12 Volt Tuning - Import Tuner Magazine

MA Audio has been building loudspeakers and amplifiers for the car audio consumer since 1989 (www.maaudio.com), and while not one of the earliest audio companies to discover car audio, it's also not a new kid on the block, having had considerable loudspeaker design experience. MA Audio is also not limited to loudspeakers and amplifiers; they produce a complete lineup of full range amplifiers and bass amplifiers, subwoofers and component systems, as well as a line of electronic crossovers, capacitors, line drivers, enclosures, installation accessories and even mobile video.

Objective
MA Audio's MA1200XL represents the latest generation of MA subwoofers. A notch down from its extremely high-powered Kore series (how about a 15" with 5kW RMS published power handling?), the XL woofers are referred to as "competition subwoofers," so their power handling overall is higher. Since this is the top line, next to the extreme Kore woofers, you would expect a lot of features, and that's exactly what you get.

Like the Orion H2 and the Pioneer TS-W2000SPL, the frame of the MA1200XL is part of the new trend of mounting the motor assembly inside the frame as opposed to bolting it to the back.During assembly the motor is loaded from the top of the frame and then the cone assembly dropped in and glued in place. The frame itself is a new patented black die cast aluminum one, which has 18 spokes with a solid case between two opposing sets of spokes, which are part of the terminal block setup. The black surface is accented by silver trim and the cosmetic appearance is great. This is also about functionality and the black coating helps radiate heat (via the black body radiation effect). Midpoint on these 18 spokes is a spider-mounting shelf that provides about 35mm of rear travel for the dual opposing spiders. Five years ago, this type of woofer would have probably had a generic frame that you would have seen on a dozen different brand names, but with the low cost of tooling in China, making a custom frame for each model is not a problem.

Everything below the spider shelf has a perforated screen inserted on the inside of the frame, along the outside perimeter of the spokes, and covering from the front plate up to the rear spider. MA has provided a completely open path across the plate and voice coil for enhanced thermal cooling, which, along with the 1.75-inch-diameter pole vent, forms MA's patented thermo-cooling motor structure.

Providing the horsepower for the MA1200XL are two 172mm-diameter Strontium ferrite magnets (a stronger grade of magnet than standard ferrite). The pole is extended 8mm, approximately 50 percent of the gap (front plate) height, which is optimal for increasing linearity in the forward-going fringe field.

The cone assembly is also fairly feature laden, beginning with a non-pressed silver-colored paper compound cone, which is light and stiff and additionally treated with a water resistant PVA (Poly Vinyl Acetate) emulsion. A five-inch-diameter vacuum-formed polypropylene dustcap with a raised MA Audio logo covers the voice coil neck joint and also adds stiffening to the cone. Attaching the cone to the frame and providing part of the needed suspension compliance is a 26mm-wide and 18mm-high, three-layer injected and treated foam surround. While the surround has a series of 24 ribs that look like they must be doing something, these are of the same thickness as the rest of the surround, so are more cosmetic than anything.

Remaining compliance is provided by a pair of opposition-mounted seven-inch-diameter spiders made from Dupont cotton material. These are progressive-type spiders that decrease their compliance (have more resistance) as they reach the end of their travel. This is especially important if you plan to use the MA1200XL in a vented box. Coupling the cone to the motor system is a 311/44-inch (82mm)-diameter dual voice coil wound with copper-clad aluminum wire on a high temperature Kapton former. The dual two-layer voice coils are terminated with tinsel wire woven into the top spider and terminated to two sets of platinum-plated terminal blocks. Each voice coil has two terminal blocks, which have two screw-down connectors that accept up to 12-gauge wire.

