User’s Manual for JBL CBT Calculator Version 1.00 100312The CBT Calculator is a precision engineering tool, allowing audio professionals to design CBT Constant Beamwidth Technology™ line array column loudspeakers into a wide variety ofvenues. The CBT Calculator shows the vertical coverage, sound level capability, and evenness of coverage of either one or two CBT speakers, set to various settings, in a room with up to 4 independent listening planes. This calculator provides the resulting SPL vertical coverage mapping of a proposed design, and computes the frequency response of up to 6 listener locations as well as an SPL summary ofthe microphone locations over user-defined frequency bands. Installing the Software – If you already have a previous version of CBT Calculator on yourcomputer, the software should uninstall it automatically. I that doesn’t occur, then please uninstall all previous versions using the Windows Control Panel to Add/Remove programs. Unzip the file you were provided into a directory and then run the “setup.exe” program. Yourcomputer will need to have the latest version of Microsoft .NET 3.5 (the installer will download this automatically if your computer requires an update). JBL’s CBT Calculator requires a PC with Windows XP or newer. System Design Example Shown in This Manual -- The system design example we are using in this manual shows a venue with a CBT 70J+70JE array system covering a main seating area with slightly raked seating and a CBT 100LA mounted higher up on the same front wall, covering a balcony. We are looking at the frequency responses and SPL sound levels from 5 microphone locations. We are not necessarily recommending this as the best solution for this venue, but rather it is a display that allows us to run through the various functions of the CBT Calculator for the purposes of this User’s Manual.
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8/4/2019 User's Manual for CBT Calculator Rev 1.00 100312
The CBT Calculator is a precision engineering tool, allowing audio professionals to design CBTConstant Beamwidth Technology™ line array column loudspeakers into a wide variety of venues. The CBT Calculator shows the vertical coverage, sound level capability, and evennessof coverage of either one or two CBT speakers, set to various settings, in a room with up to 4independent listening planes.
This calculator provides the resulting SPL vertical coverage mapping of a proposed design, and
computes the frequency response of up to 6 listener locations as well as an SPL summary of the microphone locations over user-defined frequency bands.
Installing the Software – If you already have a previous version of CBT Calculator on your computer, the software should uninstall it automatically. I that doesn’t occur, then pleaseuninstall all previous versions using the Windows Control Panel to Add/Remove programs.
Unzip the file you were provided into a directory and then run the “setup.exe” program. Your computer will need to have the latest version of Microsoft .NET 3.5 (the installer will downloadthis automatically if your computer requires an update). JBL’s CBT Calculator requires a PCwith Windows XP or newer.
System Design Example Shown in This Manual -- The system design example we are usingin this manual shows a venue with a CBT 70J+70JE array system covering a main seating areawith slightly raked seating and a CBT 100LA mounted higher up on the same front wall,covering a balcony. We are looking at the frequency responses and SPL sound levels from 5microphone locations. We are not necessarily recommending this as the best solution for thisvenue, but rather it is a display that allows us to run through the various functions of the CBTCalculator for the purposes of this User’s Manual.
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The Coverage Display Window shows the sound level projection from the CBT loudspeakers.Colors correspond to the Sound Pressure Level (SPL) chart to the right of the Coverage
Display. This display shows a Sectional View (ie, side view) showing the vertical coverage of the speaker within a room having one to four listening planes.
ADDING LISTENING PLANE – Right-click any blank spot within the Coverage Display windowand then click “Add Plane”. An additional Listening Plane will appear.
MOVING THE ENDS OF A PLANE – The ends of the planes can be moved by dragging themto a new position. Place the cursor at the end of the plane. A circle will appear. Drag thecircle to the new location.
MOVING AN ENTIRE PLANE – Place the cursor at the center point of the plane. A circle willappear. Drag the circle to the new location.
LOCK PLANES – Checking this checkbox locks the planes in place so that they cannot bedragged and so the ends, too, cannot be moved by dragging. (Note that this does NOT lock outbeing able to make changes via manual entries in the Room Dimensions cells in area #3 – see“Room Dimensions (and Plane Locations) Section”, below.)
DELETING A PLANE – Right-click on the plane and click “Delete Plane”.
