Although Image Dynamics is often saddled with acclaim aplenty courtesy of its engineering acumen, haste is one attribute noticeably absent from its accolade list; evidenced by the fact that, despite being in business since 1993, this American-born company has only refreshed its subwoofer stable but a handful of times. Rest assured there is logical reasoning behind this decision – and no, it’s not just lethargy. 
Taking into account multiple factors with consumer feedback as precedence, Image Dynamics adheres to the idiom “if it isn’t broken don’t fix it”. History will reveal that Image Dynamics subwoofers, even to this day, are easily able to hold their own when put into competition against younger generation subwoofers, often dominating with such degree of aplomb that it borders on the embarrassing. 
Nonetheless, Image Dynamics has never been one to rest on its laurels and, despite its stellar track record, continues to slowly work away at its subwoofers, sprinkling intricate improvements as it goes about the business of attaining subsonic deity.
No ID crisis
As mentioned above, there’re various tiers within Image Dynamics’ subwoofer stable, ranging from the entry level ID and IDQ models through to the mighty IDMAX. Never one to shy away from a challenge, we’ve selected the IDMAX 12D4 V.4 for review. Now in its fourth generation the new IDMAX looks similar to the previous versions although, reality is, the new design incorporates numerous new technological advances. 
Starting at the top you’re faced with a two piece diaphragm comprising a foundation layer of thick pressed treated pulp material thus chosen because it’s combination of minimal weight and intrinsic qualities are conducive to highly accurate and natural sounding sub-bass. Forming the other half of the equation is a black aluminium cap featuring the Image Dynamics logo. Much more than a simple dust cover, this device sports a parabolic profile and is strategically positioned in order to resist against the cone, with both elements together returning a winning combination of superb damping and sound projection. 
Circling the cone is a butyl surround boasting the profile shape made famous by Image Dynamics all those years ago. Taking a step back; when you examine most 12-inch subwoofers you’ll see many suffer a wide surround in order to allow them their full range of linear motion. Now, because of this the piston diameter, which is in effect the actual part that’s exciting the air molecules, can measure as little as 8.5-inches diameter. This leads to significantly less kinetic air flow. In order to overcome this challenge Image Dynamics developed its peculiarly shaped ‘Extended Range Of Motion’ surround, colloquially known as EROM. Looking at its cross section it rolls up and over before extending down deeper than any standard semi-circular design, thus meaning the surround is able to move an extraordinary distance linearly without impacting upon its ability to manage excess radial float. To the tune of the IDMAX12 offering a physical peak-to-peak excursion ability just shy of 85mm! 
Yet despite the wonderment that is the surround, it only forms half the suspension equation and lurking quietly below waiting to handle reciprocal movement is a progressively rolled polycotton spider which is quite firm, returning a sensitivity of 85.20dB and remarkably low resonant frequency of 27.77Hz. Together the twin suspension elements work flawlessly as the subwoofer moves throughout its frequency range of 20Hz to 200Hz. 
The spider is attached firmly to the former top just beneath the point where it interfaces with the lower diaphragm. Constructed from solid cardboard, this material was selected because of its magnetically inert properties and impressive thermal attributes. Wrapped upon this are twin 4-ohms, four layer, square-wind copper-clad aluminium voice coils. The voice coil’s neutral position is quite high in relation to the densest parts of the magnetic flux, a stance that doesn’t seem to make a lot of sense; until you see that motor in action that is. 
When talking magnetic forces the densest portion of the flux is often around the corners of the magnet. Ergo we attempt to keep the motor moving between those two extremities which often lends itself to a shallow Xmax figure. This means that when playing loud the motor structure flies around like a garden hose with no end because it has moved well beyond these controlling fluxes. In situating this voice coil where it has Image Dynamics has provided minimal flux effect when the subwoofer is requiring minimal demand in control. However, when it’s being absolutely flogged to within an inch of its life the voice coil is reciprocating at a higher excursion which inherently puts it right in the middle of those two flux densities. Meaning even at full tilt that motor continues to enjoy enormous control throughout its entire 39mm Xmax!
