On second thought it's not a compound dipole (but is a subwoofer with cheap ($65 retail) Eminence Alpha 15" drivers!

I thought Quadrupole designs used all four drivers in the same plane which the Emerald subwoofers do not, so I don't know what to call them other than dipoles. They use ultra-cheap high Qts. drivers and relatively small baffles = lot's of EQ would be needed.

Theoretically a quadrupole with all four drivers in the same plane (see link) has less bass output than a dipole, which seems like a disadvantage.

Compound driver mounting, called Isobaric by one speaker company, uses the output of one driver to "push and pull" the cone of an identical driver. There is a "column of air" between the two drivers. Both drivers can face the same direction connected in phase, or face in opposite directions connected out of phase.

The Legacy Whisper speaker uses 15" bass drivers firing at the back of identical 15" bass drivers a few inches away. But there is no "column of air" linking them -- so I think the term "compound dipole" is not a proper name for this design even though I've heard others use the term. Maybe "compound dipole" is an oxymoron.

The Emerald subwoofer looks like an unusual dipole that uses cheap 15" high Qts. Eminence Alpha drivers with a retail price of $65 each.
This is the bottom-of-the-line Eminence 15" driver (and Eminence is known for cheap drivers -- I have nothing against the company as my own Adire Audio Tempest driver is manufactured by them).

These drivers have a pitifully small +/-3.8mm XMAX, too high 41Hz. Fs, too high 1.26 Qts. and a low power handling 1.5" voice coil with a tiny 25 ounce magnet.
link: http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-407

What is really needed for a dipole design is LONG XMAX drivers with Qts between 0.5 and 0.7
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Richard BassNut Greene
My Stereo is MUCH BETTER than Your Stereo

Monopole vs. Dipole vs. Quadrupole (Open in New Window)

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Follow Ups Full Thread

Topic - What Are The Advantages To A Quadrupole Sub? - thetubeguy1954 14:25:57 10/30/06 (13)

I'd call it a compound dipole -- advantages the same as all dipoles (reduced excitation of some room modes) - Richard BassNut Greene 09:21:31 10/31/06 (8)

On second thought it's not a compound dipole (but is a subwoofer with cheap ($65 retail) Eminence Alpha 15" drivers! - Richard BassNut Greene 08:29:28 11/03/06 (0)

Compound dipole +- +- Quadrupole +- -+ - AJinFLA 15:54:35 10/31/06 (4)

Actually a compound configuration can be either +- +- or +- -+ - Richard BassNut Greene 07:37:24 11/03/06 (0)

Then A Quadrupole Is Basically An OB Bipolar Design - thetubeguy1954 05:55:23 11/01/06 (2)

With an open baffle, it's definitely not a bipole design - Richard BassNut Greene 08:53:40 11/01/06 (1)

Re: With an open baffle, it's definitely not a bipole design - thetubeguy1954 09:30:03 11/01/06 (0)

Re: I'd call it a compound dipole -- advantages the same as all dipoles (reduced excitation of some room modes) - morricab 14:17:05 10/31/06 (0)

Re: I'd call it a compound dipole -- advantages the same as all dipoles (reduced excitation of some room modes) - thetubeguy1954 10:07:22 10/31/06 (0)

Re: What Are The Advantages To A Quadrupole Sub? - andy19191 16:10:29 10/30/06 (3)

Re: What Are The Advantages To A Quadrupole Sub? - thetubeguy1954 05:52:22 10/31/06 (0)

Re: What Are The Advantages To A Quadrupole Sub? - Steve Eddy 17:40:41 10/30/06 (1)

Re: What Are The Advantages To A Quadrupole Sub? - Soundmind 17:51:14 10/30/06 (0)

Follow Ups

On second thought it's not a compound dipole (but is a subwoofer with cheap ($65 retail) Eminence Alpha 15" drivers! - Richard BassNut Greene 08:29:28 11/03/06 (0)

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