In The Lab This section is divided into two parts, Klippel analysis and LEAP 5 analysis. Using the Klippel analyzer (on loan from Klippel GmbH), Pat Turmire, CA&E reviewer and CEO of Red Rock Acoustics, performed the Klippel analysis on the MA Audio MA1200XL DVC subwoofer. Ideally, the Bl curve should be centered on the 0mm point (where the cone is positioned when there is no signal) and symmetrically decrease with the same slopes in both directions of voice coil travel. When a woofer shows an offset it may mean that the magnetic and mechanical systems have not been completely optimized. Motor strength could therefore decrease faster in one direction (usually the outward direction) than in the other, and this means more distortion at high operating levels than if it were operating perfectly symmetrically and providing equal motor strength in both directions. However, sometimes an offset is deliberately used to keep the motor more linear as it hits its primary operating range of 90-110dB. Also, it's good to keep in mind that the human ear is not very sensitive to distortion at low frequencies and 10-15% THD (Total Harmonic Distortion) really is not audible with program material, which helps to keep the concept of linearity in a better perspective.

When looking at the MA1200XL Bl(x) curve, we can see the symmetry is almost perfect. The BL shows equal energy in each direction. Note that the XBl or measured Xmax from Bl limits can also be calculated from these curves. For the MA1200XL, this is at 17.5mm, which is higher than the rating in MA Audio's literature of 14mm and a bit higher than the +15% value that is used in the tests below. Another curve that the Klippel generates is the Kms(x) or compliance symmetry. This is similar to the Bl(x) curve; however, it shows how linear and symmetrical the suspension parts (foam surround and spider) are. Ideally the Bl(x) and Kms(x) curves are similar, which means the speaker is well controlled and stable at high power levels. For many woofers this is not the case. However, for this one, the curves are nearly perfect complements of each other. During the Klippel test this really proved to be true. In free air with more than 400 watts RMS driving the speaker to 22+mm of excursion, the MA1200XL stayed well behaved, with no bottoming or mechanical noise.

Next I measured the T/S (Thiele/Small for Dr. Neville Thiele and Dr. Richard Small, two very well known names in loudspeaker engineering and both from Down Under) parameters for the MA1200XL. This was accomplished using the LinearX LMS (Loudspeaker Measurement System) analyzer with Windows 9x software, the new LEAP 5.0 Enclosure Shop CAD software, and the LinearX VIBox for measuring dynamic impedance (impedance at different voltages). Testing consisted of performing impedance sweeps with LMS, with the driver clamped in a rigid stand for the free-air measurement, and then with the addition of 75 grams of modeling clay attached to the cone. These impedance curves were made using the current source (admittance) measurement method. Instead of getting the impedance curve by a single measurement as a voltage change across a large 600-1000-ohm resistor, this method is done by measuring voltage and current separately at a series of successively higher voltage levels and each two-curve pair (voltage and current) is divided to produce an impedance curve. Measurements were taken at 1V, 1V with added mass, 3V, 5V, 10V, 15V, 20V, 25V and 30V (for a total of 18 separate sweeps with the LMS analyzer: nine voltage sweeps and nine current sweeps). This is done not only because it's better to have the woofer driven through an amplifier like it will be in "real life," but also because measuring impedance at different voltages gives you a lot more information about the dynamic behavior of the woofer. The MA1200XL was getting fairly non-linear at 30V in free air (no box), but since LEAP 5 was able to closely curve-fit the data, it was included. This body of data was copy/pasted into the LEAP 5 software and the parameter derivation utility used to create the T/S parameters and computer box simulation data.

The MA1200XL parameters found were used to create computer box simulations using LinearX's LEAP 5 Enclosure Shop (learn more about this at www.linearx.com). According to the manual, this MA woofer was intended for high SPL performance in both small sealed and small vented boxes. However, with a Qts of 0.52, I decided to go with a pair of sealed boxes. I programmed LEAP 5 to simulate the woofer's operation in a 0.75ft3 and a 1.25ft3 sealed enclosure, neither with any fill material such as fiberglass. This also was the minimum and maximum sealed box volume recommended by MA Audio in the woofer manual.

