Rockford Fosgate Power T600-2 - A Tower of Power

When I see a high-powered amp in a small chassis, I always wonder if there will be thermal problems when an enthusiastic user drives the amp hard. I'm all about the physics of these things, and I can guarantee you, there's no free lunch in the world of physics. Everything is a compromise. So to determine how any mobile amplifier will fare in the real world, many years ago I developed a special test, allowing me to predict with good certainty whether or not an amp will give the user any heat-related problems. When I thermalled the T600-2, I found more evidence of new thinking from the guys at Rockford. In the new Power series amps, Rockford has taken a page out of the thermal management schemes used by a few other brands and built an amp that will reduce its power a little before shutting off altogether. So there's the compromise that the law of physics insists on. The good news is that this practice significantly extends the amount of playing time the amp delivers under high-heat, high-output conditions. The amount of the power reduction is less than 1dB, and in most cases it will go completely unnoticed. This is one way the engineers at Rockford have been able to reduce the size of the amp, without reducing the power.

ConclusionThe Rockford Fosgate T600-2 is really a new animal from a company that has recently showed a lot of fresh thinking and a willingness to break from tradition when necessary, while still retaining the performance-oriented traditions that made them their name.

Just a few years ago, the idea of building an amp with a less than flat response or one that made less than max power until it shut off wouldn't have made it through the first product meeting. But the competition is fierce and a lot of great products are out there at very reasonable prices. They say competition improves the breed, and if this amp is any indication, Rockford has definitely thrown their hat in the ring. Drop in to see your local dealer, give it a listen, and see if you don't agree.

PERFORMANCE DATA Output power @ 1%THD, 1kHz, 14.4Volts Stereo @ 4 ohms 242 watts x 2 Stereo @ 2 ohms 389 watts x 2 Bridged @ 4 ohms 783 watts x 1 Output power @ 1%THD, 1kHz, 12.5Volts Stereo @ 4 ohms 190 watts x 2 Stereo @ 2 ohms 309 watts x 2 Bridged @ 4 ohms 602 watts x 1 Distortion at rated power, 1kHz, 14.4volts 0.05% @ 4 ohms Input sensitivity 200mV to 8.0V Frequency response ( + 1dB) <10Hz - 31kHz S/N Ratio (A weighted, full 4-ohm power, min gain) > -113.3dB Output Impedance @ 100Hz, 4-ohm load 0.02 ohms Idle current 2.7A Maximum current consumption, unclipped 83 amps @ 389 watts x 2 Efficiency at 11/43 power, lowest impedance 32.5% Efficiency at full power, 1%THD, lowest impedance 65% Crossover slope -24dB/octave Crossover range, highpass 50Hz - 500Hz Crossover range, lowpass 50Hz - 500Hz Dimensions 13.66"L x 8.14"W x 2.14"H

Any concerns I'd had about reduced power went out the window with the first couple of power measurements. Making over 380 watts per channel into 2 ohms, and over 780 watts bridged into 4 ohms, compared to the amp it replaces, this new Power-series amp makes the same power in a much smaller package and for even a little less money than last year's version. Distortion at rated power was below the published specification, and when pushed, the amp clipped cleanly and evenly, with no asymmetrical waveforms developing.

Reassured that it still had all the power you'd expect from the premium Rockford Fosgate series, I went on and measured the more intimate details and nuances. As soon as I started the frequency response sweeps, I saw that my hypothesis was correct, this amp is in fact intentionally designed not to have a flat response. With boost evident from 20Hz to 200Hz, it's no surprise the amp had a warm, rich tone to it. And on the top end, I found boosted highs from about 2kHz to 15kHz, which might have had something to do with the detail and presence I noticed earlier. The inter-channel gain difference was limited to about 0.2dB, which is good for a single-ganged pot.

Signal to noise measured very good, at better than -87dBa reference to 1 watt of output. Evidently, that EMI Shield installed between the power supply and the input circuitry was doing its job.

Efficiency at full power was about average, at 65 percent, and the amp had an input voltage adjustment range of 200mV to 8.0 volts. The crossovers measured as advertised, with true -24dB slopes, and the selected frequencies silk screened on the panel were reasonably accurate. There's about +4dB of unadvertised boost when you engage the lowpass crossover, so be sure to set your gains with the crossover selected as you intend to use it. I didn't care for the tiny adjustment pots that required a small 2.5mm screwdriver tip, but I'm old and my eyes aren't what they used to be. Still, in a dark trunk or under a car seat, these tiny fully recessed pots are going to be a pain.

Nothing too unusual here, except that the new Punch EQ circuit adds not only the usual bass boost, but also treble boost to the output if used in the all-pass or highpass modes. When Jim Fosgate first developed and subsequently patented the Punch EQ circuit, it was designed to help overcome road noise in a vehicle at highway speeds. Back then, it was done with two separate knobs, and the EQ curve on the treble boost was a little different than the one found on this offspring, but the concept remains the same. This new version should be interesting to listen to because in many cases the bass boost is needed, but the treble, not so much.

The amp protected instantly when I dead shorted it and recovered automatically when the short was removed.

One of the reasons the Cogent bench is seldom empty, is that I regularly measure and develop special tests for weird things that no one really cares about until they have a problem. In the case of the T600-2, I didn't find a problem, but I did notice that while it does turn on and off dead quiet without so much as a tick, the amp turns on a lot faster than I'm used to for a Rockford Fosgate (in less than 1.6 seconds, to be exact). I tend to prefer amps with a slower turn-on time, say somewhere around three to four seconds. Why does it matter? Well, sometimes if you have a signal processor, EQ, or preamp upstream of the amp, it can take a couple of seconds for it to "settle" when first turned on. If the amp is already on, any "junk" that finds its way out of a device upstream will be amplified, and cause a turn-on tick, pop, thump, etc. Not a critical deal, but something to be aware of if you ever have a turn-on noise issue with one of the amps.