Rockford Fosgate T1D212

Car audio for fanatics.

Pugnacious by-line sure but oh… so true. Seemingly omnipresent, American-born Rockford Fosgate is one of those companies that has always just been ‘there’. It was there back in 1973 upon its foundation and since that time has continued to evolve in order to meet trends that are changing with startling rapidity.

Take today’s clients for example; with their demands of high performance and low cost, preferably in the same package. This attitude lends itself to somewhat of a buttered cat paradox in that you simply cannot have both – somewhere along the way reality kicks in – nothing good is cheap or vice versa. Ergo the Rockford designers must have held a think tank to plan a way around this predicament without going to fiscal extremes. The ensuing T1 range of subwoofers is the representation of what they came up with which is the result of combining proven technology and materials with good old-fashioned experience.

Foot-wide
When we were selecting which subwoofer to hassle-up for review we opted for the T1D212 not so much for its physical size but more so because of the commonality – ask any audio enthusiast what subwoofer is the most-used, and desired for that matter, and the immediate answer is “12!”.

The T1D212 – and indeed the entire T1 range – is designed with what you’d call ‘the serious listener’ in mind. They’re aimed at well above the average ‘to the shops and back’ driver, however, at $699 the T1D212 is not what you’d place in the audio esoterica category either. It’s just one solid arbiter of sub-bass, able to perform in the right enclosure and perform well.

Taking a closer look at the T1D212 immediately reveals she’s no mere trinket. Tipping the scales at a healthy 11.8kg it’s a robust design, featuring a 177mm height die-cast aluminium frame that’s been powder coated black. Its perimeter features a number of elongated slots to allow for multiple mounting positions – a technology Rockford saddles with the moniker ‘FlexFit’ – and bolted to the side is a neat 8AWG push-button input terminal. By neat we don’t just mean in terms of aesthetics, but in terms of function too.

Despite it having dual voice coils it’s only got a single input on the side. What Rockford has done is most clever, in that in order to change between parallel and series wiring there’s a large jumper plate you simply invert and refit. It’s indicative of preventative thinking as this jumper makes potential wiring disasters a thing of the past. The frame material was chosen for its intrinsic magnetic properties or lack thereof, which is important considering it reaches down to wrap around the large 3.48kg double stacked ferrite magnet that concentrates its dense flux onto the motor moving within. This allows for ultra-long transients (Xmax) of up to 16.4mm each way before flux density issues begin to emerge and axial and radial float become bothersome.

The motor itself has been designed with the aid of Klippel’s three separate speaker certification programs – being DA-2, PM-8 and KQC – and consists of twin 2-ohms high-temperature aluminium voice coils which are wrapped in four layers around a thermally efficient 75.5mm former topped with a Nomex reinforcing collar for additional strength during long strokes. The extended back plate also plays a pivotal role here and allows the coil to handle peak power bursts of 1600 watts before overrun and bottoming out becomes a concern. The motor, in all its glory, is clear for all to see thanks to an over-engineered cooling system that allows it a power handling ability of 800 watts continuously.

Rockford Fosgate T1D212 Built in three parts the cooling system induction is undertaken by four large air intakes built into the bottom of the frame, immediately below the magnet. From here the warm air flows up and over the voice coil, where it’s met by additional cool air being drawn into the coil gap via large holes inserted into the cones underside support. As the motor structure reciprocates its bellows effect pushes this air down the inner edges of the former and out the large 25mm pole vent in the centre which is diffused by eight separate air outlets before exiting. The cooling doesn’t end there though, for the third part of this thermal equation is an item that Rockford calls its inductive damping heatsink, which is an overly technical term for a set of cooling fins situated directly atop of the magnet and surrounding the former. Besides helping combat unwanted electromagnetic forces, this heatsink also utilises the second law of thermodynamics as the fins draw heat away from the motor and disperse it into the frame area, where it’s dealt with via slotted air vents built into the basket itself between the web fingers.