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ADDING A MICROPHONE (for Frequency Response curve at that point) – Up to 6 microphonelocations can be defined on the Listening Plane(s). Right-click at a point on a Listening Planeand click “Add Microphone”. A colored dot will appear to show that microphone’s position. Tomove the microphone position, simply slide the dot along the Listening Plane.
MOVING A SPEAKER BY DRAGGING – You can drag a speaker to a different location. Placethe cursor at the top right-hand corner of the speaker. A circle will appear. Drag the circle tothe new location.
LOCK ARRAY – Checking this checkbox locks the array so that it cannot be dragged to a newlocation. (Note that this does NOT lock out being able to make changes via manual entries inthe Speaker Selection cells – see “Speaker Selection Section” below.)
UNITS (feet vs. meters) – To change the Coverage Display between feet and meters, click theappropriate bubble in the Units section located above the top-left hand corner of the CoverageDisplay. (Note that this also changes units for the entire page, including the Room Dimensionsand Speaker Selection sections.)
CHANGING THE ROOM DEPTH – To change the room depth, type the room depth into theRoom Depth box in the lower right-hand corner of the Coverage Display. The room heightadjusts automatically to maintain the aspect ratio of the Coverage Display window.
FREQUENCY OF COVERAGE DISPLAY – The coverage display shows the coverage at thefrequency that has been selected by the “Frequencies” bubbles located below the display (Seethe “Adjustments to the Coverage Display” section, below.) The frequency listed in the top right-hand corner of the display is the frequency that this display is currently showing.
• Note: When more than one loudspeaker is shown, this software computes and shows the SPLcoverage and frequency response in a “complex” manner. In other words, it takes phase intoconsideration and shows the cancellations and additions that occur in overlap zones. It does NOT simply show the sound level from each speaker and add them together.
In the display shown above, if there had not been delay applied to the top loudspeaker, thecomplex interference would have been more visible, such as in the Coverage Display and Frequency Response displays below:
Same design with no delay on top CBT loudspeaker, showing the resulting interference.
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SHOW RAYS – This checkbox turns off or on the dashed lines that represent the aiming axis of the speaker (short dashes) and the 6 dB down points, both above and below the aiming axis(longer dashes).
Notes:
• The 6 dB down points are based on the “polar” coverage of the loudspeaker at the selected frequency.
• For CBT 70J, the aiming axis is where the top half of the speaker is pointing.
GRAPH TYPE
SPL MAPPING – Shows SPL via colors in accordance with the SPL chart to the right of theCoverage Display window.
0 dB ISOBARS – The 0 dB Isobar view allows the pressure gradient of multiple frequenciesto be shown on the same plot. The loudest location on any of the seating planes shown inthe mapping is displayed as the 0 dB reference level. The relative distance of the isobar from the seating plane provides an indication of the variation in SPL immediately
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perpendicular to the plane. Unlike the SPL Mapping, which views one frequency at atime, the 0dB Isobar view allows you to view multiple frequencies at the same time. Clickthe bubbles for as many of the 4 frequencies shown. Adjust the frequencies by either pening the drop-down menu or by using the nudge buttons by each frequency box.
This function is available when only one speaker is enabled. It is disabled when twospeakers are enabled. For two-speaker systems, uncheck one of the speakers.
SPL ATTENUATION – The SPL Attenuation view shows relative SPL level along each of thelistening planes at up to four frequencies simultaneously. This view gives you an accurateidea of the SPL variation along the entire length of the seating planes with one quickglance.
Darker green lines are equally spaced between the listening plane and the loudspeaker array and indicate 3 dB, 6 dB and 9 dB of attenuation. 0 dB attenuation is on the seatingplane.
You can adjust the relative scale (or spacing) between the attenuation lines by adjustingthe “SPL plot zoom” horizontal slider control.
All other graphical controls for planes, loudspeaker array location and aiming are aspreviously described.
FREQUENCIES – Allows you to select the frequency at which the Coverage Display is showingSPL. Whichever frequency is showing next to the selected “bubble” is the frequency for whichcoverage is shown in the Coverage Display window. In the example shown above, the
frequency selected is 2000 Hz.
You may select up to 4 different frequencies by either clicking on the frequency window andselecting the desired frequency or by using the up/down nudge arrows to the right of thefrequency listing. By selecting 4 different frequencies in the 4 frequency boxes, clicking thevarious “bubbles” allows you to quickly compare the coverage of the speaker system(s) at those4 selected frequencies. Note: Only one frequency displays at a time in the Coverage Displaywindow.
