OVERVIEW OF THE DOUBLE FOUR
With the great success of the PJB Bass Cub, we had many requests to make a
truly affordable bass practice amp. The chellange: it had to be incredibly small
and yet still deliver the great PJB bass sound. We realized we could not
achieve this goal by using existing parts. So, our jorney started again with the
combination of new driver design, cabinet acoustic loading and the latest
digital amplifier technology.
The DOUBLE FOUR is a single channel bass amplifier that has an auxiliary
input for ipad/ipod, mp3 or drum machine. It features 3 band EQ that is
perfectly tailored for bass guitar, headphone out jack and a line out for
recording. It is ideal for all kinds of basses, and can handle the open B string
on a 5 string bass with ease.
The Enclosure
It is well known that big speakers are capable of reproducing true bass
fundamental frequencies but as you decrease the physical size of a speaker,
the bass response will fade away. This is the reason Violins are small and
Double Basses are big!
So how do you get big bass sound from a small speaker cabinet? With our
know how of using smaller drivers to get the ultimate bass sound, we applied
our vast experience to an even smaller driver just 4 inches across. It is built
with Swiss watch precision; it has to cope with the extreme signals coming in
from an amplified bass guitar. Using our extensive R&D facility which includes
the largest anechoic chamber in the bass guitar amplifier industry and the
KLIPPEL transducer measurement system (it uses lasers!), we were able to
develop the perfect 4 inch loudspeaker. We analyzed the neodymium
magnetic system, the cone behavior at all frequencies in 3D representation,
cone suspension and frame, etc., until we had achieved a transducer beyond
what anyone would have ever thought possible. Then we looked at the
acoustic loading using the acoustic simulation software and calculated
exactly the full power cone displacement at every frequency.
We designed a custom Rectangular Auxiliary Low Frequency Radiator
(RALFR®). That is a pneumatically coupled radiator loaded to the rear of the
two 4 inch speakers that operates at the lowest bass frequencies only. It
augments the output of the loudspeakers at frequencies from 30 to 150 Hz. It
also reduces the cone excursion of the speakers, allowing greater power
handling.
The proprietary PJB NeoPower 4-inch speakers have full frequency range to
the highest audio frequencies. Not only does this give greater clarity and
transparency to your instrument, but also a high fidelity sound to any backing
track fed into the auxiliary input.
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