DocID026803 Rev 1

5/29

AN4569

Overview

29

1

Overview

In the LCD-TV market the tendency to constantly reduce the thickness of thin-screen TVs

forces speaker manufacturers to design new components with very small dimensions.

The result of this process negatively impacts the quality of the sound reproduction because

the frequency response of the full range is very narrow and the sensitivity is quite low.

To reduce this issue, in high-quality LCD-TV sets the speaker system is often implemented

using a 2.1-channel active solution: 2 channels are dedicated to reproduce the mid and high

frequencies (for both left and right channels) while the lowest portion of the audio band,

usually below 200 Hz, is reproduced using a single large speaker (subwoofer channel)

enclosed in a suitable box. Each speaker is driven by a dedicated power amplifier (3 in total)

and the crossover filters are implemented using the DSP already present in the audio chain.

Although this solution should provide good performance, the audio quality the final user

perceives is not optimal because of the inferior quality of the speakers assembled in the TV

set.

configurations.

The standard application for this kind of device is a stereo BTL configuration for left and right

channels. There are other possibilities:

1. Two BTL channels (left and right) + third channel for external bridge;

2. Two single-ended for left and right channels + third channel in BTL;

3. Mono BTL configuration.

With this scenario it is possible to have a three-channel output using one or two devices.