Monday, May 28, 2007

2. Driver linearization

Driver linearization. What is that?? Basically, when you apply crossover to the drivers, you are separating the drivers so that each of them is reaponsible for a ceratinly frequency only. The frequency part the driver is responsible is totally control by the crossover. For example, a crossover can control the mid so that it will only output the frequency from 500Hz to 1500 Hz. At both ends of the crossover is a slope. This is the area where one driver is being taken over by another driver.

However, as you can see in the picture, the area between the slope is a straight line. The crossover ASSUME that the driver will behave perfectly and will always produce 0dB within the crossover range. However, this is not true. Not many driver are as perfect as that. Driver linearization allows actualy measurement on the drivers and incorporate these characteristics into the crossover. In other words, when the driver is output less amplitude, the DSP will kick it harder so that the actualy outout will be 0dB, when the driver is output too much, the DSP will pull it down abit. So the final output will be as predicted. Please see the following graph of my crossover for mid driver after linearization.

You can see the the program has too "pull" my driver down a bit in order for it to produce perfect response.
Actual setting up:
This is more complicated and there are a few changes I need to make. At the moment, I am using UcD180 to drive the drivers. it just happened that Raven 2.0 is a ribbon and to DC, it is pretty much shorted. This will active the current protection of UcD180 and the amp will be muted. At first, I add the 27uF caps in series with the output of the UcD, I can play the tune but I heard a loud "pop" when I switch on the amp. This happens because the Ucd has 2V DC output when not loaded. The cap is charged up and was discharged when the /on is pulled to ground. To solve the problem, I replace the cap with a 2ohm resistor and all problem soved. But the tweeter is not not protected from the DC.... Lets pray.

It has been one month and the tweeter is still here!


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