# change my speaker

#### glojon15

##### Estimable
my bass amp is rated 80watts / 4 ohms,,and my speaker is need to be change,,can i change the 4 ohm into 6 or 8 ohms?but in the same watts or can i change the 80 watts into 100watts at the same ohms?

#### americanaudiophile

##### Titan
In a tube amp the power will be the same for all the transformer taps. On a transistor amp if the original speaker was 4 ohms and you put an 8 ohm in the power will halve. This might not matter if the new speaker is 3db more efficient. If that was the case then you would get the same max volume even with the lower power output. If it had the same efficiency as the 4 ohm speaker then your max volume would be reduced by 3db.

#### adamwinn

##### Distinguished
If your bass amp is rated at 80 watts @ 4 ohms, then plug in to the formula Amps = Sqrt(Watts/Ohms)
sqrt(80 watts / 4 ohms) = 4.47 amps
now change to 8 ohms and get
sqrt(80 watts / 8 ohms) = 3.16 amps
or increase the wattage to 160 and get
sqrt(160 watts / 8 ohms) = 4.47 amps

IE: You can change your speaker to 6ohm or 8ohm with no problem. Always safe to use speaker with higher ohm. Not always safe to go the other way (don't try to put 2ohm speaker on the amp)

#### rexter

##### Distinguished
americanaudiophile is right and to adamwinn, though your calculation is right, that works for speakers but not the amplifier. If an amp is capable of 80 W at 4 Ohms then at 6 is about 60 W and 8 Ohms is down to about 40 W. Just think of it as a water pipe, with less resistance means more volume of water comes out. Higher resistance, less water comes out.

So with much higher wattage of 8 ohms speakers, the amplifier will have a hard time moving the coil and that will be less efficient.

When americanaudiophile talks about db efficiency, it's the speakers capability. This can be found on the speaker specification. That's why higher high db speakers are louder than other speakers consuming the same wattage. However this doesn't mean it sounds better. That's why selecting sound quality is subjective to preference of individuality.

#### adamwinn

##### Distinguished

Correct - see the first and third calculations. 80 watt @ 4 ohm == 160 watts @ 8 ohm. The second calculation is where things get different. 80 watts @ 8 ohm does not reduce the amperage by half. The capacity of the amp is fine, but the power drawn does not go down linearly. It's not relevant to the OP's question though

#### rexter

##### Distinguished
Fisrt to answer glojon15 question.

"my bass amp is rated 80watts / 4 ohms,,and my speaker is need to be change,,can i change the 4 ohm into 6 or 8 ohms?" Ans. Yes

"but in the same watts or can i change the 80 watts into 100 watts at the same ohms?" Ans. Yes, specially when speaker is very efficient. Make sure you don't crank up the volume too high or you will get clipping. speakers with 100W rating of constant power, normally can handle 400W of peak wattage.

The formula you provided and all the calculations are correct also your comment about the speakers are correct. I am only pointing it out that the calculation if for the speakers. The op can not use the same formula when finding the power output of the amplifier when an 8 ohms speakers are connected.

Now reading my previous post sounds like I am not agreeing with you. So let me rephrase that:

I agree to americanaudiophile and to adamwinn. Though the calculation works for speakers, you can not use it the same way to find power output for amplifier. If an amp is capable of 80 W at 4 Ohms then at 6 is about 60 W and 8 Ohms is down to about 40 W. With so much resistance, amp will try to power up the required output by the speakers however, keep in mind that the energy supply provided by the amp design is limited. Just think of it as a water pipe, with less resistance means more volume of water comes out. Higher resistance, less water comes out.

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