I know a lot of companies and a lot of engineers in the car audio "game" and I would have to say that JL Audio is certainly on the short list of the manufacturers I consider to be serious professionals at what they do.
This company has been specializing in car audio products since 1975 (national distribution of JL's subwoofers began in 1992), and it goes without saying that JL Audio has long been considered a major player in the subwoofer marathon that we have been witnessing for the past years. Known for their innovative engineering approach to speaker design, JL Audio has produced some very real improvements in subwoofer technology. They were among the earliest companies to use layered voice coil windings beyond four layers, and their patented vented reinforcement collar (VRC) that greatly strengthens the critical bond between the voice coil former, spider and cone was also a smart idea for its time. Not to rest on past glory, JL has recently released a W7 subwoofer series is perhaps even more innovative than any of their previous products. Which brings us to the subject of this review, the JL Audio 10W7-3.
Besides answering the body of questions I give to every driver manufacturer when they submit a product for review, I also got a technical "white paper" type of document from JL Audio that does a very nice job of describing the W7 technologies and the methods employed to design this woofer group. If you are interested in woofer "science", get a copy of this as it has some interesting insights into the inner game of woofer design. The paper begins by acknowledging the limitations of Thiele/Small simulations, correctly stating that this is a small signal representation and does not at all describe the dynamic functioning at higher power levels where listening is really done. While the T/S simulations are still a reasonable guide for developing enclosures, making a woofer that also sounds good at high volume levels goes way beyond this paradigm. If you ever wondered why woofers with identical T/S parameters can sound so very different, it's just that there is a lot more to understand about woofers than is described by this methodology (incidentally, JL Audio sort of unfairly lumped LinearX's LEAP into the category of box design software that does not take into account dynamic non-linear behavior. Even in its old DOS LEAP 4.6 incarnation, LEAP had both non-linear compliance and non-linear Bl models built into the analysis as well as dynamic voice coil temperature computation. However, the new Windows version that's soon-to-be released goes substantially further in the direction of non-linear analysis).
To understand the functioning of a driver as you turn up the volume, JL Audio looked at the current technologies such as the Dumax machine from David Clark's DLC Designs and I would also imagine another laser based non-linear analysis tool called the Klippel Analyzer, which has gained a lot of popularity among speaker companies. While Dumax can map motor strength (Bl) and suspension compliance (Cms) as the voice coil moves through its cycle, JL Audio has its own propriety modeling software (note, Dumax is a analyzer that takes measurements, not software that simulates measurements) called DMA for Dynamic Motor Analysis. This powerful software is based on an engineering modeling method called FEA (finite element analysis) and is very math intensive to the point that analyzing a speaker at multiple power levels takes between 20-35 hours on a 1GHz Pentium III computer. One of the really cool things that DMA does is to model flux variations in the magnetic field that are induced by the magnetic field of the voice coil. I should also mention that JL Audio also uses an FEA program called "Cosmos" for modeling thermal dynamics of a woofer. Enough of this engineer speak, the bottom line is that JL has done an incredible job of using very 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.
So "what's under the hood" you ask? The motor structure of the JL Audio 10W7-3 uses two 166x26mm strontium ferrite magnets (Strontium ferrite is more expensive than the standard ferrite materials normally employed and takes a stronger magnetic charge). These are sandwiched in between a milled and polished front plate and T-yoke (single piece pole and back plate). Cooling is provided by a proprietary pole venting system (U.S. Patent 6,243,479) that uses radially drilled holes in the pole piece that vent air from the inside of the voice coil chamber to the pole vent, very much like peripheral venting techniques used in pro sound woofer for many years. The pole does not open into the area beneath the dustcap, so it does a great job of channeling air over the coil for improved cooling and power handing. Also, the pole is shaped and extended 1.5" over the top plate and, to keep losses down, is hollowed out.
Additional cooling is provided by the proprietary frame design. The very deep (5.25") cast aluminum frame is suspended and attached to the front plate by six standoffs that are formed as part of the frame (called the elevated frame cooling system covered by U.S. Patent 6,219,431). This effectively creates six 1.5"x0.25" vent openings that force air to be pumped across the voice coil over the top plate for additional cooling.
