JBL 1500GTi Car Speaker
Contents
1. TTTTT T lt Vehicle Transfer Function 6 L In Car Response Curve nclosure only response with am tandard Optimum Tuning 42Hz 5 Hz 10 50 100 500 Frequency This graph shows the effect of vehi approximately 31Hz 4 1000 2000 cle transfer function added to an enclosure using standard tuning Note the peak at 50Hz with a 3dB point of Normalized Amplitude Response dB Hz JBL SpeakerShop 1 0 dB Vehicle Transfer Function 6 0 In Car Response Curve 6 A 12 18 Enclosure only response 24 Transfer Function Compensated Tuning 33Hz 30 36 5Hz 10 50 100 500 1000 2000 Frequency This graph shows the result of tuning the enclosure to compensate for the effects of the vehicle transfer function Note that the in car response is smoother and the 3dB point moves down to approximately 22Hz Normalized Amplitude Response dB Hz JBL SpeakerShop 1 0 L In Car Response with Transfer 6 Function Compensated Tuning 18 In Car Response with Standard Tuning 5Hz 10 50 100 500 1000 202. handling capabilities in different enclosure configurations Speaker Connection and Combination GTi subwoofers are 4 ohms nominal imped ance If you are connecting two speakers in parallel to an amplifier channel make sure your UBL Four woofers can also be wired as shown below in parallel series or series parallel so that the amplifier will see four ohms nominal impedance Parallel Series Series Parallel amplifier will drive a two ohm load Wiring Wiring TA Parallel Wiring 2 ohms R S 7 E Nominal Impedance z a 4 ohms 4 ohms Nominal Nominal Impedance Impedance Series Wiring 4 i gt i If your amplifier will not drive a R two ohm load we a Oo recommend that you connect the ionns Please consult your JBL dealer for information on two speakers in Impedance more complex speaker combinations series to create an 8 ohm load as shown here j JBL Consumer Products Inc 80 Crossways Park West JBL Woodbury NY 11797 8500 Balboa Blvd Northridge CA 91329 1 800 336 4JBL H A Harman International Company NMGP N 323967 001 9 95
3. system design software for a P C running Microsoft Windows available from your JBL dealer If JBL SpeakerShop or a similar program is not available the JBL Customer Service department will be happy to assist you Vehicle Acoustics The acoustics of your vehicle also influence bass performance tremendously Fortunately the small interior volume of most cars and trucks boosts low bass output enough to allow for small er enclosure sizes while still achieving good bass performance As a general rule below 50 80 Hz depending on interior size bass response increases at a rate which approaches 12dB per octave as the frequency decreases This adds a significant bass reinforcement to the actual output of the subwoofer If this rise in bass is not addressed in the design of your enclosure bass performance may be boosted to the point where it is actually too strong for some tastes For others there is never too much The enclosure design recommendations which appear on the specifica Normalized Amplitude Response dB Hz tion sheet for your particular model were chosen for optimum in car performance You may find them to be different than the recommendations from formulas used to design enclosures for in home or profes sional sound reinforcement applications These Transfer Function Compensated tuning recommendations result in small enclosures with excellent in car low fre quency performance JBL SpeakerShop 1 0
4. 00 Frequency This is a comparison of in car response curves with and without transfer function compensated tuning Enclosure Design Follow the simple steps below to design an optimum ported box for your GTi driver 1 Determine the maximum enclosure size available for your installation by measuring and multiplying the height x width x depth in inches and then dividing by 1728 This will tell you exactly how many cubic feet your enclosure will be 2 To determine the volume of an irregularly shaped box divide the box into sections calcu late the volume of each section individually then add the separate volumes to determine the total box volume Here are some useful formulas to help you calculate volumes USEFUL FORMULAS 1 cubic foot 1728 cubic inches 1 cubic foot 28 32 liters 1 liter 0 353 cubic feet 61 cubic inches 1000cm Radius 1 2 diameter Box volume height x width x depth Volume of triangular box section 1 2 base x height x length Volume of tubular duct area of circle x length pi x 3 1416 Area of circle pi x x radius Diameter of circle 2 x area pi 1 Area of square height x width 3 A Now that you have calculated the internal box volume you should subtract the DRIVER DIS PLACEMENT listed on the specification sheet while also subtracting approximately 0 1 cubic feet for the port tube if one is being used If you d like you may calculate the exact dis placem
