24 Road Tests By MarkAmundson W hen the Lab.gruppen FP+ series of power amplifi ers was introduced late last year, there was competitive skepticism on the reality of the specifi cations. How could Lab.gruppen offer a 13-kilowatt amplifi er in two rack spaces that weighed less than 30 pounds? The answer was shown to us at Winter NAMM, when the FP13000 chassis was left open for all to see. The simple math tells us that when you use a 390-volt (+/-195 volts) switching power supply into the Class TD amplifi er modules and cool them with a lot of copper heatsink, you get 6500 watts per channel into 2-ohm loads. As I did not have a need for 6500 watts in any one speaker array, I chose the less ambitious FP6000Q as a good representative of the FP+ series of amplifi ers. Even with that said, no one has previously produced this large of quad channel amplifi er in two rack spaces, much less offering the quad channel FP10000Q in the same size with 2500 watts per channel into 2ohm loads. Another nice touch is that — unlike most power amps — you do not lose close to half of your output power when moving from 2 ohms to 4. THe FP+ line is actually optimized at 2.67 to 3 ohms depending on the model. What this means is that the difference in output power between 2 ohms and 4 is token at best before current limiting. My Lab.gruppen FP6000Q came in normal cardboard packaging and weighs in at 26.4 pounds like all the rest of the FP+ series. The 19-inches by 3.5-inches by 15.6-inches overall dimensions make it a bit deeper than some compact amplifi ers in the 20 to 30 pound class, but shallow enough for most amplifi er racking. Rear rack rail kits come with each amplifi er, so there is no chasing for accessories in this series of amplifi ers. The 12-gauge non-detachable power cord with a NEMA 5-20P plug is another clue that this big amplifi er is best connected to stout power distribution in order to deliver the rated audio output power per channel. Yeah, I grabbed my 5-20R to 5-15P cheater adapter for bench tests, and the 5-amp power-on softstart in-rush draw made no visible problems By AlexFletcher If you work with sound systems of any significant size you have been at least exposed to the DriveRack series from dbx. The fact that I can say that with total confidence shows how fast this type of gear has caught on. It didn’t exist a decade ago and now everyone from TC to Yamaha to Sabine to XTA to the dude down the street make one and we all use them. The Gear RT Like pretty much every other “system controller” on the market, the dbx DriveRack line takes a bunch of gear that we used to keep in a big case called, what else, a drive rack and puts it all into one DSP-driven unit. Typically you get a number of inputs with about double that number of outputs with everything from EQ to delay to RTA and compression and crossovers. The 4800 is the “flagship” of the dbx DriveRack line. The regional soundco I work for has had four of them and we have been using them on a variety of gigs with different speaker and amp combos for about six months now. The unit is offered in two versions. The MAY 2007 Lab.gruppen on residential 120VAC circuits. There were also no audible thumps or pops through speakers when going through power-up or power-down cycles with the FP6000Q. The Gear RT The Lab.gruppen FP6000Q front panel is a stylish black face with cooling air inlet vents on both sides of a centrally organized control panel with four gain knobs for the ABCD channels. Additionally, the control panel features 7-segment LED bargraphs per channel, and a few other LEDs for abnormal operation status. On the far right side, almost hidden by the large and rugged lift handles, are two rocker switches for power on/off and the NomadLink digital interface enable selections. The rear panel of the FP6000Q is where all the action is. The top half the rear panel is where all the warm air exhaust venting is, and you can easily see the plethora of shiny copper heatsink fi ns near the venting. The bottom half of the rear panel includes four Neutrik Speakon NL4 output jacks, four XLR-F signal input jacks, three 8-rocker DIP switch banks, two NomadLink Ethernet jacks for in and out data signaling, and the strain-relieved power cord entrance. The only user interface on the rear panel is the rocker DIP switches, adjustable with a small screw driver or mechanical pencil in order to toggle the switches. Most of the DIP switch selections allow for channel-by-channel selection peak voltage limiter selection (VPL) and a hard or soft-clip choice when entering the limiter. Three common DIP switches are used to select overall amplifi er gain values from 23dB to 44dB in 3dB increments. The last grouping of DIP switch selections is four bridge mode enabling (A+B, C+D) dbx 4800 with front panel controls and the 4820 without front panel controls. They are both 4 in 8 out 2 space rack units. All I/O is on balanced XLRs. The 4820 is really meant for the installer-types who want to set up a system and then lock it down so the “volunteers” can’t screw anything up There are six parameters