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Just a little question. Sub Box

 

Silver Member
Username: Johnnylemoine

LaPlace, Louisiana United States

Post Number: 314
Registered: Aug-04
OK my friend says that you cant make a sealed box with multiple subs and not seperate the subs from each other. He says that the subs will not hit at exactly the same time so it would not be a good idea. I thought that I read a thread that said you could do this if you had all the subs running off of the same mono ch. amp. Please correct me if I am wrong about this but I dont see why you couldn't. It seems as if he always thinks differently than anyone on here or me for that matter. Any input is greatly appreciated, just trying to gain respect for yall from my friends.
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2756
Registered: May-04
You're right, you could do it and they would hit at the same time, assuming they were the same subwoofers. The problem is that if you built this box and one of the subs blew, then the complaince is thrown out of whack and the subs will see more airspace, which could cause damage. Plus, the sub that died will basically act like a passive radiator, its cone will move in and out with the other subs playing.
 

brandon kelley
Unregistered guest
you can put deviders in-between each speaker that way you can use diffrent amps and if one blows it won't hurt the others. If you use the same amp they should hit the same way.
 

Silver Member
Username: Zacdavis~

Post Number: 340
Registered: Sep-04
all open, mono, no divider, yer good,:-)
 

Silver Member
Username: Johnnylemoine

LaPlace, Louisiana United States

Post Number: 315
Registered: Aug-04
he still doesnt believe fully, he says that it would nt work with three subs. this is what he said
" cause the motion off the air on one side, if the box wasnot exact, would be differt from that on the ryt"

he also said " it doesnt matter about the amp, its the airspace in the box pulling in different ways"
I said,it wouldnt have to be a perfect box, he says it would. so this is his response.
" yes it would u could never get it to hit the same unless everything was exactlyt the same, wires length and side length"
AS a matter of fact i will post everything we said and I would love it if Jonathan would explain thoroughly why he is wrong or anyone else so I can show him. Here it is. Im crabmaster596 by the way, he is robert blahblahblah.

: hey
robert6662309: what
crabmaster596: why dont you look on ecoustics under a little thread called "just a little question. sub box" in the subwoofer section.
robert6662309: send me the site
crabmaster596: https://www.ecoustics.com/electronics/forum/car-audio/113236.html
crabmaster596: jonathan is the guy that took EE as his major the smart one
robert6662309: o well
crabmaster596: HA HA TOLD YOU YOU F*CKER
robert6662309: it would have to be a perfect box
crabmaster596: no it wouldnt
robert6662309: i said there is no way for three
crabmaster596: just built really good with supports on the inside corners
crabmaster596: braces
robert6662309: yes it would u could never get it to hit the same unless everything was exactlyt the same, wires length and side length
robert6662309: im telling u it would be a fraction off
crabmaster596: if it is on the same mono amp
crabmaster596: look at the thread
crabmaster596: and if they were the same kind of subs
crabmaster596: read them all
robert6662309: it doesnt matter about the amp, its the airspace in the box pulling in different ways
crabmaster596: if you had two amps and the gains werent exactly the same and they werent linked together it would throw them off alittle but enough
crabmaster596: how is it pulling in different ways
robert6662309: cause the motion of the air on one side, if the box wasnot exact, would be differt from that on the ryt
crabmaster596: dude the subs are all pullin down and pushin up at the same time your box is not goin to be "off" in measurements from one side to the other to make a diff.
robert6662309: yes it f*ckin will
crabmaster596: how the f*ck
robert6662309: dude ur ryt im wrong
robert6662309: i dont care cause its stupid idea

so any input would be greatly appreciated again. Thanks for all the stuff from before too.
 

Silver Member
Username: Zacdavis~

Post Number: 345
Registered: Sep-04
ok, how about this.... a box with 3 subs will work just fine without dividers as long as the subs are wired to a single channel. (and yes the subs need to be the same brand and model and all wire lengths should be equal)
how do i know?,
why should you believe me?,
who am i to tell you different?,
well prolly not much to some but being the world champion in USACI and world record holder in my class, i think maybe i know a little about enclosure design. btw, ol jonny is pretty damm sharp himself so lay off buddy:-)
not tryin to be conceited at all, just lettin you know i'm qualified on "what will work" when it comes to building boxes.
he is rite, you're wrong
there, think that will help settle your battle of whitts? lol, l8r bro
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2777
Registered: May-04
It's physics. You are attributing "x" amount of airspace to each subwoofer by building a box a certain size. Assuming the same subwoofers, their suspension compliance will be the same, their transient response will be the same. With a sealed box, it works similar to a spring, hence why it's called an acoustic suspension enclosure. It's simple in theory, smaller boxes are "tighter" while larger boxes are "looser". All 3 subwoofers move in sync with each other because they receive the same signal, at the same time, and they have the same inductance. They are simply compressing the amount of air within the box, same as if you were pushing a coil spring down. The amount of air inside this enclosure determines the stiffness of the suspension you have. Why do we put subs in this type of enclosure? Because the air acts to control the subwoofer cone. This is when we begin to get into suspension compliance. If a sub with a heavy cone and a loose suspension were put into a box, it would have more inertia and movement than a sub with a lighter cone and tight suspension. The heavier coned sub would likely perform well in a smaller sealed enclosure, while the other would work well in larger or ported enclosures (possibly even free air). The sub is also controlled by the motor (magnet) of the subwoofer. When the amplifier stops power, you basically have a short across the speaker terminals, and the speaker acts similar to a magnetic brake. This is Qes, or electrical compliance. Air will have a set compliance in a sealed box. Because the suspension of all these subs are the exact same, the air compliance and suspension compliance will perform as if each sub had it's own airspace. IF you were to put subwoofers on a 2 channel amp and the subs had different signals, then you'd have problems because the subs wouldn't fire in sync at time, and the subwoofer would see the entire volume of the enclosure because the suspension requirement would change. The reason that we do put subwoofers in dividers is because of the reasons I explained above, and also for the extremists it's a step of precaution. All materials are built within certain manufacturing tolerances, and while parameters may meet within 1/10 of a percent of less, every speaker is a little bit different, be it just a little more resistance from a solder point, or inductance because of the way a coil is wound. An extremist point of view is to divide each subwoofer so that these variations don't affect one another, although in reality it really doesn't make a bit of difference.
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 2778
Registered: May-04
"An extremist point of view is to divide each subwoofer so that these variations don't affect one another, although in reality it really doesn't make a bit of difference."

By the way, I meant as far as the subs go, they will not break on you. You will have certain people that say SQ is better when you divide the subs, but most of that is because the divider also serves as bracing.
 

Silver Member
Username: Johnnylemoine

LaPlace, Louisiana United States

Post Number: 316
Registered: Aug-04
THANKS SO MUCH ZAC and Jonathan, you guys rock so much cant wait to show him this. thanks for takin the time to explain, maybe he will get it finnaly that you guys know yalls stuff. Thanks a million once again.
 

Silver Member
Username: Johnnylemoine

LaPlace, Louisiana United States

Post Number: 318
Registered: Aug-04
i just printed this and im am going to show him what yall said. He didnt read it but i told him it was here. HE STILL DOESNT BELIEVE ME!!!!! O well, screw him. If still says no after reading the post that ZAC and JONATHAN did then he is just retarded and is trying to not be proven wrong.
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