The Path To Whole House Audio: Part 3 – The Logic Behind Powered Monitors

Speakers + Amps = Powered Monitors

Powered monitors make sense for a lot of reasons. Except for very small models they are generally bi-amped, with an active line level crossover filter dividing the high & low frequencies before the amplifier stage. Then a separate amplifier is provided for each driver. In the case of Behringer’s B2031A, there is 150 watts for the woofer and 75 watts for the tweeter.

This approach allows the designer to tailor each amplifier design to suit the specific driver in question. Amplifier/driver interaction is one of the more complicated things in audio reproduction and optimization here can bring big performance improvements. With the amps right in the cabinets there’s effectively no speaker leads to further complicate the amp/driver relationship.


Avoiding passive high-level crossovers is also advantageous. Passive crossovers are notoriously complex and expensive to do right. Complex interaction of capacitive, inductive and resistive components in high power situations can create phase non-linearity and seriously muddy the sound.

From a purely economic point of view powered monitors can be a bargain. The reality is that good power amplifiers have become cheaper over time as electronic component quality keeps improving even as costs keep falling. You get more watts/$ now than ever before. And better sounding, too.

A large part of the cost of any amp is in its physical self, the case, etc. By building the amps into the speaker cabinets a significant cost savings is achieved. On a purely practical level production facilities would often like to avoid extra wiring and external amplification in small editing and compositing rooms. Powered monitors are just the right solution providing an excellent cost/performance ratio.

It makes you wonder why the folks at many high-end consumer speaker companies like Wilson Audio haven’t made powered speakers for the ubber audiophile? The equally brilliant folks at Meridien have done so for years. I suppose there’s wisdom in playing to one’s strengths. It’s difficult to be the benchmark in many area.

Now I’m not saying that these Behringer’s are the best things that I’ve ever heard. But they are some of the best sounding, inexpensive models that I’ve experienced.

Speakers + DSP + Amps = ???

There’s another trend happening in this space. Some manufacturers are building some DSP (digital signal processing) capability into their powered monitors. The DSP engine lets them implement the crossover filtering entirely in the digital domain. It also lets them include some reasonably sophisticated programmable equalization (EQ.) As DSP chips continue to drop in price it will increasingly be possible to add digital domain interfaces and signal processing to devices, like loudspeakers, that have been traditionally analog in nature.

More involved than simply cross-over and EQ, “room correction” is a DSP based processing function that helps the monitor overcome limitations of the low frequency behaviour of the room. Essentially, the DSP corrects for room resonances. This usually involves a reference microphone and recording pink noise bursts then analysing the in-room measured response.

TACT is one purveyor of such systems although their room correction is freestanding hardware. JBL has range of powered monitors with built-in room correction.

Until recently Alesis offered a good quality inexpensive series of monitors known as their “Pro Linear” series that featured DSP based 4 band parametric EQ. I had the good fortune to find a source for refurbished Alesis ProLinear 820 DSP monitors and will soon be receiving a pair. These were well received and considered a bargain at $599 each MSRP. I was able to find them for over 50% off. I’ll probably blog about them once I’ve had some time to gain some experience with them in my home.

Whither The Power Amp Makers

In researching online it’s become clear that there is a trend towards powered audio monitoring in all applications but the largest studio monitors. The trend is so universal that some have expressed concern that it puts pressure on the makers of the extremely high-end power amplifiers that are necessary to drive passive studio mains monitors. Such companies as Pass Labs still make such products, but they are amongst the few who remain in that space.

Pass Labs Amplifier
An amplifier by Nelson Pass

Studio amps are very different from pro sound reinforcement amps. In the studio absolute sonic transparency is the goal. In live performance and fixed installations durability is major consideration, perhaps even beyond sonics. The number of companies offering very high-end studio amps has actually declined.

A Sampler Of Commercial Offerings

The number of powered monitors being offered has exploded in recent years. The trend was very likely started by Genelec, a Finnish company of very good studio monitors. Here are some manufacturers of merit:

Now these companies run the gamut from cheesy $199/pr squawk boxes to $20,000+ monster monitors. However, there is a good selection of powered monitors in the $400-$1,000/pair range. This is approachable from the perspective of my whole house audio ambitions. Of course, I’d like to spend as little as necessary to achieve my sonic goals.

It’s simply not possible for me to buy one pair of every model that I find interesting just to listen for a while. So I must often rely upon the opinions of like-minded people where available online. Here are some sources worth a look:

Where possible I have a listen in better music stores, etc. Sometimes I buy something, especially if its inexpensive, then live with it a while before deciding to keep it or resell it on E-Bay.

In part 4: Subwoofers & Halloween

3 thoughts on “The Path To Whole House Audio: Part 3 – The Logic Behind Powered Monitors”

  1. Michael,

    Very nice blog. As a result of the sursound list, I looked at the current Stereophile for recommendations on powered speakers. (Recommended components: Class D) Take a look at the Audioengine2 at audioengine.com. It’s a really small two way, powered speaker.

    A pair is truly $199…. free shipping! So I ordered a pair to see if they look (sound) good for the 3D Ambisonic array. I’ll report back.

    John

  2. I’ve looked at them and they do see like very nice speakers. Last Christmas I was considering a pair as a gift for my iPod toting brother-in-law.

    Recently I’ve been looking around for deals on semi- pro gear, which is how I found the Alesis Pro Linear 820 DSPs. They arrived Friday. One was damaged in shipping. Even so I’m running them through a break-in process right now.

Comments are closed.