Mackie HD1521

Mackie’s range of active speakers has become very well known in recent years, and the full-range models such as the original SRM450 frequently crop up in all sorts of installations and as portable sound systems. The range was revised a couple of years back with the introduction of some neodymium drivers and revised amplifier designs, and there is now a new HD range that represents a further increase in performance with even lighter weight. It features system tuning and transducer design by EAW. I had the chance to try out a pair of the new HD1521 speakers, which are the same format as the SA1521zs, ie. a fully active, two-way design with a 15-inch woofer and one-inch-exit compression driver. The other HD model currently available is the HD1530, which is the HD version of the popular SA1530z. It’s a three-way cabinet that features a dedicated six-inch mid-range section, and I understand that Mackie plan to add HD versions of their 15- and 18-inch active subwoofers later in the year, providing a complete HD range that reflects all the current SA models.

I owned and operated half a dozen SA1521z speakers for a number of years, and they saw me pretty well through many gigs, so I was interested to compare the published figures of the new HD series against the SA version. The first and most obvious difference is the change in output power rating of the LF section, which increases from 400W RMS (SA) to 700W RMS (HD). The maximum SPL is given as 135dB at 1m, however Mackie have also published their measured figure, which is 125dB at 1m, before limiting, using pink noise. This is a more meaningful measurement as it represents what the unit can actually produce and what, in the real world, you can actually expect from the product. Still comparing with the SA1521z, overall frequency response is extended downwards and now reaches 50Hz to 18kHz at the -3dB points. Interestingly, the crossover point is lower than the SA model at 1200Hz, which I’m all in favour of provided the compression driver is up to the job. The HD version is, of course, a new design rather than a tweak of an old one, and I like the new HF coverage pattern, which is slightly wider and shallower at 80 x 50 degrees, putting the power where it’s needed, ie. where the audience sits, rather than up at the sky. So, the HD1521 has more acoustic output, more amplifier power, a better frequency response, and a wider HF dispersion. But two other figures within the specification tell more of the story: overall weight is reduced to just over 36kg (nearly 10kg less than the SA) and the recommended power requirement is now stated as 5A as opposed to the 7A requirement of the SA1521z. This is no doubt a direct result of the use of neodymium magnets and more efficient amp designs, and the spec confirms that both HF and LF amplifiers are Class D, and the LF driver does indeed have a lightweight, neodymium magnet assembly.

Out of the box, the HD1521 is a square-shouldered and purposeful-looking unit finished in black. It’s quite different in appearance from its older relatives, having a flat front grille as opposed to the traditional Mackie convex look. The steel grille flexed inwards quite easily when I pushed at it, although being flat it would be difficult to put a big dent in it (my old SA1521zs used to get dented and pinged out again on a regular basis). The best thing about the front grille area is the addition of some neat black acoustic foam behind it that not only improves the appearance, but affords some protection for the drivers within. The grille extends and curves over the top and bottom front edges of the cabinet, giving it a sleek look, although it does mean that the front corners of the side panels might suffer if the unit were tilted forwards when transporting or loading. The enclosure is made from 15mm plywood and covered in a vinyl-like finish that seems to be tough enough to withstand a bit of abuse — after a couple of trips out with me and the lads they were still entirely scratch-free. The all-ply construction seems to be well put together and, even though the cabinet has 3mm thinner walls than the 18mm SA cab, it has a sturdy feel to it. I took a side handle off and had a look inside, and the joints and bracing look tight and neat.

Cabinet hardware is important on any portable equipment, and I’m pleased to say that Mackie have maintained their usual standards by providing really good carrying handles. The substantial metal recesses house comfortable, rubber-backed handles that are easy to use even when wearing rigger gloves — not something you can say for all portable PA gear, by any means.

The rear panel is almost entirely taken up by the large amplifier module that incorporates an enormous heat sink. The mains power input (IEC standard connector) and the on/off button are below the fins, and all the audio connections and controls on a panel above. Everything has been kept simple and clear — input is via a single XLR socket that is hard-wired to a loop-out XLR for connecting additional units, and there’s an input trim control providing adjustment over a plus or minus 6dB range. This is a point to note when first setting up these speakers, as a hot input signal will still produce a potentially very high output, even when this control is turned all the way down.

The HD1521 is also equipped with a useful onboard equaliser that provides three bands of adjustment. Low and high shelving controls operate at 80Hz and 12kHz respectively, and the semi-parametric mid control is a peaking EQ with an adjustable centre frequency over the range 100Hz to 8kHz. An unusual feature of these contour controls is that their cut or boost range is limited to only 3dB either way, which I think is a very good idea as it provides useful fine-tuning, but prevents any vicious and uncalled-for tweaking, especially by inexperienced users. Personally I’d like the ability to roll off a bit more of the LF, but you wouldn’t normally be using these without additional desk EQ anyway, and it would only be an issue if you wanted to daisy-chain these from an active sub (of a different make!) that didn’t have a high-pass output.

