Loudspeaker Designs and Articles for the DIY Enthusiast
A FULL RANGE PROJECT
WITH BASS ASSIST AND
A 2 way vented design featuring the SB Acoustics SB17RNXC35-8-UC uncoated paper cone woofer and the Mark Audio Alpair 10P full range driver. The
Alpair is housed in a semi open back cylindrical enclosure, while the SB17's perform in individual transmission lines that are merged at the port in a mass
Nominal Impedance: This one is definitely a 4 ohm design. As a consequence of the first order crossover the impedance curve flirts with 3 ohms at some
frequencies below 500 Hz, but spends it time above that point at 8 to 12 ohms. The worst amplifier load is 3.8 ohms and -40 degrees at 80 Hz. This
suggests the partnering amplifier should be capable of driving 4 ohm loads with good current capabilities.
Dimensions: external: 9" wide, 38.25" tall (including the 4" base) and 22.5" deep
Basic Sensitivity: Approximately 88 dB / 2.83v / 1 meter
Max SPL: (Modeled at woofer published Xmax) 104 dB / 1meter
Main / Design Goals
Halcyon (pronounced HAL C en) Denotes a period of time in the past that was idyllically happy and peaceful.
For me I remember the days as a young pup when the main entertainment item in the living was the big floor standing radio. This furniture quality wood
beauty got several bands, including shortwave and aircraft bands. -It even got AM! If memory serves, the speaker in this behemoth was 12 inches for
certain, and it had such wonderful tone, and brought much music, radio programs, and enjoyment into our home. That full range coherent sound was my
goal for this design, although with the refinements of a half century of speaker design I'm sure this design sounds much better than the original.
Of course there are many examples of full range drivers, and some provide excellent bass, or great high end performance, but rarely does one excel at
both. I found the Alpair 10P to have a nice paper sound, and great top end performance, but likely wouldn't provide the bass frequencies at the SPL levels I
was looking for. I also felt the Alpair would preform better if those lower, excursion demanding frequencies were removed from its duties. In addition, I
wanted the enclosure to have a more modern look.
To maintain that coherent sound I decided a first order crossover to the woofers would be essential. I felt utilizing a series crossover would just add icing to