Open Baffles

This project was a lesson in the folly of rushing headlong into a design without enough preparation. On the shelf was a pair of Beyma AMTs and also a pair of 12″ Fane drivers. The sound of the Beymas was a known quantity and much liked, so it was very easy to imagine them in an open baffle with help from a 12″ bass unit. This was all without considering the constraining frequency ranges of the devices and also ignoring the very important Qts figure which is crucial to matching a bass driver with an open baffle.

Notwithstanding any of this, the units were built.

After building the units the following approximate frequency ranges issues were considered:

  • Guitar 82 – 880 hz
  • Bass vocal 92 – 980 hz
  • Tenor vocal 130 -132 hz
  • Clarinet 160 – 1760 hz
  • French horn 82 – 987 hz
  • Cello 66 – 1048 hz
  • Viola 130 – 1048hz
  • Trumpet 160 – 987 hz

In considering that the Beyma unit can only start at around 1200 hz this leaves an awful lot of the main musical voices to be dealt with by a 12″ bass driver. Not the ideal recipe for success. The actuality was born out by the theory and the sound quality proved less that satisfactory.

Beyma response
Fane response
Comparison together

Although the combined plot shows a fairly balanced level across the whole frequency range there still exists a distinct hole in the middle. In summary the total was definitely not the sum of it’s parts and the project was dropped. It is felt the Beyma unit is too good to be dismissed but may be better used in a 3 way project or with a much better quality bottom end.