At the start of the year, Crown introduced a more sophisticated revision of its successful XTi series amplifiers, the new XTi 2. The original version was lightweight and powerful, with some useful DSP available, as well as a USB interface for quickly controlling and set- ting up the unit. The revision advances that same technology. The power amplifier circuitry remains largely the same between the two versions, but the XTi2 offers advanced DSP and more available presets. As with the original version, the revision offers four amplifiers, each more powerful successively, the XTi 1002, XTi 2002, XTi 4002, and the XTi 6002. I recently spent time with the XTi 4002.
As time goes by, amplifier manufacturers are including more and more sophistication in terms of internal digital signal processing as a general rule. There are certainly exceptions, but most modern professional-grade amps offer a lot more internal processing than their predecessors. Typically, such amps offer equalization, crossovers, delays, and limiting intended to protect speakers. I love getting this processing as part of the amp package—it saves rack space and my back, since I can avoid loading crossovers and equalizers, among other things, into my racks. Some amps get even more sophisticated than just EQ, crossovers, delays, and limiting, and the XTi2 falls into that category.
The details
Advanced eight-band equalization is avail- able at the amp's inputs—specifically six fully parametric bands with high and low- shelving bands, as well. Each band can be boosted or cut 15 dB. A high-pass and low-pass crossover filter is available on each channel, as well, with two topologies available—Butterworth in 6, 12, 18, and 24 dB/octave cutoffs, and Linkwitz-Riley in 24 and super-steep 48 dB/octave cutoffs. In addition, ±15 dB of bandpass gain is available in this section, along with polarity reversal. At the amp's outputs, eight bands of fully parametric equalization are available, offering 15 dB of boost or cut. All of the EQ and filtering is digital, of course, but it sounds very natural. Combining the contour capabilities of several different filter topologies in the digital domain, while maintaining high fidelity, attests to the quality engineering designed into this Crown amplifier.
Each channel has a delay of up to 50 ms for speaker alignment, and the amount can be entered into the system in seconds, feet, or meters. I like this feature because it simplifies life for users—no calculator necessary—just measure and dial it in. A sub-harmonic synthesizer is included in the amp as well, creating a synthetic clone of the low-frequency content of the input one octave lower. This feature was also found in the original version of the XTi, but in the new amp, the user has control over frequency, gain, and filter type, allowing for more complete control of the sub-harmonic signal. It seems as if some kind of sub-harmonic synthesis has become a ubiquitous staple in live sound, and it's effectively achieved here; I do love having the capacity to shake the floor a little when it's appropriate. Each output also features a limiter with control over threshold and attack and release times. Crown's engineering team says the limiters in this new version have been completely rewritten, resulting in improved loudspeaker protection, especially low- frequency, and they are designed to sound much better. The DSP offers 50 presets, 49 of them user-programmable.
Amp inspection
The amp's input sensitivity is rated at 1.4V RMS, and input impedance is 20 kΩ balanced, 10 kΩ unbalanced, while maximum input is rated at +22 dBu. Frequency response is published as 20 Hz - 20,000 Hz, and crosstalk is rated at greater than 70 dB above 1 kHz. Signal-to-noise ratio is published as 100 dB for the three lower- power models, and at 103 dB for the XTi 6002, both figures A-weighted. Total harmonic distortion is rated at less than 0.5%, and my ears told me that indeed this amplifier exhibits really no audible distortion, and is very quiet. The damping factor of this amplifier is over 500 (from 20 Hz - 1,000 Hz—where it's important), so the amp keeps a solid handle on the excursion of your subwoofers.
The amp's construction inspires confidence, and the output capacity of up to 6,000W (in the XTi 6002 in bridged 4Ω mode) is truly astonishing for a two rack- space amp. The front panel is pretty sexy in grey, and features metering and input attenuation knobs for each of the amp's two channels. Centered between them is an LCD display to indicate the amp's status in terms of DSP, bridging position, stereo/mono operation, and so on. It's a very clear display with white characters against a blue background, but a “shelf” above it restricts the viewing angle. If you're looking down from more than a modest angle you'll find yourself stooping to read the display. So you're not going to want this amp way down low in your rack, which is where I typically like to place heavy amps to concentrate the center of gravity low and eliminate top-heaviness. The top half of the front panel comprises the amp's cooling air intakes. On that topic, the amp's cooling fan is fairly sophisticated, offering three user-controlled modes, “normal, early, and full speed”—this allows the user to determine which mode is appropriate for each application, as necessary.
The amp's rear panel is just about as simple as it gets—a binding post and Speak-on outputs, XLR inputs and link- through outputs, a USB port for Harman's HiQNet, and a round vent for the fan's output. I have started growing very accustomed to having network control over the devices in my systems, and Harman International has successfully integrated HiQNet for control over Crown amps, JBL speakers, BSS speaker management, and dbx signal processing, among others. The HiQNet port on this amp is very welcome, facilitating complete control of all parameters from a computer. I'm almost getting to the point that I won't buy or recommend devices that can't be controlled by computer. On the other side of that coin, however, it's also reassuring to know that complete parametric control is available from the front panel. Even without a computer connection, the front-panel LCD screen sufficiently displays the systems' status, and includes navigation with three push buttons. It isn't quite as straight- forward as with the computer network interface, but it definitely does the trick.
Crown makes amps that sound great, and this revision of an already successful line introduces greater sophistication, control, and processing. Some of the sophisticated processing and other parametric controls in this amp are going to be beyond the understanding of un- trained volunteers, but the good news is that in most cases where volunteers are prevalent (i.e., permanent installs), most amplifier parameters will be semi-permanently established at the time of installation and tuning of the system to the room, so volunteers would rarely, if ever, have occasion to make any such changes. In addition, the presets are readily accessed and recalled, so a volunteer in a church could easily recall a setting should something need reconfiguring. The street price of the XTi 4002 I evaluated is right at $1,000, and considering the power, DSP and control capability, as well as the clean sound I would submit that this represents a truly excellent value. This amp is definitely worth a look—and a listen.
