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In Reply to: RE: cMP - the open source high-end Memory Player posted by cics on December 30, 2007 at 05:42:01
Dear Forum,It´s been a long joyful (also frustrating at times) ride between the Planar -, Digital - and cMP Forums to finally announce the result of Dawnrazor´s recommendation of the cicsmemoryplayer including digital crossovers and FIR filtering (Room Correction).
Thank you all for your help and support !So here is the poor mans DIY DEQX alternative :
In the center of the setup is the cMP2 system (cicsmemoryplayer.com) which is a State-of-the-Art Computer featuring advanced upsampling and RAM memory playback. Since the implementation of the VST plug-in into cPlay it also allows integrating FIR filters that can correct frequency response, phase behavior and time alignment between drivers in a way that no electronic or passive crossover can ever do !
The important stage in working with FIR filters is to allow sufficient control of the parameters with which these filters are calculated. The pioneering TacT and Lyngdorf equipment are nowadays flawed with too little processing power, too fixated proprietary software & hardware and the general lack of programmable flexibility. The revolutionary DEQX DHP-3 does certainly take FIR filtering a significant step up the quality ladder and is indeed a highly recommendable piece of gear, but does come with a equally significant price tag.Previously I´ve used Allocator as a more traditional crossover software (IIR filtering), but about 3 month ago the german "Acourate" FIR filter software was released with the new ability to operate within an active (bi- tri- & quad-amping) setup.
The only software that previous could do that, is the norwegian "Audiolense", but personally I regard the Acourate as the superior one, as the crossover filter characteristic can be determined upfront, and Acourate´s fine tuning of the so called "excess phase" can get the feared pre-ringing out of the calculation.
This is a very important feature within this technology.To setup FIR filters one will need following :
A PC computer of newish specifications with Windows OS + soundcard with 6 channel analog output (for a 3 way system). RME FireFace 400, Lynx Two-B, Lynx Aurora, Apogee Roestta 800 or any equally 2-in/6-out interface + measurement microphone (calibrated is best) +Acourate software (about $500 U.S.) +convolver software (free)
Connect the interface to the amplifiers & respective drivers, and to the microphone (positioned at your listening chair). Select samplerate and the desired crossover filter parameters. Linkwitz-Reilly 8th order for example. When running the Logsweep Recorder of Acourate the program generates a series of advanced pulse and frequency sweeps on each driver, and records the results. These sweeps contain 130.000 samples (!) of information from each driver and the reflections in your room. The generated Pulse files are now run through a series of parameters that ensure you´re not stressing the loudspeaker more than necessary and that you get the desired behavior from the system. Once that´s done you can finally calculate a "reverse" or "mirrored" filter that can be read in the playback software (cPlay & convolver) and allocate the outputs to the D/A converters and pass them on to the amplifiers.
Since Acourate can calculate different scenarios and has a very flexible approach, you´re never stuck to only one result. Just run a new calculation with a different set of parameters and listen to the result.
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cMP2 Computer: i3-540 Core cPlay039 >FIR filter w/ convolver> Lynx Aurora 8 FireWire /192kHz throughout. 2x AcousticReality Ref. 202 & 2x AcousticReality Ref. 601´s ICEpower. Magnepan MG3.3R beechwood frames & custom stands. Miller chokes
Edits: 06/26/11Follow Ups:
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