4 ohm amp into 8 ohm cab- will I blow the speaker?

[Jordy4strings]

I have a 4 ohm amp 500 watts and a 8 ohm cab 300 watts. If I crank the amp will I blow the speaker or does the difference in impedance mean I will only get half of the wattage going from amp to speaker, thus making it impossible to ruin the cab?

Thanks in advance for any help you can give me. Have a great day.
Jordy

 

[Stumbo]

I have a 4 ohm amp 500 watts and a 8 ohm cab 300 watts. If I crank the amp will I blow the speaker or does the difference in impedance mean I will only get half of the wattage going from amp to speaker, thus making it impossible to ruin the cab?

Thanks in advance for any help you can give me. Have a great day.
Jordy

Why do you want to do that?

Yes, you can still blow speakers. Better to add another 8 ohm cab for more volume.

 

[Redbrangus]

Your assumption about the output power of the amp is correct--that the power is reduced to half because the 8-ohm load, so it is basically safe to operate that cab with that amp. However, don't presume that it would be impossible to ruin the speakers just because they are a reasonably good match for the amp...it's possible to burn up a speaker system if you run it loud enough for long enough, even if the power applied is within the specification.

 

[Downunderwonder]

No safety in those numbers. Use your ears. Too much power in low frequencies shreds speakers, easy to hear if you are playing clean tones, not easy to hear alongside distorted tones.

Too much power all told cooks speakers, it gets quieter before it goes silent, also not easy to hear.

If you crank it up with a clean tone until it won't go any louder without distorting and then back it off a little you should be safe to then add some effected distortion so long as it doesn't boost volume.

 

[chris_b]

What amp and what cab?

 

[mmbongo]

Since you say you have a '4 ohm amp' I'm assuming it's a large tube amp? Yeah you cannot use an 8 ohm cab if your amp is on the 4 ohm setting. Your cab must match the transformer setting on your amp.

And yes, a 500 watt tube amp will shred right through a 300 watt speaker cabinet if you get crazy with the volume.

 

[Redbrangus]

Since you say you have a '4 ohm amp' I'm assuming it's a large tube amp?

I'm not sure how that follows, but I made a similar mistake by assuming the OP was referring to a SS amp that produces 500 watts at 4 ohms...partly due, I guess, to the relative paucity of 500-watt tube amps. So OP, how 'bout it...what amp in particular are you talking about? And what speaker cab, for that matter...some manufacturers are more uhmm...'generous' in their ratings than others. Besides, speaker power specs are not really an absolute number in the first place...they are nominal ratings.

 

[lug]

Unlikely he has a 500 watt tube amp so I'll go with "safe" but as others say, ratings are no substitute for "use your ears!" OP, you eliminate a lot of speculation by actually listing the amp and cab you have/are looking to buy.

 

[And I]

If you crank the amp you'll probably blow the speakers. Wattage is not a "turn the knobs all the way up if the numbers match" game. If you set the amp to where you think it needs to be volume-wise, and the speakers sound like they're straining--you're going to damage them if you keep it up. If you need to turn the thing all the way up to be heard, get a second 8 ohm cab. More speakers is WAY more effective than more wattage when it comes to producing more volume. Also, consider a high pass filter. Removing the subsonic rumble will help the speakers produce more usable volume before they crap out.

 

[Jordy4strings]

I'm not sure how that follows, but I made a similar mistake by assuming the OP was referring to a SS amp that produces 500 watts at 4 ohms...partly due, I guess, to the relative paucity of 500-watt tube amps. So OP, how 'bout it...what amp in particular are you talking about? And what speaker cab, for that matter...some manufacturers are more uhmm...'generous' in their ratings than others. Besides, speaker power specs are not really an absolute number in the first place...they are nominal ratings.

its solid state, im not playing wembley stadium haha

 

[two fingers]

I have a 4 ohm amp 500 watts and a 8 ohm cab 300 watts. If I crank the amp will I blow the speaker or does the difference in impedance mean I will only get half of the wattage going from amp to speaker, thus making it impossible to ruin the cab?

Thanks in advance for any help you can give me. Have a great day.
Jordy

Disregard all stats and numbers, including the one on all gain/volume knobs on your amp. Use your ears. Your speaker will tell you if it's struggling. When it starts to sound like it's struggling, back off the volume.

The very best way to get more volume is to find another cabinet identical to the one you have and run them together.

You did the right thing by asking before you start to damage something.

 

[JimChjones]

The old rule of thumb was that the speaker capacity should be double the rated power of the amp if you wanted to be really safe. That was mainly for the days when both amps and speakers had limited capability so both were being thrashed. Amp rated at 500W into 4 ohms ought to be fairly safe into a 300W 8ohm cab if you don't go silly. If you do all bets are off.

[added]
Oh, and the other gotcha is whether both amp and cab are rated with the same watts. If the amp is rated at 500W RMS and the speaker at 500W peak or program or something then all bets are off and tears likely. Best to go back to manufacturers web sites to check that.

 

[mmbongo]

its solid state, im not playing wembley stadium haha

Thus the importance of specifying the exact amp you're using...which you still have not done

Saying you have a '4 ohm amp' is the confusing part, as that only matters if you have a tube amp.

 

[Redbrangus]

its solid state, im not playing wembley stadium haha

Then, in the absence of additional pertinent data, I stand by my original post...it sounds like you're in the right ballpark, power-wise. Again, as everyone else has said...if the speakers are crapping out, it's too dang loud.

I will note that the OP never said that he wasn't loud enough or was not being heard...he merely asked if he would thrash the speaker if he turned it up too much given the parameters specified.

 

[JRA]

Jordy4strings , FWIW: identifying the components for your 'group-think' exercise will help you get better feedback from the herd --- crummy info = crummy advice!* so, it's on you! good luck with your rig!


* even though these cats would like to help you!

 

[Redbrangus]

Hey, what else do you need to know besides he's not playing Wembley Stadium?

 

[mmbongo]

Hey, what else do you need to know besides he's not playing Wembley Stadium?

So here's the plan so far:

1) The OP has an amp, believed to be solid state.
2) He's not playing Wembley stadium.
3) .......
4) Profit!

 

[Richard Martin]

crummy info = crummy advice

Like we used to say. Garbage in, garbage out. Like a few smart people here have already said, tell us the name, make and model. It may or may not work. There's no way to tell given the information that the OP has provided.

 

[Richard Martin]

So here's the plan so far:

1) The OP has an amp, believed to be solid state.
2) He's not playing Wembley stadium.
3) .......
4) Profit!

Or Loss! depending on his actual situation.

 

[mmbongo]

I'm getting Deja Ju here....

4 ohm head into a 8 ohm cab