Un-Active

The Powered Advent Loudspeaker of the late '70's: engineering triumph; commercial flop, just like virtually every other fully active broad-market design before or since.

Fully powered, or “active” loudspeakers have a lot of very real advantages. Here’s a punch-list of the top 5:

• Lower distortion

• Better dynamic potential

• Extended response

• Managed phase and other time-domain characteristics

• Packaging efficiency and cost advantages

I’m going to go into each of these a bit deeper, but first, by way of a counterbalance, here’s a list of all the serious-performance active loudspeakers that have made real commercial successes in the broader consumer electronics market over the past thirty years or so:

Impressive, inn’it? Yeah; there haven’t been any. Which is strange, since any audio engineer much past freshman year would agree that packaging together the power amplifier and transducer components (the drivers) of any audio “b-chain” is by far the most logical, and cost-effective way to ensure optimal reproduction. And that’s true even if we look only at my five key advantages, ignoring the dozens of others we could name.

Lower distortion: Since an active speaker has the luxury of dividing and directing tweeter-signal and midrange- and/or woofer-signals at line level, before reaching the power amplifiers, it does not require the passive, high-power-dissipating (and phase-mangling) dividing network (crossover) found in virtually every conventional passive speaker. And crossovers are notorious power sinks, introducers of substantial harmonic distortion (both the familiar total-harmonic, and some more arcane types), and are limited to just a few practicable choices of filter-slope, none of which is wholly ideal.

Better dynamics: In passive speakers the crossover network inevitably absorbs some measure of power-amp juice (dissipating it as heat) before this ever reaches any transducer’s terminals, and some degree of non-linearity in doing so is all but unavoidable. This contributes to dynamic compression. Perhaps more important still, in an active-speaker design the engineer knows precisely how much power each driver can successfully exploit, and can design its individual amplifier accordingly, while adding instantaneous, non-invasive “Smart” driver-protection instead of relying on old fashioned, slow, and arguably sonics-sucking fuses.

Extended response: This one’s no-brainer. To take the simplest example, if you’re designing a dedicated amplifier for a known woofer, with a known roll-off in your chosen enclosure alignment, you can easily “cheat” an extra half-octave or so of bass extension by adding in reverse EQ to the woofer amp. More subtly, you can “shape” midrange and/or tweeter responses in an effort to complement each transducer, yielding idealized driver-to-driver integration, optimized overall system response, or both. And since all of this amplitude-domain equalizing happens at line level the consequences in terms of distortion and phase can be made very nearly nil.

Managed phase and time-domain behaviors: In today’s digital age, if we introduce DSP to the mix, a whole ‘nuther world (as we say here in New Hamp’shuh) of engineering potential opens up. Active-speaker designers can now command system directivity (to an extent), and individual and relative phase and other time-domain behavior, to achieve just the multi-driver wavefront they desire.

Packaging efficiency and cost advantages: These are almost too numerous to name. By building the power amps into the loudspeaker cabinet – which mostly is just wasted air-space anyway – you eliminate the need for a bulky external power amplifier or receiver. (And with active-EQ the speakers themselves may be made smaller at little sacrifice in extension; witness all those super-slim “power-towers.) And exploiting multiple small amplifiers, each dedicated to a finite few octaves, is more cost effective than producing a single huge, full-range one that’s able to produce enough power to drive all those transducers, and heat the crossover network. And it’s not just the cost and size of the power amp itself we save, including its enormously expensive chassis and fascia; there are its packing materials, owner’s manual, logistics costs, and the shelf on which it would have to reside – plus the differential of energy we’d have needed to power it.

So why don’t we have any active speakers in the rational-price high-performance hi-fi space? It’s pretty simple: people won’t buy them. And it has ever been thus. The classic example is probably that of the Powered Advent Loudspeaker, an active variant of the top-selling Large Advent 2-way produced by the Cambridge, MA maker back in the late 1970’s. Same basic drivers, same bulky, rectangular cosmetics, almost identical size. The Powered looked just like a Large Advent (except for a couple of pilot lights), and it sounded just like a Large Advent—one that played twice as loud, went a good half-octave deeper, and displayed dynamic punch and transient clarity and excitement that rivaled those of speakers absurdly more expensive.

Everyone in the industry who heard them agreed that the Powered Advent was a genuine tour de force. (The P.A.L. was the brainchild of Tom Holman, late of U.S.C. and Lucasfilm/THX, now chief of audio at Apple.) Yet nobody—but nobody—would buy them. And not many even remember them today. I haven’t seen or heard tell of a pair in at least 20 years. (Anybody else?)

