Thinking inside the box

[Bassick]

To anyone with knowledge, be it professional or novice, but only serious answers. Just as the title implies I'm thinking inside the box. I am a huge advocate of car audio, I'm 40 years old, matured in the mid 90's. Been into car audio for a long time as a hobbyist, and for the last 3 years all the technical stuff from T/S parameters to 8th order bandpass enclosures are now making a lot of sense to me. So with that said, here is my question. How would a ported enclosure or sealed for that matter, behave if there where smaller chambers inside the enclosure (we will say 2 more). So picture this inside your head, take a enclosure sealed or ported, and on the back side of the enclosure you cut out a port to what ever size is relevant to the enclosure, now you build another enclosure perpendicular to that side of the original enclosure, and then repeat that process one more time. Each additional chamber would be somewhat smaller than the next.View attachment 26544535 This is my first time posting, I hope this attachment illustrates it better. My goal is to produce a enclosure that would tune itself according the lowest frequencies present. The open port would be tuned to a given freq, as the second port unloads because of its tuning, that would make the first port tuning freq change. Its very hard to contemplate what happens after that. Someone with really good knowledge please reply to what is really going on in such a setup.

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[itsblown 10+ year member]

So youre bassically saying a ported enclosure with two ports, one port firing into another ported enclosure? Im not sure if theres a name for that but Im assuming its some kind of 6th order 8 quasi bullshit, I have no idea, I just dont think its a good idea... why? because I dont know.

 

[ThatChevyGuy 5,000+ posts]

mind blown

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[hispls 5,000+ posts]

The chamber without a driver in it should be ported as well. It's called an ABC box commonly but there's a couple other names for it. When done correctly the chambers are 1/3 and 2/3 of the total volume and ALL ports are equal size and length. You tune the ports so that the full box volume is tuned to your low frequency with 2 identical ports.

The smaller side of the box will peak much higher and below that the port between chambers unloads so that the rest of the box volume and that port becomes loaded... you essentially get 2 peaks. They sound really nice and can get some impressive response out of small cone area, but they're tricky to build and rather picky about getting everything right. Also they take up a lot of space.

http://www.caraudio.com/forums/general-discussion/567204-pics-current-abc-box-aperiodic-bi-chamber-dual-tuned-reflex.html

Very good picture of one done right. There's a huge thread in Termlab forum archives on this style box. Some searching may find it.