JL Audio ACP112LG-TW1: Single 12TW1 MicroSub+™ with DCD™ Amplifier, Ported, 0.25 Ω

DCD™ Amplifier Technology

Summary:
The most efficient subwoofer amplifier technology on the market delivers impressive power with minimal current draw and heat.

Detailed Information:
The conventional way to get high power in a car amplifier is to use a switching power supply. This increases the battery voltage from its nominal 12V to something higher–the more powerful the amplifier, the greater the required voltage. This power conversion is never perfectly efficient–about 10% of what goes into the amplifier is wasted and ends up dissipating into heat.

JL Audio's Direct Conversion Class-D Technology (DCD™) innovates by eliminating the need for this power conversion step entirely. Because we are still bound by the laws of physics, the lack of a step-up power supply means we have to extract as much power as possible from the vehicle's 12V supply. If we were to connect a DCD™ amplifier to a conventional 4-ohm subwoofer with this limitation in place, we would only achieve about 25 watts, and we all know that powering a subwoofer requires a lot more power than this.

To overcome this obstacle, the DCD™ amplifiers have been designed to drive extremely low impedance speaker loads–as low as 1/4-ohm (0.25 ohm)! With these very low impedance loads, we can deliver up to 500 watts of clean power, subwoofer power. Those who know Ohm's law and that nothing is free realize that this will require a lot of current to flow, and that's exactly what DCD™ is engineered to deliver...over 50 Amps peak into a speaker!

To deal with these high current amounts, the special, very low-impedance JL Audio subwoofer drivers used with DCD™ amplifiers are engineered with unique voice coils and tinsel leads. Connections between the amplifier and speaker are made using special heavy gauge speaker cable, with special attention paid to connection integrity to deal with the high current output.

The benefit of all this effort is that DCD™ amplifiers completely avoid the losses associated with a switching power supply, allowing the entire amplifier to achieve total power efficiencies in the 91-94% range. This is very close to the theoretical limit for Class-D efficiency and results in very little heat being generated. All of this allows for a very compact, powerful amplifier that can fit in some of our most space-efficient enclosed systems.

V-Groove MDF Construction

Summary:
This advanced cabinet-building technique uses CNC-machining to create precise panel joints that make enclosure assembly more efficient and exact.

Detailed Information:
We begin with quality medium-density fiberboard, which is then machined on our CNC-controlled KOMO woodworking stations. These powerful machines are able to cut a wide range of features onto a sheet of MDF, with minimal waste and absolute precision. The KOMO machines cut out the woofer holes, terminal holes, cut dado grooves, create countersinks and most importantly, cut the angles at the edges of the panels that form the enclosure's main shell so that these panels fit together precisely, with no gaps or leaks.

Once the panels are cut, assembly technicians line them up in the correct order and glue their outer faces onto a long piece of carpet, creating a "wrap": a long series of panels, hinged temporarily by the carpet. In the next assembly step, our wood assembly teams fill the V-grooves between the panels and any dado grooves that receive dividers or secondary wraps with wood-glue. Once the glue is applied, the enclosure shells folds together along the V-grooves, capturing dividers in the dado grooves and secondary wraps, and evenly spreading the glue throughout the joints. One line of mechanical fasteners is applied to hold the structure together while the wood glue dries.

The V-groove technique greatly improves assembly efficiency, and also results in a far stronger and better sealed enclosure than the typical butt-joint construction found on imported enclosures. The quality of the MDF used in JL Audio systems is also vastly better than the typical "China-Grade MDF" used in the imported products.

Flared Slot-Port

Summary:
The flared slot-port design reduces turbulence at the port mouth so as to minimize any audible airflow effects common to ported enclosures.

Detailed Information:
While ported enclosures deliver important efficiency advantages over their sealed counterparts, they also present unique design challenges. In car audio, the desire for lower tuning frequencies from small enclosure volumes leads to long port lengths that often require compromising the port area. These compromises lead to higher airflow speeds through the port, which can create noise as the air is driven across the the edge of the port. The flared port design minimizes these airflow effects by providing a smooth transition for the high-speed air flow, rather than an abrupt termination. The result is less noise and cleaner-sounding bass.

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 15W3 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:

1. Linear motor force over the speaker's operational excursion range
2. Consistent motor force with both positive and negative current through the coil
3. 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.

