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TüN® 4: Creating Target Curves

A powerful feature of TüN® Software is the ability to create target curves. Targets can be viewed and modified individually and can also be summed which will display what would happen if those signals were added together. A common application for this would be a multi-way sound system. For example, if a user has a 4-way sound system (tweeter-midrange-woofer-subwoofer), a 4-way target can be built as a 'goal' to match the acoustic response to. If a user wants to understand how different filters affect frequency response, phase response or impulse response, they can be learn about these things using Targets Mode.

Switching to Targets Mode:

To create or load a target, switch to Targets Mode, by clicking on “Targets” which is located under the master mute icon, on the right side of TüN® software. Switching to Targets Mode will allow users to load and manipulate, or create their own target curves, using the same controls that are typically used for DSP control. While in Targets Mode, any adjustments made in the CROSSOVERS, DELAY/POLARITY, LEVEL TRIMS and EQ Panels will only affect the selected target and NOT the outputs of the DSP. To switch back to normal DSP control, select “Outputs” which is located right under the Targets Mode selection.

While in Targets Mode, the top of the CROSSOVER, DELAY/POLARITY, LEVEL TRIMS, and EQ Panel will be highlighted orange, in addition to the clickable Target button on the right side. Additionally, the lettered outputs and individual mute icons will switch to the list of targets (T_1 through T_S) and include icons to enable or disable each target and a checkbox to select if the target is part of the summed target response (T_S).

Screenshot 2023-10-10 at 4.13.06 PM.png

Image shows TüN® Software with Targets Mode selected

 

Loading a Pre-Defined Target:

JL Audio has included pre-defined target curves for 2-way, 3-way and 4-way audio systems, in addition to a few other helpful target curves. The default target files all share the same summed target shape but include individual targets for each channel/speaker. The default target curve is one that the team at JL Audio has used with great success for many years. T_5 - T_8 are targets developed by Nicholas Ames (Sr. Electro-Acoustic Specialist) and are also great curves to try.

To load a target for your system, switch to Targets mode and click the “Load” button near the bottom right corner of the screen, then select the desired target file. The default location on the computer for all target files is: Documents/JL Audio/TuN/Targets. Within the Targets folder is a subfolder called "Other Targets" which includes some other targets! The default target file name's include 2-way, 3-way or 4-way. A 2-way system is a system where there are 2 passbands that are used to play the entire 20Hz - 20kHz spectrum. For example, a pair of coaxial type speakers and a subwoofer. The subwoofer would typically play 80Hz and below, the speakers would typically play 80Hz and above. A 3 and 4-way system would be broken into passbands and follow the same principal. A 4-way system would typically have a tweeter, midrange, woofer and subwoofer. After loading a target, color coded passband specific targets and a yellow summed response will be displayed on the graph window. 

Creating a Target:

When creating a target curve, the user can define the the overall shape of the targets and determine how many individual targets create the Target Sum. When in Targets Mode, CROSSOVERS, DELAY/POLARITY, LEVEL TRIMS, and EQ Panel will affect the targets that are displayed in the graph window. Additionally, they will be highlighted orange and display “Targets Mode”.  To switch control from Targets Mode to control the DSP outputs again, select “Outputs” under the highlighted “Targets” button on the right side of TüN™ Software.

The targets color and trace style can be changed by navigating to the Input Combo Box which is located in the top right corner of a graph window and right clicking and selecting "Resave As" on the desired target name.

