RF T400X4ad

For those about to…

PDFsRockford Fosgate has been there since the beginning. From the days of Jim Fosgate developing amplifiers in his garage, to the purchase of Hafler and the expansion into international markets, Rockford Fosgate’s history is one of innovation and quality.

The company became the first in the industry to license Dolby Pro Logic Surround Sound Decoder technology. First with high powered amplification for automobiles. In 1973 after finding that its amplifiers were too powerful for the speaker drivers of the day, it simply formed a partnership with a speaker manufacturer, and proceeded to build better drivers themselves, going on to improve sound quality with nearly every product. Very early on, it also recognised the need (and the market potential) for differentiating the premium brands from those they wanted to sell through the major retailers. So they developed budget products to suit, while still retaining the loyalty they’d built up through specialist retailers and installers. Along with innovations such as the Punch Equalisation Circuit and implementation of MOSFET technology, Rockford Fosgate seems to be very good at staying ahead of the game, in what is often a volatile and highly competitive industry.

Rock hard design
Rockford FosgateDavid Baker, Rockford Corp.’s director of electrical engineering, states: “The new Power line-up of ultra-compact stereo and mono amplifiers are built on high efficiency Class-AD and Class-BR technology. The Class-AD models feature multi-impedance Constant Power, and all models come equipped with input/output clip detection, top mounted controls, dual fan forced induction cooling, and optional Punch Level Control (PLC-2). CEA-2006 compliant, they are perfect for hybrid, electric vehicles, cars, trucks, motorcycles, and side-by-side UTVs.”

Couldn’t have put it better myself! Out of the box, the T400X4ad oozes quality from the very first touch. With its black satin finish, all alloy casing and heat sinking all around, this promises to be a cut above the average offering. The Control Panel on the top is especially interesting, but more on that later. Speaking of boxes, the contents of the T400X4ad may come as something of a surprise. Included are a “Birth Certificate”, wiring diagram, and a Test & Set-up CD.

The Birth Certificate (or Certificate of Performance Verification) is a most interesting document. Providing the date of manufacture – 14/04/2014 in this case – it also gives full test results for the amplifier. Idle current, DC Offset, Frequency Response, Common Mode Rejection (CMR), Signal to Noise Ratio, Input Sensitivity, Individual Channel Power at 1% THD – which on the review sample was 141 for the front channels, and 146 watts for the rears. Total power (at 2-ohms) was 574 watts! Pretty stout I’d say. Rail Voltage, Gain Tracking, Channel Separation, Total Harmonic Distortion and Thermal Tests are all thoroughly documented.

There are stories online of customers opening up their T400Xad for the first time, only to find it had tested well in excess of the rated output. One sure way to guarantee some very happy campers. The included Test CD has 27 Tracks of Level Setting Tones, Polarity Tests, Pink Noise, Sine Sweeps and Frequency Sweeps. Almost everything you need for a thorough test and evaluation of your install.

The rest of the kit is equally comprehensive. Plugs for inputs and outputs are supplied. Speaking of inputs, there’s the option of high level inputs, as well as the normal line level. Very handy if adding the T400X4ad to an existing factory head unit without line output. Wiring and plugs are good, solid quality too.

As mentioned, the top panel of the T400X4ad sports a block of controls. These are for the front and rear speakers and offer variable EQ. Crossovers are 12dB/Octave high and low level Butterworth. Along with the Test & Set-up CD, tone controls for treble and bass with settings from 0-18dB, in-vehicle tuning is both simple and fast. The ability to vary input and output levels on both front and rear speakers, along with the separate EQ and Crossovers means this amp will almost “do it all” without the need for EQ from the head unit. Again, something than lends itself to a “power up” for a factory installation.

Hot rock, rocks on
One thing we noticed from the get-go is that the unit gets quite hot, reasonable quickly. Not dangerously so, but I would advise mounting with plenty of ventilation. The two internal fans also run almost constantly. Again, this isn’t a problem, seeing the ambient noise of a car interior, plus the fans are almost silent.

Listening. In just about every criteria within its capabilities, the T400X4ad rarely puts a foot wrong. Yes, of course it will run out of puff if it’s pushed hard enough. But with Rockford Fosgate’s patented C.L.E.A.N. clipping, it does so without distortion and simply cuts out. But up to this cut-off point, there’s no compression or distortion audible.

Given the multitude of adjustments, you’re able to tune the T400X4ad to almost any source and driver package it can cope with. I actually ran it on some 4-ohms moderately efficient 3-way floorstanders for a while and it had no problems giving me very high level peaks without clipping. Pretty cool for something that almost fits in the palm of your hand.

The midrange has a lovely smooth character to it. Plenty of definition and no glare. Treble is clear and clean with plenty of extension. Bass has the kind of slam and punch that Rockford Fosgate’s higher-end amps are renowned for. It was also interesting to note that the T400X4ad has an essentially “neutral” presentation. There was nothing that really stood out, no matter whether it was playing Dead Can Dance or Def Leppard, Rachmaninov or Roxy Music, it simply let the music through. There’s no trace of fatigue or harshness, even at silly levels. (In fact, if you like to listen loud, this would be a great choice for an amplifier).

Furthermore, the T400X4ad can also do subtle. On the infamous Jazz At The Pawnshop album, there are a number of small sounds and rustles on the recording from the people in the venue. Having listened to this album to the point of almost hearing it in my sleep, I can assure you that the T400X4ad is quite capable of doing the “Audiophile Thing”, and giving you every last bit of information your source is able to supply. Above all, the T400X4ad passed my own personal test criteria. This is actually a very simple one and the self-quote is, “Do You Want To Play It More?” 

I think you’ll find the answer is a resounding ‘Yes!’ Box of discs in hand, I cycled through eight or ten favourite cuts while in the process of writing this review and continued listening while getting on with other work.

I stopped to repeat tracks or passages that caught my attention. This is actually a rare thing when you’ve heard a lot of kit, as you can sometimes get a bit “jaded” with the whole process. To have a component come along that measures and performs so well, and then goes on to produce such musical enjoyment, is simply a bonus.

So, is this the elusive “Perfect” amplifier? Well no, of course not, no amplifier ever is. But, at its price point and within its performance boundaries, it comes closer than most things

I’ve heard. If I had to be picky, I’d say the heat output might cause me to carefully assess placement options. I’d also want to mount it somewhere accessible, so I could fiddle with the top panel controls. Hey, but that’s just me. Highly recommended.

Rockford Fosgate Power T400X4ad 4-channel amplifier

Cost: $649

FOR: Powerful, clean & neutral sound, Good feature set, Well engineered

AGAINST: Runs quite warm  

Type: Class-AD 4-channel amplifier

Power: ‘Constant Power’ 4 x 100 watts RMS at 4-ohms and 2-ohms

Features: Class-AD technology,

Low and high level inputs, C.L.E.A.N. clipping detection circuit, low- and high-pass filters

Product page: Directed Australia