Last Posted in 2009… Now I’m Stuffing Two 18s into My Attic Return – Help Me Not Blow Up the House
omfgppc
Posts: 10
Hey everyone,
My last post here was way back in 2009 — It's great to see the forum still going strong!
Life got in the way for a while — bought a house, got married, the usual ups and downs — but I’m finally jumping back into the audio hobby. Loving good music again and putting together a clean, minimalist 5.1 setup in the main listening room, plus piping tunes downstairs for drinks with my wife, the dog, and friends around the firepit.
Current Main 5.1 Setup (2nd floor TV/listening room)
Denon AVR-X4800H (arriving today — early birthday/Christmas gift!)
Oppo BDP-83 universal player
L/R: Polk Monitor 8T (silver coil)
Center: Polk CS10 (just won a Monitor 5 on eBay that’ll be here soon — planning to swap it in)
Surrounds: Polk Monitor 5jr (silver coil)
Sub: ancient powered Yamaha from a relative’s old HTiB… it’s embarrassing
Which brings me to the subwoofer plan…
The house is a 1950s expanded Cape. The right wall of the listening room backs onto an unfinished, uninsulated attic. There’s an old 14" × 25" A/C return cutout in that wall (bottom of the opening is 50" off the floor, top at 75"). Seems like the perfect spot for an infinite baffle sub!
IB Sub Plan
(2) Dayton Audio UMII18-22 Ultimax II 18" drivers
Small sealed enclosure ~10" × 24" × 24" built from ¾" MDO plywood, mounted between the studs
Cover with a grille to match the room
Powered by a Behringer NX3000D (with DSP)
Basically turning that giant unused return into a huge manifold straight into the attic — should have basically unlimited airspace back there.
Any thoughts, gotchas, or “you’re gonna hate this” warnings before I start cutting and ordering drivers?
Thanks!
My last post here was way back in 2009 — It's great to see the forum still going strong!
Life got in the way for a while — bought a house, got married, the usual ups and downs — but I’m finally jumping back into the audio hobby. Loving good music again and putting together a clean, minimalist 5.1 setup in the main listening room, plus piping tunes downstairs for drinks with my wife, the dog, and friends around the firepit.
Current Main 5.1 Setup (2nd floor TV/listening room)
Denon AVR-X4800H (arriving today — early birthday/Christmas gift!)
Oppo BDP-83 universal player
L/R: Polk Monitor 8T (silver coil)
Center: Polk CS10 (just won a Monitor 5 on eBay that’ll be here soon — planning to swap it in)
Surrounds: Polk Monitor 5jr (silver coil)
Sub: ancient powered Yamaha from a relative’s old HTiB… it’s embarrassing
Which brings me to the subwoofer plan…
The house is a 1950s expanded Cape. The right wall of the listening room backs onto an unfinished, uninsulated attic. There’s an old 14" × 25" A/C return cutout in that wall (bottom of the opening is 50" off the floor, top at 75"). Seems like the perfect spot for an infinite baffle sub!
IB Sub Plan
(2) Dayton Audio UMII18-22 Ultimax II 18" drivers
Small sealed enclosure ~10" × 24" × 24" built from ¾" MDO plywood, mounted between the studs
Cover with a grille to match the room
Powered by a Behringer NX3000D (with DSP)
Basically turning that giant unused return into a huge manifold straight into the attic — should have basically unlimited airspace back there.
Any thoughts, gotchas, or “you’re gonna hate this” warnings before I start cutting and ordering drivers?
Thanks!
Comments
-
-
As someone who has ran an infinite baffle for a decade.. You need to find a way to mount this thing to something other than the wall. It needs to be floating in the wall cut out and not directly attached. It needs to be secured in your attic.
That wall will vibrate like crazy!
Otherwise best theater/gaming bass bar none.
Terrible for music- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
Also I would reach out to fi audio in regards to their Ib drivers, they will perform much better than the Ultimax- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
-
I would add that if you don't want excessive amounts of bass bleeding over into the other rooms that share walls/floors/ceilings with that attic space then invest in some rock wool insulation to minimize sound transfer.Expert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you! -
If my memory serves me correctly, one of the reviewers in the early days of the absolute sound magazine (PHD, Philip H. Donnlicot(?)) had a couple of 18-inch woofers installed into his floor. Might want to check out some of the back issues from the 1980s.
-
I'm planning a Dual-Opposed Manifold - force cancelling... to supposedly handle the vibration, and using the Ultimax II because I want the slightly stiffer suspension for transient response. Love the feedback here! Partially inspired by "Eric's Home Theater"
https://sites.google.com/bucknell.edu/ericshometheater/erics-home-theater/infinite-baffle-subwoofer?authuser=0
-
Infinite baffle subs are pretty cool but they can be tricky. You don't have much wiggle room on being able to fudge a baffle/enclosure design for them. You have to be dead on with your dimensions otherwise you might end up with a one note wonder that hits a resonance sweet spot that just shouts at that one frequency point while the rest of the response range gets attenuated.
One thing I used to do with infinite baffle or "free air" installations in cars, especially ones with the "dual opposed manifold" design like you are planning is I made every wire the same length. Depending on your mounting location and the distance from the signal source to the amp and from the amp to speaker, you have the chance that signal lead length could create a cancelation effect because the distance traveled creates a time alignment issue. Especially in a house where a signal lead or speaker lead can be a significant distance.
In a tandem baffle situation where all the drivers are facing the same way, it's not such a big deal. But when you have to oppose them and wire them to compliment each other, being out of sync even slightly can cause audible anomalies and unwanted resonances from distortion due to misalignment of the drivers.
With signal wires like RCA leads or optical cables, it's not a big deal as they are typically congruent in length for the channels used if it's not a mono channel. But speaker leads, unless you purchase them already made and terminated, you really need to pay attention to your lengths and terminations on the ends.
Just food for thought, especially given how finicky an infinite baffle design can be.Expert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you! -
Mine are mounted like yours
Your entire house will move, isolated from the wall will be Good move- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
As someone who has ran an infinite baffle for a decade..
Has it really been 10 years already?
"....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963) -
Almost, 2018... Time flies
Best subwoofer I've ever owned for movies!
Seriously though, for music it's pretty slow but it's good for like around the house. Dedicated 2 channel? Like a tank chasing a ferrari- Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit. -
Man, now I want to go build a subwoofer enclosureExpert Moron Extraordinaire
You're just jealous 'cause the voices don't talk to you!
