Si  you've been to a biggish gig or a festival in recent years, you've had the pleasure of hearing line arrays of loudspeakers in action. But why are line arrays the current 'best practice' in large–scale PA, how did they evolve, and will they ever filter down to more modest gig venues?

Esta es una oportunidad para demostrar lo que sabes sobre ingeniería de sonido en el lugar.La función del sistema pa es la de...

That wasn't hard, was it? But in case you're struggling, the function of a PA system is to deliver your sound to the audience, and deliver it well. It's as easy as that. But hang on, it doesn't seem to be all that easy, does it? Whenever have you experienced perfect sound as an audience member? And when have you ever felt that your band's sound has been delivered to the audience as well as it should have been? There must be additional criteria that need to be fulfilled to achieve satisfaction. And yes, there are. Three...

• Adequate level, in relation to purpose (clearly, heavy rock music needs to be louder than a classical guitarist).
• Low distortion, low noise and a flat frequency response.
• Adequate clarity, in relation to purpose (speech requires near–100 percent intelligibility; all the words in a theatre musical must be easily understood; other forms of music may not need to be absolutely crystal clear).

Achieving adequate level is never a problem. It hasn't been a problem since the 1970s, when PA systems as we know them today had fully matured. All you need is a recognition of how many watts you require for a particular venue, usually calculated by rule–of–thumb and reference to past experience, and the budget to hire enough amplifiers speaker supplier and loudspeakers. Achieving low distortion, low noise and a flat frequency response hasn't quite been fully solved, although if the noise level of your PA is audible to the audience there's a fault somewhere in the system: power amplifiers in general have a better signal–to–noise ratio than just about anything else you'll find in the whole of sound engineering. The frequency response of PA loudspeakers, however, leaves a lot to be desired, and it is definitely true to say that the only thing that produces more distortion than a loudspeaker is the lead guitarist's screaming Marshall on overdrive. But even though not all is yet perfect regarding the above points, most people find the sound quality of a decent PA system acceptable. And the typical sound of a PA has almost defined people's expectations of what a PA should sound like. A circular argument, perhaps, but there's a lot of truth in it.

Una cosa más: la claridad.Es posible realizar un análisis detallado dentro del sistema pa.Sin embargo, cuando se despliega en escenas de conciertos de la vida real, no parece claro.Como oyente, debes haber pasado por muchas cosas, ese sonido borroso te tapa las orejas, pero no puedes realmente descomponerlo en música.Por consiguiente, la claridad es la última esfera no conquistada de Pensilvania y la última cuestión importante que sigue siendo difícil de resolver.

A este respecto, necesito volver a una solicitud de la pa, que ya he dicho que se ha resuelto: el sistema pa debería ser lo suficientemente grande.Si tienes el presupuesto suficiente para que sea lo suficientemente fuerte, no es difícil, pero debe ser lo suficientemente fuerte para todos los espectadores, es un problema que no se puede resolver necesariamente con mucho dinero.

Hay dos escenas: una en la que el público se sienta y la otra en la que actúa libremente.Si el público puede moverse libremente, se pueden establecer diferentes niveles en diferentes partes del complejo.A los que les gusta gritar les atrae el megáfono.Los que quieran hablar en el programa van a estar más lejos.Sin embargo, de repente la situación se vuelve más difícil cuando el público está totalmente sentado.No quieres que el público de la primera fila se quede sordo, sino que el público de atrás se esfuerce por escucharlo.La pa no cumple plenamente su objetivo si sólo transmite un nivel suficiente a determinados oyentes, en lugar de ser demasiado silenciosa o ruidosa.Por lo tanto, permítaseme resumir la solicitud de la pa en una simple declaración: que todos los oyentes tengan una voz de calidad suficientemente alta y clara.