on each of the four inputs: mix (source selection, gain, and pink noise), GEQ, A.F.S. (auto feedback suppression), a nine-band parametric EQ, mono compression and time delay. And there are six parameters on each output: source select and gain, crossover (this is very deep and includes includes filter selection, slope, polarity, phase and gain), six-band parametric EQ, mono limiter, output delay and composite graph viewer. Obviously the 4800 can do a lot, so you are going to want to spend a little time getting to know the thing before your first date. That is one of the things about having a lot of power — it allows you to do pretty much whatever you need to do to tune the system, but it also allows you to totally screw yourself if you don’t know what you’re doing or how the 4800 works. You don’t just www.fohonline.com FP6000Q Power Amplifier and intelligent fan enabling that slows up the fan speed when no signal is present. Like most tour grade power amplifi ers, the Lab.gruppen FP6000Q features a very wide frequency response (6.8Hz to 34kHz) at a 0/- 3dB fl atness and 112dBA signal to noise ratio. The THD is a modest less than 0.05% at 1kHz, and 0.1% over the 20Hz to 20kHz range at one watt. For power ratings, the FP6000Q does 1500, 1250, 625, 320 watts at 2, 4, 8, 16 ohms loadings respectively. And when channel bridged the power ratings are 3000, 2500, 1250 watts at 4, 8, 16 ohms loadings. The Gigs RT After completing the shop tests and playing with the NomadLink communications software for remote status and power on/off control, it was time to rack up the FP6000Q and do a couple gigs. With the 1250-watt ratings at 4 ohms, the FP6000Q was a natural for top box mid-range speaker drive with the other two channels nicely available for high-frequency drive of the horns by dropping down the VPL DIP switches to lower selections. In this application, here is a great example of a single two rack-space amplifi er replacing two amplifi ers to save weight and space. I found the FP6000Q outstanding in performance, and even more high-fi delity that what I experienced with the older fp6400 and fp3400 touring amplifi ers. And this 120VAC version (65 to 135 VAC) seemed to have better foresight when adapting the 230VAC power supplies to 120VAC. My next application and gig was with the FP6000Q driving biamp wedge mixes, and I ran both lo-hi/lo-hi confi gurations, plus DriveRack 4800 throw this in the rack and head out to the gig. One sidenote: Yes, all of the parameters and control is accessible from the front panel. But there is an awful lot that the 4800 can do and that can make navigation via the front panel a bit tedious compared to using a computer. I have been in this business for nearly 30 years and have watched lots of stuff develop and have to admit I never thought I would say this, but you’re gonna want a laptop on the gig with you. The HiQnet software is a review all on its own and we are not going to really get into it here, but let’s just say that even if the 4800 is the only piece of HiQnet enabled gear you are using, the wireless Ethernet control alone makes it worth having that four channels of below 1250Hz, with another quad amp handling the easier horn driver tasks. Even with tough rock ‘n’ roll wedge mixes with pairs of 8-ohm and 4-ohm loading (one or two wedges per mix), the FP6000Q handled everything with ease and fi delity. Overall, I liked the capability for the size and weight; plus the effi ciency that the switcher PSU and Class TD amplifi er stages on lightly consuming power. To visualize Class TD, think of normal Class D switcher amplifi er but with stepped power supply rails like a class H analog amplifi er. Then you can see why very little heat exits this amplifi er when under heavy loads. Looking for weaknesses, I came up nearly empty handed. The only thing that will slow up FP+ series sales would be the expensive price tag. But while pricing always looks daunting to us club-gigging soundcos, the FP+ series is a bargain when you think of the size/weight shrink and the lower transportation costs for touring soundcos. What It Is: Tour-grade power amp Who It’s For: Larger soundcos and anyone who needs really big power in a small package Pros: Compact size/weight for the huge power, great sound Cons: Touring amp price tag may deter local soundcos. How Much: Lab.gruppenFP6000Q: $5695 MSRP Web site: www.labgruppen.com laptop. It’s just much quicker and easier to use a laptop with the software for setup and tweaking. The Gigs RT Like I said, we have been using 4800s for six months, which means probably something like 100 gigs. They have run the range from loud outdoor rock shows to corporate events to you name it. What do I think after that many shows with the 4800? Basically, this unit kicks ass! I work in Las Vegas, Nev. — you know, in the desert, where climate conditions can be a bit on the extreme side. Despite that fact we have not had a single failure from heat or other conditions on these units, and they are going into their continued on page 33
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