JL Audio 12W6v2-D4 Subwoofer Review
It’s always a pleasure for me to review a product from JL Audio. I not only know many of the "players" at JL Audio personally, but I have a tremendous respect for its engineering. Unquestionably, JL Audio is on top of the list of the brands that come to mind when you talk about car audio subwoofers. The company has been specializing in car audio products since 1975 (national distribution of JL Audio’s subwoofer line started in 1992), and has long been considered a top contender among subwoofer manufacturers. It has developed an enviable reputation for not only building a quality product but has released a constant stream of serious no-nonsense subwoofer innovations over the years. It was among the earliest companies to use layered voice coil windings beyond four layers, and its patented vented reinforcement collar (VRC) that greatly strengthens the critical bond between the voice coil former, spider and cone is impressive. I know a lot of companies and a lot of engineers in car audio and I would have to say that JL Audio is certainly on the short list of the manufacturers I consider to be truly professional at what they do. Much like the JL Audio 10W7-3 I reviewed last year, the recently released W6v2 series brings on yet another batch of interesting and patented technologies.
If the W7 woofers are JL Audio’s full-tilt boogie statement describing the best performing subwoofer it could envision, then the W6v2 series is its attempt to take that showcase product and make it a little more affordable. While the W6v2 series could be considered a step down, my first impression is that it’s not a really that big of a step. For starters, the W6 is built with a very similar frame as the W7 and incorporates the same Elevated Frame cooling technology. While the W7 woofers have six sets of split spokes, this frame has five sets and attaches to the front plate and motor system with adhesive and five bolts, one for each dual spoke section. In between these connection points are the five 2 x 1/8-inch vent holes. Since these are located at the top of the front plate, they encourage airflow across the motor top plate with the air immediately surrounding the exposed forward moving end of the voice coil. All this cooling technology is aimed at keeping the operating parameters of a woofer as stable as possible over its entire dynamic range.
The motor (the thingy you probably refer to as the magnet) of the JL Audio 12W6v2 uses a large, single 167x40mm ferrite magnet. This is unusual as most large magnet motor systems typically employ a series of either two or three stacked magnets. This gonzo magnet is sandwiched between a forged 9.5mm-thick front plate and a single piece T-yoke. JL Audio employs a lot of science in developing a motor system like this. All of the current technologies, such as the laser-based, non-linear analysis tool called the Klippel Analyzer, an FEA program named CosmosM for modeling thermal dynamics of a woofer, and Maxwell for magnetics, were obviously maken use of. The company has also developed its own proprietary modeling software called DMA, for Dynamic Motor Analysis. This powerful software is based on an engineering modeling method called FEA (finite element analysis) that’s so math intensive, analyzing a speaker at multiple power levels takes several hours on a 2.8GHz Pentium 4 computer. The result of this high performance technology is that JL has done an incredible job of using these powerful tools to make a woofer that stays very linear up to the extreme volume levels, and this means lower distortion, higher accuracy and better transients.
Cooling, in addition to the frame vent scheme, is provided by yet another new proprietary pole venting system. The W6v2 has a patent-pending dual-pole venting system. Vent holes are located at the attachment point of the voice coil former and the cone and at the rear of the large pole vent. The exhaust is not the usual open "hole" that you see in most subwoofer motors, but is instead covered by a metal exhaust port device. This device consists of a flat plate that sits about 1/8-inch above the vent in the pole piece and forces air through a series of 15 small vent holes. The metal plate provides a pneumatic loading that forces air to flow in and out of both the top vents near the cone and the rear vent. This innovative pole venting system offers a balanced flow in both directions to maximize cooling efficiency. For increased motor linearity, the pole is extended above the front plate about 5mm.
The cone for the W6v2 is also similar to the W7 cone. JL Audio uses a two part polypropylene cone: a shallow profile oversized dust cap (this finishes the front of the speaker) with a W-shaped cone (profile) adhered beneath. It is this shape that gives the cone its name, the W-cone. The combination of these two results in a very light and extremely stiff cone assembly. The lower, W-shaped cone also has a trough indentation that gives the voice coil lead out wires a little more room to move.
Providing compliance and cone control is a foam surround that measures 30mm in width by 15mm in height. The remaining compliance is supplied by the nearly 8-inch-diameter, progressive roll, poly cotton-impregnated spider. The distance from the spider mounting shelf to the top plate is a substantial 15/8 inches, which allows plenty of clearance for long rearward excursion.
Attaching the spider and voice coil to the cone is accomplished by yet another proprietary system called Plateau-Reinforced Spider Attachment. This is a variation of the JL Audio VRC attachment collar that increases the stiffness of the neck joint so that the cone does not deform on long excursion strokes. The company claims this allows for better alignment of both parts and is called FCAM, for Floating Cone Attach Method.
