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Series Or Parallel? Linking Loudspeakers Properly
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Parallel connection means that the amplifier output current flows through both of the voice coils simultaneously (a current divider), in proportion to their impedance.

If they are the same impedance (the most common condition), the current through each will be the same.

The output voltage of the amplifier will be the same across each voice coil, since all “+” terminals are connected together and all “-” terminals are connected together.

The load increases (the total impedance gets smaller) as more loudspeakers are connected in this fashion.

Parallel connection is the preferred method for configuring a multiple loudspeaker system, because adding additional loudspeakers does not change the power flow (or loudness) through the existing loudspeakers.

The sound level from existing loudspeakers remains the same as additional loudspeakers are added.

Parallel connection, the preferred method for multiple loudspeaker systems. (click to enlarge)

Care should be taken to avoid overloading the amplifier - a condition that occurs when too many loudspeakers are paralleled. This produces a total impedance that is too low and draws excessive current from the amplifier.

When loudspeakers are “daisy-chained” they are being connected in parallel.

The interconnecting cable buses all of the “+” loudspeaker terminals together and all of the “-” loudspeaker terminals together.

This is often confused for series connection, but it is not since the current does not need to flow through one loudspeaker to get to the next.

Series-parallel is useful within loudspeaker enclosures to allow a target impedance to be achieved with multiple devices. (click to enlarge)

An open voice coil in one of the loudspeakers will not produce a level change in the remaining loudspeakers, making this configuration ideal for distributed ceiling loudspeaker systems.

Series-parallel connection combines both of the above and is useful within loudspeaker enclosures to allow a target impedance to be achieved with multiple devices (i.e., dodecahedron loudspeakers, guitar amplifier cabinets, etc.).

It is sometimes employed to achieve an impedance value that would otherwise be too high if series connection alone were used, or too low if parallel connection alone were used.

This method works fine when used internally in a loudspeaker box (like a six 10-inch-loaded “guitar cabinet”), but should be avoided if the loudspeakers are to be distributed around a facility.

Such a system would be difficult to expand and difficult to service due to the non-standard method of connection.

Pat and Brenda Brown own and operate SynAudCon, conducting training seminars around the world.

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Comments (2) Most recent displayed first
Posted by Tony  on  07/16/10  at  11:51 AM
Seriously disappointing article. The concepts are important but sloppy use of terminology will lead to more confusion than any assistance in understanding. Speakers don't draw current. Lower impedance is a smaller load (not bigger). The lower impedance results in higher current flow per Ohm's law. Maybe this sloppy vocabulary was used to try and simplify the concepts but in the end it just perpetuates the myths that cause the confusion on this topic in the first place.
Posted by Tony  on  07/16/10  at  11:43 AM
"As the load impedance is decreased, the load on the amplifier is increased, because it must work harder to supply the demand for current." This is a mis-leading and borderline inaccurate statement. This implies that the speakers are demanding a certain level of current which is not the case. The speakers resist current (impedance) but the lower the impedance the more current is allowed to flow from the amplifier.
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