• Can Audio Spotlight systems be used outdoors?
  • Can these speakers be used in a stereo application?
  • What is the frequency response of the system?
  • Can you create custom sizes?
  • Is there any bleed outside of the sound beam?
  • What happens when the beam hits an object?
  • At what distance does the sound become audible?
  • How far can the Audio Spotlight speaker beam sound?
  • Can the Audio Spotlight be used to fill a large area with sound, like a night club?
  • How do Audio Spotlight systems compare to other directional audio products?
  • What additional hardware do I need?
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    Q: Can Audio Spotlight systems be used outdoors?


    A: Though our current models are not designed nor certified for outdoor use, the materials are naturally very weather-resistant, and many customers do use them outdoors with success. For increased protection, some used plastic sheeting over the back of the speaker panel to prevent water from entering, and placed the amplifier in a waterproof plastic box. While there are no specific plans to produce a special outdoor design, if sufficient application opportunities were available, we could certainly do so.

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    Q: Can these speakers be used in a stereo application?


    A: The word "stereo" means nothing more than "two speakers." Our systems are sold individually, and while you can certainly use them in stereo configurations, it is really not needed in essentially all applications. Due to the unique acoustic properties of the technology, the sound appears to envelop the listener, and is heard as almost "inside the head," so the stereo separation helpful for traditional loudspeakers is really not necessary with the Audio Spotlight.

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    Q: What is the frequency response of the system?


    A: Inherent in the use of ultrasound to reproduce audio is a trade off between maximum output level and low frequency response. This is controllable on the amplifier. A rough guideline for practical frequency response is about 200 to 400 Hz at the lower limit to 16 kHz or so. The AS-24 offers an additional octave of low frequency response and twice the output level compared to the AS-16.

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    Q: Can you create custom sizes?


    A: Holosonics does regularly offer custom sizes and shapes, and you are welcome to contact us with your requirements. Please note that, as with all sound sources, there is a direct relationship between the size (active surface area) of the speaker, and its output volume and frequency response; moving more air creates more sound. Therefore, larger speakers will produce greater output volume with a wider frequency response. The smaller the speaker unit is, the less output and range it will have.

    In addition, the coverage area of the speaker is directly related to its size, and should suit the application. For example, our AS-16 speaker provides a suitable coverage area for comfortably targeting one or two people. A 6" unit would produce a very small coverage area, reaching a single listener, as long as it was precisely aimed.

    These are general guidelines for our most common applications, and we are always happy to produce any size that is requested.

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    Q: Is there any bleed outside of the sound beam?


    A: While not precisely zero outside the beam, bleed is extremely quiet, with sound levels dropping over 90% one step outside the beam. It's best to use a lighting analogy: Our systems "shine" beams of sound onto a very specific area. Just like it is easy to see the light from the beam of a flashlight in a very dark room, it is sometimes easy to hear very quiet sounds in a silent room. Typical background noise helps to mask the bleed, just like ambient lighting makes a flashlight beam invisible unless it is aimed right at you.

    The dramatic drop in level should be plenty to maintain the quiet outside of the focused area. In the absence of all ambient noise, complete silence outside the beam is impossible, as the human ear is sensitive enough to hear 0.0001% of the energy; but just as this is a non-issue with light beams, it is usually not an issue with beams of sound.

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    Q: What happens when the beam hits an object?


    A: Audible sound created by Audio Spotlight technology, while in a tight beam, is absorbed, reflected, and scattered the same as all sound waves. However, if the reflective surface is flat, such as a wall or floor, the beam maintains its directivity perfectly, reflecting like a laser from a mirror, maintaining good acoustic isolation. Sound wave scattering only occurs when the reflecting object is extremely irregular at scales of audible wavelengths, such as an acoustic diffuser panel designed specifically to scatter sound.

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    Q: At what distance does the sound become audible?


    A: Audible sound is being produced along the entire distance of the sound beam, from right at the speaker and onward. Detailed sound coverage is shown on our Technical Specifications (pdf).

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    Q: How far can the Audio Spotlight speaker beam sound?


    A: There is no exact measurement for how far the sound will travel. It's a bit a like trying to specify how far a flashlight will shine. The audible distance is heavily dependent on ambient noise levels and physical objects in the beam path, but we have noted clear audibility at distances of 200m.

    Audio Spotlight systems are much less sensitive to listener distance than traditional loudspeakers, and while maximum performance is attained at roughly 1-2m (3-6 ft) from the listener, we have also had systems mounted eight stories up on a building rooftop, beaming clearly audible sound to street-level in Manhattan.

    Related link: A&E's Manhattan billboard "whispers" with the Audio Spotlight

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    Q: Can the Audio Spotlight be used to fill a large area with sound, like a night club?


    A: Our systems deliver sound to tight, narrow areas, just like spotlights. Multiple systems can be used to create a larger sound area, similar to track lighting. Our Technical Specifications (.pdf) show how much area is covered by each system.

    Filling an entire dance floor with sound would nearly require tiling the ceilings with Audio Spotlight systems, rendering this quite impractical.

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    Q: How do Audio Spotlight systems compare to other directional audio products?


    A: Since Holosonics created the market for directional loudspeakers, a few traditional loudspeaker manufacturers have released systems that claim isolation and directivity. These systems take the form of speaker panels, arrays, and domes. It is important to note that all loudspeakers become more directional as their size increases. Therefore, a large speaker (or array) is more directional than a small speaker, and this is what these manufacturers are selling. Another trick that some manufacturers use is to specify directivity only at an unusually high frequency, where sound from all loudspeakers is more directional.

    These "directional" products feature 30 degrees or more of spread, with hardly a difference in level, and even then only at high frequency. Holosonics believes that "directional" sound should be comparable to light, or a laser - such as the 5 degrees of spread of the Audio Spotlight system.

    None of these products even remotely approach the directivity or sound isolation offered by the Audio Spotlight, as you would need a speaker dozens of feet across to mimic the directivity offered by our system! Only the Audio Spotlight creates a true beam of sound, with a 90% drop of level one step outside the beam.

    More information: Fundamental Limitations of Loudspeaker Directivity.

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    Q: What additional hardware do I need?


    A: Our systems consist of a speaker panel, amplifier/processor, universal power supply and all connection cables. The power supply accepts worldwide power input, and we will include the appropriate power cable. The systems are compatible with any standard playback device, including mp3, CD and DVD players, computers, projectors, and more. We offer a variety of mounting options, shown in detail on our Mounting Options (.pdf) catalog.

    Our systems are based on unique acoustical physics, and are not compatible with traditional loudspeakers or traditional audio amplifiers. Do not attempt to connect any Audio Spotlight devices to this equipment as it could lead to equipment damage.

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    Manufactured exclusively by Holosonic Research Labs, Inc., of Watertown, Massachusetts ©1999-2009
    Holosonic® and Audio Spotlight® are registered trademarks of Holosonic Research Labs, Inc.