Precisely what can be controlled?

Users have total control of the loudspeaker system. It is possible to set the electroacoustic or IT parameters of an individual enclosure or a group of enclosures selected by the user (e.g. the various modules making up a line array system for a concert or permanent installation).


The following is a list of parameters controllable via computer (PC or Mac), Tablet or Smartphone (iPad, iPhone, iPod touch):


• Gain

• Mute

• Polarity

• Delay

• Filters

• Impedance measurement (in “live” mode  with a music signal and in “warehouse” mode, via a test signal)

• Limiter (RMS/Peak)

• Compressor (RMS/Peak with variable knee)

• Bypass of all functions

• Ghost technology: for the creation of “steered” arrays and separate control of a group or single enclosure

• Network settings (static/dynamic IP)

• Variation of network communication speed (to ensure the best network topology match)

• Enclosure description (the enclosure’s name)

• 3-level system update (application, presets, operating system)

• Type of input: analogue/AES3 digital (two channels with possibility of selection)

• Sensitivity: +10dBu/+20dBu (to optimize interfacing with analogue devices)

• Power LED (a power LED lights up, enabling the enclosure in question to be identified at a glance)

• Amplifier Mute 


Twin compressor-limiter per channel and up to 2 seconds delay

iMode also provides a double dynamic processor for each channel (peak/RMS), to ensure greater reliability.

If a large sound system has to be controlled – e.g.: multiple Outline Mini-COM.P.A.S.S. Vertical Line Arrays - and a delay has to be set, iMode technology provides up to 2 seconds for each channel, in single sample steps: something that can normally only be done with a matrix.

This is a feature that clearly distinguishes the loudspeaker system from competitors’ (which normally provide a few milliseconds to align enclosure’s LF and HF sections).


Indicators (sensors/diagnosis):

• Input Overload

• Signal

• Temperature

• Protection

• Limit

• Amount of limiter intervention

• RMS VU meter

• Peak VU meter with highest value stored

• Number of clips through time

• Preset management


Linear-phase crossover filters

An important feature added to the system, indispensable in some professional quality audio applications, is the possibility of using linear-phase FIR digital crossover filters, which follow the amplitude curve of the classic Butterworth and Linkwitz-Riley models (24 or 48 dB/oct), with the possibility of setting high-pass and low-pass separately, thus ensuring loudspeaker enclosures’ phase response coherence in any practical context.

Figure: Frequency response of a 4th order Linkwitz-Riley filter at a crossover frequency of 1 kHz. It can be seen how the sum of the two responses (green line) is flat for all frequencies.


Raised Cosine filters for really superior precision

The tools provided by iMode technology to control sound systems’ response include modern Raised Cosine filters. Compared to traditionally implemented parametric functions, they provide better transfer curve shaping, controlling intervention frequency bandwidth more precisely while maintaining minimum-phase response.


Figure: iPad iP24 Manager App screenshot showing the four kind of "Raised Cosine" filters: Peaking, Band-Pass, Low Shelving and High Shelving.


WFIR vs Multi-rate FIR

Users have the possibility of effectively changing the input channel’s frequency response: as opposed to other digital processing techniques, such as Multi-rate filtering, which guarantee adequate coverage at low frequencies at the cost of additional delay that affects the overall system, the solution adopted by the iMode system has zero latency.

This result - a great advantage in live installations - has once again been possible thanks to the use of evolved processing techniques focussed on audio signal processing: it is not necessary to introduce latency, because the system was designed precisely to ensure the best performance also low and mid frequencies.


Figure 1:

Graph showing the frequency resolution curves, comparing FIR, WFIR, logarithmic scale and Bark psychoacoustic scale. 

Figure 2:

Graph showing the frequency resolution trend, demonstrating how, by means of WFIR technique, it is possible to move the resolution towards the low frequencies, without altering the number of taps, but changing parameter λ.

Figure 3:

Example of equalization (target function), via FIR filtering and with WFIR technique, for filters that have the same computing weight. The TARGET transfer function line is almost totally covered by the WFIR line.

Figure 4:

Example of equalization (target function), via FIR filtering and with WFIR technique, for filters with the same number of taps. The total inadequacy of FIR filtering at mid-low frequencies can be seen.


Complete efficient management of groups of loudspeaker enclosures

To ensure control total of loudspeaker systems even in the most complicated situations, iMode has the advantage of an advanced processing structure that gives users the possibility of setting each enclosure as part of up to 8 distinct groups, easily controlling gain, delay and up to 32 filters for each cluster; for an overall response of every individual loudspeaker enclosure which can involve up to 256 filters, thanks to transfer function synthesis.


“Real-Time” Synthesis

The goal of comprehensive efficient management of numerous functions has been achieved by implementing modern FIR filtering specifically for audio applications: WFIR (Warped frequency) technique, which is based on the idea of distributing the frequency resolution over a semi-logarithmic scale, as does the human ear. The integration of this upgrade in the iMode system has been carried out without coming to any compromise on reliability and smooth interaction: in fact, Outline’s proprietary communication protocol enables the enclosure to always know the form of the transfer function created with the software and to recalculate WFIR filter coefficients in real-time, thus ensuring absolute coherence without in any way jeopardizing the application’s interaction, which remains top-grade.


What about audio quality? iMode interacts with the amplifier

From the point of view of mere numbers, Outline iMode offers the highest audio quality currently available (24 bit/192 kHz).

The processing power of the on-board PC and its architectural peculiarities (CPU) ensure higher performance (e.g. WFIR filters) than those currently available with the latest processors on the market.

Nevertheless, the best “plus” of the iMode project is having considered the audio chain as a whole and not each individual component. In fact, this is a case of the total integration of technology in a loudspeaker enclosure.

iMode “knows” the amplifier it interacts with perfectly.



-- Outline’s proprietary iMode technology | Texts originally written in Italian by Michele Noselli - English translation by Mike Clark | Videos by Daniele Pagani --