Description
If a filter is convolved​​​ with another filter the filter length doubles. Since the convolved filter needs to be the correct length for further use, Cut 'n Window allows it to be “trimmed” down to size.

Options:

• Length: Specifies the output filter length
• Position/Count: Together with the radio buttons to the right and the checkbox below, specifies where the new filter starts and ends
• Start position: If selected, Position/Count specifies the beginning sample of the new filter relative to the beginning of the input filter
• before Peak: If selected, Position/Count specifies the beginning sample of the new filter in samples before the peak of the input filter. Higher Position/Count therefore moves the first sample of the new filter to the left, or earlier in time, which is the opposite behavior to the case where Start position is selected.
• Before peak in area ! not allowed !: Don't select this option. [It allows the new filter to have a first sample before the first sample of the input filter. If you need this, you know who you are.]
• peak symmetric: The new filter starts exactly half its length before the peak. If checked, Position/Count is ignored.
• Remove DC: Removes any zero frequency components of the output filter. Usually a good idea to leave checked. (Leave it checked unless you have a specfic reason and know what you are doing. DC needs to be removed before filters are used to drive loudspeakers.)
• Window (Blackman Optimal): Occasionally needed when Cut 'n Window is used to shorten filters if the beginning or end of the output filter occurs at a time when the value of the input filter is significantly different from zero. In this case it removes spurious high frequency components that would otherwise be created, at the cost of some modification of the frequency response. However a filter so short inevitably leads to compromises.