![[Under Construction]](images/undercon.gif){kind=small}
Controls and Room Correction
INTRODUCTION
What would a state-of-the-art budget speaker be without some niceties and sophisticated room correction?
DESCRIPTION
For this part of the project I decided to use the Microchip PIC microcontroller as an all-in-one-chip low-cost solution. It forms the heart of this project, duties include:
 | LCD display |
| Remote control receiver |
| ADC and DAC |
| DSP room correction |
| Serial Communication |
Obviously, a budget chip serving so many functions has got to have certain compromises.
| Firstly, it is not a DSP chip, but it does have a hardware multiplier which reduces the computation time. |
| Secondly, a 20 point FFT (assuming) is going to limit maximum usable bandwidth to 1khz (Assuming 2x Nyquist Rate), thus limiting the possibility of correction only to subwoofer frequencies. |
| Thirdly, the program cycle causes an absolute phase lag, but that has been proven to be insignificant at subwoofer frequencies. |
| Fourthly, the raw SAR DAC input and PWM output will cause more distortion than a Delta-Sigma approach. However, the human ear is less sensitive to low frequency distortion so that remains to be seen (heard). |
| Lastly, serving other interrupts such as remote control will cause a lag, which will cause unpleasant noises. Alternatively, the subwoofer output can be muted during that period. |
The next few sections below will go into greater detail of the general design.
DSP Room Correction
The basic approach is to sample the measurement and store the response in memory. During normal operation, the input signal is superimposed on the stored response and output to the subwoofer. Further details are unfortunately a trade secret :o)
Remote Control
Under construction!!
LCD Display
Under construction!!
Digital Volume Control
Under construction!!
Serial Interfacing
Under construction!!