Full power into one speaker?

[StingRayBoy42]

Apologies if this is a stupid question or it's been asked before, or (most likely) both.

My amp gives 500W @ 4 ohms and 300W @ 8 ohms.

I have one 8 ohm speaker.

Is there a cheap and simple way to get the full 500W of power into my one 8 ohm speaker?

Is there such a thing as a 'fake' 8 ohm speaker that I can plug into the other speaker output?

I don't want to buy another cab, or solder anything. 

Cheers

[Skybone]

1 hour ago, StingRayBoy42 said:

Apologies if this is a stupid question or it's been asked before, or (most likely) both.

My amp gives 500W @ 4 ohms and 300W @ 8 ohms.

I have one 8 ohm speaker.

Is there a cheap and simple way to get the full 500W of power into my one 8 ohm speaker?

Is there such a thing as a 'fake' 8 ohm speaker that I can plug into the other speaker output?

I don't want to buy another cab, or solder anything. 

Cheers

 

To get the full 500w into the cab, you'll need a 4 ohm speaker, capable of handling 500w, which won't be cheap.

 

[chris_b]

The difference between an amp running at 4 ohm and at 8 ohm into 1 driver will probably be minimal. Add a second cab and the increase in SPL will be noticeable (because you are moving more air) and that will make your sound better.

[Sparky Mark]

Unless your single cab has more than two speakers it's likely that your amp's 300 watts is already capable of driving it to its maximum sound pressure level. Once that is achieved additional power is only going to be dissipated as heat. The wattage rating of your cab is a thermal rating and doesn't necessarily correlate directly to how loud it'll go.

As has been advised, if you want more volume, you need more speaker area.

[Bill Fitzmaurice]

4 hours ago, StingRayBoy42 said:

Is there a cheap and simple way to get the full 500W of power into my one 8 ohm speaker?

There's no point. Power and decibels output are only indirectly related.

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Is there such a thing as a 'fake' 8 ohm speaker that I can plug into the other speaker output?

It's called a power soak. Using one is akin to driving with your parking brake engaged so that you can get all the horsepower out of your engine. 🙄

[Sparky Mark]

25 minutes ago, Bill Fitzmaurice said:

It's called a power soak. Using one is akin to driving with your parking brake engaged so that you can get all the horsepower out of your engine. 🙄

Aren't these used when someone (guitarists mainly?) is wanting to get the power amp over-driven tone but at a lower volume?

Edited January 3, 2023 by Sparky Mark

[lownote]

Having pushed the same questions around with my nose in the past, my technical understanding from others is that the difference between 300 and 500 watts is not what it might like in raw numbers.  And from personal gigging experience this year I have found that number/ size of drivers is far far more important (as someone says above).  I variously ran a BF 4 ohm 2x10 and a Mark Bass  410 8ohm off my 500w head. The latter cab completely blew the former out of the water, especially outdoors. Just my tupenny worth.  

[BassmanPaul]

One inconveinient fact that bears on this subject is that to get twice as loud you'd have ti increase your output power by ten times!

 

Going from 300 to 500 Watts will be barely noticeable.

[Bill Fitzmaurice]

1 hour ago, Sparky Mark said:

Aren't these used when someone (guitarists mainly?) is wanting to get the power amp over-driven tone but at a lower volume?

Yes, with a valve amp, so that the output valves can be pushed into hard clipping while keeping the voltage to the speakers low so that they're not too loud and not overpowered. Tom Scholz sold one, and I believe Marshall did as well. Useful as that is on guitar it's not what I'd want to use with electric bass.

[Gwilym]

It's not really clear why you'd want to do this, even if you could. 

[StingRayBoy42]

5 minutes ago, Gwilym said:

It's not really clear why you'd want to do this, even if you could. 

Me stupid think more watt mean more loud  🤪


Thanks for all the replies, folks!

[Downunderwonder]

More watts make more loud until speaker until speaker say enough of this malarkey.

 

The power soak angle isn't applicable to a 500w solid state amp but there is a sort of corollary with some users of Genz Benz Streamliner amps.

 

It's possible to rewire 4 ohm load worth of parallel drivers to be 16 ohms instead. With a Streamliner driving hard into 16ohms it will do the hard driving tone with much less power coming out than normal.

 

Still no help to OP as the answer to the question is a simple hard no.