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This section allows you to choose whether there will be 1 or 2 speakers, to select which CBT
speaker model(s) are being used, select the Voicing (Music or Speech), select the VerticalCoverage (Broad or Narrow), select the Tap (if there are 70V/100V taps on that model of speaker), set the aiming Tilt, set the speaker location within the room (both horizontally andvertically), adjust the gain to the speaker, set the signal Delay to the speaker, and set the EQ.
SP. 1 and SP. 2 CHECKBOXES – To enable only speaker 1, check the Sp. 1 checkbox only.To enable only speaker 2, check the Sp. 2 checkbox only. To enable both speakers, checkboth checkboxes.
SPEAKER LOCATION – The boxes under this heading position the speaker in the roomhorizontally and vertically, relative to the bottom left-hand corner (the 0,0 location). Enter theHoriz (X) value (this horizontal setting applies to any of the 4 speaker bubbles selected under
this box) and the Vert (Y) value (this vertical value is specific to each of the 4 speaker speaker bubbles). This positions the top right-hand corner of the speaker.
Notes:
• Vertical Height Settings for CBT 70J vs 70J+70JE Array System – For the CBT 70J and the CBT 70J+70JE array, the sound is shown as coming from the center of the CBT 70J. This is indeed where the acoustic source is on the individual 70J and on the array system of the 70J+70JE. You may wish to switch between a 70J and a 70J+70JE to determine what the affect will be of theextension unit. For that, you probably want the sound to emanate from the same location on the
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display. However, the number in the Vert (Y) box represents the top right-hand corner of the topspeaker, which is a different distance to the center of the 70J. Therefore, the Vertical height listed for the 70J+70JE array combination must be entered as 0.7m (2 ft) higher. Then the sound of the
two systems will emanate from the same location on the Coverage Display.
• With a horizontal setting of “0”, the speaker itself may not be visible. Moving the speaker slightly to the right with a setting of “1” or “2” brings the speaker back into visibility.
GAIN (dB) – At a setting of “0”, the speaker is driven at its full rated power level. You shoulduse only negative gain figures, which indicate the dB of attenuation from full rated power. Youmay either type the entry into the box or use the nudge buttons to the right of the Gain box. If you are designing a system with two CBT speakers, this Gain box allows turning down one of the speakers relative to the other. In the example above, the lower loudspeaker (Sp.1) isturned down 6 dB as compared to the top loudspeaker (Sp.2) in order to even out the SPLlevels on the main seating are as compared to that of the balcony.
•
Note: For a low-impedance speaker (4Ω or 8 Ω ), “full rated power level” in this software is its 2-hour continuous average pink noise power capacity rating from that model’s specification sheet (pink noise with peaks 6 dB higher than this rating). For 70V/100V settings, “full rated power level” is with a full 70V or 100V signal. It is recommended that to represent Maximum AverageSPL with Music or Speech (such as is used in JBL’s DSD Distributed System Design and CSC Ceiling Speaker Configurator software) that the gain be set to -4 dB for low-impedance settingsand to -8 dB for 70V/100V settings. This places the peak capabilities (considering typical power amplifiers used in these systems) at 10 dB above the average. It represents the maximumaverage sound level that the system is able to produce continuously on program content that hasa 10 dB peak-to-average ratio, which is more typical of music and speech.
DELAY (ms) – This is particularly useful when you are using two CBT speakers. You canenter the desired delay in the box or you can use the nudge arrows to the right of the Delay box.
(Note that the nudge arrows increment at 21 ms increments, which are the delay settings thatare available from DSP units that have the common 47 kHz sampling rate.)
Applications Suggestion for Using Delay for Systems with Multiple CBT Speakers --Because of the strong directivity of the CBT speakers, it is often a good idea to use adelay setting on one of the speakers to eliminate combing in any overlap coverage areason the Listener Planes. This purposely misaligns the speakers, which results in moredense combing, which is usually considered to sound better. In stage situations withtop and bottom speakers, it is often the top speaker that gets delayed in order to bringthe image down to the bottom speaker which is typically closer to the stage.