The cone assembly for this woofer is likewise full of innovations. Probably the most striking is what JL calls the OverRoll Surround (U.S. Patent 5,687,247 and 5,949,898). If you follow the reviews I do in CA&E, you certainly have read my comments on large surround woofers. My typical comment is that when you make the surround very wide, then the cone diameter has to be reduced. By reducing cone area you increase the need for the woofer to excur further to produce the same SPL produced by a larger cone and more narrow surround. Bottom line is that many of the large surround woofers that are touting long excursion capabilities have no greater dynamic range than woofers with larger cones and more narrow surrounds. The problem then is how to get the cone travel benefit from a wide surround (for a given frame size that is) and still maintain the same cone area as you would for a standard driver design (if there is such a thing). The solution JL Audio came up with is really creative. The reason the cone is smaller using a wide surround is attaching the wide surround to the frame edge in a conventional manner. But if you could attach the cone to the very outside edge of the frame diameter instead of the normal mounting shelf built into virtually all woofer frames, then your cone would be much larger. Right? Well, doing that is a real trick. JL built a little vertical lip around the outside edge of the frame, molded a foam surround that fit just over that lip at the outside edge of the frame and then held it in place with a metal hoop that holds the surround firmly to this lip. The result is a mechanical bond to the frame, not the normal glue bond. When you mount this driver, you remove the hoop and clasp-type trim ring, lift up the surround and then have access to the mounting holes! When you get all the screws in place, you reverse the process and refasten the cone with the hoop and trim ring. Very slick. I compared Sd number (cone areas in square meters) for two recently reviewed 10" woofers and the numbers were 0.0314 and 0.0227. The Sd for the 10W7-3 is (using the same criteria that incorporates about 1/3 of the surround) 0.0337. Typical Sd's for conventional narrow surround woofers is about 0.0350 to 0.0380, so JL's OverRoll definitely gets them a lot more surface area.
The cone itself is a polypropylene type that is also proprietary and is actually two cones combined, a shallow profile single piece cone (kind of like an inverted dustcap that covers the whole cone) with a more conventional profile cone called a W-cone (U.S. Patent Pending). The W-cone is like a regular cone shape with a small inverted cone attached at the neck joint that connects between the bottom W-cone and the large dustcap like top cone. The result is a very light and extremely stiff cone assembly. Dual cones are nothing new, but the connection method is definitely a great enhancement. Attaching the cone to the frame, using the OverRoll attachment system, is a 37mm wide (22mm height) surround. Remaining compliance is supplied by the 7.7" diameter progressive roll (the compliance gets great as the excursion gets longer) poly cotton impregnated spider. Attaching the spider and voice coil to the cone is accomplished by yet another proprietary system called plateau-reinforced spider attachment (U.S. Patent 6,118,884). This is a variation of the JL VRC attachment collar that increases the stiffness of the neck joint so that the cone does not deform on long excursion strokes. The driver is also put together somewhat differently in that the voice coil and spider assembly are glued up first, and then glue is applied to the Plateau device. The cone and surround are then put into place. Most woofers have the entire cone assembly glued together first (cone, voice coil and spider) and then the whole assembly to the frame/motor in one operation. The company claims this allows for better alignment of both parts and is called FCAM for Floating Cone Attach Method (U.S. Patent pending).
Driving the cone assembly is a single 2.75" 2-layer voice coil wound on high temp Kapton former with round aluminum wire. This departs from the 4-6 layer coils seen in previous JL designs. However, since the design goal for this was likely to keep efficiency reasonable while incorporating a very long coil (22.86mm), 4-6 layers would have added way too much mass to the cone assembly. The lead wires from the voice coil to the color-coded push terminals are also non-conventional in nature. While the entire industry uses tinsel lead wire, JL got "out of the box" and went with four tinsel lead wires jacketed together (two leads for each connection).
I began analysis of the JL 10W7-3 by calculating the T/S parameters using the LinearX LMS analyzer with the new LMS4 Windows software (a big improvement over the original DOS version) and LEAP CAD software (also soon to be replaced with a hot new Win9X version). Impedance was measured using a LinearX VIBox (current source method), which means that the analyzer was connected directly to an amplifier driving the woofer. Rather than creating a single impedance curve, the procedure produces separate voltage and current curves (also called an admittance curve) at a 1V drive level that are divided (V/I=Z) using the LMS post processing menu. I normally use the test box method (delta compliance) in addition to the free-air impedance test; however, the unique mounting method for the 10W7 makes testing in this method somewhat tricky. Instead, I used an equally effective added mass technique (delta mass). These two curves were then transferred to the LEAP program to calculate the T/S parameters. The resulting parameters and computer box simulation data are given in the Data Chart with the LEAP sealed box simulation graph shown in Figure 1.
The measured parameters shown in the Data Chart were used to produce two different box simulations, a 1.375 ft3 sealed box with 50% fill material (fiberglass) and a 1.80 ft3 sealed box, also with 50% fill material. Both box sizes are recommended by JL Audio in their literature, but many other combinations are possible. With a Qts of 0.6, JL recommends both sealed and vented box formats, however, I would tend to think better music performance will come from the compact sealed boxes.
