This Crown XLi-800 with its massive toroidal transformer (linear PS) is definitely not an "Air Box" which is a descriptive term used starting in the 1970's when transistors allowed very "compact" audio component designs. The Crown is a very compact amplifier, especially considering its power rating and the fact that it is not a Class-D design.
Quite frankly, I think that the $270 Crown looks a terrific bargain for a very high-power stereo amplifier, and it could be a good choice for those on a very tight home-audio budget especially for those who listen to pop, rock or other highly compressed, limited dynamic range music.
When comparing the Crown with a couple of other mid-sized, higher-power amplifiers that were tested here at ASR, I thought of the Neurochrome 286, a $1,300 limited production 100wpc amplifier kit with a switching PS, extremely low noise and distortion, and a marketing target of home audio system use. The Neurochrome, like the Crown, is a "filled-up" chassis, but with lots of heat sinking rather than fans, and is obviously designed to be placed where convection can be effective. Notice the "wavy" profile of the cooling fins, which are tweaked for maximum solid>air heat transfer, apparently eliminating the need for "active" cooling (fans).
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The other amp that came to mind was the $3,000 "high-end" high-fidelity "pro-audio" Class-AB amp - the AHB2 from Benchmark. In
@amirm's review, he stated that "You get 500 watts of stunningly clean power." It is an "airbox," but unlike many of the larger Hypex and ICEpower amplifiers, the AHB2 has a reason for all of the empty space inside the chassis - the HUGE cooling fin area. I am guessing that the extra height is primarily to accommodate the fins and facilitate better convective (passive) cooling.
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Unfortunately, even though I am supposed to be on a tight budget, I admire well-engineered audio gear, and am willing to spend a bit more than I probably should for lower power, noise, and distortion.
I gave up on cheap Chinese Class-D mini-amps after two Topping PA3s died on me, and I now have a Classé Model 70 in my system. Its in excellent condition, and is a 30 pound, 70wpc, balanced XLR input Class-AB amplifier from the early 1990's. I bought it for $400 from a New York dealer/engineer for $400, and it is used, and was thoroughly tested. It has a bit of barely audible toroidal transformer mechanical hum, but I can live with that. I should be completely happy, but since my audio curiosity occasionally overwhelmes my budget, I also purchased a Ghent Audio (China) case with balanced XLR inputs, and will be getting a couple of 70w ICEpower modules to install in it. I expect it to be equal to the Classé - and without the hum.
For me, at age 77, and fortunately still having decent hearing, I will play with audio until I go deaf, have to give up my independent living, or die and go to heaven. And in heaven, everyone's hearing is perfect, all audio systems have zero distortion, bit-perfect playback, full orchestral dynamic range - and everything is free - a socialist's dream and a capitalist's nightmare. (Unfortunately for those who are condemned go to the hot place down below, all recorded music is played backwards on Bose mini-cubes driven into severe distortion, and all hearing is plagued with terrible tinnitus and never-ending migraine headaches.)