first of all i'd like to thank this forum for all the useful info
i used to think i was an audiophile, now i know better
i'm lucky to have a concrete basement, wouldn't of bought the house without it
that leaves me with some pretty easy assessments on paper
my room is 7.6' x 22.6' x 38.6'
which gives me concrete resonances @ 75 hz off the ceiling
50hz off the width of the room
@ the awesome primevil 14.6 hz from the length of the unfin basement
it took about 6 hours to become fluent with the helmholtz equation
written in some thread from "Savant"
now i had a purpose for these old home speaker cabinets laying around !!
after running the dims through some overlap plotter, it reveals that 15 hz & 75 hz get together @ 75, 150 & 225 HZ, for my 3 band EQ basement
the first order of business was killing the 75 @ 75
after the math, this only took a few minutes
i already had 1 speaker cabinet with the 15" driver space blanked off with wood
my calculations said an open hole about 2.85" dia would work
the whole speaker was sealed, i just removed the old midrange to give me a 4" hole
no problem, so i got a small piece of wood (3" x 6"), set a screw in one corner of the wood over the hole & played some music
to anyone that's thinking about doing this, may i say the math is the hardest part & well worth it
virtually any medium played will overlap & ring the hz you're looking for
i sat on the box & adjusted the port diameter by turning my wood valve over the port
WHOLA, the cabinet comes to life, again, it would be hard not to since the concrete room will ring there
you can totally hear & feel the resonator vibrating & making music, it tunes in to the room dim
the bandwith question answer seems to root in the physics world, where the same ring time = the same bandwith period
with only 1 set of traps, the most energy would be @ the sub, so my trap went in the corner with those
my trap was louder more eff than my ceiling @ 75 somehow & rang longer
i have a box of old clothes for rags (all clean), 1 t-shirt inside helped lots, another hurt
so i tore the second t shirt in half, closer, now add 1 sock @ a time
i'm not kidding here when i say that it's literally tuned to the sock
you throw 1 too many socks in, bandwith gets too wide & you CAN hear it fail
after simply feeling the box come alive to the room & stuffing rags in till it sounded right, it was mania time
boy did that sound better
so it was a little boomy, which i guessed was the walls @ 50HZ
the same midrange hole in the next 2.0 cu' speaker needed a 2.75" long port, if i wrapped cardboard into a cylinder, which made a 3.75" ID port
again, playing music & sitting on the box, it was very obvious when it came alive !!
the 50HZ must be padded a little with all the crap in the basement
that box took 2 full t-shirts & 1 sock to tune bandwith
@ this point i noticed the null parts of the room seem to be hearing the traps...that's when it sounded like the 50 hz box needed just 1 more sock - perfect
my 50hz box went on the floor by my subs, the 75 was on top, near the ceiling
the overall effect is forming in phase bass horizontally, not upstairs
unfortunately, bringing this into the equation sounded good, if you couldn't hear or feel 15 & 30 HZ
now everything sounded like it was going to kill you from the back of teh room & 30hz started ringing out of every thing with bass in it - fail
cabinet 14.6HZ @ 2 cu' revealed port lengths around 5' long...mmmk
or 12.87" long for 2.5" conduit i had there on the floor
the port ended up needing to be an inch longer than that
i used a rolled up piece of cardboard, taped into a cylinder, sliding tight over the conduit for a telescopic adjustment
i can't hear 14.6 very good, but was really easy tuning playing some live Sade CD, where they played some 30hz note @ the end of the some song, over & over
it goes from mud to clear definition of each wave, of that 30 hz note, in 1" of port length
as i thought, the 14.6hz box only got a half t-shirt to sound right (nothing in my basement is going to slow 14.6hz)
i tried various combinations of trap arrangements around my sub, & 1 arrangement sounds the best
i can turn the bass knob up now & leave it where the mids blend - nice
my basement windows don't rattle outside my house anymore
my basement sounds anochoic below 100hz (here @ my computer, next to the subs)
the resonances are gone in my listening area, way less fatiguing
the useable bass listening area has grown
walking across the basement used to be a disappointment to anybody with an ear, but not now
the effect trap placement has on sound seems to be just as critical, especially in nulls, where it seems like the sound is from traps only
if you sit right in front of the sub, the most beautiful bass comes out of it (ugly bass quit coming out)
yesturday, inadvertantly noticing there's allot less overall bass energy flying around, i switched inputs for a quick mute from 2000 rms...
the room gets quiet so fast, i can only hear the click of the remote button ringing afterwards (& the HVAC tin)
thanks again sound geeks !!!
edit: pop rock has become entertaining again, @ least the first listen, listening to bass strings, sliding notes, hearing exactly when the octaver pedal, oooooh, that's not mud but double foot pedals
