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Running a 4 ohm amp at 3 ohms causing damage?

Cody AOC

Cody AOC

Active Member
I have a Crown XLi 800 amp, my 8 ohm speakers 2 speakers on each channel they are not big speakers but ok size and they read 6.5 ohms each and when connected together the 2 speakers connected is 3.5 ohms and my amp is rated to go down to 4 ohms is this causing any damage? Sometimes I like to play loud in my house I bought the amp new in july 2016 and wanted to know does this cause any damage to my amp?
 
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Resistance is Measured at O cycles. Impedance is measured at the lowest point above the resonant frequency of the woofer. You should be fine, just make sure you have ample air flow space around the amplifier.
 
I don't understand your math. 1 set of speakers? How are you connecting them? 2 speakers 6.5 should be 6.5 not 3.5.
 
rwartner said:
I don't understand your math. 1 set of speakers? How are you connecting them? 2 speakers 6.5 should be 6.5 not 3.5.
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He says two speakers on each channel. I've taken it at face value, could be my mistake.

Each speaker is measured 6.5 ohms DC resistance. 1/(1/6.5 + 1/6.5) = 1/0.3077 = 3.25 ohms DC resistance.

But, the consideration is for nominal impedance not DC resistance. So, two "8 ohm" speakers on each channel nets out at 4 ohms, for which the amp is rated.

Presuming, of course, "two speakers on each channel" actually means that. :)
 
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twiiii said:
Resistance is Measured at O cycles. Impedance is measured at the lowest point above the resonant frequency of the woofer. You should be fine, just make sure you have ample air flow space around the amplifier.
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Impedance can be measured at any frequency the speaker responds to and beyond. If you look at any speaker's impedance chart, it will peak at resonance frequency, but will rise as the frequency rises. There also are no "brick walls", so while the speaker's frequency response falls off, its impedance may still continue to rise (to a point).

To the OP: The impedance rating of a speaker has been "averaged" as a specification for a general guide to the consumer. However, its impedance may vary widely, going from as little as 2 or 3 ohms up to and beyond 35 ohms (at resonance frequency). Good amplifiers will handle this variant well, poorly designed ones may may not.

Your Crown is designed for "hazardous duty", if you get my drift. It is an industrial amplifier designed for extreme conditions.
 
Cody AOC No.

Both DC resistance and AC impedance refer to to opposition to the flow of electricity.

Both are measured using the unit "Ohm".

In a circuit that contains capacitors (they have what is called capacitive reactance measured in Ohms) and or inductors (they have what is called inductive reactance measured in Ohms), the measured value of these will change with the frequency of the electricity.

When one uses a DC Ohmmeter to measure a speaker, the Ohmmeter supplies DC (direct current) so it is measuring the resistance of the speaker.

When the speaker is connected to an amplifier, it is receiving an audio signal with is an AC (alternating current). So what the amplifier sees is the impedance of the speaker (which is what is given the speaker manufacturer) which will likely be different that the DC resistance.

To restate it, resistance is what is measured in a DC circuit and impedance is what is measured in an AC circuit that contains capacitors and or inductors.

Both are measured using the unit "Ohm".
 
Measuring a raw speaker or a speaker system with an ohm meter will result in the measuring the resistance of the system or coil in a rest position. If you were to measure the resistance of a woofer, for example and push in on the woofer cone, you would see the resistance value change, because now the woofer's voice coil is engaging the speaker's magnet and that influences the resistance. I LIKE MUSIC's answer is good too. Getting too deep for the OPs question I think......
 
My post was for Cody AOC as indicated.

The reason the resistance reading changes when the woofer cone is moved, is not because the resistance of the wire in the voice coil changes, it is because there is a voltage generated when the voice cuts across the lines of magnetic force of the speaker magnet/pole piece.

Moving the woofer cone, impacts the reading on the Ohm meter, but does not change the value of the actual resistance.

If the woofer cone is moved then held steady the resistance will measure the same.
 
Run a Nissan sentra on premium gas and it'll be peppier, but corvette gas will eventually burn up your stock injectors, run an amp that's designed for 1 at 1.5 and it has to work harder, truly all you've to do is ask yourself two questions how loud do you push your equipment? because ran at relatively low levels almost no combination will cause harm right or wrong the main killer is heat so a small utility fan installed may absorb the majority of the excess from the high load making it "safer" and how much do you care about your amps longevity? Things are rated for a reason just because a receiver will go from -80db all the way up to +16.5db doesn't mean that it will like pushing it's Max end, wiring something with lower impedance IMHO is like taking your receiver and forcing it to work two times harder to do the same thing, if you want to wire three ohms get a monoblock or two channel power amplifier, that's best bet for such a large flow.
 
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WaynerN said:
Measuring a raw speaker or a speaker system with an ohm meter will result in the measuring the resistance of the system or coil in a rest position. If you were to measure the resistance of a woofer, for example and push in on the woofer cone, you would see the resistance value change, because now the woofer's voice coil is engaging the speaker's magnet and that influences the resistance. I LIKE MUSIC's answer is good too. Getting too deep for the OPs question I think......
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And that doesn't even include the calculation of the phase angle of the signal going through each reactive component and its effects on the overall reactance of the circuit.
 
I'm now confused here. If speaker ohm ratings don't mean the same thing as amplifier ohm ratings, then how do you match amp to speakers? I have Kappa 9s with LSR&D monos rated down to 2ohms-. They are perfect together. The chatter here has been as though both ratings do indeed mean the same thing, at least for all intents and purposes. So what's up?
 
In general the lowest impedance rating of an amplifier/receiver tells the user of the amplifier/receiver the safe minimum impedance of the speaker or speakers (if more than one pair is connected to a two channel amplifier) that may be used safely with the amplifier/receiver.

The lower the impedance of the speaker(s) that are connected to the amplifier/receiver, the harder it will have to work up to the point where poor sound and damage may occur.

The actual impedance of the output of a solid state amplifier/receiver is commonly just a fraction of an Ohm. There are exceptions. Amplifiers with output transformers are a different story.
 
Superampman said:
I'm now confused here. If speaker ohm ratings don't mean the same thing as amplifier ohm ratings, then how do you match amp to speakers? I have Kappa 9s with LSR&D monos rated down to 2ohms-. They are perfect together. The chatter here has been as though both ratings do indeed mean the same thing, at least for all intents and purposes. So what's up?
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Nothing is up. The OP was unaware of the difference between DC resistance of a speaker and the impedance of the speaker. The nominal impedance of the speaker is how the mfg lists it, not by the DC resistance.

Align the nominal impedance (the mfgs rating) of the speaker to the amplifier's rated load capabilities and in the vast majority of cases that's the way to go.

The exceptions, of course, are the few known "amp killer" speakers where the impedance dips way lower than nominal rating, or they have such high phase angle the amp can't properly dissipate the extra heat.
 
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