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 or below 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 limits, others 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 and can create undesirable sounds when the bowing motor is winding down.

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 (after touch, 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 in order to protect it).

The pressures hard limits, i.e. how far the bowing jack can physically move up and down, will sometimes have to be adjusted.

Mute limits

The mute also has three preset positions associated with it; mute rest position (lower soft limit), mute full mute position (upper soft limit) and mute half mute position. The mute rest position is where the mute is not touching the string even when it is resonating at peak volume and the mute full mute position is when the string is firmly clamped in between the upper and lower mute, quickly dampening the sound. The latter parameter is important because if set too high, i.e. if the instrument is trying to force the mute to go beyond the point where it is physically able to exert the required force, the instrument will will "loose track" of where the mute is actually situated which could result in strange unwanted behaviors. The mute half mute position is an auxilary position that can be set to do things like suppressing the fundamental, create pinch harmonics, or anything else your heart desires.

Just like with the pressure, the mute has two screws for adjusting the mute motor, however the mute also has an upper mute that should first be set to rest roughly 1mm above the string. Reset the mute position mechanically or use the configuration utility and press the "Reset rest position and go to rest position"-button in "Mute parameters". Slide the mute motor carriage to where the lower mute rests about 1mm below the string.

Hammer force limits

The hammer force limits are a little different than the previous limits discussed, furthermore the commands associated with the hammer are prefixed by the word 'solenoid' as this is the electrical device that actually causes the hammer action. The solenoid min force and solenoid max force parameters here are simply a convenience that makes it easier to control the instrument. A solenoid force of zero always means "no hammer action".

Solenoid min force is the lowest amount of force necessary for the hammer to hit the string and solenoid max force is the maximum force usable. The reason to set the minimum force is because without it, if mapped to for instance velocity of a keyboard, there will be a lot of "dead" values on the lower end where the hammer isn't reaching the string or even triggering the solenoid at all. The maximum amount is used because there can be an upper range where the increase of power to the solenoid simply doesn't audibly change the hammer hit, meaning the upper range would all sound the same. Another use of the upper range can be to limit the force due to the fact that certain strings, mostly thinner ones, will distort or just sound bad when hit too hard.

Tuning

Automatic calibrations