Housing made of Slate

As housing material we use only a special slate from a certain quarry. This particular variety has a very expressive and unique texture for slate. Its high hardness and stability allow only the production of curved shapes, as we need it for Stone Audio Art Products. Because of its excellent vibration damping properties it is ideal material for speaker enclosures.

Special Woofers

Two pairs of 1o" special woofers from Scan-Speak produce acoustic energy working as a dipole-transducer. This means: Within a streamlined housing type the woofers emit sound energy during the positive period in a front chamber with an outlet opening in the forward and in the negative period emit sound in the rear chamber with an outlet opening in the back. Due to the curved side walls thereby a laminar flow is established, preventing the destructive energy air turbulence as far as possible. So the woofers create sound energy in the listening room up to 20 Hz without any bass-enhancement. That, despite an apparent acoustic short circuit low-frequency sound energy is generated in the room, owes to the physical principle of the velocity-transducer principle. This is in contrast to the pressure transducer principle as represented in the closed-box-, bass-reflex- or exponential systems. The tonal preferences to velocity-transducer bass systems are: more precise, “blacker” and even more dynamic. A free sound! This principle does not require any active bass enhancement- but a steep-slope equalization band pass filtering that is performed for the AcouStone with the included bass manager. See technical description of StoneBass-manager.

Ceramic Speakers

In the mid and high frequencies, the ceramic speakers by Accuton-Thiel & Partner were used. In a unique production process the membranes are prepared by oxidation of aluminum to aluminum oxide (Al2O3 = ceramic). Its ratio of hardness / stiffness to weight is hard to beat and the internal sound speed is extremely high. They are nearly free of resonance, because the oxidation process creates inside a foam-like microstructure with high-damping effect. These membranes have an excellent transient response and an increased linear range of the transmitted frequencies.

D'Appolito Configuration

For the midrange and treble reproduction a D'Appolito configuration (vertical arrangement of two midrange to one tweeter in the center) was implemented on a convex baffle. Thus, interference between the three drivers are reduced, which occur in the same frequency transition area (2 KHz), so that a first order crossover can be employed containing only one electrical component in the signal path (both low path and high path) and with significant lower losses than in the usually employed third order crossover for the midrange drivers. With a circuit model (PNF) is nevertheless an effective slope of 18 dB/Oct. realized to establish the symmetry between low-pass and high-pass (see Dome tweeter).

Dome Tweeter with Spherical Wave Horn

The 1" ceramic dome-HT is mounted behind a spherical wave horn, which increases the sound pressure at 2-5 KHz and at the same bundles it in the main emission axis. Thus, reflections at the enclosure-brims are avoided and the electro-mechanical load on the tweeter is lower because the filtering starts now higher, and may be less steep. In this way an effective slope of 18dB/Oct. with -3 dB point at 2 kHz is reached containing only one electrical component in the signal path. Finally, having a place back due to the length of the horn, the acoustic centers (located at the voice-coil) of tweeter and squawkers are placed at the same vertical level. This will synchronize the wave fronts of both squawkers and tweeter and thereby largely increase the spatial representation.

Perfect Sound, thanks to an Optimized Design

So that no difference in sound can be perceived between sitting and standing position, the entire housing was slanted backwards, to achieve that also the lower of the two midrange on the curved D'Appolito baffle again radiates in a vertical angle to the main axis. Thus, the sound image dissolves in all three dimensions from the speakers.

Technical Data

Measurements with ground plate: W x H x D: 24,5 x 106 x 52 cm
Ground plate: 58 x 31 cm
Weight: 100Kg.
Optinal: On spikes adjustable in height.
Electrical Data: Active Bass, mid range/tweeter 4 Ohm, passive. Active high-pass filter 80 Hz. Spl. = 93 dB / 1W/1m. Max resilient at 150 W/rms. for mid-range/tweeter and 200W/rms for Bass.

AcouStone Fräse Plant 4 Plant 4 Plant 4
Plant 4 AcouStone Fräse Plant 4 Plant 4