Motor madness 
Creating this gargantuan flux is a double stacked ferrite magnet which is bolted to the imposing matt-black cast alloy frame. It’s a considerable chassis, possessing a healthy mounting depth of 210mm and featuring eight webbed fingers which have been meticulously shaped in order to present a minimal aerodynamic fingerprint. Naturally, Image Dynamics hasn’t stopped there, paying particular attention to over engineering the cooling system. This adventure begins with no less than sixteen 20mm high windows which allow for a titanic amount of air to flow into the voice gap. This takes place beneath the spider while above it reside eight oval shaped intake ports which allow air to flow from the other direction into the inner sanctum just below the dust cap. From here those zephyrs, which by now more resemble a hurricane, flow around the extremities of the former before conjoining for expulsion via the 20mm pole vent. Overall the cooling system is perhaps the most impressive I’ve witnessed to date and to that end it affords the motor a power handling ability of up to 1000 watts continuously. 
The suspension on the other hand is strong enough to handle over three times that amount before it bottoms-out against the extended steel back plate and become any cause for consternation. Yet despite this it’s fluid enough to run off as little as 200 watts. Residing upon the side of the basket 180-degrees apart are two plated terminal blocks able to accept up to 8AWG cable.
Included with the subwoofer is a comprehensive tech sheet providing various Thiele/Small parameters in addition to numerous enclosure recommendations, in order to net you the roll-off Q your particular tastes require. Also included are various warnings against daft behaviour; everything from destroying your ears through to running the subwoofer with only one voice coil connected. 
Both ported and sealed enclosures are modelled, with the sealed designs hovering between 18l and 51l. These of course are jack-of-all-trades recommendations rather than the rule because you’ll appreciate it’s impossible for Image Dynamics to know either the shape or order of the target vehicle. 
Upon conducting a little modelling and simulation ourselves, we discovered the optimum enclosure size for my IDMAX 12D4 V.4 to return a Q of 0.707 was 149l! Now this might appear a little outlandish on paper however the reality is most high-end subwoofers require substantial enclosures in order to achieve that much sought-after 0.707 Q figure. However, don’t grow too pedantic; if you reduce the internal volume back down to 60l its Q only rises to 0.9 which equates to minimal change in response.
Powering the driver with 1250 watts continuous we began the run-in procedure with a 27Hz sine wave. The suspension components are quite stiff initially and will require a little time to loosen up, upon which point you’ll be ready to metaphorically rip and tear. I must confess that I actually owned a second generation IDMAX 12 for years therefore I’m well aware what the older ones sounded like – and they remain one of my favourite subwoofers, period. 
Musical auditions began with heavier genres and it can be revealed that the latest version bears quite the resemblance to those of old. However, because of the metallurgical advancements the newer ones are far more accurate, impressively so when playing faster demands the likes of blast beat metal drumming or jazzy bassoon. Even slower more fluid bass, from instruments such as double bass and pipe organ, sounds astounding. It doesn’t matter what you ask of it, the IDMAX 12D4 V.4 simply delivers a delectable blend of deep, powerful, articulate sub-bass with authority and accuracy hitherto unseen. It’s more than able to handle the odd rush of blood to the head too just quietly; or perhaps more accurately, anything but. Easily capable of blurring your vision, it’s all but impossible to bottom out with that EROM surround starting to stretch and crease before the motor itself shows any hint of reaching its physical limits.
Put succinctly Image Dynamics has taken its award winning IDMAX platform and evolved it to a level many thought unachievable at this price point. Akin to those before it, the new IDMAX 12D4 V.4 continues to represent the perfect amalgamation of astounding accuracy and good old fashioned brute force. 
Image Dynamics IDMAX 12D4 V.4 12-inch subwoofer
Type: 12-inch dual voice coil subwoofer
Price: $849
+ Superb engineering
+ High power handling
+ Accurate, deep and powerful

- Come up trumps?
Power Handling: 200 to 1000 watts continuous, 1000 to 3000 watts maximum
Frequency Response: 20Hz – 200Hz
Impedance: Dual 4-ohms