NB50

Take the recommendations and multiply them by two. Remember that is net volume and not gross, you still need room for port displacement and bracing.

Yes, tuning matters and it will sound like poo.

BL Enlcosure Recommendations - SSA Car Audio Forum That space is only big enough for one.

A quote from the manual of what they are working on next.

Katmandu - Bob Seger

Detroit Breakdown - J. Geils Band

Any recent updates on the other amplifiers your working on?

Series the subs so they are 4ohms each then parallel them to 2 ohms. Parallel/Parallel you would be at .5ohms which IMO is unnecessary for daily driven vehicles. If your competing and know how to tell when your equipment is reaching its limits then you could do .5ohms.

Same clean power at 1 or 2 ohms, or any load for that matter, there will be no difference to the ear.

Should be fine, you could always add polyfill to make the enclosure appear bigger to the speaker.

Unclear on the question, but there is 1 ohm of difference between 1 ohm and 2ohms. Not a real big difference.

Is that 1.25ft^3 before or after the sub displacement?

Looked for the post but found a tape measure on the desk instead, it is 6.75" edit found thread. Icon Motor - SSA Car Audio Forum

I've posted it before, cant recall right off hand but I believe it is 6.75".

The higher tuning is because of displacement and RE calculators inaccuracy.

Should be fine, it is tuned closer to 35hz though.

BTL Enclosure Recommendations - SSA Car Audio Forum

That design only calls for 3/4". And your going to need to take off more then 1" of port length to raise the tuning to 32hz. From my rough calculations it should be more like 6.75" of port length taken away. Which would put the box at 4.26ft^3 @ 31.86hz.

Can't download the sketchup file.

You can't magically not need port area, the material and shape of the port won't matter round or square, you still need similar port area. Its not magic. A flared port reduces turbulence and compression which would allow you to run less port area compared to a port with no flares.

Measure the actual area for port area not the flare. You can get away with using less port area when using a flared port compared to a non flared port.

Either way you won't notice a difference. Leave it the way you have it.

What are the specs of your box ie width, height, depth, port lengths etc. Sounds like the box isn't tuned to what you think it is.

More then likely your 4 channel is going to have a set on them that passes the signal through them. You can hook a set of RCAs to that and run to your mono block.

Light hair.