Best powered subwoofer under $400, for stereo (not movies)

[Hermann]

Has to be a sealed port if you want clean low end.

Doesn't have to be sealed. Just make sure it makes no chuffing noises.

 

[JeffKeryk]

It varies a lot.

Vinyl Beggars Banquet on the turntable. So clean and well recorded, Rolling Stones growling rock sounds good on this set up. I think the Marantz amp does it justice told by jumping from "source direct". This record was amazingly clean out of the well yellowed inner sleeve. I probably bought this around 1975, not 1969.

Begger's Banquet and Let it Bleed are the most progressive Stones albums. And the best.
Stray Cat Blues for the win!

 

[SubieRubyRoo]

Can agree on that, I run dual 8" sealed subs (blocked ports).
Find that I have to adjust the phase dial if I unblock the ports, which is kind of weird.

Not really. When designing ported boxes, port length is always a factor with phase. It even affects sealed boxes, but usually to a much smaller degree. Most good box design software will have a phase calculation to show how the box affects the sound phasing.

In all reality, you’d probably be much happier with the sealed box sound if you built the proper sealed box for it rather than stuffing the port closed, as this is a double handicap; sealing the port likely isn’t 100% so you get some leakage, and secondly, the “sealed” volume likely isn’t optimal for the sub either, which is why it was designed the way they built it. In a ported box, the port volume is “not” part of the enclosure per se; once you block the exit you’ve now lost the tuning frequency boost of the port and added volume that’s not quite as convenient a volume for the sub to utilize.

Quarter-wavelength transmission lines are a great way to “cheat” your way to better low end, but they can be quite massive since they’re utilizing a different method of sound reinforcement and tuning. However, done properly, a transmission line enclosure will go deeper than sealed or ported for a given speaker size, and usually provide sound output between the lower output of sealed, but slightly less than a standard ported box around its port frequency.