< Project intro
The measurements were surprising, better than expected based on the sims.
What is a 6th order bandpass? Think of it as a vented box (the rear chamber and port) that has an acoustic front chamber added. This chamber creates another tuning point that sets the upper bandwidth limit. It filters harmonic distortion as well.
Red: rear port
Blue: front port
The front port does not have the predicted peak, it is quite flat. I also discovered that I had tuned it too low hence it doesn't reach the 300 Hz target. You can see the front port has surprising extension and the rear port
Electrical crossover filters have been added.
The box was measured with the box in the middle of the main speakers. Hence there are some modes that haven't been tamed.
It's hard to comment too much because, as you can see above, there are some room modes in the response that normally I would have dealt with. The peak around 44 Hz is probably related to the sense of the bass being much more tactile than usual. It's fun and novel for a short burst, but would probably bother me over time because everything takes on a certain "sameness." However, for a thrown together box not fully integrated, all the signs are there that this is going to work well.
I have a couple of specific goals with this box:
- cover 40 - 300 Hz using bandpass to increase the efficiency at the top end
- effectively meet the horn at 300 Hz with the acoustic source close to the horn (achieved with the slot port at the top)
- reduce the "thermal load" on the subs with music
- fit inside the large corner bass traps I have planned
So far it appears that this project will work out well.