Anyone can stuff a powerful amp inside a decent speaker cabinet, but a huge advantage of decent integrated active designs is the ability to match every component in the system to optimise performance. Getting the very best out of an active speaker is more than this, though, and the HD1521 employs some sophisticated signal processing that takes account of some very detailed aspects of driver characteristics to produce the desired result. As you’d expect, the ‘HD’ in the model name stands for ‘high definition’, and there’s an explanation of what this means on the manufacturer’s website at http://www.mackie.com/products/hdseries/pdf/HD_EXPLAINED.pdf, which is worth a read. Suffice it to say that the EAW engineers have been doing much detailed analysis and design, and have developed (and patented) acoustic correction algorithms that smooth out the response by addressing anomalies specific to the driver systems used in each model. The onboard DSP includes time correction and phase alignment between the HF and LF sections, and there’s automatic signal limiting to avoid overdriving the speakers. Thermal protection will shut down the power amps in the event of overheating and restore normal service when everything is back within acceptable operating parameters.

For my first test, I set up the HD1521s on tables in a conference room and listened to my usual CD test tracks at low to modest volume. The first thing I noticed was the detail in the top end, which at low volume almost sounded like listening on a huge pair of headphones. The mid was pretty smooth, and the bass sounded well under control and not overly thin, which can often be an aspect of high-powered speakers when running at low levels. Turning up the wick produced impressive results, with very sparkly and clear acoustic guitar and vocals on various songs. I pushed the volume still further with Mary Black’s ‘Speaking With the Angel’, and everything remained very clear, focussed and enjoyable in the room. When I’d reached the limit of what was bearable indoors I took the HD1521s outside and put them on the grass, pointing away from the building across the nearby fields. I then turned them up to a serious level. I was impressed with the clarity and detail, which projected well and remained constant — as far as I could tell — over a fairly wide area that I guessed was something like the 80-degree coverage mentioned in the spec. The low end was full and deep without sounding flabby but, as I was working on my own at this point, I didn’t try and mount the speakers on stands to see how much of the bass would be lost when putting the horns at head height.

For a road test, I took the HD1521s along to an outdoor town carnival event where music playback was required for various dance groups. As most of the sound requirement was for arena announcements and there were no live bands, I didn’t take along any subs, which I regretted as I had to stand the Mackies on the front of a mobile stage to get them high enough and over the heads of the public. This was a good test of them used as full-range boxes, and I had them operating just below limiting for a good hour without the heat sinks getting hot. The music playback was clear and projected well into the front part of the grass area where the dancers were performing, although I really would have preferred to use these in conjunction with at least one, preferably two, subwoofers per cabinet. The advantages of using the HD1521s as mid/high units, rather than full range, would be to unleash all their power on a smaller frequency range, and also to give them something to stand on in order to achieve a good operating height. I suspected that I might be working the speakers a bit hard but this was, after all, part of a test run and I gave them more of a caning than perhaps was strictly necessary. The ambient temperature was high too, with a lot of direct sunlight on the speakers, but despite working hard all afternoon they didn’t miss a beat. The dance groups liked the sound, and said so, which is always nice to hear; the only complaint was from an elderly chap who apparently needed to stand directly in front of one of the speakers and kept putting his fingers in his ears and scowling at me. In terms of simplicity, you can’t beat active speakers when it comes to setting up, and I spent much longer trying to remove the big ‘blurb’ labels than I did connecting the leads and getting them working. I would have left the labels there if they hadn’t been stuck partly across the horn flare!

In practical terms, the HD1521s are easy to handle and, because of their output capability, can handle a wide range of applications. They are easy enough to lift and can be moved around by one fit person, although I wouldn’t try to mount one on to a pole without assistance. Their straight-line cabinet design means that they transport well, and the rear-panel controls are recessed enough to allow the unit to be laid on its back, provided it’s on a flat surface. The standard of finish is very good, and all the metal parts fit neatly on to the woodwork. A quick ‘quality check’ found that all the screws were nice and tight, and there’s an impression of practicality and attention to detail about the general design and construction.

So, after using these new Mackies I was left with two main thoughts, namely that I really liked the detail in the sound, and that I would almost always want to see them sitting on top of some matching subs. The HD1521s are pleasing and not fatiguing to listen to at high volume, and I bet their top-end clarity would reveal — and even exaggerate — differences between microphone types. They project well enough and have more than enough power on tap for any medium-sized indoor venue. Personally speaking, I would be happy to specify these for medium installations in clubs, churches, halls and the like, especially as they can be flown vertically or horizontally using appropriate rigging hardware (the horn assembly can be rotated to facilitate this). They’re not the smallest or most compact full-range speakers around, although they are unquestionably powerful. For portable band-in-a-pub PA they would sound great, but I’d find them a bit on the big side for more modest venues. Given the space, and stacked on a couple of 18-inch subs each, I reckon they’d easily be in the ‘blow you away’ category. 0

Mackie HD1521

Active loudspeakers