Thinking of designing a plug for my 2×6″ horn reflex bass cabinet, so I can use it as a closed cabinet subwoofer in a 2.1 system with software EQ.
Checking Hornresp, if I plug the end of the horns, I get a closed cabinet with a Qtc of 0.70. Max SPL (quarter space):
| Original | Closed 16L | |
| 30 Hz | 74 dB | 90 dB |
| 40 Hz | 85 dB | 95 dB |
| 50 Hz | 94 dB | 99 dB |
| 60 Hz | 102 dB | 102 dB |
| 100 Hz | 126 dB | 111 dB |
That’s actually a useful level, I think? Max SPL is mostly independent of volume so I don’t have to think too much about the shape of the plug(s), driver volume etc. It would however need a lot of EQ to get some bass out the 12db/oct declining response. Actually a 2nd order low pass at 30 Hz might already give a decent response as well as could function as a 2nd order crossover around 150 Hz? Phase is then -90 degrees around 150 Hz, might have to reverse polarity.
Let’s look at power. Assuming the above active EQ, and aiming for max excursion at 30Hz, power requirement would be 60W total into 4W. A TPA3116D2 or TPA3221 module according to their datasheets should be able to reach that at 24V, but without headroom – a TPA3255 module >32V might be a better fit. Or TPA3223/TPA3250/TPA3251 at 32-36V.