A7S-450 Design and Construction

Introduction

Iowa grown Elemental Designs has been quietly building its products and reputation from car audio roots at the University of Northern Iowa. Founded in 2002, the company history reads as a textbook entrepreneurial story arc, growing from car audio specialty manufacturing to home theater and an eye towards professional sound gear. As to the quiet growth, Elemental Designs lays claim to word of mouth from satisfied customers to move product rather than shouting through advertising.

Happy customers in lieu of advertising propaganda; what a great concept.

Low key advertising keeps costs low, allowing money to be ploughed back into manufacturing and R&D based capital expenditures as well as to pass savings back to customers. There is nothing worse than big advertising budget products where customers are saddled with the cost of procuring other customers for the company. Elemental builds subwoofers to order and delivers them direct to customers, alleviating the retail middleman, which also helps keep prices low.

Having little previous familiarity with Elemental Designs, my curiosity was peaked when Gene asked if I would like to review a 150 pound subwoofer. Being a glutton for punishment, I of course said yes.

Fortunately, for me, when this beast arrived, my wife made the UPS guy bring it into the house rather than leaving it in the garage for me to lift in as he suggested.

Design and Construction

With an 18” driver and at 150 pounds it should be clear that the A7S-450 is a brute force solution to producing low end frequencies. There are bigger and heavier subs, but not many.

The review subwoofer came with a black finish and seems to be the only color option available. Elemental Designs, eD, their nomenclature for short, states in the literature that the cabinet finish is applied by a proprietary method, which produces a seamless, rugged skin on the cabinet. This finish is the definition of utilitarian: black, plasticy, and bumpy. To be completely honest, the finish looks like it would be most at home in a guys dorm room or a frat house, a point driven home by eD comments about the finish resisting beverage cans without coasters and children. While the A7S-450 will not win any awards for architectural interiors/décor, if the potential for damage to the finish is an issue in selecting a subwoofer, I am inclined to believe eD when they claim that the finish will hold up well under abuse.

Editorial Note on Cabinet Finish

According to eD, the rugged finish of my review sample has actually been discontinued and they have since then moved to a matte finish which is standard. This (previously upgrade charge) finish is now the only one shipped with this cabinet so the new units shipping are now little bit smoother looking.

The cabinet is custom manufactured by eD on order using CAD based designs and CAM manufactured by CNC machine. In fact, eD claims to do 100% of their own design work, cutting work, paint work, and materials work in house in Iowa. As for exterior cabinet features, the A7S-450 cabinet features radiused corners and all of the components built into the cabinet are mounted flush to that exterior. The front firing driver is recessed an inch into the two inch thick baffle, which also happens to be deep enough to accommodate the specified driver excursion limit, providing it some protection.

The driver diaphragm material is not specified in any eD literature that I found, but is likely coated polypropylene. The cone itself has a silvery appearance with a large inverted dome dust cap with the company name scripted across it. The only point that I found to question the quality of manufacture comes in with that logo which was not leveled across the cap. It is likely that logo was applied before the cap was secured to the rest of the cone. A minor point as I am sure very few manufacturers make sure that dust caps are put on at any particular orientation, but if the company name is scrawled across it, it does draw attention to itself.

The A7S-450 offers a choice of rear plate amplifiers that are custom manufactured for eD by a company called Keiga Electronics. The standard LT/550 produces 550 watts RMS into a four ohm impedance load while an $85 upgrade to the LT/1300 provides 1300 watts RMS into a four ohm impedance load. For the review, I was provided the more powerful LT/1300 amplifier configuration. Considering the small overall cost increase involved, spending the extra for the upgraded amplifier is definitely recommended.

Both the LT/550 and the LT/1300 amplifiers offer the requisite continuous variable output level adjustment and low pass crossover, but for some reason, the base LT/550 seems to provide a continuously variable phase adjustment between 0 and 180 degrees, according to eD literature, while the upgrade LT/1300 has a basic 0/180 degree toggle switch. The internal crossover system for signal input is adjustable from 50 to 100 Hz, but I was unable to find the crossover slope listed in eD literature for the A7S-450. The LT/1300 amplifier upgrade includes a toggle to kick in a 25 Hz boost of unspecified magnitude. Both amplifiers feature an automatic on/off function switch for power. The amplifiers have speaker level, binding post input/outputs and stereo line level input/outputs with a separate mono LFE input/output in lieu of a crossover bypass switch. Power to the A7S-450 amplifier is provided through a detachable power chord and controlled by a rocker switch with a user selectable 115/230 voltage switch located between the two.

