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Loudspeaker Designs and Articles for the DIY Enthusiast
The
Uluwatu
A high sensitivity  
high SPL design
Preface

When I designed the Stentorians, I made sure there would be plenty of drivers
available for the near future. I was assured there were several thousand on hand.
That sounded like a good supply to me, but the supply seemed to run out sooner
than I had hoped. Doing the math, several thousand drivers, used a dozen at a
time, equates to only a couple of hundred pairs of Stens, give or take. When Adam
at Madisound suggested I try something similar with the SB Acoustics SB13PFC25-
08 woofers, and the SB29RDNC-C000-4 tweeter, it didn’t take too much
investigating to get me on the bandwagon.  
Major specifications

A 2.5 way vented design
with 6 SB Acoustics SB13PFC25-08 woofers in a series parallel
configuration graced by the quite capable SB29RDNC-C000-4 ring radiator. The 94 dB tweeter
sensitivity came in handy…

Nominal impedance:  6 ohms The impedance curve stays well above 5 ohms for the most
part. Where it dips below 5 the impedance phase is nearly resistive, so it will be an easy load
for any competent amplifier.

Dimensions: 8.5” wide, 47” tall, 15” deep

Basic sensitivity: Conservatively rated at 92 dB / 2.83v / 1 meter

Max SPL: (Modeled at the woofer published Xmax) 118 dB / 1 meter  
Main / Design Goals

Similar in concept to the Stentorians, but the tinker in me
refused to be satisfied reinventing the wheel again. Since
I was using more expensive drivers, it seemed logical that
the design should also exhibit better performance as well.
Fortunately, I had some ideas in both driver layout and
crossover that turned out favorably to enhance the
performance of the design. The SB13’s favored a vented
alignment, and you will notice I broke with tradition and
front mounted the port. Based on the room position
preference of many Sten users this speaker is designed
for near wall placement.

–Yes, that is a 4” flared port. The air velocities at high
SPL’s demanded this diameter.


While the max SPL model’s somewhere around 118 dB,
there is another advantage to using six midwoofers per
line: The combined surface area of the six drivers nearly
equals that of a typical 15” woofer. This design exhibits a
surprising amount of tactile presence.
*Uluwatu: the coolest surfing Beach in Bali
All pictures courtesy of  Alejandro Fernández Valdespino
Links to:

Main / Design Goals

Driver Selection

Cabinet Construction

Crossover Design

Measurements

Listening Impressions
All pictures courtesy of  Alejandro Fernández Valdespino