5. GTi Automotive Intercooled Subwoofer Application and Installation Guide Table of Contents Staple or clip your original bill of sale here W Welcome to Club GTi 020 5 Autosound at its Best 0 00055 Unleash Maximum Performance Enclosure BasicS 000 espe aeeaee Vehicle Acoustics Enclosure Design Enclosure Construction Tips Points on Power Handling E N a Speaker Connection and Combination Welcome to Club GTi Thank you for purchasing one of the finest automotive subwoofers that JBL has ever pro duced As a GTi competition series owner you are a member of a select group of people who enjoy the most advanced mobile audio products avail able We call this group Club GTi By sending in the customer information card that you will find packaged with this product we will automatically register you as a Club GTi member which will give you access to exclusive Club GTi apparel and other special offers we will make available from time to time We suggest you fill the card out at your earliest convenience Also be sure to save your sales receipt in a safe place It will be necessary to use this docu ment as proof of purchase should you need war ranty service Autosound at its Best The GTi Subwoofer is built to meet the same rigorous standards of construction and perfor mance that have long established JBL s r
6. e in the voice coil to overheat and burn out Too much cone motion can cause the cone to mechanically limit and damage the subwoofer e Depending on the subwoofer model the GTi motor structure can easily handle an amplifier rated to deliver from 300 600 watts of continuous power This is an electrical rating dependent upon an enclo sure design which keeps the woofer cone from reaching its mechanical limits when the amplifier delivers high power Properly designed Vented and Band pass enclosures are capable of this control At the same power levels Infinite Baffle designs no enclosure sometimes called Free Air allow greater cone motion and the power rating of the subwoofer must be reduced to reflect this see the specifications At the same power levels Infinite Baffle subwoofer installations will have much longer cone excursion than subwoofers mounted in an enclosure Sealed enclosures exert some control over excur sion as a result of the air inside the enclosure acting as a spring against the woofer cone motion Large enclosures typically allow higher excursion than smaller boxes Vented and Band pass enclosures have the lowest excursion as a result of the port tuning effects However vented enclosures will allow for high excursion outside the port tuning range Single tuned Band pass enclosures provide the lowest overall cone excursion See the specifications sheet for details on the GTi subwoofer power
7. enowned home and professional speaker systems The GTi Subwoofer achieves its exceptional performance with leading edge technologies that push the per formance envelope in automotive sound The exceptional sound of the GTi Subwoofer comes from an Aquaplas coated fiber cone for extra stiffness and resonance elimination The cone motion is controlled by a synthetic rip stop suspension which resists tearing for safe effortless high power use The cone is driven by a massive motor structure utilizing a 3 or 4 edge wound OFC copper wire high temperature fiberglass voice coil This motor structure includes JBL s patented Symmetrical Field Geometry SFG to create a uniform magnetic flux field through the coil and thus lower distortion The frame and cone are contained in a high strength die cast aluminum frame for maximum rigidity and higher magnetic energy concentration on the coil What does all this technology add up to A driver with smooth frequency response excellent transient response high output efficiency and high power handling in a rugged package able to deal with the rigors of high performance car audio The result is exceptionally powerful dynamic and accu rate sound reproduction that cuts through the road noise and provides a solid musical foundation Unleash Maximum Performance Because this is a high performance product which may be used in many different configura tions we strongly recommend that you have the subw
8. ent of the port tube by utilizing the for mula listed above Volume of tubular duct Using the GTi Enclosure chart shown on your GTi driver specification sheet choose a desired box volume on the vertical chart axis which fits within the size limit you have established Draw a line across from this point until it intersects the recommended tuning frequency Draw a line down to the horizontal axis and read the corre sponding tuning frequency We have drawn an example on the chart Use the Port Nomograph on the Driver Specifica tion sheet to determine the port diameter and length based on the enclosure volume and tuning frequency determined in step 4 Follow these steps to determine the port Port Dimension Calculation 1 Draw a line from the chosen enclosure volume to the desired tuning frequency Continue this line until it intersects with the Lv Sv construction line Lv port length Sv port opening surface area This is called the construction point 2 Draw a horizontal line starting from the con struction point straight through the chart Note that the Lv Sv axis also appears at the right of the chart to help keep your line parallel all the way across the chart 3 Select the curved line with the port diameter you would like to use Locate the point where this curved line intersects with your horizontal construction line and draw a vertical line from this point down to the bottom of the chart NOTE T
