On Powered Speakers (And Other “Black Boxes”)

The commoditization of live-sound is enabled by manufacturers removing unknowns from their equations.

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The opinions expressed are mine only. These opinions do not necessarily reflect anybody else’s opinions. I do not own, operate, manage, or represent any band, venue, or company that I talk about, unless explicitly noted.

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When I talk about a “black box,” I’m not thinking of an aircraft’s flight recorder. I’m not even thinking of a device enclosure that’s black.

And seriously, as much as we say that there are a lot of ugly, black-colored boxes in live-sound, let’s be real. Most of them are really just a very deep gray. If they were actually black, they would absorb all light and completely disappear when they were in shadow. Like ninjas. Ninjas that amplify bands. (That would be a great movie.)

Okay, where was I?

When I say, “black box,” what I’m getting at is a concept. It’s the idea that the user of a device doesn’t know how the device works – or, they might now, but they aren’t required to know. Whether or not people are conscious of it, this is a central factor in the commoditization of technological devices. That is, for people to regard technological thingamabobs as “common, everyday” sorts of tools, those folks have to be in a world where understanding the internal functioning of the tool is not required.

A fine example of this is the personal computer. As the years have gone by, hardware and software manufacturers have progressively “black boxed” their offerings. In the computer’s infancy, operating a computer meant you had to have a lot of detailed knowledge about what the computer was doing. Nowadays – not so much. Almost everything is handled invisibly (which is great, until something breaks). Whether or not you think this is good or bad, this reality of “it just works” has allowed the personal computer to become a thoroughly mundane item. Having and using a computer isn’t a special thing anymore…in fact, it’s rather more surprising if someone DOESN’T have a computer that they use regularly.

In the same way, live-sound is also far more commoditized than it used to be. For instance, I’m betting that most readers of this site have never constructed a power amplifier. I know that I haven’t. Most of you probably haven’t built your own mixer. I know I haven’t.

But, in the early days, building your own gear from the ground up was often required. You couldn’t just head on over to the store and browse a vast selection of poweramps, loudspeakers, mixers, and whatever else. Before pro-audio (as we know it) really took hold as a market segment, the people pushing the boundaries were working by building things that either didn’t exist, or didn’t exist in enough quantity that they could be easily gotten “off the shelf.”

Now, pretty much every audio device you can think of is already in existence. You can go online and positively drown in a million iterations and manufacturer-specific takes on all manner of gear. Even if you’re thinking of something rather narrowly defined, like a 2-way active crossover, you won’t have any trouble finding a bunch of options to pick through.

It’s funny that I just mentioned active-crossovers, because it’s possible that you may never have to buy one. That’s because of one particular class of “black box” product: The powered loudspeaker.


The powered or “active” loudspeaker is hardly a monolithic sort of entity. They exist in all shapes and sizes, with some being vastly more capable than others. There are plenty of active loudspeakers that put on a facade of advanced engineering, but really aren’t much more complicated than you or I connecting a rackmounted power amp to a “full-range” loudspeaker. Even so, every powered loudspeaker on the planet shares a common trait:

They all encapsulate devices with diverse operations into a single, functional unit.

In other words, powered loudspeakers stick components with very different purposes into one box. In the most basic case, you have a power amplifier bundled up with a loudspeaker. The power amp takes a relatively small input voltage and delivers a corresponding, high-voltage, high-current signal to a load. The loudspeaker takes a high-voltage, high-current signal and transduces it into sound-pressure waves. Obviously, these two actions are complementary, but they’re also very different. Encapsulating the two actions reduces complexity for the user. Where they once had to manage and connect the amplifier and loudspeaker as separate units, they now only have to look after one unit and one signal connection.

What can be missed, though, is that this simplification by encapsulation involves a very profound “exchange.” This exchange puts tremendous capability in the hands of people who would not be able to access it otherwise.

