The Detailed Story of Neotropical Audio
A Heavy PigWe are field biologists who work with avian acoustic signals in Amazonian rainforests. In 2010, we realized that most of the speakers we used for wildlife playback were designed to reproduce the frequencies of musical instruments or the human voice. They also used big, heavy, clunky batteries. They also didn't didn’t prioritize their power towards the frequencies we wanted (1kHz-15kHz) and rarely featured a voltage indicator to indicate when the battery was getting low (very important for experiment prep). Most speakers lacked wireless connectivity. Durability was always a problem in the humid, wet tropical conditions (especially for electronics.) No one was building consumer-priced speakers for field biologists and field guides who work with passerines in rugged, tropical environments. Research-built equipment was available, but at an extremely prohibitive cost.
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A Heavy Pig. 2010 using a playback speaker to conduct experiments in amazonia. These popular speakers used large non-rechargeable D-size batteries and a single woofer, voiced for musical instruments.
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The "green monster" (bottom right). The speaker in this photo has 2 field seasons of heavy use in the neotropics. The large tweeter on the upper left used a polymer cone. The woofer on the right used a paper cone, but a hydrophobic coating provided water resistance (appears light grey).
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The Green MonsterWe built our first speaker in 2014 out of a solid state amp, an oversized tweeter with a small mid-range woofer (the opposite layout of most commercially available speakers). Power came from an extremely energy-dense lithium-polymer battery. And for our speaker housing? A waterproof tupper. We called this the “green monster” due to the green polycarbonate paint applied to the interior of the tupper. The total cost for the setup was less than a hundred dollars. These speakers were louder, sounded clearer, lasted an outstanding amount of time between charges, and were half the weight of what we had used in the past. We still wanted to make improvements. Charging them was tedious, as you had to remove the lithium battery and charge it on a separate, lithium-specific charger. The tweeter housing was too large and heavy. The housing cracked after a few seasons (see photo). And finally, the system lacked Bluetooth connectivity.
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Beta 1.0 NeomorphusOur second iteration speaker was custom built for a professional field guide. He asked for a speaker that could “call in antwrens (>8 kHz) as well as Nocturnal Curassow (< 3 kHz) ”. We built him the Beta 1.0 Neomorphus speaker, featuring bluetooth connectivity. This speaker used a smaller, lighter waterproof tweeter for high frequencies as well as a polymer-cone waterproof woofer for lower frequencies. Audio source was switchable from Bluetooth to 3.5 aux input, and a battery checker on the side kept tabs on a 12v, 4,500 mAh lithium polymer battery pack. We moved the lithium charger permanently within the amp to simplify the power supply to any 12v source. Finally, the speaker was housed in a rock-solid aluminum housing. The Beta 1.0 Neomorphus speaker was the Lamborghini of field speakers, and proved itself over several months of work in the Brazilian Amazon.
The Beta 1.0 Neomorphus speaker still had room for improvement. The Bluetooth connective distance was limited. The housing had large seams. The voltage indicator did not have a clear read-out. The speakers protective grills pushed outside of the square form factor. |
The Beta 1.0 Neomorphus speaker showing its external speaker grills and battery check (blue button). The photo on the right shows the 3,000 mAh lithium-polymer battery pack and the 2x35 watt solid state amp before final assembly. We also opted for a waterproof, lighted "on/off" button that was recessed. Connections and inputs were kept on the side of the speaker to reduce the chance of water entering the housing.
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Beta 2.0 Neomorphus speaker after 3 months of use in amazonian field site conditions. The Bluetooth 2.4 GHz antenna extends the receiving signal range in the forest. The ABS speaker grill is designed to remove the appearance of two circles (eyes), has large opening to allow high frequencies to pass unobstructed, and features a downward sloping port design to drain water away from the speaker cones.
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Beta 2.0 NeomorphusThe Beta 2.0 Neomorphus speaker was built with these field-use priorities
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The Beta 2.0 Neomorphus speaker was built within a 3-d printed carbon-fiber and ABS polymer shell. All of the above priorities were addressed, and the speakers were tested during a 3 month field season in the rainforest. The final changes and tweeks have resulted in the final design of the Neomorphus speaker. Several more projects are in the works, including smaller form-factor options, different battery chemistry options, and non-speaker custom field equipment.
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