Of course OB requires EQ because of the raising 6 dB/octave up until the dipole peak. I'm running the twin 10" from 70 to 500Hz which is still below the dipole peak, and the 8" from 500 to 1500, also below dipole peak, so to insure constant directivity behavior. At 1500Hz the waveguided AMT takes over. I used Linkwitz 2nd order xo just because I didn't know what tends to be better for OB. Anything better I should use?
Then onto linearizing the drivers...a challenge in and of itself! Linearizing the tweeter was as usual, done nearfield. But the midrange and midbasses didn't seem a good idea to measure nearfield because I would be missing the bounce from the back wall. So I measured at the listening position. For this 1-speaker setup the listening position 1.5 meters away from the speaker, on axis horizontally. I took a Logsweep with the linearized xo, applied Room Macro 1, and the result is displayed on the red curve.
You can see the large drop around 100Hz. Subs are xo at 70Hz, which is the last peak you see before the drop. When establishing the target curve to avoid the suckout at 100Hz, I ended with about 20dB attenuation. The amp driving the twin 10" has plenty of power (Hypex UcD400) to drive the two 10", and it looks to me like I could take advantage of the linearization process and apply a normalization to a play at a higher level, so the response would be significantly higher at 100Hz, which in turn would push up the 200-300Hz region too.
I wasn't able to to extended listening yet. Last night I played a couple songs and was a bit underwhelmed.
- What are good crossover types to use in OB?
- How should I raise the 70-500Hz midbass region to avoid the huge attenuation at inversion? I'm thinking like +10dB. Or al alternative approach?
- Where should I measure to linearize OB drivers?
- Any additional input from very welcomed!