Twin Towers BUILD LOG

This is only going to cause more debate and more argument, but I'll try to explain my OPINION anyway. 1st problem: I am 99% concerned with 20Hz on DOWN only! But that statement will go nowhere with many. So for one plot I put a LOW PASS filter on the IB because I want more output from 10-20Hz and little output in comparison from 20Hz on up. 8 18's would be WAY overkill from 20Hz on up, but comparable to 20Hz on down with just 2 in my enclosures.I plotted to get as close to Xmax without exceeding as I could using SSF/HP filters on the vented boxes, and no filter on the IB allowing it to not exceed Xmax till 7Hz allowing electronics rolloff to take care of it real-world.

RED 125 cubs 13Hz HP 13Hz 1500 watts

GREEN 125 cubes 10Hz HP 10Hz 1100 watts

PINK 1111 cu ft sealed (IB) no HP, 1 pic with LP 10Hz 2700 watts (Fi rated them 550 watts to 20Hz, appeared correct, but I must be good to at least 10Hz)








One of the best pics doesnt always show up...bandwidth exceeded:

 

2 problems 1 at a time: I have a 7.1 receiver, I run an HDMI from my Blu-Rey to the rceiver, but I only get 5.1. The rear speakers do not light up on the little map on the display, even when DTS is detected or True HD...nor is there any sound ever from the 2 rears

 

alright guys... I thought HD was all discrete 7.1

it is not. checked my movies, they are 5.1

 

Now that I have the 7.1/5.1 figured out.. I thought HD was always discrete 7.1... owell moving along...

problem 2 is clipping. for movies, as expected, I have WAY too much power @ 40hms...which is why I ordered dual 4's... so I'll *only* have 3X the power I need at 8 ohms. But right now, with movies, the sub still has too much excursion with the gain only on 14... but for music I have to turn it up to 26 to get resonable output. At 26 the sub wants more, has plenty of room...but the amp starts clipping a touch above that. 2 more clicks and it clips HARD on higher frequencies but not lower. So is my electrical bad? I have RCA to XLR. I have the receiver sub maxed at +12.5dB.


So anyway, I no longer have my helper ( NOT my wife, NOT my girlfriend...a really nice gal..that is a friend of mine..I am just as unconventional in every other aspect of my life I don't have girlfriends or wives )

Now I know many people are gonna say "how about port support!" but I am not sticking with a 6.5Hz tune! Read the entire thread before posting! I need a 5" long port with a 12" sonotube in 125 cubic feet for a 15Hz tune! 5" port length! 10Hz I think was 17"... I am leaving 5" of overhang on the outside so that I have 2 free ends... 11.25" will be just fine...but I know I will hear just as much over that as I have over my bracing. and NO I am NOT bracing anymore than those 2 little 2x4's making that X... thanks for the ideas, thanks for the suggestions, but you can say I told you so after the box explodes.

















um... didnt mean to upload these but may as well post... I overcaulk initially, always...owell... then after it cures I usually go back and put a 2nd layer in the corners and smear for extra support and air tight seal...then a 3rd. Only 1 extra layer this time...it will make it easier to finish pulling them apart after they implode due to lack of bracing.










also keep in mind, these 12" ports may be taken out and increased to 14" 16" or even 18" if they can't fully support 22's

 

first vid 11Hz sine wave at a pretty moderate level, shakes the whole house and rattles windows in the opposite end of the house a little louder than the old box used to...but the old box did it at 18Hz, this is 11!

YouTube - 11hz low volume.AVI

So then I do it again, but part way in I turn it up to at least 2.5" p-p maybe even 3"... they still have room to go... but my clip indicators are solid... no clipping... I was barely even pushing the amps... and the subs had zero complaints!

