter can be very useful: it is desirable that the maximum power of the speaker be at least twice as high as that of the amplifier. This will reduce the risk that a power surge will damage the speakers.

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 range of audio frequencies that the amplifier is capable of processing. The standard hearing range of the human ear is 16-20,000 Hz, but for some people these limits can be much wider. In addition, low-frequency vibrations, already inaudible to the ear, but extremely close to the lower threshold of audibility, are perceived by the entire surface of the body at high sound power, which creates the impression of the most saturated sound (although care must be taken with this, because infrasound can have a bad effect on well-being).

In general, the wider the frequency range of an amplifier, the richer the sound it can provide. However, this is not an unequivocal guarantee of high sound quality — a lot also depends on the amplitude-frequency characteristic, signal-to-noise ratio (see below) and other features of a particular device. Yes, and the connected speakers must also correspond to this range — otherwise the signal will be "cut off".

Also note that many monoblocks (see "Number of channels") have an upper range limit of only a few hundred Hz — these models are designed for use with subwoofers, and high frequencies for them would be an unnecessary overkill.

One of the main parameters that determine the sound quality of the amplifier as a whole: it describes the ratio of the useful signal (in other words, “clean” sound) and various extraneous noises. This takes into account almost all noise — both due to external causes (for example, electrical "pickup"), and created by the device itself (for example, due to heating during operation). Accordingly, the higher the signal-to-noise ratio, the less audibility of various interferences and the clearer the sound is obtained (of course, under normal operating parameters). The average for car audio is 95-100 dB, but in advanced models this value can be significantly higher.

At the same time, this parameter is not critical for monoblocks designed for subwoofers — most of the interference is high-frequency and will simply not be heard on the low-frequency speaker. The sound quality in this case is highly dependent on the characteristics of the speaker (much more than in multi-channel models), and is weakly related to the “noiselessness” of the amplifier.