Looking for info on "Loading Issues"

[P4killer_]

So I Posted a random box design, sombody said id have "loading issues".. I got to wondering.. i know it has to do with how far the subs are from the port and the flow of air through the port... like if two subs were right next to the port and another far away.. or if the port was directly in front of a sub etc etc...

i know about loading walls, to increase pressure and help cone control/ excursion

im wondering what exactly is "Loading issues"

what happens

how it happens

why it happens

just looking for info

google turns up little, ill loook some more

thanks

P4Killer.

[Boon]

Umm... how to put this, it's quite technical ;/

Yes it's to do with how close the subs are to each other, surfaces, corners and the port.

Basically if you have 1 sub really close to the port and the other quite far away you will have inconsistent pressure in the box, especially if it's a large port. The subs will play differently - the ones right by the port will probably play like they're in a higher tuned box because the back wave never builds, it just slops out the port...

Argh I haven't had enough coffee to get technical right now sorry.

[fritosaregood]

Im interested in this too.

[Andrew2944r]

what happens - In most cases a sub will unload, typically a crazy overexcursion spazm, typically the sub that acts like it is getting less power will be your problem, almost acts as a passive radiator getting no power.

how it happens - Example: My last box had 3 18's in a triangle each sub sat in A B C axis of the triangle, I copied a design and made a few changes and put no spacers between each sub, so sub A was loading off of sub B and C and B and C were loading off the back wall, also in this design I had depth played a big part in the design which I did not have and created a worse than usual sub spazm.

why it happens - poor box design and sub placement

Just a problem I have had with one of my wall designs for daily SPL setup

[tristan560]

Ok now say you are having loading issues will how do you go about getting rid of em? Or what can i do to prevent it from happening? Im building a wall for my 4 15's right now and fear that there will be a problem. Basically looking just like this...

[raytard]

ideally, a port is equilateral to all point sources of air movement (for ease, lets just call it the center of the cone, backside

now look at a kicker prefab box, since you all have seen one. it has a big port on the side and 2 subs on the front. the port ends, literally in the dead center of the box, this means the pressure waves from both subs have the same time to develop and hit the port opening at the same time (the angles are different, but remember this is a "pressure" wave, and for all intents and purposes omnidirectional)

a box like mine, is essentially too long. it was a case of "making it fit", and it was the only way it would work. It does work, it is calculated, designed, and built correctly (and very overbuilt) but because the port opening is so far from the subs (over 5 feet) seemingly no air moves through it. if i was able to make a box the same size but a perfect square, and make a port on the bottom facing forward the samee size as this one, it would move alot more air, just because of how the pressure wave would it it.

and a box like meade's, his port is centered between the 2 back subs, but doesnt extend back far enough to be equidistant to all 4 subs. technically his subs are loading differently, but between the relatively small size of his box and the power he is running it makes no difference and works very well since the subs can effectively pressurize the entire box at once as opposed to making a rolling pressure wave through it

its an imperfect science and sometimes it just doesnt work or just does. Just like with that 4-15 wall where thhe port is on one side and the subs are on the other. on paper the left and right pairs should load differently, but it may be too small of a difference to notice, or it may not even happen.

[Boon]

and a box like meade's, his port is centered between the 2 back subs, but doesnt extend back far enough to be equidistant to all 4 subs. technically his subs are loading differently, but between the relatively small size of his box and the power he is running it makes no difference and works very well since the subs can effectively pressurize the entire box at once as opposed to making a rolling pressure wave through it

Precisely Lots of cone area + smallish box + smallish port area = massive internal box pressure so loading is less important. Also means the port is always pressurized too.