The Ekdahl FAR - Limits
Hard and soft limits, the range of possibilities and need for calibration
Before getting into the weeds of how to change strings and bowing wheels, you should know about the concept of hard and soft limits.
Within automated machining, a hard limit is simply a point beyond which a machine will not function - an example of a hard limit in the Ekdahl FAR is for instance the maximum speed of the bowing wheel; at a certain point the motor simply cannot go any faster. A soft limit is a point before the hard limit where the machine in question technically could go further, but beyond which it may not be reliable, could potentially run into trouble due to external circumstances, or simply won't provide any benefits. An example of a soft limit in the Ekdahl FAR is the maximum pressure of the bowing jack; at some point the bowing wheel can be pressed so hard into the string that the motor simply won't have the power to keep up, this could result in the motor not emphasizing the correct overtones, the string distorting - or worst case, the motor overheating and being destroyed�. A soft limit is placed before this point so that you won't run into these problems. All soft limits can be set by the user, but care has to be taken with limits that are there to protect the Ekdahl FAR. Other limits that are simply there to enhance the usability of the instrument can sometimes be tweaked to allow for "unmusical" behavior, which sometimes creates the most interesting sounds.
The Ekdahl FAR offers ways of automatically calibrating some of these features, certain other features will have to be manually set. Currently there are hard and soft limits for the pressure position, mute position and the hammer force.
Pressure limits
The bow pressure has three preset positions associated with it; bow pressure position rest, bow pressure position engage and the bow pressure position max. The bow pressure position rest is the lower soft limit and bow pressure position max is the upper soft limit. All of these presets can be changed by the user and saved into the instrument. The bow pressure position rest is where the bowing wheel is completely disconnected from the string, thus starting the bowing motor in this position will not cause any contact-vibrations in the string (though the string could still start to resonate due to air turbulence created by the bowing wheel). The Ekdahl FAR will normally stay at the rest position when no key is pressed.
Having the rest position correctly set is crucial in getting the most rapid action from the Ekdahl FAR, a rest position that is too far from the string will cause a noticeable latency from key press to wheel contact when playing, a position that is too close will result in the bowing wheel still touching the string when the bowing motor is winding down, creating an audible sound.
The bow pressure position engage is the point where the bowing wheel first makes contact with the string, this position is basically where the bowing wheel will normally go at a key press when all pressure modifications (aftertouch, pressure knob etc.) are set to zero. This position may or may not produce any audible sound as it should barely touch the string at this point.
Bow pressure position max represents the maximum soft limit, any added pressure at this point will be ignored as further pressure could make the bowing motor be unable to keep its speed or make it go over its power limit (which will cause the motor to immediately shut down).
The pressures hard limits can be set by loosening the two screws holding the pressure motor and sliding the carriage back and forth. This adjustment should rarely have to be performed as it should be pre-set, but if you change the height of the bridges, change into a string of a different thickness or a differently sized bowing wheel you may have to. The position of the carriage should be set so that when the bowing jack is at its lowest mechanical point, the bowing wheel is roughly 1mm away from the string. The easiest way to set the bowing jack to its lowest mechanical point is to use the configuration utility and click the "Reset pressure rest and go to rest position"-button in the "Basic bow parameters". This will set the bow pressure rest position to zero and tell the bowing jack to go to the bow pressure rest position. If the shield is taken off of the Ekdahl FAR you can instead, while the unit is off, rotate the corkscrew that controls the position of the bowing jack to its minimum position.