Tag Archives: speakers

HiFiBerry & Raspberry Pi Put New Life into Old Loudspeakers

If you have some old stereo speakers stored away in your basement, chances are they connect through the old way—with wires—to an amplifier, and that is the reason they were banished to the basement. With HiFiBerry Amp+ and a single board computer, such as the Raspberry Pi (RBPi), you can resurrect your vintage speakers. Using the latest in open source technology, you can now use the renovated loudspeakers wherever you want, since they now operate wirelessly.

HiFiBerry offers their Amp+ as an amplifier for the RBPi. As it is a Class-D power amplifier, it is highly efficient as a stereo module, and you only need to connect the loudspeakers. This high-quality amplifier is ideal for setting up multi-room audio installations.

The amplifier is stable enough to drive 4-Ohm loudspeakers and those with higher impedance as well, pumping out 25 W of output power. However, the best part is the RBPi can fully control the amplifier. As the amplifier includes on-board digital to analog converters, you do not need external sound cards or DACs to provide the 44.1 KHz and 48 KHz sample rates. The board connects directly to the RBPi without needing additional cables, and this provides a full digital sound path for optimal audio performance.

The HiFiBerry Amp+ comes as a pre-fabricated kit, so it needs no soldering. It is a daughter board for the RBPi, and when the RBPi plugs into it, you need to connect only a single external power supply of 12-18 V to supply both the amplifier and the SBC, as the RBPi draws power from the Amp+. You can use the Amp+ with all RBPi models that have the 40-pin GPIO connector. The board sits on four small plastic spacers that come with the kit.

The specialty of the Amp+ kit is it converts the digital signal into audio with far greater clarity than the RBPi can, and delivers that to the speaker as a 25 W audio amplifier. On the reverse side of the board, the female connector is easily visible, so it is easy to plug in the GPIO pins of the RBPi.

On one side of the board are a jack for powering the board, and six wire-terminals. If for some reason you cannot use the jack to power the board, use the two wire-terminals on the left. The rest of the four wire-terminals are for connecting to a pair of stereo loudspeakers, using two audio cables per speaker.

As the board takes in 12-18 V supply and delivers power to the RBPi as well, it is important to not power the RBPi from its usual 5 V power supply. This reduces the number of wires to the assembly. As the Amp+ board is very small, it does not protrude beyond the RBPi. It is important to mount the board on the four plastic spacers to avoid breaking the GPIO pins.

The SD card for the RBPi can be of the 8 GB type and people have reported better performance with Transcend cards. However, you can use 16 GB cards as well.

Speakers: Sound From Any Surface

Although accustomed to thinking about speakers when we hear of sound reproduction, nature uses several methods of producing sound or amplifying it. For instance, a cricket makes a chirping sound by rubbing its hind legs against each other, while perching on a large leaf to amplify the sound it produces. A guitarist amplifies the sound from the wires by coupling it to the guitar’s wooden box.

Traditionally, the size of the cone and the driver of a speaker determine the frequency and range of sound it produces. That is why several small portable speakers sound tinny, as they are unable to offer the deep bass because their driver can deliver limited frequency ranges. That is also the reason high fidelity audio systems have separate speakers for reproducing extremely low frequencies through subwoofer speakers.

A new type of speaker in the market does not require a cone to reproduce sound. This speaker uses the Incisor Diffusion Technology to diffuse sound across and through any surface upon which it is resting. It uses the surface to act as its cone and the surface diffuses the sound into the surrounding area.

Created by Damson, all its products using the Incisor Diffusion Technology offer a full audio frequency range from the surfaces they are placed upon. However, as different surfaces have varying resonance properties, the audio they produce will sound somewhat different. This unique way of reproducing sound offers the hearing impaired to feel sound through vibrations—just as Beethoven did.

As Damson pushes the capabilities of sound reproduction to newer frontiers, the need for different speakers to provide bass, middle, and high frequencies is fast dissolving. A regular speaker has a coil fixed to a permanent magnet, the arrangement being known as the driver. The Incisor Diffusion Technology from Damson replaces the coil with teeth or incisors. While they act in the same way as a coil does, they also power the different frequencies pushing the through to the surface. The reaction of the Incisor Diffusion Technology with the surface transfers the sound through it. For instance, placing on of Damson speakers on a window diffuses the sound through the glass, allowing it to be heard on both its sides.

Along with the size and shape of the surface, its type also affects the sound that it delivers. For instance, a bigger surface produces more sound than a smaller surface does, as it has more area and moves a greater amount of air—just as a bigger speaker is louder than a smaller one is. Any elastic surface will work to amplify the sound through it.

That means some surfaces work better than others do when reproducing sound. For instance, you will not hear sound from surfaces made of granite or stone, thick solid wood, sand, tarmac, grass, mud, asphalt, and concrete. On the other hand, thin wood is an ideal surface for sound reproduction, as is glass such as windshields, shower screens, windows, and tables. Metals surfaces are also good for sound production, so one can use the car bonnet, hood, or the roof. Now Redux is planning to use this technology on the screen of smartphones as a replacement for tiny speakers.

SOUNDBOKS: Batteries to Power the Next Speakers

Your next portable speakers may be able to violate county noise ordinances without the necessity of them being plugged into a vehicle power inverter, a portable generator or even a wall socket. This is what Soundboks is claiming, and their speakers will be battery-powered.