Engineered Lead-Wire System (U.S. Patent #7,356,157) 

Summary:
Carefully engineered lead-wire design and attachments ensure controlled, quiet lead-wire behavior under the most extreme excursion demands.

Detailed Information:
Managing the lead-wires on a long-excursion woofer is one of the trickier aspects of its mechanical design. To address this, many long-excursion woofers today rely on a simple solution that weaves the lead-wires into the spider (rear suspension) of the driver.

The biggest problem with this approach is that spider limiting behavior plays a hugely important role a woofer's performance. Lead-wires that are attached or woven into the spider material can alter the spider's "stretching" behavior. The tinsel wire naturally has less 'give' than the fabric material of the spider leading to asymmetrical spider behavior and non-uniform stress distribution around the spider circumference. The wire attachment points can also cause localized pulling and tearing forces at the spider's excursion limits. As such, longevity becomes a major concern and makes the woven-in design less than ideal for very long-excursion designs.

While a traditional 'flying lead' design does not compromise spider linearity or radial stability, it creates its own challenges on a long-excursion woofer. Managing the 'whipping' behavior of the wire and making sure it does not contact the cone or spider is one challenge. Another is ensuring that the leads do not short one another or the frame of the woofer.

To overcome these issues, JL Audio's engineered flying lead-wires work in conjunction with carefully engineered entry and exit support structures molded into the terminals and the voice coil collar. Some models also feature jacketed lead-wires to further reduce the likelihood of shorting and fatigue. The result is flawless high-excursion lead-wire behavior, with outstanding reliability and none of the compromises inherent to a woven-in lead wire system. Building woofers this way requires much more labor and parts complexity than the simpler woven-in approach, but the payoff is in reduced distortion, reduced mechanical noise and improved reliability.

Concentric Tube Suspension (U.S. Patent #5,734,132 & #6,095,280)

Summary:
Our patented Concentric Tube Suspension™ technology delivers unprecedented excursion in a low-profile woofer.

Detailed Information:
The biggest challenge in any low-profile woofer design is to create enough mechanical clearance for the speaker to generate enough excursion to meet its output and low-frequency extension goals. Since these goals were very ambitious in the development of JL Audio's low profile woofers, achieving them required development of a new suspension architecture.

JL Audio's patented solution employs a molded structure which spans over the edge of the motor system, supporting the spider on the outside of the motor's boundaries and the large diameter voice coil on the inside. The large diameter voice coil permits the magnet to sit inside it, rather than surrounding the coil as is typical in most woofers.

The concentric tube structure and the elimination of a conventional top-plate helps us place the motor system higher up into the cone body's space to further compress depth, while still permitting excellent mechanical excursion.

Tab-Ear Frame Design

Summary:
This frame design feature facilitates mounting the subwoofer driver in tight spaces.

Detailed Information:
By employing a tab-ear mounting system, the driver's overall outside dimensions are reduced, permitting it to be mounted in a space that is very similar to that required by the next smaller round woofer frame.

In this example, the “Tab-Ear” frame design allows a 13TW5 13.5-inch driver to fit in a space only slightly larger than a conventional 12-inch woofer requires (only 0.44 in. / 11.2 mm bigger)

Built in U.S.A. with Global Components

Summary:
JL Audio's Miramar, Florida loudspeaker production facility is one of the most advanced in the world.

Detailed Information:
At a time when most audio products are built overseas, JL Audio’s commitment to in-house loudspeaker production continues to grow. To pull this off in a competitive world market, our production engineering team has created one of the world’s most advanced loudspeaker assembly facilities and established a global network of quality component suppliers who build to our specifications. This, combined with our commitment to state-of-the-art assembly technology, allows our skilled workforce to efficiently build JL Audio products to extremely high quality standards, right here in the U.S.A.

Since most of our premium loudspeakers incorporate proprietary, patented technologies requiring specific assembly techniques, we find it is vital that the people who designed them have close access to the people manufacturing them. The following JL Audio products are built in our Miramar, Florida factory, with global components:

• Subwoofer Drivers: W7, W6v3, TW5v2, TW3, TW1, W3v3 
• Enclosed Car Subwoofers: Stealthbox®, PowerWedge™, ProWedge™, H.O. Wedge™ & MicroSub™ Enclosed Subwoofers
• Marine Loudspeakers, Marine Subwoofer Drivers and Marine Enclosed Loudspeakers
• Home Subwoofers: Dominion™, E-Sub, Fathom® and Gotham®