Every so often, I’ll be doing some consulting work (or just be in earshot) when musicians start asking about PA gear. Since loudspeakers very much represent the “business end” of a PA system, the conversation will often turn to these mystical transducers of electricity into sound.
These boxes are often bewildering. There are a great many to choose from, and what makes one implementation better than another can be very tough to discern.
Covering all that ground is far beyond the scope of what I can do here.
One thing I can do, however, is talk a bit about the phenomenon of “powered” speakers. Powered loudspeakers, which may also be referred to as active speakers, are often an excellent choice for people creating a PA or monitor rig. When working correctly, they simplify your gear spec and setup; Powered speakers remove the need for you to pick out and deploy separate power amplifiers, while also tending to reduce your overall footprint. (Jamming the amplifiers into the actual speaker boxes means fewer flightcases to wrangle in and out of vehicles/ venues/ houses/ etc.)
One pitfall, though, is that the label of “powered” on a box is what I call a “sloppy metric.” Because a good number of active speakers truly are packets of highly engineered, carefully tuned technology, it becomes easy to assume that all specimens able to be referred to as “powered” share similar traits.
This is not the case.
It Doesn’t Take Much To Be Powered
Let’s say you have a really cheap, passive loudspeaker on hand. It’s full range, with a cone driver for low(er) frequency content, and a horn-loaded compression driver for high end. You take the output of a basic power amplifier, and run that to the speaker input. Behind the jackplate, a relatively simple crossover network divides the power amplifier’s output into two frequency ranges, and each range is connected to the appropriate driver.
And that’s it. No other technology is involved.
If a person finds a way to package that amp such that it can be conveniently mounted inside the loudspeaker enclosure, with the connection to the crossover handled internally and the amplifier input placed on the outside of the whole shootin’ match…
…you have a powered speaker.
The setup is not really any better, from an audio standpoint, than the original. The logistics may be easier because a separate equipment enclosure has been eliminated – and that may be enough. Still, it’s a logistical advantage only. You have the same speaker, with the same capabilities, and the same amp (also with the same capabilities). It’s just that you’ve combined them.
A lot of inexpensive active speakers are that way. They’re a simple bit of engineering to get some better logistics. You might have some EQ on the back panel, but other than that, the package as a whole is very basic.
There’s nothing wrong with that, but there’s more to be had.
As a powered speaker’s manufacturer gets more ambitious, there’s a lot they can do.
For instance, they can biamp the speaker.
Biamping is running an entirely separate amplification channel for each driver. Instead of one amp feeding a crossover that divides the audible spectrum, the incoming audio is filtered BEFORE it reaches the amplifiers.
When all things are equal, this can result in better performance overall. It might not be immediately obvious just by listening, but biamping allows for things like better overall headroom, and greater signal processing flexibility.
If none of that made sense to you, don’t worry. The intent here is not to make live-sound an end in itself. It’s just to make clear that some powered loudspeakers are really basic, and some are not basic at all.
With a really dedicated manufacturer, all kinds of splendid magic can be done on a powered box. Some of these goodies include:
- The speaker can be precision-equalized at the factory, which (in some cases) can save you some work on getting the box to sound good yourself.
- With every part of the loudspeaker system being known to the manufacturer, the amplifiers and drivers can be optimized to each other’s limitations such that the maximum reasonable output is very definitely available to you (with no guesswork).
- Also because of everything being known, lots of protections against damage from overpowering can be put into place. The protections can even be dynamic, so that they “relax” when the box is at low output, and then become more aggressive as more output is called on.
In the simplest form, I would say that, if you’re shopping for powered loudspeakers, accept nothing less than a biamped configuration. It adds very little to the price of the unit anymore, so you may as well go for gear that’s had some extra science put into it.
Identifying a biamped loudspeaker from marketing literature usually isn’t too hard. Many builders are very happy to tell you outright that an active box is biamped. They may also say that there are “dual power amps,” or list the available power to the HF and LF drivers separately.
I do need to point out that biamping is not a guarantee of quality, nor does it mean that one little box can magically handle the audio needs for a full stadium. It is, however, worth looking for as a sort of minimum indicator. It tells you that more than just a desire for the marketing advantage of a “powered” label went into the design of the speaker.
Spending a little more can be worth it, especially when it comes to the input and output ends of your signal chain.