Duntech's reputation has been built on technical excellence and international leadership in audiophile quality loudspeaker design. In a highly competitive international market place, an ongoing investment in research and development capability is considered vital to increasing market share and winning new markets.
Duntech design philosophy involves a combination of technologies specifically:
- symmetrical arrangement of loudspeaker drivers
- time alignment
- first order crossovers
- a patented, acoustic, sound absorbent felt material of critical size, shape and placement, designed to reduce diffraction distortion
- high quality drivers
DUNTECH loudspeakers are 'pulse coherent' - i.e. a combination of technologies that will reproduce complex musical waveforms with minimum distortion or alteration to the shape.
The company's technical objective is to develop loudspeakers which have the following attributes:
- The ability to reproduce individual frequency components which arrive at the listening position at the same time, and with the correct relative phase to each other.
- Reproduction of a spectral balance approximating that of the original performance.
- Arrival of the amplitude and phase components of the sound reproduced by each speaker at the ear in a manner which recreates an accurate sound stage with good location and depth.
- Inaudible levels of non-linear distortion, viz. harmonic, intermodulation or vibratory.
- Presentation of a reasonably consistent and resistive load impedance to the amplifier, so as to avoid amplifier-induced distortion.
Performance requirements for each of these attributes are known quantities and are built into the design of every DUNTECH loudspeaker.
Unique driver arrangement.
Duntech employs a unique physical arrangement of drivers that permits the realization of several design goals important to the accurate reproduction of complex musical sounds. These may be summarized as follows:
- Accurate alignment of path lengths between individual drivers and the preferred listening position.
- Symmetrical radiation patterns.
- Simulated point source radiation.
To assist in understanding how this arrangement works, Figure 1 provides a sequence of drawings which illustrate the concept of apparent sound centre and effective source of radiation. In Figure 1, the drivers are depicted from both the front and side. A dot is used to indicate the location of the sound source within each driver, with respect to the initial time of radiation.
The centre image that occurs when monaural sound is fed to a pair of stereo loudspeakers can illustrate how the pair of woofer drivers also yields a centre image, that is, creates an illusion of a sound source mid-way between them. Thus, a listener some distance in front of the loudspeaker will perceive sound radiated by the two woofer drivers as if it emanated from a single driver, shown by dotted lines, located in the same place as the tweeter.
In the same way, bass and mid-range drivers create an accurate illusion of a single driver located in the same place as the tweeter. Therefore, the combined radiation from all of the drivers results in a listener hearing sound which appears to originate from a single, point source radiator, located on the tweeter axis.
Also, because all of the drivers have their effective source of radiation arrange along an imaginary, equidistant, vertical arc, the sound energy from each of the drivers arrives simultaneously and in-phase at the ears of a listener located at a distance of three to four metres (9-13 feet), on the tweeter axis.
First order type crossover network
The crossover, or frequency dividing network, is the very heart of a loudspeaker system. Its purpose is to divide the electrical input signal from the amplifier into separate, overlapping frequency bands. This is necessary because no single loudspeaker driver exists which can reproduce sounds over the entire audio spectrum, with acceptable accuracy and loudness to meet the criteria for true high fidelity reproduction. By utilizing separate drivers to cover each of the ranges, it is possible to individually tailor them to meet the often divergent needs required for different portions of the spectrum.
Replication of highly complex waveforms with the highest possible precision requires that considerable attention be given to the design of the crossover network, along with properly time aligned drivers as mentioned earlier. Figures 2 and 3 provide a comparison of the results obtained when using first order and second order networks to reproduce a 1 KHz square-wave signal with a time aligned, bass and treble loudspeaker system. The crossover frequency is 1 KHz. The separate outputs of the high pass, treble, and low pass, bass, sections of the first order crossover network are shown in Figure 2A, along with the input signal. The combined waveform, the sum of low-pass and high-pass sections, appears in Figure 2B and may be seen to be a nearly perfect replica of the original square-wave. By contrast, Figure 3 illustrates the very serious waveform distortion which results when a second order crossover network is used, a popular second order Butterworth design. Higher order networks, such as third and fourth order types, produces an even greater degree of waveform distortion.