Many Unknowns For The User, Almost No Unknowns For The Manufacturer

A non-encapsulated system is a pretty complex thing to build and deploy. Let’s take the case of a fully-processed, biamplified loudspeaker. (Biamplification is the use of independent amplifiers for low and high-frequency signals.) To construct and operate an un-encapsulated, fully-processed, biamped audio rig, the following has to happen:

  1. You have to pick out, purchase, rackmount, and connect some sort of equalizer.
  2. You have to do the same for an active, two-way crossover.
  3. You might also want some dynamic filters – or even full-fledged dynamic EQ – for each crossover output.
  4. For both crossover outputs, you will need to have a limiter. If you want to get fancy, you’ll need two limiters – one that can determine and limit the RMS level of a signal, and one that “brickwalls” peak levels.
  5. You’ll need an alignment delay for one channel or the other. (Alignment delay is fraction-of-a-millisecond control over when a signal arrives. Effect delay has much coarser control over the time involved, and it’s also mixed with the unmodified signal to create the sound of an echo.)
  6. You will need two channels of amplification. The power available from each channel will need to be more than what the drivers can handle. I’ll explain why in just a bit.
  7. Now you can add a cabinet with an LF and HF driver.

If you’ve got all that done, now you get to do a bit of science. First, you pre-configure the crossover based on recommendations from the loudspeaker manufacturer.

You next have to figure out what input voltages to the amplifiers correspond with output voltages that – just barely – won’t destroy your drivers. You set the peak-stop limiter accordingly, with the RMS-sensing limiter in place as a backup. The reason that you got a “too powerful” amp is that even VERY heavily limited signals usually end up having a continuous power that’s one quarter of the peaks. As such, getting the maximum, “sane,” real-world performance possible means using amps that can deliver more continuous power than the drivers are rated for…and then limiting the continuous power to something safe while letting some of the peaks through. (If you want to be really dangerous, you could set RMS limiter only. It will probably be a while before something gets destroyed. Maybe.)

By the way – if you end up trying any of this, and you blow something up, I am NOT liable. It’s your funeral, okay?

Now you have to find an environment that’s as anechoic as possible (or go outside), and set up a measurement rig. The first thing to do is figure out which driver’s sound arrives “late” when compared to the other. You then apply the alignment delay to the “early” driver, so that signals from both the HF and LF elements hit the listener at the same time. Next, you measure the whole thing and apply EQ to make the response as flat as possible. If you’re ambitious enough, you run up the system to full-throttle and note how the response changes. You can then set dynamic EQs to keep the response flat (or filter out damaging LF energy) at high levels.

Oh, and you can always try some different crossover slopes to see what has the best phase and amplitude response.

So, yeah. You could buy all that for hundreds or thousands of dollars, and spend all that time dialing it in (assuming that you know what you’re doing), or…

…you could live with all of the above being unknown to you, but known to the manufacturer. If you’re willing to do that, then for a few hundred bucks you can purchase a powered box. That powered box will have had that whole mess up there done for it already. You just plug it into the wall, put some signal into it, and off you go.

See, when all of those components are encapsulated by an equipment builder, there’s an exchange that’s basically inevitable. The inner workings of the system become an unknown for you, the user. In trade, the configuration of all those components is now intimately understood and highly optimized by the manufacturer. This creates an integrated, powerful, black-box system that you can just use, with minimal effort. This especially gets around some of the problems I discuss in Dirty Secrets About Power: Manufacturers don’t have to deal with as many unknowns regarding how their equipment will be used, and you don’t have to deal with semi-knowns about what amp to mate with what loudspeaker cabinet.

In closing, let me be clear. I advocate being curious. I’m in favor of knowing what’s happening inside your gear, at least to whatever extent is practicable. I’m all for building things, and doing experiments. I’ve got access to some gear that I want to rebuild, to see just how effectively I can do a “biamped, externally powered and processed” loudspeaker rig. At the same time, the reality is that black-box products have created a world where you can just plug something in and get decent (if not stellar) results.