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Description
The SPB-8420 Low-Z Speaker Patchbox is a versatile helper for correct speaker-cabling in installed
multi-speaker low-impedance sound systems. After a brief setup, this unit helps to achieve proper
connectivity, correct amplifier load impedance and equal cable lengths within an arrangement of 2, 4
or 8 speakers. The SPB-8420 hence makes small-to-medium-scale low-impedance speaker installa-
tion easy and simple.
Why low-impedance?
While it has become a habit for installers and contractors to install 70V/100V line systems in
distributed sound reinforcement systems, the advantages of such systems mainly relate to
Systems with a very large number of speakers to be driven
Systems with an odd number of speakers or an unsymmetrical layout of speakers to be driven
Systems with relative large distances (> 20m) of the most remote speaker to the driving amplifier
Systems with accepted limitation of the audio bandwith such as paging systems or very low-volume
background music systems
Fact is at the same time that
The average non-department retail stores in malls are sized between 120 sqm and 160 sqm, with
ceiling heights typically being about 3.00...3.50m.
Average restaurants start at about 120 sqm to about 400 sqm, averaging at apout 180 sqm, with
ceiling heights typically 2.50...3.00m. Bars tend to be smaller.
Retail stores and restaurant rooms are mostly of rectangular shape, with side ratios of 1:2...1:3
Non-department retail stores, restaurants, bars and coffee shops tend to have a very low paging
necessity, instead mostly play contemporary music at medium levels as a background program.
Sound systems for such venues are hence well served with speakers systems containing between 4
and 8 speakers. Such system must be able to reproduce contemporary music in full bandwidth at up
to medium levels. In a larger venue of about 200 sqm, this would yield an 8-speaker system with a
distance between the furthest speaker and the amplifier of about 20m. Venues of this size are not
subject to any of the advantages delivered by a 70/100V line system, but rather suffer from their
disadvantages:
Higher system cost due to transformers needed both on the feeding (amplifier) side and the
receiving (speaker) side
Limited full-band frequency response due to saturation effects in the used transformers. While this
can be improved by transformers of superior quality, cost will even be higher in such case, and
full-band music reproduction is still hard to obtain.
This is why small-to-medium-sized retail and hospitality venues are served with better sound and lower
cost by using a low-impedance system. Connecting multiple low-impedance speakers to a single ampli-
fier output however requires a proper cabling arrangement to achieve a suitable amplifier loading;
such cabling arrangement will require suitable parallel/serial wiring or a combination of both. The
SPB-8420 helps doing this with ease and simplicity.
8-Ceiling-speaker
arrangement in a
typical 200sqm
(10x20m) venue
USER MANUAL - SPB8420 LowZ SPEAKER PATCH BOX
