Najda currently makes available 2 processing strategies described hereafter. More strategies will be included with future software and firmware upgrades - Najda is indeed a fully upgradeable system.
Najda's control application is real-time in the sense that any change made in the software is immediately transferred to the board.
Both strategies share a common structure where the stereo input enters the Input Processing block. The Sum and Difference signals are generated here - they are useful for feeding subwoofers or building a 3-speaker stereo setup that comprises an additional centre channel. The Input Processing block includes long delay lines (8192 samples), gains as well as a filtering stage.
All 4 pre-processed signals Left, Right, Sum and Diff follow thereafter their journey in the Channel Processing block, which consists in a routing section, gains, delays (4096 samples), polarity switches and more filtering stages.
Classic Free Routing
This is the most common filtering strategy among cross-over systems, and it will be familiar to all users. It comprises the traditional analogue filters transposed to the digital domain. All biquad sections are implemented with double precision on both feedforward and feedback paths, which guarantees that low-frequency filters will be on spot even at higher sampling rates. At 96 kHz, Najda will process the signals through over 120 such biquads freely distributed among channels.
Available filtering blocks are:
- Butterworth 6, 12, 18, 24, 36, 48 dB/oct
- Bessel phase-matched 12, 18, 24, 36, 48 dB/oct
- Linkwitz-Riley 12, 24, 36, 48 dB/oct
- Peaking filters
- Low/high shelving filters
- Custom biquads defined by their Direct Form 1 coefficients
FIR Engine mode
This mode is a FIR convolver and is less common among cross-over systems. The user is expected to supply raw filtering coefficients. At 48 kHz sampling frequency, the number of taps exceeds 8500, freely distributed among channels. Prospected upgrade in this mode is a decimation stage.
Additionally to the above processing configuration views, the software includes tools for assisting in the setup and adjusting parameters.
The Monitor view includes VU-meters for the selected active input as well as VU-meters for all 10 processing channels.
It also signals, in form of a led or OVF meter segment, if any part of the processing is clipping, inviting to review locally the gain structure.
The Monitor includes as well load-meters for each DSP core that display precisely how much computing load is been used and how much is available for additional processing tasks.
Lastly, as keypad and IR receiver are disabled when connection to host computer is established, a controller section enables muting channels individually or collectively, adjust the volume, balance and bass/treble.
The Graph utility allows loading and displaying measured data, or instead using default flat responses when measured data is not available. All processing parameters - gains, filters and even delays - are applied to the original responses so that processing outcome can be estimated.
Configuration and management dialogues
The Preset Manager dialogue allows storing processing configurations into the non-volatile memory of the board. The preset name typed in this dialogue will appear on the display when the preset is active. This dialogue allows also erasing a preset that the user would want to discard.
The Najda is capable of driving various types of displays. The type used is set in the Display Options dialogue, where the user can also customize the names of connected sources as they should appear on the display.