The Young Person's Guide To SRM450 Design History
ACTIVE DOESN'T JUST MEAN POWERED.
Back in the day, all sound reinforcement speakers were unpowered. An external amplifier was connected to a passive crossover inside the speaker, which distributes frequencies to the transducers (Drawing A). Done right—REALLY right, the way EAW does it—there's nothing wrong with this approach. But at prices mere mortals can afford, passive speakers spell serious compromises (more on that later).
A powered speaker is just a regular passive design with some sort of amp stuck on the back (B). The only benefit is that there's a shorter wire between the amp and the transducers. You're still stuck with a passive crossover and no particular sonic benefits.
Active Mackie speaker systems have sophisticated internal circuitry, including a phase-accurate electronic crossover (C). Their power amplifiers are 1) optimized to work perfectly with each transducer and 2) tightly coupled to the transducers via servo feedback circuitry. In other words, the transducers can "talk back" to the amps. This closed system means total, precise control and far better sound. Plus, having sophisticated signal processing electronics on board allows you to exercise total control over a wide range of critical functions that you cannot get from a passive crossover system.
Bottom line: active technology, executed correctly, is how we're able to create the unique electronic features found in the SRM450.
ACTIVE = UNRIVALED RELIABILITY
The SRM450 has a superb warranty because its active technology controls these variables. Built right in are a number of limiting, EQ, and protection circuits, including some that are pretty unique.
Example: Because the SRM450 is capable of extreme output at very low distortion levels, we designed special protection circuitry that doesn't get in the way of the listening experience. When the FOH engineer pushes the master mixer faders to +12 dB (which would horribly distort most other speakers), the SRM450's sliding filter begins operation. As the low frequency amplifier goes into clipping, the filter starts sliding from 20Hz on up as far as 120Hz until clipping stops. If the operator continues to overdrive the system, a compressor takes over to protect the LF transducer. There is also a separate compressor for the high frequency driver. Combining sliding filters and compressors allows you to reach extreme output levels with complete safety and without audible distortion.
As a final level of safety, the SRM450 has thermal protection devices on board that monitor the amplifiers and power supply. The result is a system well equipped to deal with the realities of life on the road.
A BACK PANEL ONLY MACKIE COULD BRING YOU
In typical Mackie fashion, we've added wicked extras galore. First, the obvious part: We naturally included a built-in mic preamp so that you can directly plug in a dynamic mic. Perfect for speeches and presentations where you don't need an external mixer.
As a hidden plus, the mic input is also the line input! No messing about with switches or separate inputs. No loud pops when somebody pushes the mic/line button. The SRM450 internal preamp has so much input range (40dB) that it can handle weak mic levels and input-frying line feeds from a Mackie mixer. And of course, there's also a signal pass-thru connector so you can hook one SRM450 to another and it can also be used as the primary input, depending on the gender of your input plug.
BACK PANEL LAYOUT
1 Thermal Protection LED
2 AC line cord connection
3 Big, easy-to-locate power switch
4 Power on LED
5 Contour Equalization switch
6 75Hz low-cut filter switch
7 Male XLR input/pass-thru (balanced/unbalanced)
8 Female XLR input/pass-thru (balanced/unbalanced)
9 Peak LED
10 Signal Present LED
11 Mic and line-level adjustment
12 Timed Turn-Off switch
LEVEL SETTING CONTROL WITH PEAK INDICATOR
Why rely on your ears alone when LEDs are so cheap? This knob and LED let you correctly adjust mic or line input levels so that the internal preamp and power amplifiers are running at their optimum level.
SIGNAL PRESENT LED
This sensor is placed in the circuitry before the Level control so even if the volume is turned down, you can see that a signal is entering the speaker. Great for troubleshooting.
Adds a gentle (3dB) boost below 100Hz and above 12kHz. It's handy when the SRM450 is used as a recorded music playback device. In live applications, it also provides extended bass and high-frequency performance without requiring you to excessively increase SPL levels.
75Hz LOW-CUT FILTER
A Mackie trademark. Reduces wind noise, stage rumble, mic stand clunks, P-pops, and infrasonics that cause cone flutter.
Though the SRM450's FR Series amps have a generous heat dissipator, there is a limit to its capacity. If the heat exchanger gets dangerously hot, a thermal protection circuit kicks in to protect the amps' output devices—and the Thermal light goes on.
SRM450s can be mounted almost anywhere - including places where they're hard to reach. When you activate the Timed Turn-Off feature, the SRM450's active circuitry turns itself off automatically after three minutes of no input signal. Any time the circuit senses an input level of as little as -45dB (the snap of a finger, for example), the amps turn on again automatically—think of it as a sophisticated Clapper
YOU SIMPLY HAVE TO HEAR THIS SPEAKER
Grab some of your more sonically demanding CDs and head to your local Mackie dealer to conduct your own "shoot-out" between the SRM450 and anything remotely in the same size or price range. We think that the first sound reinforcement speaker that's as accurate as a studio monitor will literally blow you away.