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Joseph Crowe

3D CAD files for Horn No.1915 --- ES450 Biradial for Altec/GPA 288

Regular price $200.00 USD
Regular price Sale price $200.00 USD
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By downloading these plans you will automatically receive via email the required 3D CAD files to either 3D print or CNC machine the horn (for personal use only). Horn No.1915 is designed specifically for the Atlec/GPA 288 which uses a 1.40" diameter throat along with 3/8" mounting bolts spaced 4.75" apart. The horn achieves a 450Hz cutoff frequency (Fc). We recommend a crossover point in the 600Hz-800Hz region so that a standard 2nd order crossover slope can be achieved to match slopes with the low frequency driver's low pass function. 


  • 3D CAD files of upper and lower halves of horn (.iges and .STL format)
  • Designed for ease of CNC machine with draft angles for CNC cutter clearance 
  • 1.40" throat diameter 
  • Matched physical transition between horn and driver for smooth frequency response
  • Designed to minimize even and odd order acoustical reflections which smear time domain performance
  • Even off-axis coverage 
  • Good coverage in upper treble allow for 2-way applications 
  • Works with Altec 288 or Grain Plains Audio 288-8H
  • Accommodates 3/8" diameter bolts x2 spaced 4.75" apart 

Below are the files included in the zipped folder which is emailed after ordering. 

The below assembly drawing is shown as an example system comprised of the 1915 horn along with the 1838 bass cabinet which is a 200L cabinet using the Altec 416 woofer. This configuration represents a reasonable setup where the off-axis coverage is perfectly matched at the crossover point. This creates an even power response into the room. 


Below is the sectional view of the 288 compression driver transitioning into a smooth horn flare curvature for low edge diffraction. The ES Biradial technology has virtually zero acoustical resonances which makes it devoid of any horn coloration. This unlocks the true sound quality potential of your compression driver, providing audiophile sound quality that is free from honkiness, shout, and harshness. 

Please see our guide on finding a CNC shop for local manufacture.