Flush Mounting Dome Tweeters

Vifa PL27TG35-06 RAW Frequency ResponseFig 1 – Baffle Width=10″  •  Black plot=Flush Mounted  •  Red plot=Surface Mounted  •  1 meter On-Axis  •  No Smoothing

The plots in Fig 1 show the importance of flush mounting dome tweeters. The Black plot is of my Vifa PL27TG35-06 when it is flush mounted in a box with a baffle width of 10″.  The Red plot is with the same tweeter when surfaced mounted. The effects of diffraction is the unwanted peak at 5kHz. That’s caused by the step between the tweeter’s face plate and the front baffle when the tweeter is surface mounted (Fig 2).

Fig 2 – Surface Mount and Flush Mount

In designing speakers, I  generally do not flush mount tweeters in my test boxes because I can’t afford the time to rebate every tweeter cutouts. Furthermore, I cross between 2.5kHz~3kHz, not at 5kHz where the diffraction is. However, when building my projects, I strongly recommend all dome tweeters be flush mounted to avoid this diffraction. 

MOREL CAT 378 RAW FRFig 3 – Surface Mounted Morel CAT378 Frequency Response

An exception is horn loaded tweeters. The plot of the Morel CAT378 in Fig 3 is with it surface mounted. No diffraction is observed. This is because horns are not omni-directional whereas dome tweeters are. Hence, horn tweeters can safely be surface mounted with no detriment to performance.