EX12 bandpass: specs, ports?

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Systems
Systems Posts: 14,873
edited May 2003 in Car Subwoofer Talk
I am considering to built a bandpass box with dual EX12's.
I've read alot of reviews in which poeple are raving about the EX12 in bandpass applications.

I am stepping up from a single 15'' power acoustik **** sub, which has non-existent SQ, but truly shakes the whole car!!!

My problem is however......SQ!!
How do these perform sound quality wise in a BP box? i dispise the lag some bandpass enclosure have!!

I am planning to built my own custom box since I do not have much trunk space available ('94 Honda prelude), and I was thinking of placing the box directly against the back of the backseats and letting the ports fire into the cabin (there is a plastic centerconsole between backseats which I can get the ports through).

My questions:
- front chamber displacement
- back chamber displacement
- number of ports
- diameter of ports
- port lenght(s)

i have the owners manual of these subs, in which all info is given, but still want to know if other measurements will enhance SQ with a bit of SPL.
I also need info on port lenghts when I take it out of the box to stick into cabin

Thanks!!!!
Testing
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  • Mervin
    Mervin Posts: 6
    edited May 2003
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    Thanks for your advice, however, I have raed that the group delay will not sound as obvious if good quality midbass druivers are used (should be crossed over right also).

    I have relatively good drivers in doors and rear deck, and am really inclined to a bandpass system, since I have nasty experiences with trunk rattling and sound cancellation.

    When I had the ported 15'' sub installed, I could really feel the vibrations, but it didnt seem that loud. I also experienced this with a Kicker 12L7, which was reasonably loud in a friends car, but didnt cut it in mine!

    So I just think it would be best to channel all acouustic energy through the ports directly into the cabin. This will effectively eliminate ralltes, and possible cancellation.

    In my owners manual I noted that the tuning frequency is 46Hz, which I personally find a bit low, especially since I will not have any cabin gain (ports firing directly into cabin).

    Can anyone forward specs for a lower box frequency? I do not know my cars frequency gain, but will calculate it with F=565/L (EX12 manual).

    I really hope someone can help me with this!

    Thanks in advance

    PS: I assume that the bandpass specs in the manual are with the ports in the back chamber?
    Sorry for the novel!
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  • Mervin
    Mervin Posts: 6
    edited May 2003
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    Yo guys, I finished the plans for the B-P box, using WinISD.

    I am no pro at this, but got some help from very friendly online WinISD guru's.

    It seems that this program will plot the best results by itself, but I just tweaked it a bit to emphasize some frequencies.

    It is just that the program kicked out: Vf = 1.7, Vb = 2.0 @Frq = 58Hz (per two subs)

    This is a huge difference from the spec in the manual which are: Vf = 1.5, Vb = 1.44 @ Frq = 46 (specs are submitted per one, so multiplied by two)

    How come the difference is that big, or did Polk already account for the transfer gain?

    Can someone also shed some light on the issues group delay and phase plot?

    Thanks in advance.
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  • PoweredByDodge
    PoweredByDodge Posts: 4,185
    edited May 2003
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    *scratches head*.... this is why i stick to sealed and vented boxes.
    The Artist formerly known as PoweredByDodge
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