Hifonics Xx-Goliath- Test Report Amplifier

by CAE, Aug 01, 2006

ManualThe Goliath comes with a 12-page full-size manual, covering all of the Generation XX amplifiers. It gave me all the info I needed - the text and accompanying drawings explained the features and controls fairly well. There are two pages devoted to system design and setup, and a very simplified page for troubleshooting various problems. Another page allows you to compare all the specs of the Generation XX amps and look up the specifics of the one you bought. All in all, it's a pretty adequate manual that covers most issues you'd encounter during install and setup. It includes warranty info and tells you how to contact Maxxsonics, the parent company.

On the signal side of things, I was pleased to see high-quality, low-tolerance parts used throughout the input stages, and even though this is a bandwidth-limited amplifier, the caps in the circuitry were very good and easily could have been used in a good full-range amp. A lot of manufacturers cut some corners here, but not in the Goliath. Nice.

I'm sitting at my test bench one day pondering the inner workings of some device I was testing, and in walks the technical editor for CA&E, Casey Thorson, carrying a REALLY big box. And by the way he had it propped up on his hip, I knew it was pretty heavy. He tells me it's the new 20th anniversary edition Hifonics Goliath amp and asks if I'd like to test it out in the lab.

ConclusionThe Hifonics XX-Goliath from the folks at Maxxsonics does what you'd expect, and more. It offers good control features, the ability to add a second Goliath as a slave unit (those poor woofers!), and is a high-quality, well-built amplifier. Its prodigious power has to be experienced. There is nothing like having thousands of watts on your car's subs. Even if you don't usually "crank it," the additional headroom is there and you'll notice it. At about $5,000, this amp is not cheap, but this is an area where spending a little more dough pays off. Here's to another 20 years!

ListeningWhen it comes to evaluating the sound quality of a Class D subwoofer amplifier, many learned folks would tell you they all sound the same: bad. I don't necessarily agree with that opinion. I've got a favorite subwoofer system that I've listened to for thousands of hours and know very well. Using a couple dozen of my favorite tracks, I can readily pick out something that's "different" in my subwoofer system. I hooked up the Goliath to the system and settled in for a couple hours listening to some of my favorite tracks for evaluation of the bottom end.

Not surprisingly, the Goliath showed that it had a ton of headroom in the power department, and easily handled most tracks. Power-hungry, very dynamic tracks like the Atlanta Symphony Orchestra's "Fanfare for the Common Man" and The California Projects' "I Get Around" were also handled without any signs of stress. This kind of power on your subs can be addicting.

Listening carefully to Level 42's "Physical Presence" and Don Dorsey's "Toccata in D Minor," I thought the amp lacked a bit of speed in handling the dynamics of either the synthesizer or Dorsey's pipe organ. I also noticed a bit of rolled-off response in the extreme bottom end when listening to Avril Lavigne's "Sk8er Boi." I'll admit here to usually using an amp that is flat down to 5Hz, so I think what I heard was the effect of the previously mentioned subsonic filter. Other than those small foibles, the Goliath sounded controlled and ultra strong.

I ran frequency response plots and found the response of the Goliath to be within 1.0dB from 18Hz to 195Hz. These limits are caused by the amps filter features: The subsonic limits the low end, and the crossover controls the roll-off at higher frequencies.

TEST RESULTSOUTPUT POWER @ 1%THD,100Hz, 14.4 VoltsMono @ 4 ohms 1,708 wattsMono @ 2 ohms 3,062 wattsMono @ 1 ohm 4,696 wattsOUTPUT POWER @ 1%THD,100Hz, 12.5 VOLTSMono @ 4 ohms 1,237 wattsMono @ 2 ohms 2,223 wattsMono @ 1 ohm 3,512 wattsDistortion at rated power, 100Hz, 14.4 volts 0.1% @ any impedanceInput sensitivity 216mV to 9.0 voltsFrequency response (+1dB) 18Hz – 195HzS/N ratio (A weighted, below clipping, min gain) -78.3dBASlew rate 2.52V/µSDamping Factor @ 100Hz, 4 ohms 157.5 Idle current 8.0 ampsMaximum current consumption, unclipped 465 amps @ 4,696 wattsEfficiency at 1/3 power, lowest impedance 71%Efficiency at full power, 1% THD, lowest impedance 70%Crossover slope 24dB/octaveCrossover range, lowpass 15Hz - 250HzLow-frequency boost +18.5dB @ 45HzDimensions28” (711mm)L x 11.2” (285mm)W x 2.6” (66mm)H

As you'd expect with a Class D amp, the slew rate, damping factor and S/N ratio are not exceptional, although still decent for this topology. I measured a slew rate of just over 2.5V/S and damping factor was high for a Class D amp at 157.5. Idle current was pretty high at 8 amps, but considering the amount of devices in this giant, not out of line at all. When you put a 5,000-watt amp in your trunk, you're probably not too concerned with overall system efficiency. With the Goliath, it seems you can have your cake and eat at least some of it, too. At full power into 1 ohm, it was an average 70%, but at full power into 2 ohms, it jumped to 82%. That's a really good number from such a large amplifier.

There is a lesson here for all you bass heads: Buy an amp large enough to give you the power you need without having to push it to its design limits and you'll be rewarded with a cooler running, better sounding, more efficient system.

I did notice that it took about two seconds for the amp to stop playing after I removed the remote turn-on voltage, not a problem in and of itself, but it could cause a turn-off noise in your system if you have a source upstream that shuts off before the amp. On the bench, the amp exhibited no turn-on or turn-off noise.

Circuit DesignThe Goliath is a Class D amplifier, in the traditional sense. That is to say, it is bandwidth limited and designed to be used only for subwoofer applications. A look inside confirms my earlier suspicions about the weight. This amp is built for some serious current flow. In addition to the two pairs of power connectors, the amp uses large heavy-duty buss bars to distribute the current to the board. The type of PCB is very good quality, double sided, plated through and glass epoxy, which resists heat and vibration extremely well. This is a good thing because a powerhouse like this can generate plenty of both. On the main PCB, all of the parts are the through-hole variety, but all are high quality, low tolerance 5% or better. There are surface mount parts on the two daughter boards, used for power supply control and the Class D controllers.