SPEAKER SELECTION AND SETTINGS –
SPEAKER MODEL – Click the drop-down arrow to the right of the model box and select thespeaker model. You may want to have each of the 4 rows be a different CBT model, or you might want to have one or more boxes be the same CBT model but with differentsettings, allowing you to quickly switch back and forth to compare. You can select onlyone of the lines at a time.
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MUSIC/SPEECH VOICING SWITCH SETTING – All CBT models have a Music/Speechswitch on them. Click on the left-hand Setting button to toggle between M (for Music) and S (for Speech).
BROAD/NARROW VERTICAL COVERAGE SWITCH SETTING – The CBT 100LA, 70J and70J+70JE have a Broad/Narrow Vertical Coverage switch on them. The CBT 50LA doesnot. Click on the right-hand Setting button to toggle between B (for Broad Coverage) and N (for Narrow Coverage).
TAP – The CBT 50LA and 100LA have built-in 70V/100V transformers as well as the direct4Ω or 8Ω setting. Clicking the drop-down arrow to the right of the Tap box brings up thesettings that are available for the speaker selected in that row. Select the Tap (or 4Ω or 8Ω) setting. (Note that the CBT 70J and 70J+70JE do not have selections because theyare low-impedance only.)
TILT(°) – This sets the down or up aiming angle of the speaker. Either enter the tilt number
(in degrees) into the Tilt Box or use the nudge buttons to adjust the tilt 1°at a time. (Notethat the speaker tilts around the Speaker Location point, which is the top right-hand corner of the speaker.)
EQ – Clicking the EQ button located in the top section of Sp.1 or Sp.2 areas opens a 31band graphic equalizer. Any changes made on the equalizer are implementedimmediately on the frequency response graphs (see the Frequency Response Chartsection, below).
Each row has its own EQ. The EQ being adjusted at any time only affect the equalizationfor the speaker row that is currently selected (the one with the green bubble; ie, the rowthat is not grayed out). When you select a different row, its EQ starts out flat and can beadjusted separately. To adjust the EQ of a row, first select that row (by checking itsgreen bubble). Then click the EQ button to adjust that row’s EQ. The EQ setting for onespeaker only affects that particular speaker selection row.
Click FLAT to flatten all the sliders to 0 dB. Click OK to accept the settings and close thewindow, or CANCEL to not accept the settings and close the window.
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_ 3 _ Room Dimens ions (and P lane Locat ions) Section
This section shows the exact locations of the end points of the Listening Planes. You can
drag the endpoints within the Coverage Display or you can set them precisely in this section.Set the Horizontal (X) and Vertical (Y) points relative to the 0,0 point located at the bottomleft-hand corner of the Coverage Display. To change the figures between feet and meters,click the appropriate bubble in the Units section located to the left of this Room Dimensionssection.
• Note: Inputting a deeper listening plane does not automatically re-size the display to show theentire listening plane. To increase the size of the “room” so that the Coverage Display showseverything you want to see, type the room depth in the “Enter Room Depth” box at the bottomright-hand corner of the Coverage Display.
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This section displays the frequency response(s) (from 100 Hz to 10 kHz) for each of the
microphone locations that you’ve places on the Listening Planes in the Coverage Display.
COLORS – The color of each frequency response curve corresponds to the color of the dotrepresenting a microphone location in the Coverage Display.
ADJUSTING THE SCALE – The vertical scale of the frequency response chart (SPL) alwaysrepresents a range of 40 dB. The absolute values of the scale can be adjusted up or downusing the nudge arrows in the top left-hand corner of the chart.
• Note that the frequency response curves are 1/3rd
-octave averaged.
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This section allows you to answer the questions “What is the average SPL throughout the
space (or for one of the listening planes)?,” and “How even is the coverage?” You canselect two different frequency ranges and within each of the two frequency ranges, you canobserve the:
a) The average SPL (in dB), and
b) The overall “variation” (“Flatness (dB)”) of the sound level within the space (in plus andminus dB).
You can also observe the overall average SPL (in dB) for all selected microphones as well asthe overall Flatness (in plus and minus dB).
SELECTING THE TWO FREQUENCY RANGES – Select the From (Hz ) frequency and To (Hz) frequency of the first inquiry in the two left-hand boxes located in the top of this section.Select the From (Hz) frequency and To (Hz) frequency of the second inquiry in the two right-hand boxes located in top of this section. For each selected frequency band (left-handselected band and right-hand selected band), the SPL (sound level) and Flatness figuresbelow them are the Average SPL and the variation in SPL for each checked microphonelocation, within that frequency band.