Not much has changed today. The marketplace has quietly accepted active design as de rigeur for desktop computer speakers and Bluetooth boombox-equivalents, but for serious audio and home-theater systems we still insist on passive speakers all around, and bulky amplifiers and receivers. Hybrid, active-woofer designs from companies like Definitive Technology and GoldenEar have made a good deal of noise. But only a couple of ultra-high-end firms such as Meridian and Bang & Olufsen—brands that can, presumably, afford to do the right thing and let consumers catch up—have seriously pursued active-speaker design.

Good for them. But there’s no categorical reason why all the active goodness should be the exclusive province of those rich enough to afford these searingly expensive if admittedly brilliant designs. The benefits I’ve outlined above are all eminently scalable. And it’s about time somebody got busy and started scaling them.

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COMMENTS
rhirschey's picture

Between multiple speaker brands (including Revel) and the amplifier expertise of Mark Levinson/Harman Kardon, Harman could bring their engineers together to build an awesome, powered, Salon3. I'd save up for that in a heartbeat and I bet it would sell.

Photoacoustic's picture

The consumer hi-fi space may have ignored active monitors, but they are the rule in professional studios. JBL (which is a Harman company), Genelec, H/K and others make studio monitors that are, for my money, the best designed and engineered speakers in the world, and that includes any of the boutique or exotic hi-fi brands. These speakers are designed for ultimate accuracy, low distortion, exceptional power response, and ear-bleeding volume levels. They are what mastering engineers and producers use to get the sound of the recordings we all play. I own a pair of JBL LSR6328P active studio monitors, designed by Floyd Toole. They are the finest speakers I’ve owned, and the finest I’ve ever heard for their size and price.

Actives never caught on in the consumer audiophile market, because equipment makers and vendors stood to lose a lot of money if they could no longer push sales of high priced gear, especially amps. After all, an active speaker, owing to the absence of a reactive crossover in front of the drivers, requires lower powered amps to achieve the same output as a standalone amp with a passive speaker. Also, the raw drivers don’t need to be as well behaved as in a passive system because the line level active crossover filters better than a passive crossover, while direct hookups to the amps provides ultimate damping. In short, an active system would have cost less, and often much less, than an amp and passive speakers for an equivalent amount of performance. Imagine: no costly amps, no ridiculous cables, no overpriced passive speakers. A big part of the hi-fi industry would’ve been gutted.

rhirschey's picture

Good point on JBL. Totally forgot their "professional" lines would have an abundance of speakers.

You make an excellent point regarding the cost (and thus benefits to dealers) of having separate amps, cables and speakers.

pw's picture

The expensive Genelec monitors look very good. They may seem expensive but you don't have to pop for an amp. I'm guessing with many hobbyists owning expensive tube and Mcintosh equip. it's hard to wrap your mind around the price. And the tossing of beloved equipment.

Photoacoustic's picture

@rhirschey - JBL Pro stirred up the recording community last year with the announcement of their M2 Master monitor. It uses outboard amps and digital crossovers This is their no-holds-barred design, along the lines of KEF's Blade series. It looks pretty amazing (though it's 4 feet tall and 130 lbs!).

@pw - I've heard a pair of Genelecs, and they were outstanding. A small pair of Dynaudio actives were also very good, and very low priced.

One additional thing that actives bring is crossover control for room tuning, ranging from basic built in parametric EQs , to DSP implementations. The closest thing I ever see to that in a passive is the occasional switch or jumper to tilt the response on either end.

jnemesh's picture

All Linn speakers and amplifiers can be upgraded to be active. You tell the dealer which speakers and amps you own and cards are installed in the amps, specific to the speaker and the driver being powered. A fully active Linn system is out of this world...you HAVE to hear one!

dnoonie's picture

I just did a quick count of active studio monitors at B and H. They have over 20 brands listed.

I currently own Alesis actives (rear surround) and Dynaudio actives (front mains).

Other brands I'd seriously consider for myself in the future would be:
*Focal
*Event
*Neumann
*Tannoy

Other Active studio monitors I've used or owned are:
* Genelec (Can have a harsh mid-range in the wrong environment)
* JBL (Can have a harsh mid-range in the wrong environment)
* Samson (not bad for the money, more neutral than m-audio)
* Mackie (look like Genelec knock offs, sound similar to Genelec but with distortion, a fraction of the cost of Genelec)
* Yamaha (Good for the money, more neutral than m-audio)
* M-Audio (scooped/bump and sizzle, consumer sound, good for the money, ideal for a demo for people that think the scooped sound is good, I've owned a number of m-audio monitors but didn't buy them for myself)

briguy's picture

Emotiva has some great sounding powered speakers. Just bought a pair 2 weeks ago and I am very satisfied with the sound and their price!

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