8ohm amp 4ohm speakers


New member
Aug 10, 2019
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at the moment im using a roksan kandy k2 intergrated amp with the roksan kandy k2 power amp these are both rated at 8ohm at present these power b&w cm7 speakers also rated 8ohm, im considering replacing the speakers with monitor audio silver rx8's rated 4ohm, is this a miss match? would i be better sticking with the cm7's?

i dont get the ohm thing at all so any help would be a big help


New member
Jun 10, 2011
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This is never as straightforward to answer as it appears.

Trying to keep this very simple.

1. All power amplifiers are considered to be "constant voltage" devices when it comes to their speaker output. That means that in theory they are unaffected by speaker "loading". In other words an 8 ohm or a 4 ohm speaker will not alter the output.

2. The lower the "ohms" the more current is drawn even though the output voltage is the same. A 4 ohm draws twice as much as an 8 ohm at any given voltage. That then becomes a harder load for the amplifier.

The problems are,

Speakers are not not a constant load. The "ohms" actually varies for different frequencies.

We now change the word ohms to "impedance" but think of it as the same thing. My B&W 703's are called an 8 ohm speaker but in reality dip down to 2.8 ohms at various parts of the spectrum. That's low.

In practice I suspect you will be fine... and as always a dem with your amp is recommended.

The B&W's may actually be a "tougher" load than the MA's even though they are 4 ohms... it all depends on the impedance curve which we don't know.

The other big big factor is efficiency. An efficient (measured in xx/db at 1 meter) speaker needs a lot less power to give the same level of sound as an inefficient one.


Lower ohms = more work for your amp. Halving the ohms doubles the current and so some amps will struggle at higher volumes. Its a bit like doubling the weight of your car and keeping the same engine, performance won't be as sprightly.


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