JL Audio 15W0v3-4 15" Subwoofer Driver

Dynamic Motor Analysis - DMA Optimized Motor

Summary:
JL Audio's proprietary Dynamic Motor Analysis system is a powerful suite of FEA-based modeling systems, first developed by JL Audio in 1997 and refined over the years to scientifically address the issue of speaker motor linearity. This leads to vastly reduced distortion and faithfully reproduced transients... or put simply: tight, clean, articulate bass.

Detailed Information:
Since 1997, JL Audio has been at the forefront of Finite Element Analysis-based modeling of loudspeaker motors and suspensions. This research is aimed at decoding what we refer to as the "Loudspeaker Genome"... a project aimed at understanding the true behavior of loudspeakers under power and in motion. A major component of this integrated system is DMA (Dynamic Motor Analysis). Starting with the 15W3v3 and the W7 Subwoofers in the late 1990's and early 2000's, DMA has played an important role in the design of all JL Audio woofers sold today, including our component woofers.

DMA is a Finite Element Analysis (FEA)-based system, meaning that it takes a large, complex problem, breaks it down into small solution elements for analysis and then assembles the data to form an accurate, "big-picture" solution. DMA's breakthrough is that it actually considers the effects of power through the coil as well as coil/cone position within the framework of a time-domain analysis. This gives us a highly accurate model of a speaker's actual behavior under real power, something that the traditional Thiele-Small models or other low power measurements cannot do. Because DMA does not rely on a steady-state model, it is able to consider shifts in the circuit elements being analyzed. These modeling routines are intense, requiring hours to run for a whole speaker.

DMA is able to analyze the real effects of fluctuating power and excursion upon the magnetic circuit of the motor, specifically the dynamic variations of the "fixed" magnetic field. This delivers intensely valuable information compared to traditional modeling, which assumes that the "fixed" field produced in the air gap by the magnet and the motor plates is unchanging. DMA not only shows that this "fixed" field changes in reaction to the magnetic field created by current flowing through the voice coil, but it helps our engineers arrive at motor solutions that minimize this instability. Analyzing this behavior is critical to understanding the distortion mechanisms of a speaker motor and sheds light on the aspects of motor design that determine truly linear behavior:

• Linear motor force over the speaker's operational excursion range
• Consistent motor force with both positive and negative current through the coil
• Consistent motor force at varying applied power levels

Our ability to fully analyze these aspects of motor behavior allows our transducer engineers to make critical adjustments to motor designs that result in extremely linear, highly stable dynamic loudspeaker motor systems.

The payoff is reduced distortion, improved transient performance and stellar sound quality.

Elevated Frame Cooling (U.S. Patent #6,219,431 & #6,229,902)

Summary:
JL Audio's patented Elevated Frame Cooling design delivers cool air through slots directly above the top-plate to the voice coil of the speaker. This not only enhances power handling, but also sound quality by minimizing dynamic parameter shifts and power compression.

Detailed Information:
Many speakers employ venting techniques to enhance voice coil cooling. This is typically accomplished by having big holes in the sides of the frame just below the spider attachment shelf. While it provides a modest cooling benefit, this low-velocity air-flow does not blow directly or strongly on the voice coil.

Our patented design improves upon this cooling technique in a number of ways. By elevating the frame above the top-plate of the motor (via stand-offs integrated into the bottom of the frame) a narrow, high-velocity air-path is created between the bottom surface of the frame and the top surface of the top-plate. This air path leads directly to the voice coil and then turns upward into the spider air cavity. By utilizing the pumping action of the spider through this focused air path, a large volume of cool air hits the coil windings directly.

Another important benefit is that the upper surface of the top-plate (one of the speaker's hottest parts) is directly exposed to cooling air flow, whereas on a conventional design it is isolated from the air flow by the lower flange of the frame. The elevated frame technology greatly increases thermal power handling, reduces compression effects and does so without any additional parts.

Specifications

General Specifications

• Continuous Power Handling (RMS) 500 W
• Recommended RMS Amplifier Power 150 - 500 W
• Nominal Impedance (Znom) 4 Ω

Physical Specifications

• Nominal Diameter 15.0 in / 380 mm
• Overall Diameter (A) 15.5 in / 394 mm
• Mounting Hole Diameter (B) 13.75 in / 349 mm
• Bolt Hole Circle (C) 14.56 in / 370 mm
• Magnet Diameter (D) 6.3 in / 160 mm
• Mounting Depth (E) 7.15 in / 182 mm
• Driver Displacement 0.109 cu ft / 3.09 L
• Net Weight 15.8 lb / 7.2 kg