In a very compact 1.375 ft3 sealed box this woofer produces an F3 of 39.0Hz with moderately damped box "Q" (Qtc) of about 0.77. The maximum linear operating level was 113.4dB where the driver reached its maximum linear excursion limit of Xmax + 15% (26.3mm), but was reaching a voice coil temperature that indicates that this woofer is more likely to be thermally limited than excursion limited (note that while LEAP does keep track of the thermal coefficient of the aluminum used in the voice coil and increases the voice coil temperature as voltage increases, it cannot account for the various different types of cooling systems that are used in woofers). However, given the extent of the cooling system in this high technology woofer, I definitely wouldn't want to be sitting in the car when you finally heated it up sufficiently to fail. Like all high performance subs, this woofer is capable of very high SPL and should be treated with respect.
The larger sealed box is of course better damped and plays somewhat lower in frequency with an F3 of 37.9Hz and a box Qtc of 0.73. However, since the larger the sealed box, the greater the excursion, it takes less voltage to push it to its excursion limits. At 60.5V the simulation predicts 112.7dB, the numbers before noticeable distortion using program material probably 3-5dB higher. As can be seen in the LEAP graph, damping changes appreciably at these voltage levels (LEAP uses non-linear models of BL and compliance plus dynamic changes in voice coil temperature to simulate this with a good degree of accuracy), but that's normal.
I'm guessing that with all the techno stuff I've been hurling at you, you are probably thinking, "Hey, forget all this. I know the JL guys are smart, but how does this thing sound on tunes?" I can generally get some idea of whether a woofer is going to be good musically from my analysis, so I'm betting up front that Eric loves the you-know-what out of this woofer. So just how does it sound Eric? --V.D.
Listening
OK, so this big cardboard box with legs sticking out the bottom comes walking into my store. (No this is not the joke about the horse and the long face.) I see that there is a JL Audio logo on it. So, the JL box starts out by saying, "Hey Eric, here's the new JL Audio 10W7 subwoofer that you need to test." Well, to my surprise, out steps my magazine boss and the Car Audio & Electronics' Head Honcho, Rodney "Wonder Boy" Wills from behind this behemoth box. Now, I'm not saying that Wonder Boy is short, I mean he has all kinds of stature in the industry (how's that for kissing up!), what I'm saying is this JL Audio shipping carton is big and heavy!
Being the calm, peaceful, detached observer type that I am, I hungrily ripped open the box to get a look at this baby! The packaging is impressive to say the least. The 10W7-3 comes mounted to a sheet of MDF board. JL even adds another ring of MDF behind the woofer for the screws to get all the traction possible.
In the box on top of the woofer, so that you cannot miss it, is a color instruction manual that says in bold letters, "Please review the mounting procedures thoroughly before attempting to remove the speaker from its shipping baffle." Heck, after looking over the shipping carton and the unusualness of the woofer, I decided to follow this piece of advice.
The JL Audio 10W7-3 does not mount or install like any other subwoofer on the market. JL has developed a clever way to increase excursion and not sacrifice effective cone area. This is done via the outer edge of the surround of the woofer not being glued into place, as is normal. (And as we go along, you will see that this subwoofer is anything but normal.) The outer edge of the surround is held in place with a steel "O" ring, and an extruded aluminum clamp. Having been responsible for subwoofer design, and seen the results of what dealers and consumers can and will do to that design, it would be fair to say that I was skeptical when I heard that JL was going allow the end user to position the surround on the frame during the installation. Now that I have first hand knowledge of the design and its workings, I have to give JL Audio thumbs up on the clever meter. Yes, you could damage the surround by not removing the aluminum clamping ring properly or by being a "jerk" with the surround when you are mounting or unmounting the subwoofer, but you would have to really try to do it.
The directions for unpacking this subwoofer are very complete and informative. READ THEM! I wish I had. It would have saved me from trying to pull the woofer out after removing eight screws like most woofers use. But, no! JL put in 12 screws to hold the 10W7-3 in place. All kidding aside, this is an impressive job that JL Audio has done.
So I get the 10W7-3 out of its shipping carton and I give Steve Turrisi, Director of Technical Services at JL Audio, a call to ask for the company's official recommendations on the proper style and size of enclosure to achieve maximum sound quality. He recommended a sealed enclosure with a net volume of 1.25 ft3. Steve told me that the 10W7-3's displacement is a healthy 0.09 ft3. (As a comparison, many 15" subwoofers are about the same displacement.) With this in mind, I installed the 10W7 into a sealed enclosure of 1.34 ft3 gross volume. This should net out to the recommended 1.25 ft3 that Steve prescribed for maximum sound quality.