[Bill Fitzmaurice]

22 minutes ago, StingRayBoy42 said:

Me stupid think more watt mean more loud  🤪

Not your fault, industry fault. What makes speakers go louder is increasing the voltage output of the amp. Watts never should have been used to define amplifier output, or speaker capacity. But they were, and now we're stuck with it.

[DGBass]

I've been down this road experimenting on a one cab solution with a 4 ohm and 8 ohm version of the same driver, in the same cab, with the same (class AB) amp and the same bass plugged in. It did in my experience make a noticeable difference running at 4 ohms and the amplifier sounded more dynamic and more responsive at high volume. Whether the full power of the amp was ever achieved at any point I'll never know. I was able to back off the master yet still achieve the same percieved loudness with the 4 ohm as I did with the 8 ohm speaker and amp working a bit harder. At 8 ohms it was plenty loud, at 4 ohms it sounded like there was just more headroom to help get a cleaner and deeper tone, especially down on an open e-string.

I did the same thing with a class D amp I have to compare and in that situation there was negligble difference. At 4 ohms and up loud, the class-d amp sounded compressed and actually seemed happier working with an 8 ohm cab. Both amps were rated around 500 watts @ 4 ohms by their manufacturers, both also quite capable of gig volume easily with a single 8 ohm cab. As has also been mentioned, finding good high power 4 ohm drivers is a very expensive option. So, basically there is no simple or cheap way to utilise a potential gain running a single 4 ohm cab with your amp.  A second cab is probably the cheapest option tbh.      

[Bill Fitzmaurice]

9 minutes ago, DGBass said:

I've been down this road experimenting on a one cab solution with a 4 ohm and 8 ohm version of the same driver, in the same cab, with the same (class AB) amp and the same bass plugged in. It did in my experience make a noticeable difference running at 4 ohms      

It will, but it has nothing to do with power, everything to do with voltage. The amp puts out the same voltage into any load. (A good thing that is, because the actual impedance isn't a constant, it varies with frequency, so if this wasn't the case every frequency would be at a different level.) If all else other than impedance is equal, which it never is, with the same voltage applied the cone of the 4 ohm driver will move further than the cone of the 8 ohm driver. This results in a 3dB increase in output. There can be tone differences as well, because all else isn't equal, including but not limited to inductance and moving mass. As for the perceived increase in dynamics at high levels, that's also voltage related. An amp's dynamic response suffers when it's pushed close to its voltage output limit. Using a lower impedance driver gives more voltage headroom from the amp, which gives better dynamic response. This begs the question 'why not always use low impedance drivers?'. The answer is that the lower the impedance the higher the current draw, which can create its own set of problems. 

[BassmanPaul]

Didn't we go through all this before they kicked me off TalkBass? LOL

[paul_5]

Yes, and we probably will again. It's all part of life's rich tapestry.

 

I find stuff like this really interesting and educational though, especially when some of our better educated and more experienced posters dumb things down into lay terms; it's what keeps BC great.

 

 

[Bill Fitzmaurice]

28 minutes ago, BassmanPaul said:

Didn't we go through all this before they kicked me off TalkBass? LOL

I quit going there before they could kick me off. Maybe it's different now, but ten years ago it was one of the worst moderated forums I've ever come across.

Quote

especially when some of our better educated and more experienced posters dumb things down into lay terms;

IMO anything that can't be said in a paragraph using non-technical language is a waste of time for all involved. KISS isn't just the name of a band. 😉

[DGBass]

1 hour ago, Bill Fitzmaurice said:

It will, but it has nothing to do with power, everything to do with voltage. The amp puts out the same voltage into any load. (A good thing that is, because the actual impedance isn't a constant, it varies with frequency, so if this wasn't the case every frequency would be at a different level.) If all else other than impedance is equal, which it never is, with the same voltage applied the cone of the 4 ohm driver will move further than the cone of the 8 ohm driver. This results in a 3dB increase in output. There can be tone differences as well, because all else isn't equal, including but not limited to inductance and moving mass. As for the perceived increase in dynamics at high levels, that's also voltage related. An amp's dynamic response suffers when it's pushed close to its voltage output limit. Using a lower impedance driver gives more voltage headroom from the amp, which gives better dynamic response. This begs the question 'why not always use low impedance drivers?'. The answer is that the lower the impedance the higher the current draw, which can create its own set of problems. 

