Mackie HR824

Paul White hooks up Mackie's new monitors, nails down the furniture, and settles down for a long listening session.

Mackie have been making mixers for so long now that when they come out with a studio monitor, they still give it a name that makes it sound like a mixing console! You might think that they don't seem the obvious company to diversify into the monitor market, but I've followed the development of this particular project for around 18 months now, and can report that they've gone into it very seriously, making considerable investments in both test equipment and experienced designers. The fruit of their labours is a compact, two‑way active nearfield monitor, though I don't think the term nearfield really does it justice, as the frequency response extends to around an octave below that of many other nearfield designs.

Design & Construction

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.

It's not immediately obvious where that extra octave of gut‑punching bass end comes from.

The cabinet itself is made from 0.75‑inch black ash finish MDF with a 1‑inch front panel, and the side edges are radiused to help minimise cabinet edge diffraction at high frequencies. An internal H‑shaped brace stiffens the cabinet and the tweeter sits in a cast zinc waveguide that works on a similar principle to that used by Genelec; the idea is to maintain an even dispersion at high frequencies rather than allowing the dispersion angle to narrow as the frequency increases.

Inside the cabinet is an open‑cell foam material to attenuate internal reflections. The active circuitry is mounted on a sheet‑metal chassis on the rear panel, covering the passive radiator. Ventilation slots allow the bass radiator's contribution to pass through with little attenuation, and I'd imagine the significant air flow this causes also helps a little with the cooling.

Active Facilities

Both balanced jack and XLR inputs are fitted, along with an EC mains inlet, and these face downwards rather than rearwards to allow the monitor to be mounted close to a wall when required. The power switch and LED are mounted on the front panel along with a clip warning LED, but the rest of the controls and switches are on the rear panel, on which the small legending can be a little tough to read in poor lighting conditions. Perhaps the first unusual feature on the rear is the three‑way power switch to select on, off or Auto mode. In this third mode, the amplifiers come on when an input is detected and turn themselves off after five minutes of continuous silence — very eco‑friendly, and useful for those who don't have a centrally switched power source for their studios!

An input trim control sets the gain of the active circuitry, which is designed with a nominal +4dBu sensitivity. If you find your mixer output is always turned right down to get the right listening level, you can reduce the input sensitivity on the monitors to let you work at a more realistic mixer setting.

The three‑position switch named Acoustic Space may take a little explanation. When a loudspeaker is mounted away from walls, very low frequencies radiate in all directions, rather like the ripples on a pond, so the available energy is shared out over a full 360 degrees. This is known as Full Space operation (the first switch position). If your speakers are positioned right back against a solid wall, all the energy that would have gone to the rear is reflected back into the room, and if the monitor/wall spacing is small, this will be in phase with the forward radiating sound, resulting in a doubling of the bass energy at the listening position. In this situation, all the energy is concentrated into 180 degrees. To compensate for this, the bass end needs to be dropped by 3dB, but as few home studio walls are completely solid, Mackie have given the switch a 2dB cut in the Half Space position.

Quarter Space conditions (the third setting) occur when a monitor is placed in a corner, because now it can only radiate into 90 degrees, and as you might expect, the bass level doubles yet again, so further cutting is required to compensate. Mackie provide a 4dB cut to handle this, but as corners can be acoustically unpredictable places, mounting the speaker against just one wall is likely to produce a more accurate bass end. Still, it's nice to have the option if room size forces you to put your monitors in corners.

Another factor affecting bass is room size, and in a typical domestic room, the dimensions aren't big enough to support deep bass, so all the really low energy just makes the room boom. Because the HR824s can go right down to 38Hz, they can sound a little out‑of‑control in very small rooms or those with poor acoustic treatment, so Mackie have added another three‑way switch to raise the bass cutoff frequency to either 47Hz or 80Hz. The 47Hz position still provides plenty of kicking bass in a small‑to‑moderate private studio, but keeps out the really low stuff that sets your room booming. Few rooms are so small that the 80Hz position is essential, but if you want to check what your mixes might sound like on a small home stereo, you can flip to this position and check.

High‑frequency adjustment is also provided, again on a three‑way switch that provides the option of 2dB cut or boost, as well as a flat position. Those who like the over‑bright, 'West Coast' sound [what, Cornwall or Bristol? — geographically concerned Assistant Ed] can opt for the +2dB setting, but if you're one of those people whose mixes always sound dull on other systems, choose the ‑2dB setting. This will make your monitors sound a little less toppy, which means you'll probably add more top when mixing to compensate. The result should be brighter mixes in the outside world.

Listening Test

Armed with my Sunday‑best CD player, a handful of test material and a pair of metal speaker stands, I positioned the HR824s about a foot away from my office wall, slotted in an Enigma album and promptly felt my breakfast trying to get re‑acquainted with the outside world. The speakers are shipped with the rear switches in their normal positions, which means maximum bass extension and Full Space bass settings, and in my 12 x 13 foot office, that produced the kind of bass more often associated with cinema sub‑bass units during disaster movies. Impressive though it was, I felt the 47Hz and Half Space settings produced a more natural sound balance, but the depth of bass was still unbelievable compared with most other small monitors I've tried. The servo amplification system obviously works, because even at levels close to clipping, the bass remains firmly in control.

The mid and high end is best described as crisp and detailed, with a slightly forward characteristic, but not enough to make the sound seem rough or fatiguing. Tested with solo voice, the delivery is natural and dynamic, but again with that slight forward character that lets you hear every breath and lip smack in close‑up detail. I'm not usually a fan of metal tweeters, but I think these represent an excellent compromise between absolute neutrality, and the ability to deliver loud, detailed sounds without distorting. I have heard sweeter‑sounding soft‑dome tweeters, but usually in much more costly monitors, and at rather lower volume levels.

More complex material shows the HR824s to be capable of good imaging over a surprisingly wide sweet spot, and even at high levels, the bass doesn't seem to cloud the mid range or high end. The user‑tweakable bass and treble settings are actually very useful in matching the speakers to different environments and tastes, and as someone used to very neutral speakers, I found things more comfortable with the treble set to the ‑2dB position. The difference is relatively subtle, but having the facility is well worthwhile.

Summary

Servo feedback, passive radiators and waveguides have all been used before, but never to my knowledge in a studio monitor of this type. Indeed, I've only ever seen passive radiators before in hi‑fi systems. However, Mackie seem to have combined them to tremendous effect, no doubt after extensive late‑night listening and tweaking sessions.

After prolonged listening tests with a variety of CD material, plus a stint in the studio, I have to acknowledge that the HR824s are quite remarkable little monitors, not least because they offer such a high level of performance at a most attractive price. I find the voicing to be just slightly on the forward side of neutral, but the overall character is comparable with existing big‑name active studio monitors costing upwards of twice the price, and being honest, I think most people feel happier with a speaker that errs on the side of crispness rather than dullness. The degree of genuine bass extension is extraordinary, and the all‑important test with solo vocals shows no apparent defects or anomalies at the crossover frequency.

I feel that most home studio owners will be better off selecting the 47Hz bass position rather than leaving the system wide open, and because even with that setting, you can hear further down into the sub‑bass than with regular nearfields, it may take a little while to get used to mixing with the HR824s. Even so, any effort will certainly be worth it, as the HR824s deliver main monitor performance for a nearfield price, and on a nearfield budget. What's more, the small size and reasonable weight means these would make great portable references for the travelling producer, not to mention great home cinema speakers for a Dolby Pro Logic system. You have to hear these to believe anything so small could sound so big.