EAW CSC723X, CSC923X manual

Voice Coil to Surround = 6.3 inches Voice Coil to Dustcap = 6.8 inches

Voice Coil

Radial Slots

Dustcap

Surround

Cone

Traditional Mid Cone with Phase Plug, Side View Cutaway

VA4 Phase Plug uses Radial Slots to Maintain Source Directivity

problem at the source. The cone transducer’s tempo- ral smear is corrected by precisely aligning the cone/ dustcap/surround geometry to maintain temporal unity. The distance to the dustcap is slightly longer to compensate for differences in material density.

The phase plug, whose geometry is matched to the cone, then serves to leave this unity intact. Expand-

ing radial slots within a compressing frame lower the

mechanical reactance of the load facing the transducer without modifying the directivity associated with the

source. This allows for faithful reproduction of the upper mid-frequencies without any narrowing of beamwidth.

The wavelets (below) illustrate the difference between old and new mid-frequency cone/phase plug technologies. These wavelets represent data gathered at 1

meter from devices mounted in a pseudo-infinite baffle wall. The vertical axis indicates frequency, the hori- zontal indicates time, and color indicates dB SPL with each color change indicating a 1 dB drop in level. The first illustration represents data obtained from a conventional midrange transducer. Particular attention should be paid to the upper midrange above 1 kHz. Note that the energy at the top of the passband centered

around 2.1 kHz is slightly leading the rest of the broadband energy and also remains considerable after.

This difference of microseconds is difficult to observe without precision measurements, but the phenomenon is quite audible. The resulting reproduction would take a finite sonic event (a Foley door

slam, gunshot, or footstep, for example) and reproduce it over a longer period of time than it had actually taken. The source has been compromised and the events’ clarity and impact degraded. With the harmonics leading and/or lagging the fundamental tone, the timbral quality of the acoustic event is lost.

The next illustration results from an identical measurement taken on a new CSC mid-range trans- ducer. Needless to say, the temporal inconsistencies have been eliminated through the implementation of a more logical transducer geometry.

In the end, the mid-frequency sub-system of the CSC Series exhibits the temporal clarity of a com- pression driver alone (as in a two-way system) and the natural low distortion sonic reproduction of a cone transducer (as in an EAW three-way system) while remov- ing crossover transi- tions from the vocal region and maintain- ing the spatial perfor- mance required for broad band constant directivity.

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