9. oofer professionally installed to unleash its full performance potential However if you feel you have the skills necessary to build a subwoofer box read the following information on enclosures before proceeding Enclosure Basics The enclosure you build plays a profound role in the performance of your subwoofer The size and vent tuning frequency where applicable determine the low frequency performance and output capability of the subwoofer system Your GTi subwoofer will pro vide excellent performance when used in Sealed Vented Infinite Baffle and Band pass applications that are properly designed Each of these applications have limits and advantages that should be considered GTi woofers are most commonly used either in Vented enclosures or Infinite Baffle Instructions which follow will give you a simplified design method to build a Vented enclosure for your subwoofer Another option is the Infinite Baffle free air installation which doesn t require complex design and construction and can sound very good when solidly installed However because there is no enclosure to control cone motion the power handling and maximum output level of an Infinite Baffle installation is reduced from that of a Vented enclosure Refer to the Points on Power Handling section for more information For more complex designs such as single and dual vented Band pass types we suggest you opti mize your design with JBL SpeakerShop a speaker
10. rd AREA 3 14 sq in 2 7 07 sq in 3 3 Joint Construction All joints should be glued and screwed no nails The cabinet should be airtight and must include adequate bracing to minimize resonance 4 Fiberglass Application Apply a 1 blanket of fiberglass or polyester to interior walls except the baffle board of all vented enclosures For sealed enclosures no ports fill the entire volume with fiberglass or polyester 12 16 oz per cubic foot If you do not wish to use damping material then make the box size 10 larger than recommended by the graphs 5 Ports Construct port tubes from PVC pipe or cardboard tubing with a wall thickness of at least 1 16 The end of the port tube must be kept one port diameter away from either the inside of the box or any surfaces in the car If a port tube is not available you may also construct a square rectangular vent Changing the shape of the vent will not effect the length as long as the surface area of the opening stays the same We ve supplied a chart that lists some standard dimensions for square rectangular vents 12 57 sq in 4 19 63 sq in 5 28 27 sq in 6 CIRCLE DIAMETER VENT h x w 1 75 x 1 75 2 x 3 50 2 x 6 25 3 x 6 50 3 x 9 50 Points on Power Handling The power handling of any subwoofer is related both to its ability to dissipate heat and to the maximum cone excursion limits Too much electrical power can cause the wir
11. ry to use a port tube no smaller than 1 3 the diameter of your speaker Using a smaller diameter port can result in whistling or breathing noises 4 The required port length is found at the point where the vertical line you ve drawn intersects with the scale at the bottom of the chart NOTE The recommended port tube dimensions should be considered a starting point Since it is impossible to predict in car response exactly you may find that a port length slightly longer or shorter than that recommended may produce slightly better results Experiment Lay out plans for your box using the information determined in the above steps and the box con struction tips listed on page 6 Enclosure Construction Tips The GTi Subwoofer will only sound as good as the enclosure it is mounted in Build an enclo sure that meets the guidelines listed below and you will get the high performance bass you sought when you stepped up to GTi 1 Box Dimensions Try to choose subwoofer enclo sure dimensions height width and depth which are not equal or multiples of each other This will mini mize standing waves and resonance in the cabinet Example Ideal 26 h x 17 w x 10 d Not ideal 30 h x 15 w x 9 d 30 is a multiple of 15 2 Enclosure Material and Thickness Use MDF or particleboard at least 3 4 19mm thick With high powered amplifiers or subwoofers of 12 diameter or larger use 1 25mm thick MDF or particleboa
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