Loaded into the 0.75ft3 sealed box, the MA1200XL yielded a low-frequency roll-off of 56.4Hz with a box Qtc of 1.03. The graph curves showed the SPL at 2.83V (blue curves) in half-space, 2.83V in a small 154-cubic-foot car compartment, about the size of a Mitsubishi Eclipse GT, and at the SPL at a power level required to get maximum linear excursion. Increasing the voltage input to the 0.75ft3 computer simulation to 108V pushed the woofer excursion to Xmax +15% and yielded a loud 118dB.

The larger 1.25ft3 box simulation produced a lower F3 of 49.2Hz with a lower box Qtc of 0.88. Since larger boxes take less voltage for them to over excur, the 1.25ft3 computer simulation required only 87V to reach a maximum linear SPL of 116dB, loud enough to tweak your ears a bit but still 24dB below the threshold of pain. Since these numbers are based on steady state (sine wave) analysis, the performance with program material will be at least 2-3dB greater before noticeable distortion.

MA Audio has a good reputation and the XL series has the right kind of features in this price range at $200. The MA1200XL produces some good numbers and looks to me to be very well built. Performance on paper is one thing, and how it sounds playing music is another. So, how does the MA1200XL sound, Eric? -VD

Subjective Well Vance, this is an interesting and cool looking subwoofer. From the packaging barrel that the MA1200XL comes in, to its massive frame and magnet structure, the MA1200XL has a commanding presence.

Installation To get MA Audio's official recommendation for the enclosure size and type to achieve maximum sound quality, I spoke to marketing coordinator and one-time star of The Discovery Channel's hit TV show, Monster Garage, Kevin Kuenzie. Kevin, a man of very few words (he kind of reminds me of my brother Patrick), recommended either a ported enclosure of 1.0ft3 with dual 4-inch-round ports, 16 inches in length, or a sealed enclosure with a net volume of 1.1ft3.

I had my guys at Speaker Works bust out some enclosures in which to install the MA1200XL. A word of caution: The MA1200XL does not fit into a standard 12-inch subwoofer cutout. It is about 1/4-inch bigger in diameter than a standard 12-inch. Kevin told me that the MA1200XL's basket is a proprietary design, and it is a good-looking basket, but it would be nice if MA Audio had stuck within the size convention.

A couple of other tips when installing this subwoofer are as follows: I recommend that you use an extra length of wire in the enclosure so that the subwoofer can be placed upside-down next to the enclosure when you are hooking it up. The wire terminal screws are on the bottom of the frame and hard to get to unless you have the subwoofer turned over.

Also, be careful when you go to insert the MA1200XL into the enclosure. The MA1200XL has dual 4-ohm voice coils and the wire terminals are on opposite sides of the frame, with heavy-duty gold plated terminal blocks. These are nice and have a positive install feel but the speaker wire exits are perpendicular to the circumference of the subwoofer-in other words, the speaker wires stick out of the side of the frame. Now, this would not be a problem with most subwoofer frames, but the MA frame is very square in cross section. There is almost no taper in the basket and the protruding speaker wires are very easy to rip out of the connectors when you are installing the subwoofer in the enclosure if you do not route them between the frame spokes. Not a big deal, but it is something to help you save effort and allow you to learn from Speaker Works' experience.

Once I got the MA1200XL 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 MA1200XL worked best with the enclosure on the floor of the cab between the front and back seat, with the subwoofer facing the passenger side of the cab.

To power the MA1200XL, I used 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 reference 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.

Listening
I started my listening session with Seal's latest album IV, track one, "Get it Together." The upper bass response was humpy and a little boomy. Impact was good but the overall response was loose. The real deep notes (below 40Hz) were light in level compared to the bass at 40Hz and up. Imaging was not to bad. There was some pulling to the rear, particularly in the upper frequency range where this subwoofer is boomy.

Staying with male vocal, I dug out Lenny Kravitz's album Lenny, track five, "Believe In Me." This track has a great opening bass line, and a tightly recorded drum kit that will really exercise a subwoofer. Frequencies around 80Hz still bloomed on this recording, but it was not one note-ish like other subs that have a resonance bump. The MA1200XL is loud and delivers a fair amount of impact but is not in the same league for impact as some of the other high-end subs that we recently reviewed.

