Lowther is well known for making wideband drivers. There are not a lot of measurements of these drivers out on the Internet, so I decided to take a few of the DX3 for a baseline. I don’t want to argue too much about the merits or demerits of this driver. Objectively, the frequency response from the mids on up is pure shit. The only reason I’d consider using the Lowther DX3 is because it’s amazingly resolving and extremely efficient.
Below is a frequency response measurement at 36″ away. The DX3 is mounted on a 12.5″ x 17″ open baffle, so the rolloff below 500Hz, along with a bump and subsequent dip after this spot would be expected. Note that the plot only goes down to 200Hz. In hindsight, I should have mounted the DX3 on a larger baffle; but for all intents and purposes, the measurements from 1kHz and above should be reflective of what we would hear if the driver were mounted in finished speaker.
Now let’s take a look at the off-axis response for the DX3, at 11.25 and 22.25 degrees:
Green = 0 degress on-axis
Yellow = 11.25 degrees off-axis
Purple = 22.5 degress off-axis
LOL, this explains why all the Lowther guys say listen to the driver 15 degrees off-axis. Frankly speaking, the Lowther DX3 on-axis sounds nasty. The lower and mid treble peak is enough to disintegrate mosquitoes! However, 10-20 degrees off-axis is much better and quite tolerable, although there is a bit of bump at 2kHz (the “Lowther shout”, common to many other widebanders, e.g. Fostex). Keep in mind that the dump and dips between 500Hz and 1kHz are the result of the open baffle.
Stay tuned to see what happens when the DX3 is mounted in an Oris horn.