Driving the cone assembly is a 2.75-inch-diameter, four-layer (two, two-layer coils) voice coil wound on a high temp Kapton former with round aluminum wire to keep the mass of the cone/voice coil assembly as low as possible. This dual voice coil version with two 4-ohm voice coils is the only version available on this model. The lead wires from the voice coil are also non-conventional in nature. While the entire industry uses tinsel lead wire, JL Audio got innovative and went to a flat insulated four-conductor (two leads for each voice coil connection) co-extruded ribbon wire. The ribbon wire connects to a new type of terminal jumper system. This terminal block has two color-coded push terminals to connect to an amplifier, but also has four output lugs that are the connecting points for each of the two voice coils. Using the two supplied 4.5-inch jumper wires, a user can easily configure the JL Audio 12W6v2 with either both voice coils in parallel or series. Last, the W6v2 series includes a removable trim ring that can be painted to match any installation theme and an optional mesh grille.
In The Lab
This section is divided into two parts, Klippel analysis and LEAP analysis. Using the Klippel analyzer (on loan from Klippel GmbH) Pat Turnmire, CA&E reviewer and CEO of Redrock Acoustics, performed the analysis of the JL Audio 12W6v2-D4 woofer and provided the Bl (X) curve shown in Figure 2 (below). The dark curve is the Bl curve and shows the motor strength of the woofer as it moves in both directions from center. The lighter curve is a sort of displacement curve — if both curves lie on top of each other, the motor system would be perfectly symmetrical. Ideally, the Bl curve would be centered on the 0mm point (where the cone is positioned when there is no signal). When a woofer shows an offset, which is the result you get from most woofers, it means that the magnetic and mechanical systems have not been completely optimized and motor strength will decrease faster in one direction (usually the outward direction) than the other, and this means more distortion at high operating levels than if it were operating perfectly symmetrical and providing equal motor strength in both directions. Looking at the
JL Audio 12W6v2-D4 Bl(x) curve, all I can say is that this is about as close to perfection you are going to get this side of Nirvana (the spiritual high plane, not the band). In our conversation regarding the 12W6v2’s performance on the Klippel machine, Pat commented that this was hands down the most linear woofer he had examined to date. So what does all of the techno speak mean? It means the JL 12W6v2-D4 should maintain its sonic integrity and have only minimal changes in its subjective sound quality throughout its operating range — and that’s a good thing.
Next I measured the T/S parameters. This was done using my usual battery of test equipment from LinearX; the LMS analyzer with Windows 9x software, the new LEAP 5 Enclosure Shop CAD software, and the LinearX VIBox. Once all of the data was collected, the LEAP 5 software was used to generate the T/S parameters and computer box simulation data provided in the Data Chart.
The parameters listed in the Data Chart were used to develop computer box simulations using LinearX’s LEAP 5 Enclosure Shop. The JL Audio 12W6v2-D4 was intended for high SPL performance in small sealed or vented boxes but since I personally prefer small sealed enclosures with Qtc’s in the range of 0.7, I programmed LEAP 5 to simulate the woofer’s operation in two closed boxes, one with a net internal volume of 1.0ft3 and the other with a net internal volume of 1.25ft3. Neither box was simulated with any fill material, such as fiberglass. However, you would be able to get the same box Qtc’s in smaller boxes if that technique were employed.
In the 1.0ft3 sealed box, the JL Audio 12W6 v2-D4 produced a low-frequency roll-off of 48.3Hz with a box Qtc of 0.81. The LEAP 5 graph curves shown in Figure 3 (below) depict the SPL at 2.83V (blue curves) in half-space (imagine a woofer mounted flush in a car door that had been removed from your car, and that the door measured about 10 miles by 10 miles: that’s half-space), 2.83V in a 154-cubic-foot car compartment (black curves), and the SPL at a power level required to get maximum linear excursion (red curves), also calculated in the half-space measurement domain. To keep them separate, the 1.0ft3 sealed box curves are solid lines and the 1.25ft3 box curves are the dashed curves. Increasing the voltage input to the 1.0ft3 computer simulation to 100V increased the woofer excursion to roughly its point of maximum linearity (above which distortion starts increasing) which is Xmax + 15% and yielded a serious 116.5dB.
The alternate sealed 1.25ft3 box simulation resulted in a lower -3dB frequency of 45.0Hz with the expected lower box Qtc of 0.75. Ancient Chinese wisdom (and solid engineering practice) dictates that the larger the box is for a given woofer, the less voltage it takes to make the woofer over excur. For the 1.25ft3 computer simulation, it required only 90V to reach a maximum linear SPL of 115dB. OK, now for my usual comment about hearing damage and loud music: life goes on for a long time, so don’t be stupid with your hearing at a young age and go get that Radio Shack sound level meter for your car so you know how loud the music really is. Trust me, this sub will play louder than this and still sound good.
Like I said in the beginning of this review, the W6v2 may be a step down from the W7, but it’s not a huge step. Like the W7, this driver delivers some really outstanding performance numbers. I can generally get some idea of whether a woofer is going to be good musically from all this technical analysis, so I’m guessing up front that Eric thinks this is a pretty hot ticket. So just how does it sound, Eric? —Vance Dickason
I have to agree with you, Vance. The JL Audio 12W6v2 is an impressive subwoofer and the company has an awful lot to be proud of with this product. The original W6 was like catching lightning in a bottle. It broke new ground and created new concepts in applications and thinking. And it looks to me like JL Audio has once again bottled that lightning with the all-new W6v2 series.
