Corner Dipole Subwoofer

Corner Dipole Subwoofer


Designer:
Mark Bushinski

Project Category:
Subwoofers

Project Level:
Beginner

Project Time:
8-20 Hours

Project Cost:
$500 – $1,000

Project Description:
Have a interest to build a dipole bass system but don’t want to have speakers pulled out four feet from the wall? Then keep reading about this corner dipole subwoofer.

Dipole speakers are directional even in bass frequencies which results in less reverberation and more clear bass reproduction. However, due to sound waves wrapping around the baffle and cancelling out, the lower frequencies will need to be boosted with an eq. More basically, pure SPL is somewhat sacrificed for more sound quality.

Design Goals:
Low distortion articulate bass reproduction was the goal of this speaker. It was a joint project with my stepson and was a good way for me to teach him introductory woodworking and electronics.

Driver Selection:
Two Acoustic Elegance IB15HT dirvers are used. If sourcing from parts express the 15″ ultimax Part # 295-514 would also work. The ultimax may give more SPL with it’s higher Xmax and power handling but might require more EQ because of a lower .QTS

Enclosure Design:
This design was based of a 2004 article by George Danavaras but his design was modified to fit 15″ drivers with bracing added.

Enclosure Assembly:
Miller dowels were used to strengthen corner joints. 3/4 baltic birch plywood was used with a double thickness baffle. Bottom is removable to facilitate easy installation of the drivers.

Crossover Design:
miniDSP is used for the crossover to mains, a 30 hz high pass and EQ.

Conclusion:
I’ve built many different subwoofers, a 3 cu ft sealed 12″ dayton titanic, a 6 cu ft 20 hz ported 12″, a seven foot folded horn and a 10″ sealed peerless xxls car sub and I’ve never heard any that match this for it’s low distortion and power from 28-40 hz. It will shake my listening chair that is 5 feet away.

I also find the articulation in the bass notes to be unbeatable. Listening to Bob Marley’s Concrete Jungle through these I can hear every bass guitar note.

Using miniDSP and the iMM-6 calibrated mic I’ve been able to achieve in room response of 28-100 hz +/- 5 db. See attached pink noise graph.

I’ve also included sine wave RTA distortion plots at approximately 5% distortion this is in a small room at about 5 feet away.

However if massive deep bass SPL is your thing I would not recommend this approach as i can easily get these to bottom out above 95db at 30hz and I have applied a 30 hz high pass because 20 hz is basically a distortion machine.

About the Designer:
I’ve been building DIY speakers for 20 years, my favorite so far is a Bill Fitmaurice 3-way floor stander that includes a 7 foot folded bass horn. Another speaker building highlight was the battery powered PA system I designed and built for me and my wife’s outdoor wedding.

Project Parts List:

Dayton Audio iMM-6 Calibrated Measurement Microphone for Tablets iPhone iPad and Android
miniDSP 2×4 Kit Digital Signal Processor Assembled Board
Penn-Elcom F1687 Rubber Cabinet Foot 1.5″ Dia. x 0.375″ H

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