ABC boxes.

[TaylorFade 10+ year member]

I have searched the net and have a handle on the basics of ABC's. Has anyone tried one? Advantages? Disadvantages other than the box being a bit larger? Any info would be great as I am considering one for my new build.

Thanks.

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[spltuscon 10+ year member]

I have tried one for a single twelve and I like it a lot. Loud, clean and smooth response. I have mine tuned to 28hz and the upper response is a little better than a standard ported box would be tuned that low.

It does take up quite a bit of room and takes longer to build but that seems to be the only disadvantage.

 

[TaylorFade 10+ year member]

Cool, thanks. As far as I can tell it's only bigger by the volume of the 3rd port so that's not so bad. Well, that and having to use 2 externals instead of one big one.

So if your is tuned to 28hz, that means it's 28/56, right?

 

[soloXgt 10+ year member]

had one and liked it a lot. I forget tuning, but like spltuscon said, clean and smooth, but a pain to build

 

[TaylorFade 10+ year member]

The pain to build that you speak of- that's the headache of having to build 3 ports instead of one, right? I plan on using Aeros instead of slots so it really doesn't seem all that bad from what I have seen.

 

[supermaxx123 10+ year member]

someone explain ABC to me... I'll build one.

 

[spltuscon 10+ year member]

This was a post from someone on Termpro back in 1999 and what I based mine on. Its pretty basic but it seems to work well.

Quote from screenname Buzz:

" 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.(these numbers were based on a certain 15" sub, you'll need to figure box size and port length for your application)

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."

My design uses 3 4" PSP Aeroports (internal) and has a removable top in case I decide to change tuning (you have to be able to get to the port that goes between the two chambers).