In a smaller enclosure the MA1200XL was tighter and has better impact than in the 1.1ft3 enclosure that I ended up using but the upper bass resonance got way out of control for sound quality. I ended up trying three different enclosures with the MA1200XL before I decided that the 1.1ft3 sealed enclosure worked the best. It really struck the best balance for sound quality and control.

Swapping rock for rap, I put in Will Smith's Born to Reign album, the title cut. The MA1200XL imaged better with rap music and the impact was still good. The release of the bass notes was sloppy but livable. While this subwoofer was not as tight or punchy as I was expecting, it did a really good job in reproducing the sound of each bass instrument. Linearity was not as good on the deep stuff as I would expect for a subwoofer with an MSRP of $275.00, but the MA1200XL appeared to be a loud subwoofer on sustained bass notes, and the later SPL results (see chart) will show this to be true.

I found what the MA1200XL really likes when I broke out my Boston Acoustics Music for Bottom Feeders demo disk. The third track is by Ramsey Lewis and it's called, "People Make the World Go 'Round." It opens with a lot of jump and energy from both a bass guitar and percussion. The MA1200XL was fat and rich on this cut. The upper resonance peak was smoothed out and the note shifts were good and with proper timbre. Some of the fine details were a bit muddy but the track was reproduced with great sonic integrity. To make sure that the MA1200XL was not just performing well on this track, I popped in Sade's Lovers Rock album to verify. Oddly enough, it appears that jazz is the preferred genre for this sub. Again, smooth, rich and thick on the bass line.

To finish off my listening test I put in the Bass Mekanik's V5.0 album, track six, "Dubalicious." The bass on this track is loud, strong, deep and moving. I like this track because of the variety of bass and its mix of sustained and punctuated notes. The MA1200XL seemed to struggle with the fast-paced base line. The articulation of the separate notes was muddy and the volume linearity from the really deep frequencies to the upper bass notes a problem. But the sound of the bass instruments and tones was enjoyable.

Conclusion
MA Audio has produced an awesome-looking subwoofer with the MA1200XL. While it has some control and impact deficits, it makes up for a lot of that by reproducing a tonally accurate bass line. It was a serious threat in the SPL readings too, where it came within 0.2dB of matching the Orion H2 12-in that I reviewed a few months ago for the unofficial CA&E SPL Crown. -V

Data Chart
Brand MA Audio
Model MA1200XL
MSRP $275.00 (street price about $175-$219)
Warranty 2 years with original receipt

Mechanical Specifications
Weight 23.25 lbs.
Rear Mounting Clearance 6.31"
Woofer Magnet Dim. (dia. X ht. in mm) 172 x 25 x 2

Voice Coil Diameter 82mm (3.25")
Voice Coil Winding Layers 2x2 (two, two-layer coils)

Measured T/S Parameters
Nominal Impedance (ohms) 8 Revc (ohms) 6.94 (both 3.47-ohm voice coils connected in series)Sd (cone area in sq. meters) 0.051

Bl (motor strength in Tesla Meters) 20.0
Vas (in liters) 59.9
Cms (micrometers per Newton) 160.9
Mms (grams) 186.1
Fs (Hz) 29.3
Qms 4.26
Qes 0.59
Qts 0.52

Power and Excursion Data
Sensitivity (2.83V/1M in dB) 86.5
Continuous Power Handling (watts RMS) 600
Peak Power Handling (watts) 1200Xmax ([coil length - gap height]/2 in mm) 14

Computer Simulation Data
Enclosure size for simulation (cubic feet)
Sealed 1: 0.75 (no fill material)
Sealed 2: 1.25 (no fill material)

-3dB (F3) at 2.83V
Sealed 1: (Qtc=1.03) 56.4Hz
Sealed 2: (Qtc=0.88) 49.2Hz

Voltage to achieve Xmax +15%
Sealed 1: 108V
Sealed 2: 87V

SPL at Xmax +15% (8.5mm)
Sealed 1: 118.0dB anechoic
Sealed 2: 116.0dB anechoi

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