YouTube - 11hz turned up part way through.AVI

 

MTC4Life? you're the **** magn! So these vids are for YOU!



the white trash redneck did it again.. the plan all along was a 14Hz tune, as 13Hz starts a slight dip and the dip just gets bigger as I tune lower. So WinISD plots at 14Hz are exactly what I want... flat flat flat till 15-16Hz starts to show the beginning of a HUGE spike at 14Hz. I'll snap a pic of the plots later..but anyway I retuned to my final 14Hz and played a 15Hz sine wave for a full minute at full excursion and didnt even get warm.

http://www.youtube.com/watch?v=ltRuKA8zLJ0

http://www.youtube.com/watch?v=pbz7bKnDbaA

jordan powell

kryptonitewhite

 

http://www.youtube.com/watch?v=VLzSuwCA12g

 

so I figured why not leave the ports at 48", the way i got them, and stick them out 12" for a 12" clearance from the rear wall for a 6.5Hz tune for fun... then cut them down to 16" for a 10Hz tune to see what that was like..then land on my final cut, 5", a little under 14Hz tune to keep from any dip in FR...and I get that AWESOME peak from 12Hz-20Hz... PERFECT!

Well I cut her down, I'm re-watching WOTWs... and it is cherry. The platform resembling bleechers can't hurt either...8'x'8 square soaking it all up and wobbling!

 

ok I pushed them harder today... during music the receiver lights dim so bad when it hits, then it trips the receiver breaker... but I brought the IB3 18's out there pretty dar on a 15Hz sine wave and it makes the door on the opposite end of the house flop.

http://www.youtube.com/watch?v=n6jQTaDAQjw

 

my house is 2 bedroom, then there's a livingroom/dining room divided. I slept in the bedroom the 1st 3 nights, but after that i always fell asleep watching TV on the computer..so I brought my other bed from the other bedroom out lol. mSince then, now i sleep in the living room/rntertainment room. My PC is now in the other room with a long HDMI cable running to the entertainment stand so I can watch HULU.com Anyone watch Flashforward? I'll be catching up on that tonight I also watch House and Grey's

 

so Ive been thinking, I remember when I had my old Fi IB3 18" in my Aztek, 21.5 cubic feet, 7.5" diameter port, 15Hz tune...and I experimented with it like I did the towers and cut it down to a 20Hz tune, then a 25Hz tune, then I ripped the port completely out..therefor I had a 3/4" port length..the thickness of the wall. I still don't think that 3/4" port length tuned the enclosure past a certain point.

I think the port volume acts as a slug of air, Fallen once explained it best that way...

that slug of air is just like a speaker cone in that it moves in and out, has excursion. when you have a 16.5" cone moving in and out 3.25" inside a given volume of air, the enclosure, you are moving the air in and out of the port. How much does the air slug move? What is it's excursion? The same as the driver? No... 1st off.. the driver area is bigger than the port area, so if it were this simple... you'd have to think volume. If the 17" cone moves 3", then the 7.5" slug must move:

well, 17/2= 8.5*8.5=72.25*3.14=226.865*3=680.596

about 681 cubic inches?

7.5/2=3.75*3.75=14.0625*3.14=44.15625

681/44=15.5

The air slug in the port would have to move 15.5" for the same Vd... 5 times as far

to double check,

7.5/2=3.75*3.75=14.0625*3.14=44.15625*3=132.4
680/133=5

but, as we move further from tuning we get less gain... and at tuning we dont get exactly double the output... we get a lot more, depending on the enclosure.

So really IDK what I'm talking about, but, I don't think a 3/4" long port 7.5" in diameter will fully handle an 18" subwoofer moving full excursion 3.25" p-p.. whether it's in 2 cubic feet (less port gain) or 22 cubic feet (more gain).

Just as well, I don't think my 12" diameter port 5" long fully supports my 18" in 128 cubic feet...even more port gain.

For my VAN build, I plan on using about a 20" port for the 4 18's.... I am thinking about ordering 1 long 20" sonotube and using the scraps for the Two Towers. 127 cubic feet, 20" port, to tune to 14hz needs to only be 22" long... drivers remain under Xmax with only 600 watts, showing an airspeed of 8 m/s at tuning!

 

for realz dude!