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- Change Speed
The Change Speed Filter is designed for use in several applications:
The Change Speed Effect
The following is a summary of the control parameters and the range of adjustment provided for the Change Speed filter:
Curved Line (4 Green Cursors)
Constant (Start and End Track each other)
The Graph shows you how you have programmed the speed to change as a function of the selected .wav file time axis. You can use the mouse to drag the two green cursors to establish the time relationship that you desire. Often, a flat line is appropriate; however, sometimes the speed of the cutting lathe would slow down towards the end of the recording. The reason this occurred is that some of the early recording lathes used wind up mechanical motors with governors rather than electrical hysteretic synchronous motors. To correct this defect, a pitch decrease (negative pitch slope) is necessary towards the end of the recording. When the curve shape is selected, two additional green cursors appear. The new green cursors can be moved both vertically and horizontally allowing you to create numerous curvilinear pitch vs. time relationships. Curvilinear correction is useful for fixing the speed of non-capstan based tape recordings that have been transferred using a capstan-based machine. It can also be used to create interesting special effects when used in conjunction with the looped preview or looped play mode.
Use the following Formulae to calculate the % Pitch Change required when using fractional speed mastering:
Δ Pitch (%) = ((R/T) – 1)(100)
Wherein:
T = Actual Turntable Speed (RPM)
&
R = Rated Recommended Record RPM
(see the RPM Chart in the Glossary of Terms section of this manual to determine the correct recommended Record RPM)
One method for determining the pitch change required for a particular recording is to measure the line frequency “Hum” on the signal. This can be accomplished with your Diamond Cut Spectrum Analyzer. Deviations from the ideal values (50 or 60 Hz) can be compensated using the Change Speed feature by applying simple ratio proportions based on the measured hum frequency value compared to the ideal value.
Note: The Change Speed Effect will not appear in the Effects list if no file has been opened.
Automatic Change Speed Compensator
Sometimes, it is hard to determine what the correct pitch correction factor that should be used for a particular recording when the line frequency hum of the original recording can’t be discerned from other noise components. But, if you know the length of the piece, you can use the Automatic Change Speed Compensator to correct its pitch. Often, the time duration of a particular track is published in the liner notes associated with the recording. Simply do the following:
A. Make sure that the recording is trimmed carefully with no lead-in or lead out dead-time. You can always add back into the file some silence after the speed compensation process has been completed.
B. Click on “Set” and then enter the published value of time into the “Resulting Time” data entry field.
C. Run the filter and thereafter the pitch should have been corrected so long as the published time duration for the track is accurate.
This method can also be used to take a track that may be a little too short or too long for a choreographed performance and correct it per the contest rules (within reason). Another feature to consider for this type of situation would be the Diamond Cut Stretch and Squish time compression algorithm, especially if large time changes are required.
Note: The Automatic Change Speed Compensator should only be used in Straight Line Slope mode.
The Change Speed Filter is designed for use in several applications:
- It can be used to correct the speed of a recording.
- It can be used for fractional speed mastering. This feature is important in any of the following three instances:
- You have available a 45 RPM turntable but do not own a 78 or an 80 RPM turntable and need to play those formats.
- You want to play 80 RPM records, but only have a 78.2 RPM turntable without variable speed.
- Your turntable will play all speeds, but the record you are attempting to transfer is so warped that the stylus skips off the record due to the vertical undulations of the tone arm.
- It can make speech transcription easier by slowing it down to the rate at which you can scribe. Also refer to the Stretch & Squish filter for this functionality. Note: The Change Speed tool will alter the pitch of the audio, while the Stretch and Squish Tool will lengthen or shorten an audio file without changing the pitch.
- It can be used to produce interesting special effects.
- It can be used to “tweak” a musical piece to meet a contests time requirement for a choreographed performance.
The Change Speed Effect
The following is a summary of the control parameters and the range of adjustment provided for the Change Speed filter:
- Starting Pitch Control: -50% to +100%
- Ending Pitch Control: -50% to +100%
- Display Pitch Range (3 ranges):
- +/-1%
- +/-10%
- +100 / -50%
- Shape (Pitch vs. Time):
Curved Line (4 Green Cursors)
Constant (Start and End Track each other)
- Graphical linear or curvilinear Pitch inflection points (green square cursors on graph)
The Graph shows you how you have programmed the speed to change as a function of the selected .wav file time axis. You can use the mouse to drag the two green cursors to establish the time relationship that you desire. Often, a flat line is appropriate; however, sometimes the speed of the cutting lathe would slow down towards the end of the recording. The reason this occurred is that some of the early recording lathes used wind up mechanical motors with governors rather than electrical hysteretic synchronous motors. To correct this defect, a pitch decrease (negative pitch slope) is necessary towards the end of the recording. When the curve shape is selected, two additional green cursors appear. The new green cursors can be moved both vertically and horizontally allowing you to create numerous curvilinear pitch vs. time relationships. Curvilinear correction is useful for fixing the speed of non-capstan based tape recordings that have been transferred using a capstan-based machine. It can also be used to create interesting special effects when used in conjunction with the looped preview or looped play mode.
Use the following Formulae to calculate the % Pitch Change required when using fractional speed mastering:
Δ Pitch (%) = ((R/T) – 1)(100)
Wherein:
T = Actual Turntable Speed (RPM)
&
R = Rated Recommended Record RPM
(see the RPM Chart in the Glossary of Terms section of this manual to determine the correct recommended Record RPM)
One method for determining the pitch change required for a particular recording is to measure the line frequency “Hum” on the signal. This can be accomplished with your Diamond Cut Spectrum Analyzer. Deviations from the ideal values (50 or 60 Hz) can be compensated using the Change Speed feature by applying simple ratio proportions based on the measured hum frequency value compared to the ideal value.
Note: The Change Speed Effect will not appear in the Effects list if no file has been opened.
Automatic Change Speed Compensator
Sometimes, it is hard to determine what the correct pitch correction factor that should be used for a particular recording when the line frequency hum of the original recording can’t be discerned from other noise components. But, if you know the length of the piece, you can use the Automatic Change Speed Compensator to correct its pitch. Often, the time duration of a particular track is published in the liner notes associated with the recording. Simply do the following:
A. Make sure that the recording is trimmed carefully with no lead-in or lead out dead-time. You can always add back into the file some silence after the speed compensation process has been completed.
B. Click on “Set” and then enter the published value of time into the “Resulting Time” data entry field.
C. Run the filter and thereafter the pitch should have been corrected so long as the published time duration for the track is accurate.
This method can also be used to take a track that may be a little too short or too long for a choreographed performance and correct it per the contest rules (within reason). Another feature to consider for this type of situation would be the Diamond Cut Stretch and Squish time compression algorithm, especially if large time changes are required.
Note: The Automatic Change Speed Compensator should only be used in Straight Line Slope mode.