Audiofrog A150.4D Manuale - Pagina 7

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Setup and Adjustments:

Crossovers: The primary function of a

crossover is to keep small drivers safe. The

secondary function of a crossover is to

provide an appropriate division of low and

high frequencies to ensure an inaudble

transition from one speaker to another.

In order for a speaker to play high frequen-

cies well, it has to be small and the dia-

phragm along with the rest of the moving

parts must be lightweight. Small speakers,

tweeters especially, aren't designed to

handle a lot of power. This is OK, because

most music doesn't contain a lot of signal

at the highest frequencies.

For tweeters, choose a high pass filter

frequency that's about twice the tweet-

er's free air resonance (Fs). You can find

that information in the owner's manual, For

midrange and midbass speakers, choose

a high pass filter frequency equal to or

higher than the speaker's free air reso-

nance. Speakers make the most distortion

at and around Fs, so avoiding that range

of frequencies is an easy way to make

your system sound better.

For subwoofers, we don't have any choice

but to use them around their resonance,

Fortunately, our hearing is less sensitive to

distortion at really low frequencies.

Using a high pass filter on a subwoofer in

an infinite baffle installation or in a vented

enclosure is very helpful in preventing over

excursion which sounds bad and will even-

tually destroy the speaker.

When using the crossovers in the A150.4D

and the A600.1D:

1. Be sure that the HIGH PASS filter frequen-

cy is set to a frequency lower than the

LOW PASS filter frequency.

2. Don't set a bandpass filter less than an

octave wide. The low pass filter frequency

should be set to at least two times the high

pass filter frequency.

3. The flter slopes in these amplifiers are

12dB/octave. 12dB/octave crossovers

change the phase of the signal by 180 de-

grees. Alternate the polarity of adjacent

crossover bands to fix this condition. For

example, if you are driving tweeters with

one pair of channels, midrange with the

other pair of channels and a subwoofer

with an A600.1D, connect the tweeters in

the proper polarity. Reverse the polarity of

both midrange speakers and connect the

subwoofer in proper polarity. This ensures

proper crssover performance.

Phase Control (A600.1D) Use the phase

control on the A600.1D to align the phase

of the subwoofer with the phase of the

front speakers. You can do this with an RTA

or by ear, if you don't have an RTA. The

setting that provides the most midbass

impact is correct.

Levels: The LEVEL controls for each

channel are intended to match the input

sensitivity of the amplifier with the output

signal of a radio or signal processor. In car

audio systems, we also use these level set-

tings to set the balance between different

frequency bands, to ensure that amplifiers

and speakers don't produce excessive

amounts of distortion and to minimize the

amount of noise present in the system.

There are many ways to test signals and

set levels and the appropriate process

differs depending on whether you're using

the speaker level outputs of a factory

head unit or amplifier, an aftermarket

radio witih preamp outputs or a DSP.

Please see the Audiofrog Tech Blog at

www.audiofrog.com for process sugges-

tions for these varous circumstances and

for system configuraton suggestions.

Never, under any circumstances, should

you use sine wave tracks to set your sys-

tem levels with the tweeters or small mid-

range speakers connected to the amplifi-

er. Doing so will burn the voice coils in an

instant. ALWAYS disconnect tweeters and

midrange speakers during this procedure if

you choose this method.