View Full Version : abc boxes

06-13-2008, 03:07 AM
ok my friend just designed me a abc box... are abc boxes better than a regular ported box??? just thought i would ask before i build

06-13-2008, 03:42 AM

06-13-2008, 03:44 AM
no need to bump when your thread is already at the top

06-13-2008, 10:30 AM
When built right ( Accurate )... They can be WONDERS. If inaccurate on calculates... They can be either: Waste of time, money, & effort... Or what you call it... a " Half box "

" Half box " - meaning only dominate on 1 side ( Low end or High end ) of the Hz scale.
... Hits the lows it's tuned @ 28.... or Hits the highs like it's tuned @ 47 - 56

06-13-2008, 10:32 AM
Any want to inform me and every one else on what an ABC box is?

06-13-2008, 10:58 AM
A quick summary I found:

Build a box with 2 chambers, one at 3 cuft and the other one EXACTLY half of that, ie 1.5 cuft. Next cut 3 ports all IDENTICAL in length. Put one in the face of each chamber and the third in the wall separating the two chambers. In this instance each port would be either 12.5" long for a little deeper response or 8" long for a little more SPL.
Now you have a box with a big chamber with a vent in it, a small chamber with a vent in it, and a third vent in the wall between the two. The woofer also mounts in the large chamber.
The way they work is that, at low frequencies, it all functions as one big box with 2 ports, and is tuned to 30Hz (12.5") or 35HZ (8"). At higher frequencies the middle port starts to restrict air movement and the second chamber begins to act more as a resonance chamber but not as part of the box. At this point a second tuning frequency develops 1.9 times (almost an octave) higher than the lower one , ie. either at 57Hz (12.5") or 67Hz (8").
This is similar to a vented bandpass but has more output and smoother sound due to the woofer not being tucked inside the box. The results are that it plays both low and loud, while being relatively nice sounding. The drawback is the box size.

06-13-2008, 11:05 AM

PV Audio
06-13-2008, 11:46 AM
No, there are no advantages. The design is decades old, and there's a reason it isn't widely used: its benefits are minimal.

06-13-2008, 01:04 PM
well i kinda liked the idea

06-13-2008, 08:06 PM
The only real advantage is reduced cone excursion over a wider frequency range, but even that advantage is honestly marginal at best, especially with today's high xmax woofers.

Jeremy M
06-14-2008, 12:12 AM
so in theory, with a box like this could u throw more power on a sub....?, because it reduces cone excursion or .....

06-14-2008, 12:24 AM
so in theory, with a box like this could u throw more power on a sub....?, because it reduces cone excursion or .....

Yes, in theory, but it also reduces efficiency, so if you're thinking that dual chamber reflex = more power = more output then that is not correct. Dual chamber boxes will have greater box losses than a simple ported box.

This type of design isn't really about lots of power on big subs but rather, for example, preventing overexcursion of full range driver with 1 mm xmax.