I got a hold of Steve Turrisi, JL Audio’s Area Technical Director, to ask him what his thoughts were on the set up and enclosure recommendations for the best sound quality when using the 12W6v2-D4. He told me to use a sealed enclosure of 1.25ft3, and to hold onto my hindside because this subwoofer was going to shake it off. At the time, I was thinking that was a pretty bold statement for a technical wonk to make, but after testing I was definitely converted to Steve’s way of thinking. But I am getting ahead of myself.
The 12W6v2-D4 has dual 4-ohm voice coils. JL Audio has helped make the hook up of the dual voice coils easier by having both voice coil hook-ups on the same side of the basket and by using four voice coil configuration tab terminals. These are located behind the main input connecters and are used to interconnect the dual voice coils in one of two ways: either in a series connection at an 8-ohm nominal impedance or a parallel connection with a 2-ohm nominal impedance. I went ahead with the factory configuration of a paralleled 2-ohms and my guys at Speaker Works busted out a 1.25ft3 sealed enclosure for the 12W6v2-D4.
Once I got the sub into its enclosure, I headed out to my Scorched-Earth Black Ford F-350 truck to finish up the installation and set up the listening test. I found that the 12W6v2 worked best with the enclosure on the floor of the cab between the front and back seat, with the subwoofer facing the rear of the cab.
To power the second generation W6, I installed a Zapco C2K-9.0XD amplifier. The 9.0XD features a 24dB-per-octave crossover and will pump out a throbbing 2000 watts of power at 2 ohms mono. The front half of my speaker system consists of a pair of USD Audio B-62 WaveGuide separates. I am powering these with a Zapco Competition C2K-6.0X amplifier at 150 watts per channel. The built-in high-pass crossover filter was used to block the bass to the component system. These amps are fed via Zapco’s Symbilink balanced line driver SLB-U. There are no other signal processors in the signal path.
To open the testing, I inserted the Fine Young Cannibals’ The Raw & The Cooked album into my head unit. I like this album because it is well recorded and was mastered for duplication by a friend of mine, Ellen Threatt-Smith. She has a fantastic pair of ears and a brilliant mind. I learned a ton about sound just by listening to her talk about it.
In "As Hard As It Is," the bass line opens with the bass guitar pumping out eight notes per bar, with the kick drum alternating between a single strike and double strikes at the first beat of each bar. The bass guitar is tight and clear and the kick drum hits hard with a ton of impact and no hangover, but the kick drum is not all that audible. Note shifts are clearly audible in the bass guitar and the imaging is fantastic. All of the subwoofer information images completely up front with nothing pulling the image to the rear.
Moving to a new piece of music, I popped in Steven Curtis Chapman’s album Speechless, track 11, "With Hope." Again the 12W6v2-D4 has no trouble keeping the image of the bass guitar up in the front of the soundstage. This demonstrates how successful the JL Audio engineers have been in controlling harmonic distortion. The bass guitar notes are forceful and tight. Note shifts are clear with no blooming in the upper bass frequencies like a number of the other subwoofers that I have tested in the past. The detail in the bass line is great. The 12W6v2-D4 has got to be the most linear subwoofer in frequency response that I have tested.
Moving on to a jazz track, I selected Ramsey Lewis’ "People Make the World Go ‘Round." This track opens with a lot of jump and energy from a bass guitar and percussion. The 12W6v2-D4 is smooth and easy to listen to and has the impact and hit that gives this track its excitement. The playback is full and exciting to listen to.
My usual lead off test tra
ck is Tracy Chapman’s "Heaven’s Here On Earth." It’s an awesome recording that features a bass drum, toms and a bass guitar in the bass line. The track opens with the bass drum, one beat in every other bar as a pick up note for the next phrase. The bass guitar and toms are added and maintain the bass line for the phrase. All of the instruments are clearly defined and individualized with no blurring.
To finish off my listening test I put in the Bass Mekanik’s V5.0 album, track six, "Dubalicious." On this album, there is nothing delicate about the recording of the bass. It’s loud, it’s strong and it’s deep and moving. I like this track because of the variety of bass notes and its mix of sustained and punctuated notes.
The W6v2 has been just about flawless up until this point. It has been punchy, tight, smooth and a wonderful listen, but on "Dubalicious" I heard a flutter (a mechanical noise) in the opening bass line that should not be there. I checked the enclosure, the wiring and panels but the flutter persisted on this opening section of 80Hz sustained notes. Once the pitch changed the flutter was gone and the 12W6v2 was fantastic, throbbing and punchy bass delivered to your body like someone smacking you with an axe handle.
While I was not able to figure out the fluttering noise that I heard, it was frequency specific and could not mar the overall performance of the JL Audio 12W6v2-D4. I would have to say that the 12W6v2-D4 is the best sounding subwoofer that I have tested for CA&E. Its low distortion, powerful impact and overall musicality give it a wonderful sound and invisibility in imaging. If the 12W6v2-D4 is any indication of what JL Audio is engineering for its home audio line, other home speaker manufacturers need to be reinventing themselves or JL Audio will roll right over them.