U.S. Amps Bass Mekanik Owner's Manual And Installation Manual - page 6
BRIDGING YOUR U.S. AMP
All U.S. Amps listed in the following section can be used in the BRIDGED mode, meaning that both
channels of the amplifier are used together as a powerful single channel, usually to drive a group of
subwoofers. Since subwoofers come in a wide variety of types and impedances, U.S. Amps
makes different groups of amplifier models to work best with specific speaker systems. To get the
most power from your amp, match it by model and code to one of the following diagrams. Great
care has been taken to optimize your amplifier’s performance when wired as recommended, so
please follow these diagrams carefully. The on-board SAT “SMART AMP TECHNOLOGY”
protection circuit on the USA-150, 300, 700T, and 2000 types carefully monitors and records
amplifier performance, including the suitability of the load in comparison with the amplifier type.
Think of the speaker as an electric motor and the Amp as the wall-current that makes it “run”. The
two principals in fact, are very similar. All speakers have a motor, consisting of the permanent
magnet at the rear of the speaker and a “voice coil” that attaches to the speaker cone and rides
back in forth in the center of the magnet. Just like a motor you would plug into the wall and say,
vacuum the floor, the amp powers the voice coil which in turn reacts to the permanent magnetic
field by pushing and pulling against it. The resultant motion moves the speaker cone and wall-la!
You have sound! (Normally U.S. Amps wouldn’t care about speakers, but we have been asked to
explain this function in greater detail-Harrumph!)
Each voice coil has a resistance, or impedance, that is crucial to the way it reacts with a given
model of U.S. Amps and vice versa. This resistance is measured and expressed in OHMS, or
Put simply, OHMS are the things that keep the amplifier speaker leads from
shorting together, which is a no-no. The less OHMS a speaker has, the closer the electrical
potential of the amplifier will be to shorting.
Speakers are typically available with 8, 4, or 2 ohm coils. There is a great deal of difference
between these ratings, as with the order of magnitude of the numbers 8,4, and 2 themselves. As 4
is TWICE as much as 2 and 8 is TWICE as much as 4, the amount of current an amplifier must
provide to drive a 4 ohm speaker is TWICE that required to drive an 8 ohm speaker, a 2 ohm coil
requires TWICE the current of a 4 ohm coil. While all this seems academic, is nonetheless of vital
importance, and is perhaps the most overlooked and unfortunate reason for expensive system
failure. Just like an electric motor and the wall socket, it is possible to stack more motors on the
circuit than it can handle.
Before you form the opinion that higher current amps are obviously better, forget it. High current is
simply a way to get power under a different circumstance. All amplifiers have current and voltage.
Really, one comes at the expense of the other, but they are both equally effective at delivering
power. “Power” is measured in WATTS, like a light bulb, and is the product of a mathmatical
equation that takes into account the current and voltage output of the amplifier in relation to the
resistance, or OHMS of the voice coil or voice coil combination. (Impedance is another word for
resistance, and the two are often interchangeable.) Let’s totally geek out together and examine
this formula, as it will help you understand the role voltage and current play in relation to speaker
impedance and power:
SPEAKER MYSTERIES EXPLAINED
HIGH CURRENT OR HIGH VOLTAGE?
Ohms of resistance.
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