Need Help: Tempest in an 18" Tube (1 Viewer)

[Gil D]

I'd like to keep the footprint down and want to go with a smaller diameter tube over the popular standard 24" EBS design (what is EBS anyway?) My use will be primarily HT but would like the sub to deliver tight and tuneful bass for musical scores on concert/music dvd's and occasional multichannel SACD.
I have a custom DIY sub modeled after the TN1220HO sub with the 12" Hsu driver that does a great job for both HT/music. The HSU is powered by a Parasound 240W/4ohm monoblock and shakes the floor and vibrates picture frames on the wall clear across the house. The Tempest however will for a different room and I'm also curious as to how a Tempest based DIY sub might compare to my TN1220 or an SVS 1646CS+.
The Tempest will go in a room approx. 21'x14'x7' with concrete floors. I'm concerned that I won't feel the bass in this room due to the solid floor and not sure about the room effects.
I plugged in some numbers quickly with LspCad using the 18" sono using an 8" port and came up with 7.5 cubic feet tuned at 19Hz resulting in a 5 ft Tall 18" sonotube with 8"x36" port with what looked like a flat frequency response beyond 20Hz with 3dB down at 17Hz. Not sure if I did this right and how accurate the model is with freq response especially in my room. What else do I need to consider? I'm not even sure what SPL this thing is gonna deliver and the 8" port is big enough to swallow my cat
What do you guys think?

 

[Scott Page]

EBS = Extended Bass Shelf. It is a design with the lowest extension. With your smaller "box" size you would be looking at more the Adire Alignment. Download the Tempest Application notes from Adire if you haven't already. This alignment has nearly the same extension as the EBS design with the potential for higher SPL's and is great for music and movies.

Specs:

214L or about 7.5 cubic feet

Tuned to 15.4Hz

Port: 6" X 37 inches (with an 8" it would have to be 68.5")

You would get plenty of output and would likely have no problems reaching reference levels in that room with that amp. I have an EBS Tempest that peaks at 14Hz. Driven with only 150 watts in a larger room and it is really all the bass that I need. It kicks hard. You should be very happy with this. You could up the tuning but these are tested designs so I wouldn't mess with the design without Dan's blessing. You can email Dan and he will get back to you.

 

[Dustin B]

I built a 260L Tempest tuned to just under 17hz with a 6" port using 18" sonotube. I'm powering it with an AVA250 (so 10 watts more than you; like that would make a difference). I have absolutely no problem with port noise using the 6" port. And I love it for both movies and music. Very clean powerful bass
My room is 2 feet narrower and 3 feet shorter. However, that does ignore the L in my room. So with the L, I likely have a larger room. Dan sent me a box file that had the numbers he figured would correctly model my room.
With those numbers LspCAD says my sub is +/- 3db centered on 104db from 12hz to 80hz with the peak output being 107dB at 18hz. This is at the listening position (not 1m) which is 14-15 feet from the sub as well.
I have a fairly extensive write up on my sub at my website. Just follow the link in my sig.