I was really just saying that there was a noticeable real world difference with my setups when running into a 4 ohm cab and I thought that may be of interest to the OP if they ever decide to get another cab or maybe even a single higher powered 4 ohm cab. I've been lucky enough to try about a dozen different amps mostly class AB types into the same cab at 4 or 8 ohms at some point over the years and they all felt much more responsive with the 4 ohm cab option. I would agree all sorts of variables will come into play depending on how an amplifier is used whether its a 4 ohm or 8 ohm load. I haven't blown a driver or an amp fuse or smoked anything so far( in the last ten years at least) using single speaker 4 ohm cabs or 8 ohm cabs and I'm using the amps within the manufacturers ( claimed ) limits/ specs. So I'm assuming the setups i've used can handle any vairiables or additional stresses running at 4 ohms may introduce comfortably.

 

[BassmanPaul]

In my mind it's a case of diminishing returns. You work your single driver way harder for not much increase in volume.  Compared with a second driver to share the load the difference is marginal. Two drivers trump a single driver every time and increases reliability!

[Bill Fitzmaurice]

He has a point. If one driver is sufficient to provide all you need, or ever expect to need, for output then 4 ohms has its advantages where the amp voltage headroom is concerned. But 4 ohm tens and twelves are rare, because 2x cabs are far more common, and manufacturers aren't going to make many 4 ohm drivers when most of the demand is for 8 ohms. The exception is fifteens, which are more commonly offered in 4 ohms because most fifteen users only need one.

[Stub Mandrel]

On 03/01/2023 at 17:05, Bill Fitzmaurice said:

There's no point. Power and decibels output are only indirectly related.

It's called a power soak. Using one is akin to driving with your parking brake engaged so that you can get all the horsepower out of your engine. 🙄

 

Even worse? Wouldn't 250W go into the dummy load leaving a reduced 250W for the speaker!

[Stub Mandrel]

1 hour ago, Bill Fitzmaurice said:

He has a point. If one driver is sufficient to provide all you need, or ever expect to need, for output then 4 ohms has its advantages where the amp voltage headroom is concerned. But 4 ohm tens and twelves are rare, because 2x cabs are far more common, and manufacturers aren't going to make many 4 ohm drivers when most of the demand is for 8 ohms. The exception is fifteens, which are more commonly offered in 4 ohms because most fifteen users only need one.

 

Indeed. But it was reflecting on some of your thoughts that made me choose a 4R 2x12. I knew that two 2x12 8R cabs would be twice as powerful, but also that a single 8R 2x12 would be half as powerful (more or less).

 

I had the sense to realise that if I was ever in the situation of needing two cabs then that would only be because there was a big pa which would make big backline redundant anyway.

 

The extra headroom/power offered by 4R wasn't really needed (or so I thought) but in practice has opened the door to a greater choice of options as I can use lower power amps.

 

I would also say speaker efficiency trumps everything. A quality speaker that has a good wide range response and is 8 to 10 dB more efficient will be louder and more flexible with more headroom than any practical increase in amp power. And probably mord reliable as you won't have to work it so hard.

[agedhorse]

Basic electrical engineering absolutely links voltage to power. Since (solid state) amps are generally considered an ideal voltage source, it’s also an ideal power source. 
 

While a speaker has a reactive component, when the capacitive and inductive regions are averaged out with the DCR of the speaker, the net result is an average or nominal impedance.
 

The amp must provide voltage x current to drive this load which is power. In the inductive regions the current lags voltage and in the capacitive regions the current leads voltage. 

 

Regardless of phase angle, the amp must be able to deliver both voltage and current, this is something an experienced power amplifier designer has to deal with.

 

A 500 watt, 4 ohm single driver compared to a 300 watt 8 ohm driver is likely to have a lower sensitivity, quite possibility 3dB lower, which would make the 8 ohm speaker (slightly) louder at 300 watts than the 4 ohm speaker at 500 watts.

[Chienmortbb]

Hoping not to get too teknikal, but it's hard not too.

 

In this case, the Class D amp was current limited. It simply could not supply the extra current required. The Class A/B amp had a more powerful power supply. It had nothing to do with amplifier class. If you put a 16 ohm speaker on both amps, both would probably not get loud enough for you as they would be voltage limited,