Now that the 10W7-3 is in the enclosure, I head for my Stealth-mobile, the Ford F-350 Super-Duty Diesel truck. Once in the Ford, I found that the 10W7-3 worked really well in just about every position. A good sign! I settled with corner loading the subwoofer.
To power the JL Audio 10W7-3 subwoofer, I installed my custom-built Zapco Competition C2K-6.0X amplifier. "Yeah Baby" (with Austin Powers accent), I'm talking about the one that's been "Peak'd'n Tweek'd", on which I used the built-in crossover. The 10W7-3 has a single 3-ohm voice coil, and the Zapco C2K-6.0X normally makes a hefty 600 watts mono into this load. But mine kicks out a shattering 1200 watts mono. (All you have to do is play with the rail voltage -- call Zapco for the insider's info!)
The front half of my reference speaker system consists of a pair of USD Audio B-62 WaveGuide separates. This system features a pair of USD Audio 622, 6.5" midrange/woofers, a pair of the BC-300 horn loaded compression driver tweeters called the WaveGuides and a pair of specially tuned passive 2-way crossovers called the PX-BCs. I am powering these on a Zapco Competition C2K-4.0X amplifier in stereo at a conservative 100 watts per channel. (I did not run the rear surround speakers that are in my truck.) I am using the built-in high-pass crossover filter to block the bass to the component system. Both of these amplifiers are fed via Zapco's Symbilink, balanced line drivers SLB-U and SLB-TP4. There are no other signal processors in the signal path.
The JL Audio 10W7-3 is a great sounding subwoofer. Let's get that right up front. It's full, impactful, and powerful. To my delightful surprise, the JL Audio 10W7-3 sounds a hell of a lot like my reference subwoofers, the USD Audio Y-210's that I use every day. And that my friends, is the first time I have ever had the pleasure of saying that.
On just about all program material, the 10W7-3 does the job wonderfully. But, it does seem to reproduce the bass line more forcefully and louder than you would expect or think is correct at higher volumes. JL has taken great pains in the design of the W7 line of subwoofers to cool the voice coil. This should result in decreased power compression. Meaning that the voice coil of the 10W7-3 is so well cooled that it does not experience the drop-off in SPL that other subwoofers do from retained heat. (Power compression happens when the voice coil heats up the resistance of the voice coil wire increases, lowering the output of the subwoofer.)
For example, on Al Jarreau's Tomorrow/Today, title track, the skipping, Latin-flavored bass line is reproduced with bounce and impact. Really solid and tight. But from a soft to loud volume I found that I wanted to decrease the volume of the subwoofer to maintain the standard linearity that I have experienced my entire life, rightly or wrongly. Scott Atwell, my friend and speaker engineer tells me that this is the future, get used to it.
On Sade's Lovers Rock album, title track, the bass line is very good at 40 Hz and lower. The 10W7-3 is not as tight as the Alumapro 12-H2O or the Focal 5WS that I wrote about earlier, but the lower frequency extension of the 10W7-3 puts them to shame. At 02:12 through 02:20, the bass line steps through a series of note changes that the 10W7-3 reproduced wonderfully.
Next, I listened to Lenny Kravitz' album Lenny, track 5 "Believe in Me." This track has a great opening bass line, and a tightly recorded drum kit. The 10W7-3 reproduced this bass line with chest pounding impact. The 10W7-3 has a flat response curve. Many of the subwoofers that I have listened to and tested will have mid bass peaks in their frequency responses or they will have rolled-off lower frequency response. I do not hear this in the JL Audio 10W7-3. Fantastic.
I wrapped up with 10,000 Maniacs' album In My Tribe, track #7, "Peace Train." This track opens with a deep repeating 30 Hz "kick drum." The kick drum is tight and punchy, but lacking the "skin detail" of the mallet strikes that other subwoofers have reproduced. The full fundamental note is reproduced and accurate. Overhang is slight and fully acceptable with the 10W7-3.
SPL in car measurement at 2.83 volts, at 1 meter Peak reading non-weighted
40 Hz.................100.5 dB
80 Hz.................100.8 dB
Max SPL...............130.6 dB
Somebody else has already said that the JL Audio W7 series is a "Tour de Force" of engineering and performance. I must agree and echo that sentiment. These subwoofers are on the pricey side of the street, the 10W7-3 retails for a hefty $549.95 each, but you get an awful lot of performance and technology for your money, not just a bunch of BS chrome and girlie advertisements.