Quest Engineering QSA Series Active Speakers
Substance and Style
The QSA range is composed of three models of self contained powered speaker from an 8 inch two way through to 12 and 15 inch self processing two way systems.
With their extensive experience in concert audio, the designers of the QSA200/300/400 looked to the latest technological innovations for inspiration. It is enough of a challenge to build high quality road going audio products when price is not a concern. Yet to create a first class professional product at a realistic price, that does not happen often.
The 8 inch QSA200 is the only box in its class that has the additional feature of being able to rotate the top end horn flare through both vertical and horizontal planes, making it a versatile and effective monitor for super compact foldback and installation applications.
From the start, the design of the QSA addresses the area where most powered speaker systems are compromised; the basic components. Just as a gourmet meal starts with quality ingredients, the QSA series starts with a foundation of heavy duty speaker components, high quality pre amp and a power amplifier stage that would equal many of the top pro power amps and a high tech built in system controller as an added bonus.
The end result is an outstanding price/performance ratio that would look good in any professional audio inventory.
The Technical Challenge
One of the big problems in building a self powered system is weight. Nobody wants a little box that is a two person lift. Most designers get around this by cutting back on the heaviest part of the amplifier, the power supply. Many will also reduce the size of the heat sinks and use light weight (small magnets and thin press steel frame) speaker components. Locating cooling fins on the back can be a problem. When you attempt to use a powered box as a foldback wedge they frequently overheat as the heat can't escape efficiently. The protection networks they generally have are very basic. At best they turn down the sound and at worse, they shut the sound off. Due to all the compromises, the current generation of powered boxes have performance that is little better than the traditional powered mixer, but they are certainly convenient to use.
At the other end of the scale, the powered systems used in the Concert Audio business are generally heavy, forced air cooling, beefy high powered boxes designed to be flown in the air from dedicated rigging and installed by certificated professionals. This is where the concert sound experience at Quest Engineering gets employed.
Real power amplifiers
The amplifier design is an actively crossed over, bi-polar split rail; highly efficient and won't loose power as it heats up as many mos-fet designs presently used to save weight will. All the heat sinks are on the inside of the box where the operation of the bass driver effectively blows cool air over them. This means the box can be turned on its front, back, upside down, however you wish with no danger of it overheating. The amplifier is assembled to withstand continuous vibration and has 20% extra tolerance over industry standards, so it will take any beating a hire company may give it.
Comprehensive input section
No pushing the wrong button here. Separate XLR-Phono inputs for high and low gain signal governed by a master volume means more than one signal source can input simultaneously. Three band EQ and electronically buffered line output allow for individual tuning and stable signal if a long "daisy chain" is required. An impressive battery of status indicators show everything from signal presence to limiter function.
The right protection
A common failing in plastic powered boxes are the bass drivers. High powered drivers are heavy so most manufacturers use light weight drivers and hope that a limiting circuit will protect them. Some circuits roll off the low frequencies so when you drive them hard, all the bass disappears. This is often followed by the box shutting down, causing the greatest crime for an audio operator; No music. Concert Audio boxes are protected by system controllers that monitor and manage the power and make necessary adjustments without noticeably affecting the sound. This is the heart of the QSA system.
Thanks to sophisticated analysis circuitry, the controller will prevent damaging peaks and long term excessive level from damaging components, but it does it in a way that is virtually inaudible. No disappearing bass or top end and definitely no silence.
Heavy duty components
As a final insurance, the bass driver has a power rating twice the rated maximum continuous power of the low frequency power amp. This helps protect the driver from over heating when a highly clipped input signal is present. This can happen when low priced disco mixers are driven into the red.
There's plastic and there's PLASTIC
Not only are the speaker components more than big enough for the job, the impact resistant plastic injection moulded case contains considerably more plastic, to brace it through all the hard knocks it will get in a pro audio environment. The rigid construction also protects the audio quality from the other box builder's enemy, resonance and vibration.
QSA Series Downloads
- QSA Series Sales Brochure [375KB]
- QSA 200i User Manual [809KB]
