Measurement and system optimization

Beam topology logic

The whole HOLOPLOT environment is specified by the logic of beam, not array. Each array can utilize:

• 5 Optimized Beams

  • Coverage beams

  • Optimized Virtual sources

• 8 Parametric Beams

  • Parametric Beams

  • Virtual Sources

Beams are expected to have unique channel number which means that for the measurement workflow we can easily route measurement signal directly from our measurement software to the beams. This ability allows you to quickly switch between multiple beams during measurement and apply EQ and delays in HOLOPLOT Control to each individual beam.

Coherent vs non-coherent signals

Managing multiple beams per array requires careful monitoring of the signals directed to each beam and their simultaneous playback. Utilizing coherent signals within the array, active beams can interfere with each other, leading to:

• Directivity behavior: Coherent signals may cause interference that disrupts the directivity of the beams.

• Array headroom: Summation of coherent signals at the same level can lead into reducing the available headroom by 6dB.

Alternatively, using non-coherent signals impacts:

• Array headroom: Summation of non-coherent signals at the same level can lead into reducing the available headroom by 3dB.

Beam latency

X1’s low-frequency option is the subwoofer within the MD80-S. It is a 6th-order bandpass design whose group delay features two bumps at 30 and 74Hz. The MD96 also features a bass reflex design for its mid-range drivers that peaks the group delay at 90Hz. Compensating for these peaks holds the challenge of phase optimization.

Shaping the low-end magnitude response with the target curve of the optimization is not affecting the group delay response. Adding EQ on top of it will alter the phase response.

Time alignment

In line with previous descriptions, HOLOPLOT employs beam topology in its system design. The placement of the time alignment point(spatial crossover) is crucial.

The strategy includes:

• 01 - Coverage / Parametric Beam: The spatial crossover (XO) point is typically located in the shared area among two or more beams.

• 02 - Virtual Source: When a focus point is combined with a coverage beam, the position of this focus point serves as the spatial XO point.

• 03 - Reflection (Reflected Virtual Source): This unique application uses reflections from specific surfaces or walls. The spatial XO point is at the center of the coverage area of the reflected source. Due to its longer sound path, the reflection is generally the time reference.

Target curves

Optimized Beams can set target contour curves based on the specific use case. The shape of these Optimized Beams are heavily influenced by the balance between power and homogeneity. The graphs illustrate two use cases for HOLOPLOT target curves:

Music LF Shift: LF3,6,7 are curves recommended for music content. The extent of the LF shift varies according to the musical style and desired SPL.

Speech HF Shift: For scenarios where speech intelligibility is a priority, a slight HF shift can significantly enhance clarity.

Both the LF and HF shifts substantially impact the array’s headroom and must be carefully implemented, keeping the array configuration in mind.