Column speakers have been incredibly successful, especially in recent years, in a variety of areas, ranging from congress/conference to retail, from places of worship to museums, from restaurants to hotels, and generally all cases where sometimes high room reverberation can cause a serious deterioration in the quality of perceived sound resulting in poor intelligibility of speech or musical program.
The main reason for this success, although not the only one, is due to the fact that a “true” column loudspeaker (one in which the distance between adjacent drivers is close enough to constructively interfere with each other to increase the throw) behaves, at least within a certain frequency range, in a manner similar to a line array, that is, a speaker consisting of a number of speakers, stacked vertically and aligned, operating as a single sound source by summing their emissions in a coherent manner. The ability of line arrays to generate sound waves that are (almost) cylindrical in shape, rather than spherical, results in their pronounced directivity in the vertical plane, which allows them to minimize ceiling and floor reflections when the speakers themselves are installed indoors. In essence, they offer the advantage of directing sound energy to precise listening areas while avoiding “hitting” acoustically over-reflective surfaces or walls with sound.
Italy’s Outline, one of the most prestigious companies represented by Audio Effetti, boasts within its catalog two passive column installation loudspeakers – Ai81 and Ai41 – belonging to the Architectural series, to be combined with the AS6 subwoofer. Ai81 is a passive column consisting of eight 1.3-inch extended-range drivers and a 0.7-inch dome tweeter capable of handling 320 W peak power and generating a max. SPL of as much as 112 dB. It is 46 mm wide, 570 mm high and only 25 mm deep! The smaller Ai41, on the other hand, adopts four 1.3″ extended-range drivers and a 0.7″ dome tweeter and bears 160 W peak power for a maximum SPL of 107.5 dB. Same width and depth as Ai81, with height limited to 350 mm.
Let us now take a closer look at what technical motivations led to the development of this type of loudspeaker.
Understanding speech in reverberant environments
In an enclosed place, where only one speaker is present, a listener placed at some distance from it will perceive direct sound and a multitude of delayed reflected sounds due to the room walls, floor and ceiling. The energy contribution of the direct sound is, in this case, preponderant, given the proximity from the source (speaker) to the listener, while that due to the reflected/reverberant field is less. End result: speech intelligibility is, in general, good.
However, when the audience becomes large and the area to be covered extends, the first thing that comes to mind is to gradually increase the number of speakers. This is a common mistake, since the energy of direct sound increases only marginally by increasing the number of speakers themselves, while the energy associated with reflected sound increases proportionally, with the ultimate effect of worsening the intelligibility of the sound message. Due to the room reflections that add up destructively, too many loudspeakers penalize speech comprehension. On the one hand, we are faced with the need to minimize the number of loudspeakers compatibly with the size of the room and the size of the audience present; on the other hand, we must ensure listening at an adequate sound level, without distortion.
Over time, various solutions have been devised to control the directivity of the loudspeakers in such a way as to concentrate their emission only in the desired area, that is, toward the audience, trying to minimize the energy incident on the floor or ceiling and obtain a strong direct sound and uniform coverage for good acoustic comfort, solutions that have led to the much-vaunted line arrays. When we talk about line arrays, we are not only referring to large concert systems, with the well-known “J” shaped clusters, but also to column loudspeakers, which exploit-in a small way and with some limitations-the same principle, at least within a certain frequency range.
Point source and line source, advantages and disadvantages
In point source type speakers, the traditional ones to be precise, where the sound originates from one or more precise points usually corresponding to the position of individual speakers, the wavefront ideally expands like a sphere as it moves away from the speaker itself. In line source speakers, conversely, the sound waves are, as we mentioned at the beginning, cylindrical in shape.
We can consider line array systems a good approximation of ideal line sources, and in turn, column speakers a good approximation of line arrays.
Point source and line source have advantages and disadvantages.
The former come in a wide variety of sizes and provide sound solutions for many different types of spaces. They are less bulky than line sources, at least in height, a generally more limited SPL, a shorter throw, and uncontrollable directivity. They are also cheaper, having fewer drivers and components in general but, as we have seen, used in reverberant enclosed spaces can create serious problems, making the sound unlistenable, especially at high volume.
The second ones (line source) are certainly bulkier-the columns can be added on top of each other to lengthen the array, up to several meters in height-but they boast a higher SPL, a medium and long throw, and a much narrower vertical directivity that can still be controlled by increasing the length of the array, or in some cases electronically via DSP.
The Outline column speakers in the Architectural series offer both of these advantages: they use the D’Appolito configuration in which the tweeter is mounted centrally between the two midrange arrays, according to a symmetrical design whose acoustic qualities are well known. At the same time, both Ai41 and Ai81 benefit from the use of the principles of line array theory, which provides excellent midrange dispersion control, a particularly desirable advantage in highly reverberant locations and which also provides superior intelligibility, particularly in the speech range. The crystal-clear high frequencies produced by the centrally placed tweeter-a rarity in column speakers that normally lack them-completes the impressive Hi-Fi-like sound signature of these speakers. Not surprisingly, some customers have chosen them to voice their stereo systems by placing them on either side of their LCD TV sets.
Column speakers, beautiful as well as effective
As mentioned in the introduction, the success of column speakers is not only related to their emission characteristics. Their subtle and elegant design, with black or white (any RAL upon request) embossed polyurethane paint finish in the case of the Outline Ai41 and Ai81, allows these speakers in particular to fit into any type of decor, combining design and technological innovation with great sound performance, both in speech and music reproduction. The use of magnetic metal grilles and the wall-mounting system using holes in the front baffle complete the technical refinements of these column speakers.
The combination with the AS6 passive subwoofer, equipped with a 6″ woofer plus a passive radiator of the same diameter, makes it a complete system for extended-range sounding of medium to large spaces. This “almost” omnidirectional subwoofer, only 120 mm deep, is capable of going down to 42 Hz (- 10 dB) and bears an impressive peak power of 1500 W! And speaking of power… the ideal partner to these audio systems is the Outline L3000 DSP-enabled power amplifier. Its flexibility and efficiency find a place in a surprisingly modestly sized chassis.
In conclusion, all the distinctive features of column speakers are found in the two Outline Ai41 and Ai81 models of the Architectural series, created specifically for fixed installations where maximum audio quality with minimum visual impact is required. The unique combination of modest size, elegant aesthetics, ruggedness, mounting accessories, and passive electronics makes them the perfect choice for a wide range of applications within recreational, religious, and residential environments.
