12 October 2008

Isobaric 6th Order Bandpass Subwoofer

Dan McGrath (from Great Britain) sent an email with a link to his recent DIY Subwoofer project. For the subwoofer project, Dan decided to use an Isobaric Sixth Order Series-Tuned Bandpass enclosure. The basic layout of a 6th order isobaric bandpass enclosure is shown in the figure below.

Isobaric 6th Order Bandpass Subwoofer Speaker Box
The enclosure was constructed using Medium-Density Fiberboard (MDF) which is inexpensive and easy to work with. To make the enclosure rigid, Dan doubled up the MDF as shown below (click photo to enlarge).

DIY Isobaric Sixth Order Bandpass Subwoofer Construction
For the subwoofer project Dan used two Eminence Beta 10 drivers. The Eminence Beta 10 is an 8 ohm, 10 inch bass driver with a power rating of 250W and a sensitivity 97 dB. With the very high efficiency of these drivers, the subwoofer will be able to produce high SPL with only modest power. The Eminence Beta 10 is readily available (often locally) and it is relatively inexpensive. The photo below (click to enlarge) shows the two drivers in the baffle.

DIY Isobaric Sixth Order Bandpass Subwoofer Box
The finished subwoofer enclosure is shown in the photo below (click to enlarge). Dan has been using the subwoofer for a few months now and is very pleased with the results. That should not come as a surprise considering the level of effort he put in to this build. Very nice work Dan.

DIY Isobaric 6th Order Bandpass Subwoofer
Dan has compiled a very detailed build log of his subwoofer project on his website and there are plenty of photographs. Take a look at his page for more information on this project.

More DIY Subwoofer Projects:

What's Playing: Emillie Mover - Ordinary Day


  1. Just wondering if you know of a site or maybe a book that has info on building BandPass enclosures,
    live how to calc the volume and wiring crossovers etc

    Looks quite nice what you have done there :)

  2. Hi darkaxi0m!

    The subwoofer detailed above is mine, thanks for your comments.

    There is a book, yes. The one I prefer and use is called "The Coupled Cavity Handbook" it's by David Purton.

    I struggled to get a copy (it's out of print I think), you might do too - but it's worth the effort!

  3. é tem que estudar muito num sabe nada sobre box pra sub ! sub é basiado em preção do ar

  4. Did you reverse the polarity on one of the drivers in order for the subs not to cancel each other out?

    1. Yes. You have to wire them in series, which he did. If he used 8 ohm drivers his combined impedance is 16 ohms. So, I'm not sure why he went that route...

      I read his site and it's a great build. I'm just puzzled by the driver choice and why he didn't go with 4 Ohm drivers...

  5. The enormous force in the 6th order bandbass ,shredds the 4ohm speaker to easily ,the more resistance it has the more punch it will have ,I had to put a weaker chassie in a zeck tsw125 ,which one sees the difference instantly ,the zeck produses 105db by one watt if someone is after real power ,but it breaks your house too ,just what one wants

  6. Have you got any dimension for your box ,emenice makes nice drivers I see your point