Daniele Coen from Alsyvox shares an interesting essays about “Why Dipole Planar Loudspeakers are Special?”…
Planar Loudspeakers
Planar loudspeakers are well known for their ability to create a wide and deep image and sound with very little coloration. This is related to the physical size of the moving part of the speaker and the absence of tonal colors coming from cones or domes and boxes that resonate.
Technology used can be electro-static or magneto-dynamic, with ribbons being a special type of magneto-dynamic. The first is using an electric power source to electrically charge a plastic diaphragm, the second is using many magnets that interact with the current passing in a voice coil extending over the plastic diaphragm.
A ribbon is an elongated diaphragm suspended at its two ends (top and bottom) when a planar magnetic is a (generally) rectangular plastic diaphragm with most of its surface covered by the voice coil (aluminum conductor).
Planar Loudspeakers Advantages
1. Isodinamic transducer. It means a sound transducer with wide and almost constant distribution of forces over its surface, no concentration. This gives less mechanical vibrations that are not proportional to sound signal ( = distortion)
2. Dipolar radiation. It means sound emission from both sides, front and back. It is responsible for most of the listenable advantages of planars as the interaction with the room is optimal, specially at low frequency.
3. Line Source. When a planar source is much taller than wide it approximates the theoretical line source. This happens at frequencies with wave length big compared to the width, so to make a line source for high frequencies we need to make a source with a width of less than 10mm. The characteristic of a line source is that the sound pressure is changing proportionally to the distance where a point source produces a sound pressure that is changing with the second power of the distance, so with a line source in close vicinity the sound is not too loud and far away it is not too weak
Planar Speakers Disadvantages
1. Lack of Low frequency. It is well know the fact that at low frequency the back radiation can partly cancel the front radiation as they are out of phase of almost 180°
2. No Pin Point Image. This is quite accepted as being not a disadvantage as the so called pin point image is an artificial construction of some stereo systems not a real music characteristic. On the contrary real music is many times coming from big musical instruments and is offering a very wide number of reflections and a huge reflected energy. We also need to be careful with the selection of recordings, it is quite easy to create a huge mouth using a microphone close to the mouth of a singer and adding some electronic delay to make it sound richer.
Why are Alsyvox Loudspeakers so special?
Alsyvox bass loudspeakers
Alsyvox bass loudspeakers How could we solve the issue of weak low frequency?
- Big surface (around 1 m2 on two channels with Botticelli) to have a better transfer of diaphragm movement into acoustic energy
- Long stroke (20mm) given by the distance between diaphragm and magnets and diaphragm compliance (low stiffness)
- High efficiency using big Neodymium magnets
- High efficiency and linearity (no compression) using Push-Pull magnetic design: magnets both in the front and in the back
Big Surface and Long Stroke
1. Big surface (around 1 m2 on two channels of Botticelli) to have a better transfer of diaphragm movement into acoustic energy
- This is the same reason why a big 15″ cone woofer is making more bass than a small 5″ woofer, our woofer has the same surface as a 30″ cone woofer or 4 woofers with 15″ diameter
- If we move a tiny 0.5″ speaker even with an excursion of 1m we will hardly get any bass, it is the physics of sound: only a relatively big surface can generate pressure at low frequency, small surface can only create movement of air but not pressure
2. Long Stroke of 20mm peak to peak A very nice big surface can make a low frequency note but to get enough pressure or dB you need a decent excursion, limiting it to Imm would not make strong bass, we decided to reach a level similar to big con sub-woofers: 20mm peak to peak
High Efficiency and Linear Field
1. High efficiency using big Neodymium magnets.
A strong magnetic field is the motor that gives acceleration and deceleration to the diaphragm, so it adds control, speed and sense of energy in the bass to a level never experienced before
2. High efficiency and linearity (no compression) using Push-Pull magnetic design: magnets both in the front and in the back.
- Compression means that when the level of signal gets higher the sounds is not following it, it stays a bit back. This is felt like a sense of less power, less strength
- Also low level sounds are often lost in the heavy and rubbery suspensions of traditional speakers, this is perceived as lack of transparency and detail as well as lack of ambient information. A light ribbon always moves even with weaker signal.
Coherency
We value coherency in the reproduction of sound on top of many other characteristic.
To achieve it we have designed transducers that share:
- The same emission type: dipole
- The same length
- The same magnets
- The same aluminum alloy foil
- The same polyester backing film and the same adhesive The same pleating of the aluminum conductors
Transducers Width
Also the width needs to be reduced coherently with the reproduced sound wave length. This is the only way to get a dispersion of sound that is always the same at any frequency. Dispersion is very important as it creates the sound response of the room.
To achieve it we have designed ribbon transducers with different width according to the frequency of sounds reproduced:
- 320mm woofer (280mm in Tintoretto)
- 75mm midrange (Only in Caravaggio and Michelangelo)
- 25mm midtweeter
- 5mm supertweeter
Mid-Super-Tweeter Unit Breakthrough
1. We have developed a single unit that incorporates both mid-tweeter and super-tweeter extending the frequency response to 40KHz.
2. The two transducers have the same length
3. The emission centers are closer than half a wave length at 5000Hz (crossover frequency), this makes the crossover seamless and completely impossible to hear in any listening position
4. The two units use Neodymium magnets and proprietary technology to make the diaphragms to achieve low distortion and high sensitivity like in the case of woofers
Crossover Slopes
To guarantee smooth and seamless transition from one transducer to the other we have decided to use only 6dB/oct slopes.
This is also the best phase response crossover design.
Only top quality transducers can sound at best with a crossover slope that is not cutting with decision all the energy outside of their ideal frequency band.
No breakup nor strong resonance can be eliminated by these gentle 6dB/oct slopes
High Value Design
1. The frame is made of thick and heavy steel, total weight of 115Kg each channel for Botticelli means strength and inertia to unwanted vibrations
2. The crossover is using only top quality components, mainly Mundorf (also the big binding posts) but also Jentzen, Jupiter and Duelund
3. The external parts are both heavy and elegant: Italian design glossy acrylic and precious solid teakwood, plus stainless steel
4. Proprietary inertial feet guarantee ideal interaction with floor
5. Each speaker comes in a professional flight case for ideal protection
and multiple shipments
6. On top of everything we make all most important parts by hand and our designer is running break-in, testing and fine-tuning on each pair personally. This is more than a signature and allows us to give a 5 years warranty