As I said before, no sub is needed but since I have twin 500v4, why not go for the gusto? smile

So with Craig's advice, I've locked in the twin 500s. These are sitting on the inside of each A-LFR. Each is fed off each DSP. Each sub is wide open. The DSP cross-overs are set to 40Hz which means the LFRs hand off to the subs at 40Hz.

What can I say? It sounds really good! You get that transparent, musical, room-filling bass the sealed Axiom subs excel at! I will experiment with running the LFRs wide open as well while the sub dial is set to 40Hz.

Here's what I did:

1. Set sub to 150Hz
2. Set DSP cross-over to 40Hz
3. Ensure sub is off, phase at 0, polarity normal, gain at 1/3
4. Play 40Hz and measure LFR SPL at MLP
5. Turn sub on, measure sub SPL at MLP.
6. Toggle polarity switch. If SPL goes up, leave it there. If it goes down, toggle to previous position.
7. Slowly turn phase and watch SPL. Leave dial wherever SPL is max.
8. Adjust sub gain for 3dB above LFR SPL
9.Enjoy.

If you have two subs like I do, in step 8, adjust each sub incrementally until you get a 3dB SPL with both working.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated