Akiyama ARX-110 Manuale d'uso - Pagina 3

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ARX series. User manual

15 min, Read me!

Before unwrapping and starting your loudspeakers there are

a few thinks you should know...

Setting input levels at the mixer:

sensibility or so to speak the level of the input signal inside the

mixer. It is paramount to set the right input level on every

channel.

Why is so important setting the correct input level?

First, we have to understand the concept of Dynamic Range of

an audio signal. The Dynamic Range of an audio signal is

defined as the ratio between the maximum level before

distortion and the minimum audible level. It is measured in

decibels and gives us an idea of the amplitude of the signal.

Dynamic Range

Dynamic range

Ratio: Max. Level vs. Minimum audible level

We want the audio signal to fluctuate away from the maximum

level (distortion begins) and away from the minimum level (or

background level), where some noise is present due the

nature of the ICs used in the electronic circuit (all ICs induce

noise into the audio signal).

At the draw, we depict this "safe" level within two discontinue

lines.

We have to set the level of input signal so that the signal peaks

do not reach saturation levels and the lower amplitude parts of

the signal are not too near the background noise level.

We have to acknowledge that a professional audio system is a

serial bounded group of professional audio devices and that

saturation or other signal deterioration present in one device

will appear someway or another at the serial bounded

following devices.

Gain pot adjusts the input

Pic (Transient)

Electroacoustic Signal

Minimum audible level

Time

SATURA ION

SIGNAL

NOISE

If we deliver saturated signal from the mixer to the power

amplifier we will not be able to get rid of this saturation

whatsoever. The power amplifier will amplify all what is given

and if noise is given (saturation at mixer), it will be amplified.

Naturally, that is bad.

Power amplifiers and loudspeakers:

power amplifiers are quite reasonably protected against

signal deterioration and excessive levels and shortcuts.

Loudspeakers are not that well protected, hence a rule or

some must be devised to use the correct speakers with a given

power amplifier.

Well, that rule is not a straightforward statement but more of an

understanding of the principles and nature of the audio signal.

The nature of the audio signal reefer to the type of music you

are playing and more specifically of its Dynamic Range. The

bigger the Dynamic Range the bigger the power amplifier

needed. If the Dynamic Range of a give audio signal is big, the

difference between the minimum level and maximum level of

this audio signal will be big as well. Therefore, we will need an

oversized power amplifier with enough power to amplify the

maximum levels without reaching the saturation level at the

power amplifier (normally, power amplifiers have red LEDs to

let you know when they start saturating).

As a vague rule we can say that Rock and highly compress

music require a power amplifier delivering a power value

slightly bigger than the rated maximum power of the speakers.

However, we recommend the power amplifier rated power be

1.5 times bigger than the rated maximum power of the

speakers. Example: if the power amplifier rated power is 200W

RMS at 8Ω, the rated maximum power of the speakers should

be 200x1/1,5=133,4W RMS at 8Ω.

Using the power amplifier:

In order to make the most of your power amplifier you must

watch two things:

1- Set the volume controls in a way that the saturation LED

lights up only occasionally (peaks).

2- Feed the power amplifier with an audio signal of the

appropriate level. What is the appropriate level? Professional

Power Amplifiers are set for an input level of 4 dBu. Do not

panic, it is easy to get to it. 4 dBu is just a fixed measure of the

audio signal that professional audio community uses as

reference level, it can be expressed also in Volts 4dBu equals

1.23 Volt RMS. So to speak, the Power Amplifier will work at its

best if feed with a signal of a level near the 4 dBu or 1.23 Volt

RMS. How do we set this level? Easy, using the mixer

appropriately. Incidentally, the nominal level for a professional

audio mixer is also 4dBu. Therefore, if we set the master

output level of the mixer carefully monitoring the output level

meters (normally LED bars), we will ensure that the level of the

audio signal fed to the Power Amplifier is near 4dBu because

the nominal level of the mixer is 4dBu and we set correctly the

output level or the mixer.

Why we should avoid saturation?

Obvious reasons aside there is a more "material" reason.

Saturated signal can damage your speakers. Although some

speakers have overload protection, a highly saturated signal

can deliver D.C. and this phenomenon can easily shatter your

speakers.

Current professional

Saturation and input levels.