Parameters

• Free Air Resonance (Fs) 24.43 Hz
• Electrical “Q” (Qes) 0.508
• Mechanical “Q” (Qms) 9.474
• Total Speaker “Q” (Qts) 0.482
• Equivalent Compliance (Vas) 5.106 cu ft / 144.60 L
• One-Way Linear Excursion (Xmax)* 0.50 in / 12.7 mm
• Reference Efficiency (no) 0.1800%
• Efficiency (1 W / 1 m)** 88.20 dB SPL
• Effective Piston Area (Sd) 122.317 sq in / 0.0789 sq m
• DC Resistance (Re) 3.555 Ω

* Xmax specifications are derived via one-way voice coil overhang method with no correction factors applied.
** Efficiency (1 W / 1 m) is not an accurate indicator of a subwoofer’s output capability and should not be used as a comparison to other subwoofers to determine which one is “louder”.

Sealed Enclosure Specifications

• Wall Thickness 0.75 in / 19 mm
• Front Baffle Thickness 0.75 in / 19 mm
• Volume (net int.) 1.875 cu ft / 53.10 L
• External Width (W) 16 in / 406 mm
• External Height (H) 15.75 in / 400 mm
• External Depth (D) 18 in / 457 mm
• F3 38 Hz
• Fc 47.14 Hz
• Qtc 0.9301

Enclosure Notes
* The enclosure recommendations listed above are external dimensions which assume the use of 0.75 in (19 mm) thick material. If you are using 0.625 in (16 mm) thick material, subtract 0.25 in (6.5 mm) from each dimension. Do not use any material with a thickness of less than 0.625 in (16 mm) as this may compromise the rigidity of the enclosure.
* All enclosure volumes listed above are net internal volumes! Driver displacement, port displacement and brace displacement must be added to obtain the final gross internal volume. All enclosure dimensions above have already taken this into account.
* When using multiple subwoofers in a common enclosure you will need to recalculate the enclosure and port dimensions. For assistance please contact your authorized JL Audio dealer or JL Audio Technical Support.
* We recommend the use of this speaker in a bi-amplified system using high-quality satellite speakers and a high-quality amplifier. We do not recommend the use of this subwoofer with a passive crossover (coil), as this type of device will adversely affect performance.
* All specifications are subject to change without notice.
Safety Notice
Prolonged exposure to sound pressure levels in excess of 100dB can cause permanent hearing loss. This high-performance speaker can exceed this level. Please exercise restraint in its operation in order to preserve your ability to enjoy its fidelity.
When installing a subwoofer in your vehicle, it is extremely important to secure the enclosure firmly. We recommend bolting the enclosure through the metal of the floorpan or the frame of the vehicle with large diameter washers for reinforcement. If an enclosure is not firmly attached, it can become a projectile in a collision. This is particularly important in a hatchback, station wagon, sports utility vehicle, or van.

Ported Enclosure Specifications

• Wall Thickness 0.75 in / 19 mm
• Front Baffle Thickness 0.75 in / 19 mm
• Volume (net int.) 2.75 cu ft / 77.88 L
• External Width (W) 20 in / 508 mm
• External Height (H) 18 in / 457 mm
• External Depth (D) 18.5 in / 470 mm
• Internal Port Diameter (ID) 4 in / 102 mm
• Port Length (L) 16.85 in / 428 mm
• Tune to 25 Hz
• F3 30 Hz

Enclosure Notes
* The enclosure recommendations listed above are external dimensions which assume the use of 0.75 in (19 mm) thick material. If you are using 0.625 in (16 mm) thick material, subtract 0.25 in (6.5 mm) from each dimension. Do not use any material with a thickness of less than 0.625 in (16 mm) as this may compromise the rigidity of the enclosure.
* All enclosure volumes listed above are net internal volumes! Driver displacement, port displacement and brace displacement must be added to obtain the final gross internal volume. All enclosure dimensions above have already taken this into account.
* When using multiple subwoofers in a common enclosure you will need to recalculate the enclosure and port dimensions. For assistance please contact your authorized JL Audio dealer or JL Audio Technical Support.
* We recommend the use of this speaker in a bi-amplified system using high-quality satellite speakers and a high-quality amplifier. We do not recommend the use of this subwoofer with a passive crossover (coil), as this type of device will adversely affect performance.
* All specifications are subject to change without notice.
Safety Notice
Prolonged exposure to sound pressure levels in excess of 100dB can cause permanent hearing loss. This high-performance speaker can exceed this level. Please exercise restraint in its operation in order to preserve your ability to enjoy its fidelity.
When installing a subwoofer in your vehicle, it is extremely important to secure the enclosure firmly. We recommend bolting the enclosure through the metal of the floorpan or the frame of the vehicle with large diameter washers for reinforcement. If an enclosure is not firmly attached, it can become a projectile in a collision. This is particularly important in a hatchback, station wagon, sports utility vehicle, or van.

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