UTCTDA2030 LINEAR INTEGRATED CIRCUIT

8

QW-R107-004,B

MULTIWAY SPEAKER SYSTEMS AND ACTIVE BOXES

Multiway loudspeaker systems provide the best possible acoustic performance since each loudspeaker is

specially designed and optimized to handle a limited range of frequencies. Commonly, these loudspeaker systems

divide the audio spectrum two or three bands.

To maintain a flat frequency response over the Hi-Fi audio range the bands cobered by each loudspeaker must

overlap slightly. Imbalance between the loudspeakers produces unacceptable results therefore it is important to

ensure that each unit generates the correct amount of acoustic energy for its segments of the audio spectrum. In this

respect it is also important to know the energy distribution of the music spectrum to determine the cutoff frequencies

of the crossover filters(see Fig. 18).As an example,1 100W three-way system with crossover frequencies of 400Hz

and 3khz would require 50W for the woofer,35W for the midrange unit and 15W for the tweeter.

Both active and passive filters can be used for crossovers but active filters cost significantly less than a good

passive filter using aircored inductors and non-electrolytic capacitors. In addition active filters do not suffer from the

typical defects of passive filters:

--Power less;

--Increased impedance seen by the loudspeaker(lower damping)

--Difficulty of precise design due to variable loudspeaker impedance.

Obviously, active crossovers can only be used if a power amplifier is provide for each drive unit. This makes it

particularly interesting and economically sound to use monolithic power amplifiers.

In some applications complex filters are not relay necessary and simple RC low-pass and high-pass

networks(6dB/octave) can be recommended.

The result obtained are excellent because this is the best type of audio filter and the only one free from phase and

transient distortion.

The rather poor out of band attenuation of single RC filters means that the loudspeaker must operate linearly well

beyond the crossover frequency to avoid distortion.

A more effective solution, named "Active power Filter" by SGS is shown in Fig. 19.

The proposed circuit can realize combined power amplifiers and 12dB/octave or 18dB octave high-pass or

low-pass filters.

In proactive, at the input pins amplifier two equal and in-phase voltages are available, as required for the active

filter operations.

The impedance at the Pin(-) is of the order of 100

Ω,while that of the Pin (+) is very high, which is also what was

wanted.

10

2

10

3

10

4

10

5

10

1

0

20

100

40

60

80

Morden

Music

Spectrum

IEC/DIN NOISE

SPECTRUM

FOR SPEAKER

TESTING

Fig. 18 Power distribution vs.

frequency

Vs+

Vs-

3.3k

Ω

100

Ω

R2

R1

C1 C2 C3

RL

Fig. 19 Active power filter

R3