Most portable speakers are limited in their size and their power output. Usually, if you want sizes and power capacity beyond those, it becomes necessary to power the speakers through AC adapters or wall plugs so they can output continuous power. That does not help when catering to outdoor gatherings, where truly wireless music at extreme volumes is the norm. With the battery-operated speakers from Soundboks, you can now expect 30-hours of nightclub-level decibels on a single charge.

In the market, one can find plenty of audiophile-grade boom-box sized speakers such as the Nano HiFi NH1 or the rugged JBL Xtreme suitable for supplying ample amounts of power for pool events, camping, or backyard cookouts. However, the portable speakers from Soundboks beats them hollow, as they house a pair of low-frequency drivers each of 96 dB, and a pair of high-frequency drivers, also of 96 dB SPL or sound pressure level speaker units, along with 42 W digital amplifiers.

With high-efficiency custom-designed amplifiers, Soundboks speakers enhance the life of the driving batteries while optimizing the sound for outdoor usage. They have designed the speakers for dual-phase boost function and these can belt out a maximum of 119 dB of sound. You can easily get an experience of a live concert, simply by turning up the volume dial on the speaker to position 11.

Weighing in at 14.5 Kg (32 lb.), the 66x43x32 cm (26x17x13 in) Soundboks speaker is not much different from other carry-on luggage used. The low weight is because of the wood and aluminum construction of the case and that makes it shockproof, weather proof and temperature resistant. The case has an integrated side handle that makes it easy to carry about on the beach as easily as a cooler filled with beverages and ice. Wireless and wired connectivity are offered. Bluetooth 3.0 with extended range allows you to connect wirelessly while a 3.5 mm audio input provides the wired connectivity.

The truly remarkable thing about the Soundboks speaker is its ability to play music for 30 hours at 113 dB. That easily violates the county noise ordinance and that too without any help from a vehicle power inverter, portable generator, or wall socket. Each speaker comes with two external batteries, which you can swap and that gives the capability to play for a total 60 hours continuously.
The batteries are special, as they are not the usual lithium-ion type. Rather, Soundboks uses LiFePO4 or lithium-Ferro phosphate batteries that need only three hours to charge, can meet power demands and are safe. Therefore, you only need six hours of charging time, and then enjoy a full weekend-long festival program or a complete week with the volume toned down. Shipments are scheduled to start this April, as Soundboks has already raised 174% of its Kickstarter goal in one day.

Why do Speakers use Ferro-fluids?

Speakers reproduce sound by moving a diaphragm to displace air. The mechanism resembles a permanent magnet electric motor. The major difference is the voice coil in a speaker moves linearly instead of in a circular motion. As the coil moves back and forth in step with the electrical signals fed to it, it moves the attached diaphragm. To prevent spurious movements and unwanted oscillations of the diaphragm, conventional speakers generally use a damper. To produce sound from such speakers, extra energy is necessary to overcome the resistance of the damper.

Additionally, the damper has its own natural frequency of vibration that restricts the speaker from reproducing sound accurately at all frequencies. A new technique using a magnetic fluid to replace the damper claims to correct this anomaly by reducing energy consumption and allowing louder and clearer sound across the entire range of frequencies the speaker is capable of reproducing. To quantify the advantages, the new speaker reduces energy consumption by 35% for reproducing the same loudness of sound as from conventional speakers and the improvement in sound quality is nearly 3dB.

NASA originally developed the magnetic fluid in the 1960’s, using it for space exploration and called it Ferro-fluid. It responds to applied magnetic fields because the fluid is infused with Nano-sized magnetic particles. They do not agglomerate or cluster together because of a coating of suitable surfactants. The unique characteristic of ferro-fluids makes them useful in a range of applications. Using applied magnetic fields to control flow or movement, ferro-fluids can replace mechanical parts such as vehicle suspensions, flow of fuel in a reactor and more.

In a conventional speaker, the damper holds several components such as the diaphragm and spring in place, even when the speaker is vibrating. However, the damper causes friction while moving, thereby distorting the original sound waves with secondary vibrations, which are manifest as noise. To overcome the friction requires additional energy while driving and that reduces the speaker’s total volume output by a few decibels.

When replacing the damper in a speaker, the ferro-fluid used has a thickness of only a few microns. The magnets of the speaker create a permanent magnetic field to which the ferro-fluid responds by holding the diaphragm and the coil in place while allowing them to move linearly without any friction. As there are no secondary vibrations from the ferro-fluid, the sound is clearer. The lack of friction allows the speaker to save about 35% of the energy as compared to conventional speakers with dampers.

Ferro-fluids used for the audio field are usually based on two classes of carrier liquids – synthetic enters and hydrocarbons. Both oils are low in volatility and high on thermal stability. The environmental considerations dictate the choice of the fluid used, along with the best balance of viscosity values and magnetization for optimizing the acoustical performance.

Using different carrier liquids and by varying the quantity of magnetic material in the ferro-fluid, it can be tailored to meet different needs. The saturation magnetization depends on the nature of the suspended magnetic material and its volumetric loading. Care is taken to use material whose density and viscosity correspond closely to that of the carrier fluid.