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OVERALL – The Overall boxes show the average SPL for all selected Mic locations and theoverall Flatness of SPL at any location.
For example, if the two left hand boxes are 1000 and 4000, then you’ve selected therange from 1000 Hz to 4000 Hz, which is the core of the midrange frequency band. Allthe boxes below that show the Average SPL (in dB) and SPL Flatness (in +dB/-dB) for each microphone location.
In the chart above, the frequency band chose on the left-hand side is 1000 Hz to4000 Hz. This frequency band is typical for seeing how good the midrangecoverage is. The average SPL shown for Mic 1 is 94.5 dB. The Flatness variesfrom +0.7 dB and -1.2 dB (as compared to that 94.5 dB average). This meansthat the SPL variation range in the 1000 Hz to 4000 Hz frequency band is 1.9 dB,so the coverage is within ±0.95 dB at that Mic location.
The left-hand boxes in the Overall row at the bottom show that the Average SPLfor all selected Microphones (in this case, Mics 1, 2, 3, 4 and 5) is 94.8 dB. Thenext box shows that the coverage is flat to within +1.6 dB and -2.0 dB, which is atotal SPL variation range of 3.6 dB, so the mid-range coverage is within ±1.8 dBoverall (at these 5 microphone locations).
Also looking at the chart above, the frequency band chose on the right-hand sideis 400 Hz to 10000 Hz. This frequency band represents the bulk of the frequencyresponse band. The average SPL shown for Mic 1 is 94.0 dB. The Flatnessvaries from +1.2 dB to -6.1dB (as compared to that 94.0 dB average). Thismeans that the SPL variation in the 400 to 10000 Hz range is 7.3 dB, so
coverage is within ±3.65 dB at that Mic location.
The right-hand box in the Overall row at the bottom shows that the Average SPLfor all selected Microphones (in this case, Mics 1, 2, 3, 4 and 5) is 94.4 dB. Thenext box shows that the coverage is flat to within +2.0 dB and -6.5 dB, which is atotal SPL variation range of 8.5 dB, so the broadband coverage is within ±4.25dB overall.
IDENTIFYING THE MICROPHONES – The color of each Mic identification corresponds tothe microphone color dot on the Coverage Display.
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CHANGING “ OPTIONS”Clicking on “Tools” and then “Options” opens the OPTIONS dialogue box.
SPL MAPPING AUTOSCALE
DEFAULT SETTING – The SPL Mapping defaults to a range of 70 dB to 120 dB.
AUTOSCALE CHECKBOX – Checking this box sets the Coverage Display toautomatically set the SPL max and SPL min dB figures to show the most variation of colors on the Coverage Display. The SPL chart to the right of the Coverage Display
shows which colors relate to which SPL levels.
SETTING THE SCALE MANUALLY – With the Autoscale checkbox unchecked, youcan change the SPL Min and SPL Max to any values depending on what you want tosee on the Coverage Display.
GRID OPTION – For Snap to Grid and setting Grid Size. This affects both the dragging of speakers and the dragging of planes in the Coverage Display.
ISOBARS (dB) – for setting the Isobars that appear in the “SPL Mapping” Graph Type and
“0 dB Isobar” Graph Type.
DEFAULT UNITS – Another way to select feet vs meters.
AIR PARAMETERS – This models takes into consideration what the temperature is andwhat the humidity is when computing coverage, frequency response and SPL summary.The system defaults to typical indoor temperature and 50% humidity. If the venue isexpected to typically have a different temperature or humidity, make those changes here.Either type the value or use the nudge arrows to the right of the boxes.
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AIR ABSORPTION CHECKBOX – Uncheck this box if you do not want the CBT Calculator to consider air absorption in its frequency response and SPL Summary computations.
RAYS SHADOWING – When checked, the Aiming and the 6 dB Down dashed linesemanating from the loudspeaker in the Coverage Display stop when they encounter aListening Plane. When unchecked, these lines continue through and past the ListeningPlane.
Changes take effect when you press Apply or OK. Press OK to close the Options dialoguebox.
For any questions, please contact your JBL Professional Sales Representative or International Distributor, or contact Technical Assistance at JBL Professional. 818-894-8850.
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