Happily mobile above all this cockamamie are not one but two progressively-rolled polycotton spiders which return a sensitivity of 86dB. These are separated slightly and kept in place by a machined retainer collar. Naturally, no lower suspension has worked without the aid of its upper compadre and to that end the cone above is encircled by a thick Santoprene surround which is carefully shaped with a triangular EROM symmetry which Rockford instead call VAST or Vertical Attached Surround Technique. Rather than consume over an inch either side of the cone with a wide surround effectively reducing the moving piston’s area, the surround instead rises up high before rolling and coming back to marry up with the diaphragm. This effectively allows for the same excursion and control but doesn’t turn your standard 12-inch subwoofer into an effective 9.5-inch item. This surround is firm but flexible, not only keeping the cone strictly aligned but also allowing for fluid movement throughout its 20Hz to 200Hz operational range.

Large caps
Last and anything but least is the diaphragm itself. Constructed from a paper pulp base for better efficiency, damping and neutrality, it’s interwoven with Kevlar fibre to give it extreme potency when dealing with traumatic deformations during playback. Laid immediately adjacent is a black anodised aluminium dust cap which enhances the strength considerably due to its size – it’s so large that it’s what you’re actually looking at when you view the subwoofer from the top. The cone itself can only be seen from the bottom through the web fingers. It’s serious business up there.

After conducting extensive testing and experimenting with multiple enclosure designs both ported and sealed, we eventually settled on a sealed 50 litre enclosure which returned a neat Q of 0.707 and a constant group delay of just over 5ms. One thing I will protest at this point is that the manual doesn’t give you an excess of in-depth Thiele and Small parameters instead settling for just the bare basic specs. Nothing major but it needed to be mentioned.

Getting the subwoofer installed and running happily is no issue, with impedance flexibility made easy by the aforementioned ‘SWIFT’ terminal setup. Post wear-in I began testing, mating it up to a Hertz HP6001 amplifier to ensure power supply wasn’t a drama. It’s advisable you do the same as no subwoofer is immune to clipping damage and the suspension system on the T1D212 is more than a little serious. The other advantage of power aplenty and competent suspension is the control exerted over the cone movement, and boy does the T1D212 possess just that in spades. Even when playing at full tilt its moving motor structure remains concentric and super controlled as it reciprocates. The cooling system’s impressive to behold too, with it sucking in massive gulps of air through the back plate and side vents.

Speaking of air; it can move serious amounts of the sonically charged stuff from the front with its surround allowing for serious distances of travel, to the tune of over 60mm when provoked. The relationship between the enclosure and the lower frequency orders is paramount; with its sound quality remaining most impressive as it descends into the sonic abyss. The combination of its enormous motor and a correctly designed enclosure permits the T1D212 to play low frequencies with deceptive ease, reproducing everything from classically-related cello, pipe organ, bassoon and double bass through to gargantuan digital bass drops of dub-step and techno with confidence.

One thing to be reiterated: Rockford Fosgate recommends a 35 litre enclosure for this bad boy and while in actuality this returns a Q of just over 0.8 which still equates to tremendous bass, for those seriously deep bass notes just give the enclosure a little more volume internally.

Conclusion
Overall the T1D212 is a hard subwoofer to make sound bad. It’s constructed well, looks awesome, and can perform with impressive control and painful force. Sure, its internal structure borrows technical ideologies from previous Rockford designs but you know the old saying – there’s no need to reinvent the wheel if the one you have is rolling perfectly… and the T1D212 certainly does just that.

Rockford Fosgate T1D212

Rockford Fosgate T1D212 12-inch subwoofer
Cost: $699

+ Thoroughly engineered; Terrific bass quality; Clever in-built wiring & installation options
- At the price… zip

Type: 12-inch dual voice coil subwoofer
Power Handling: 800 watts continuous, 1600 watts maximum
Frequency Response: 20Hz – 200Hz
Impedance: Dual 2-ohms

Contact: Directed Electronics Australia