According to eD, the A7S-450 subwoofers use a driver design based on the 190v.2 car audio subwoofer driver. How close the A7S-450 driver is to the 190v.2 is not entirely clear, if it is the same driver put into a home application or if it is in fact actually modified for home use in some way, but the eD website has quite a bit of useful technical details on the car version of the driver. Thiele Small Parameters are provided for the 190v.2 along with a cross section of the driver including dimensions, various recommended enclosure sizes for sealed and vented configurations at different tunings, and even blue prints for those enclosures. With this information, playing with the 190v.2 can be as much fun for the do it your self home audio types as for the car audio types.

The total weight of the 190v.2 driver is listed as 42 lbs, nearly one third of the total system weight. The driver design is claimed to allow a linear cone displacement of +/-0.85 inches, generating a volumetric displacement of 0.10 cubic feet of air.

The 190v.2 driver includes a number of beneficial design features and methods that eD discusses in the literature. According to eD, while the 190v.2 driver is said to be optimized for use in small enclosures, it is said to also perform well in infinite baffle configurations. Individual driver component designs are evaluated using Finite Element Analysis methods by eD to maximize driver linearity. The suspension is designed to maximize linear displacement, featuring a specialized surround design said to increase effective piston area and a spider design with the center of mass pushed forward that eD claims increases efficiency and linearity. The cone is constructed from a seamless 2 piece poly design and the connection of the cone to the spider and voice coil based on a proprietary assembly method, Zero Triple Joint Construction that is said to eliminate problems associated with true triple joint construction in high excursion drivers. Ventilation is integrated into the cone system to force air into the voice coil, reducing distortion and improving power handling. According to eD, the motor structure is said to benefit from a proprietary Co-Linear design which eD claims effectively increases the magnetic field (B) in the gap by using a tighter gap tolerance. This allows them to use a smaller diameter motor while retaining a high B. (IE. Get better small box performance with the same mass).

Accessories included with the A7S-450 are the detachable power cord and high quality machined metal carpet spikes for floor support. The spikes are solid metal and of good quality. For floor placement on surfaces other than carpeting, the carpet spikes can be used with the four small metal feet. The feet have rubber pads on the bottom and a davit on the top to accept the spikes. Compared to the spikes and considering the weight of the subwoofer, the metal for these feet seems rather thin to accept the stress concentrations from the spikes with out distortion and the thin rubber pads seem likely to compress to the point that the down turned metal lip on the feet could dig into the flooring below. So, use them with caution.

To have a look inside the A7S-450, I removed the plate amplifier, which is mounted to the cabinet by 12 wood screws. Once inside, I found the cabinet constructed of heavier 1” MDF panels rather than the more common and flimsy ¾”. Internal bracing for the relatively large cabinet is in the form of an hourglass shaped, bi-directional column mounted to the top and bottom panels. The two pairs of outward facing c sections used for bracing are only attached to the cabinet at the center of the edge at the top and bottom panels and side panels. This provides minimal reduction to the actual panel spans required for stiffening. So, while it is impressive looking, it is not the most effective configuration, structurally.

Editorial Note about Cabinet Material

Elemental Designs informed us that they have recently moved away from using MDF for their cabinets and now use a material called EFS. EFS is a higher density wood and a little more eco-friendly. Score one for the environment to eD! 

For more information about this, visit: http://www.edesignaudio.com/elementaldesigns_efs.php

The amplifier is housed in plastic case, which is mounted to the inside of the back plate by four machine screws. Once detached, I found a massive 6½” diameter by 3½” tall toroidal power transformer. Calculated from output amperages and voltages listed on the side of the transformer, I get about a 1.325kVA rating for the transformer. Transformer power output is supplemented by a capacitor rated for 10000 mF at 160 VDC. The rated power consumption listed on the back plate for the amplifier is 1200W at 115V with a T12AL 250V fuse at 115V power input for overload protection.

As for the driver (190v.2), it sports a sizable motor structure, with a magnet measuring at approximately 7.5" in diameter with a 10MM pole bump and utilizing two  25MM Y30 ferrite rings. The car origins of the driver are evident in the use of spring loaded wire terminals that are common in aftermarket car speakers. There are two pairs of wire terminals located at opposite sides of the driver, apparently to allow bi-amplification for car usage. The driver is wired from the positive terminal on one side to the negative terminal at the opposite side using 14 AWG wiring out from the amplifier and the demarcation between the outsourced amplifier and the eD driver components are as clear as the wire splice between them.