Sub Box Desgin

[talnlnky]

So... SQ comp, here's some graphs to show what I was talking about in that other thread.

I've got 3 Graphs:
1) Tangband W8-740C 8" - Shows the frequency response of ported vs sealed boxes
2) Exodus Audio Shiva X 12" - Shows the effect of box design on group delay
3) Exodus Audio Shiva X 12" - Shows the effect of power & box design vs mechanical cone movement

Looking at the pics... Red line = Sealed box, Yellow = middle tuned ported box, Blue = low tuned ported box.

1st Graph (Frequency response)
The sealed box (red line) is your reference, it will sound "tight" but won't be very strong down low.... with the cabin gain of a car it will have a near flat frequency response.

The yellow line shows a peak around 42hz, this is basically your average DECENT street beater setup. It will hit those killer low bass notes with authority, but might start to sound a bit sloppy. Like I said in the other post, eaggerated spikes in frequency response gives the illusion of sloppy sound. This yellow line only has a +3dB peak/bump... which isn't too bad. The really sloppy systems you hear often times will be tuned even higher, and would have a 6dB or higher peak in the response graph. The box for the yellow line was tuned to 39hz, its not uncommon for those sloppy systems to be tuned around 40-45hz.

2nd Graph (GROUP DELAY BABY!!!)
Sealed box (red) is still the refrence point. This would work decent in both HT and Car audio setups... small box too.

The yellow line is your basic street beater setup once again. This time it has a 6dB bump in the freq response... rap listeners would LOVE this setup.
The group delay really helps give you an idea how sloppy/tight it will sound. The sealed box is the reference, and pretty much optimal at all frequencies. The yellow line is actually fine until it drops below 60hz... The peak from 30hz to 60hz is generally where most of your bass in most rap & pop will be centered, and unfortunately will most likely sound a bit sloppy. The weird thing is.... once you get below 30hz.... it becomes very hard to tell the difference in group delay.

The blue line is actually basically what i'm running in my HT. It is virtually the same as the sealed box until it dips below 30hz. Yes, it does spike pretty high, 34ms, but it peaks at 15hz....NOBODY CAN HEAR A 15hz TONE... Human hearing range AT BEST is 20hz-20,000hz. You feel 15hz tones, you don't hear them. Going back to the idea that below 30hz, group delay differences are hard to hear, you can see that this HT setup actually is only at 10ms at 30hz... which is hardly higher than the sealed setup.

3rd graph (Cone movement)
This just helps show one of the biggest SQ & possibly safety advantages of ported boxes over sealed boxes. This sub can move 27mm each way, so the graph you see shows if 500watts of power will cause the sub will run into high levels of distortion, or even possibly start to physically tear itself apart due to moving too far mechanically.

Sealed box - sealed boxes do a VERY good job and controlling cone movement, they are the easiest, and generally safest boxes to work with because its hard to mess things up.

Yellow box - The street beater setup actually will be safe, and have low distortion down to 19hz... for cars, this perfect.... almost NO music plays anything below 30hz. What you have to be careful about is cranking up the bass while playing bass cd's like Bass Mechanic or sine sweeps.
For playing most music, including bass heavy rap, this setup will actually have lower distortion and be safer mechanically than the sealed box.


Blue box - HT setup again, the blue box design has a crazy amount of bass more than the sealed setup (6dB at 20hz more), and actually moves about 2mm less at 20hz. Basically, this setup will move the same amount as the sealed box setup except at 18-21hz and below 16hz. Its well suited for HT setups where DVD's often will play down to 20hz... or even sometimes into single digit frequencies. Unfortunately... it can't take the full 500watts below 16hz.

ported boxes are great at controlling cone movement if you design them with that in mind.

ok... if there are questions... let them fly.