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4 Ohm 200W Non-Inductive Dummy Load Resistor
Is it possible to use this resistor as an added load to change speaker impedance?
I have two Klipsch THX sub boxes with two 6 ohm 8" drivers in each one that are wired in series resulting in a 12 ohm load to the amp from each box. I was considering purchasing the APA150 and using it in bridged mode for 150watts per box. I want to use one amp per box so I can move them to different parts of the room. My question is: can I use this 4 ohm resistor in parallel with the speakers also wired in parallel to achieve a 7 ohm load to the amp and would this amp handle the 7 ohm load (it's rated only into 8 ohm loads in bridged mode)?
Adding resistors to speakers to change the effective impedance only works for tweeters. For midranges, woofers, and subwoofers, any amount of resistance above about 0.1 ohm (ie, what you'd get in the speaker wires) will dramatically affect the Q of the speaker system, and thus affect its frequency response. This usually results in a fairly large peak in the frequency response of the speaker around the bottom end of its normal frequency response. For example, if you put a 4 ohm resistor in series with a 4 ohm woofer then you'll get a large peak where its frequency response usually starts dropping off: at mid-bass frequencies.So, unfortunately your plan would not work. To answer your other question though, an amp that is rated for 8 ohms should also be able to handle 7 ohms fine. The difference between 7 and 8 ohms is so minimal that it probably wouldn't matter. Also, the actual impedance of a speaker varies dramatically with frequency, so an "8 ohm speaker" doesn't actually present an 8 ohm load to the amp at all times. "8 ohm speakers" are only *nominally* 8 ohms. Different "8 ohm" speakers from different manufacturers will have fairly large differences in the effective load they give to the amp, and really when speakers are specified as "8 ohm", "4 ohm", etc, it's mostly just for the purpose of roughly grouping speakers into groups of similar impedances. Some "8 ohm" speakers are, in reality, more like 6 ohm speakers, but the manufacturer just decided to call it an 8 ohm speaker.
Date published: 2012-02-12
what is the mounting hole spacing?
The mounting holes are 6" on center.
Date published: 2013-08-14