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8pm Wednesday 18th July, visitors welcome.
Willis Room, City of Whitehorse Offices
Maroondah Highway (Whitehorse Road), Nunawading
Melway Map 48 Ref G9
Contact: 9437 1249
When it comes to choosing or designing a loudspeaker there are two rules to consider: Rule #1; There is no such thing as a perfect loudspeaker. Every design is a series of compromises. Rule #2; One has to accept that there will be compromises and decide on a design which reduces these compromises.
This month's presenter has developed a speaker system which further reduces the compromises associated with the conventional passive loudspeaker. Rick Bond from Lucie Audio will be demonstrating his speaker system which utilises active crossovers with room equalisation by means of his DSP pre-amplifier. "Our pre-amp is built around the capabilities and feature set of the MiniDSP 2x4HD processor board. This gives us the power to process the stereo audio stream in real time to perform room corrections and digital crossover functions. Correction technology is powered by Dirac Research AB, world leaders in this field".
The process maps out the frequency and impulse response characteristics of the speakers in the room in a 3D grid around the listening position. After completing a frequency sweep with a microphone connected to the computer, a desired frequency response curve and an optimised impulse response are measured; the data and a set of filters are generated to map the two together. This data is then uploaded to the unit and stored in one of four configuration slots. This provides great flexibility in that up to four combinations of tonal response, crossover parameters and optimal listening position can be stored and readily recalled via the unit's remote control.
"To get the best from the MiniDSP hardware, we developed an active analogue volume control board. Maintaining volume control in the analogue domain provides the best approach to the gain structure".
Rick will be demonstrating his system with two sets of book shelf speakers and a matching subwoofer. He has developed these two distinct speakers to cater for the tastes of the listener. The Lucie Model One Loudspeaker is a 6.5" Point Source design. The full range driver is sourced from Dayton Audio for its zero crossover distortion. Excelling at delivering the nuances in the midrange, this design is recommended where primarily acoustic music is appreciated in a small to medium, focused listening environment.
The Lucie Model Two Loudspeaker is a traditional two-way compact speaker with drivers from SB Acoustics and Scan-Speak. Recommended and pre-set crossover slopes from the DSP Pre-Amp are set at 6db per octave and centred at a fairly high 4kHz. First-order crossover slopes are chosen for their phase neutrality, made possible by the smooth and extended response of both drivers. This bass reflex (ported) design has a greater power handling and more driver excursion, better suited to bass-heavy music. The system extends the response well below the frequency of the cabinet, giving exceptional performance for a fairly compact enclosure.
Cabinet materials are chosen for their high density and sustainability. Narrow grain carbonised Bamboo or Baltic Birch ply are laminated, no veneers are used, precision CNC cut then hand assembled and finished. Due to the laminar sheet construction inner wall profiles are able to be uniquely contoured to minimise internal reflections and cabinet resonances.
This will be Rick Bonds first public presentation at an audio event. A relative new-comer to the HiFi scene, this young man has developed a complete active system that puts DSP technology within the reach of many audiophiles.
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Melbourne Audio Club, Inc.