Establishing Filter Frequencies:

The first step to create a channel-specific target is to establish filter frequencies and slopes, which determines the passband of the channel. In the example below, T_1 will be for the tweeter, T_2 for the midrange, T_3 for the woofer and T_4 for the subwoofer, while T_S is the summed response of the checked targets. For this example, the following filters and slopes will be used for each individual target:

• T_1 (Tweeter) 24db LR HPF @ 5,000 Hz
• T_2 (Midrange) 24db LR HPF @ 400 Hz & 24db LR LPF @ 5,000 Hz
• T_3 (Woofer) 24db LR HPF @ 80 Hz & 24db LR LPF @ 400 Hz
• T_4 (Subwoofer) 24 db LR LPF @ 80 Hz


Screenshot 2023-10-10 at 4.00.22 PM.png

Creating a HPF for a tweeter channel target

 

If changes need to be made to a crossover frequency, using “HP/LP Tracking” will simultaneously adjust the frequency of the selected HP/LP filters. After selecting HP/LP Tracking, the user will have to designate the desired filters to change by clicking on the small 'dot' to the left of the frequency slot so that it shows up orange.

When choosing filter frequencies for the target, always confirm the speaker can safely operate within the target passband.

Screenshot 2023-10-10 at 4.02.29 PM.pngSummed reponse of crossovers in Targets Mode

 

After all of the passbands have been created, select the check box for each target in the Targets window on the right hand side. The checkboxes designate which targets add together to create the Target Sum.

 

Shaping the Target Sum:

After there is a full-range target curve (T_S) created by summing the individual targets, use the parametric equalizer to alter the shape of the summed target. Any changes made to T_S will also affect the individual targets. For example, making a cut at 10kHz to T_S would also make a cut at
10kHz to T_1 (tweeter).

To access the EQ Panel, select it from the bottom left corner of the graph window. There is also a Show/Hide button that will show or hide the EQ bands over the data within the graph window.

 

Screenshot 2023-10-10 at 4.03.58 PM.pngAltering the shape of the summed response with PEQ controls

 

Looking at Phase:
These targets are not only representative of frequency response, but also time (phase). The phase shift that occurs when a crossover is applied will be visible on the Phase graph. It is recommended to use 24dB Linkwitz-Riley filters for targets because they are very easy to work with.

For this example, let's look at the relative phase between T_4 (subwoofer) and T_3 (mid-bass), by selecting “Phase” from the Graph Type Combo Box. In the Targets Panel (bottom right corner), the other targets have been hidden by selecting the small image to the right of the target number. A red line will appear through the icon and the target will disappear from the screen when selected.

 

Screenshot 2023-10-10 at 4.04.32 PM.pngInitial phase response of T_3 and T_4's with crossover applied

 

The green target displayed within the graph window is representative of the Woofer and the purple target is representative of the Subwoofer. It is clear that the green and purple targets don't perfectly line up and overlap, which will impact the summed response. This happens due to the inherent phase shift of the crossover type being impacted by other filters in close proximity. The goal is to have the targets perfectly overlay one another from low frequency all the way to high frequency.

Select the undock icon for the for the Delay/Polarity Panel and engage the All-Pass Filter for T_4. This is done by selecting the icon to the left of the frequency field. Begin by typing in 20Hz in the frequency field, then slowly increasing the frequency of the APF until the purple (T_4) and green (T_3) traces perfectly overlay one another. When both phase traces perfectly overlay one another, they are properly in phase and this will improve the summed frequency response (T_S). 

Screenshot 2023-10-10 at 4.05.14 PM.pngPhase response of T_3 and T_4 after the all-pass filter is applied

 

Improving the phase response between the passband specific targets will improve the summed frequency response. The images below show how adding an APF to improve the phase relationship between T_3 and T_4, improved the summed response in that region by adding more energy between 80-300 Hz. Follow these steps for all other filter interactions (mid-bass & midrange and midrange & tweeter).

Screenshot 2023-10-10 at 4.05.55 PM.pngSum of T_3 & T_4 before aligning phase

Screenshot 2023-10-10 at 4.11.15 PM.png

Sum of T_3 & T_4 after aligning phase

 

Saving the Target:
After following the steps above, save the target by clicking on the Save button in the bottom right corner of the interface. Name the target and choose its destination, if saving outside the default location.

 

Default Target Curves:

If for any reason you lose/override/delete one of the default files, they are listed below.

 

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