Mackie Hr8 Mointer Speakers HD

Driven by lower‑powered versions of the FR power amp design used in the Mackie rackmount PA power amps, the HR824 uses a substantial 8.75‑inch woofer with a die‑cast magnesium frame and mineral‑filled polypropylene cone, complemented by a 1‑inch, ferrofluid‑cooled aluminium domed tweeter mounted in a shallow horn or waveguide to maintain dispersion at high frequencies. Servo motion feedback is used between the bass/mid driver and the power amplifier to produce a very tightly controlled sound with minimal overshoot. An active crossover with a modified Linkwitz‑Riley, 24dB/octave response comes into play at 2kHz. Switches are provided on the rear of the cabinet to match the bass level to the position of the monitors relative to rear and side walls, with further switches to tailor both the bass and high end to the user's preference (more on these in a moment). The bass/mid power amplifier is rated at 150W (350W burst power) and the tweeter is driven from a 100W amplifier with a burst power of 210W, giving a maximum peak SPL of 120dB at 1 metre (per pair). Maximum short‑term SPL is quoted as being 111dB at 1 metre on‑axis. As you'd expect, the amplifiers do not have cooling fans, so you only hear the music. The overall cabinet size is just 400 x 254 x 310mm (15.75 x 10 x 12.2 inches), with an overall weight of a little over 15kg, so it's not immediately obvious where that extra octave of gut‑punching bass end comes from. To answer this question, you need to examine the rear of the cabinet, because behind the amplifier metalwork is a large, flat‑fronted elliptical passive radiator measuring 6 x 12 inches. Earlier publicity material suggested two smaller circular radiators, so presumably this is the result of a mid‑project design revision. Passive radiators are a tried and proven alternative to traditional cabinet porting, and this example comprises a mass‑loaded piston with an aluminium‑honeycomb composite diaphragm suspended in a rubber surround. It operates rather like a bass driver with no coil and no magnetic assembly, and its job is to provide a mass that reacts with the springiness of the air trapped inside the cabinet to tune the low‑frequency response of the box. At low frequencies, the bass driver moves over a relatively small distance compared with conventionally ported designs, and a lot of the deep bass energy actually emerges from the passive radiator. This allows the cabinet to have a nominally flat frequency response right down to 37Hz (3dB down), while the aluminium domed tweeter is only 3dB down at 22kHz. Each monitor comes with its own response curve measured with a B&K 4133 test set, and this shows the average response to be essentially flat between the frequency extremes