Under-powering cabs

[aus_bass]

Just thought I'd throw this one out there, and see what the general consensus is. I've heard many differing and often conflicting ideas on this topic, over the years. Do you see any issue in under-powering a cab ?

Example: Say I have Neo 212 cab, that's rated at 1000 watts RMS @ 4ohms, not "peak", "program" or "musical" watts, as often spun by marketers. Real continuous RMS watts.
Now say I match it with a class-D head, that does 300w @ 4ohms, or even 500w @ 4ohms. What's the downside ? Is there a downside ? Is it bad for the cab in some way ? Will the cab not perform optimally, unless it's driven hard ?

I see a lot of rigs, the other way round... a 500w head (or more) into a cab that's rated @ 300w RMS. Obviously, it just takes a little common sense, with the volume knob. I rarely see rigs where the cab capacity is significantly above the output of the amp.

What say ye ?

 

[gtirard]

Alex from Barefaced says "more cabs is easier on amps, not the reverse"

 

[el murdoque]

If you're after that sound a cab makes when it is strained, then you're on the wrong path.
Apart from that, I often play(ed) a barefaced stack that is rated for more than 1000 Watts with a H&K Tubemeister that puts out a whopping 5 Watts.

Neither amp nor cabs did mind so far and I dig the sound I'm getting.

There is that theory that when you clip a SS power amp by driving it too hard, the resulting square waves can damage your tweeter.

 

[Samatza]

Running an amp flat out into a speaker that has a higher wattage rating is generally not a good idea. The amp continuously clipping can still damage the speaker.

I use a 700W amp with either one or two 300W cabs. Of course with 1 cab @ 8 ohms the amp may be putting out 450 W but I don’t run it hard at all. If more volume is required I simply add the second cab.

Use your ears is the rule and always try to have headroom in the amp so it’s not clipping.

I’ve run cabs as low as 150W with that amp in low volume settings and it has worked fine but I am careful and realistic about what these ratings mean and what the limitations are.

 

[JimChjones]

Oh grief, how on earth does one stamp on this myth? Basically its nonsense. I have driven my PA speakers with a 1W Blackstar combo*, and although it was easy to get into unlistenable distortion there was not the slightest risk to the drivers. Its pretty much a dead cert that anyone talking about square waves in this context doesn't have a thorough understanding of the topic.

There is a tiny caveat that if you drive an amplifier into very high levels of distortion it can generate enough high frequency content to damage tweeters, but even then the lower the speaker rating the more likely they are to be damaged.

Ask yourself this. If you have a 300W amp and drive it into high levels of distortion, is it more likely to damage the HF drivers in a 30W cab, a 300W cab or a 3,000W cab?

*the only amp I had that would run with the battery pack I had!

 

[Samatza]

When it comes to tiny wattages you’re probably safe, but a 50W amp running flat out can kill a 100W speaker.

I’ve seen this happen over the years and had quite a few on my work bench but today modern amps have limiters and won’t clip , they just squash the signal protecting themselves and the speakers.

 

[two fingers]

Not an issue. It was the conventional wisdom back in the 80s for some reason. I would love to know who started it.

I actually did quite a few gigs running an 1,100W RMS Epifani UL410 with a THIRTY watt Ashdown LB30. I pushed the amp on purpose because I liked the tone. No problems whatsoever. In fact, it got stupid loud.

 

[bassdude51]

Don't know exactly where to chime in. Loudness is based on a speak cab's efficiency rating. A cab with 91 db @ one watt one meter. A cab with 101 db one watt one meter. The 101 is going to be 10 times louder than the 91.

So the 1,000 watt RMS cab's loudness depends on it rating at one watt, one meter.

Of course it doesn't hurt anything to "under power" a cab as you call it.

And by the way, a small watt amp can blow out a high rated cab. So, take a 300 watt amp, turn it up to "11", go "wham city" on your bass and you WILL BLOW OUT your cab. As an amp is over ran, it can put out full current and fry speakers.

I'm sure someone will clarify what I'm trying to say here.

For loudness, you want efficient bass cabs. Anything over 99 db, one watt one meter will be max loudness with minimal power.

(There are trade-offs with low efficient cabs vs high efficient cabs. One is louder but the other has better sound.........generalizing and not always the case.)

For example, every increase of 10 dB on the decibel scale is equal to a 10-fold increase in sound pressure level (SPL). Near silence is expressed as 0 dB but a sound measured at 10 dB is actually 10 times louder

 

[Nebadon2000]

Not an issue. It was the conventional wisdom back in the 80s for some reason. I would love to know who started it.

I actually did quite a few gigs running an 1,100W RMS Epifani UL410 with a THIRTY watt Ashdown LB30. I pushed the amp on purpose because I liked the tone. No problems whatsoever. In fact, it got stupid loud.

I am not disputing your claim but distortion aggravates ears more quickly than clean power so as to perceive it is loud and a need to turn down even in actuality it is low in decibels; where as clean power may be much higher in Decibels and not sound to loud but comfortable. Hence how a 3watt AM radio in Car can sound loud, Distortion Pedals that give off loud distorted sound at low volumes for smaller places, Etc.

 

[lomo]

The idea that under powering a cab is a terrible thing is an urban myth. That doesn’t mean that somewhere along the line people haven’t blown a cab with an amp rated below the cab’s maximum capacity. A 500 W cab can be blown with a 200 W head or a 1000 W head., but it’s far more likely to happen with the more powerful lamp.

 

[JimChjones]

but a 50W amp running flat out can kill a 100W speaker.

But not nearly as quickly or easily as it will kill a 50w speaker.

 

[Samatza]

But not nearly as quickly or easily as it will kill a 50w speaker.

Oh, yeah, I agree.

What I'm trying to say I guess, is that in some cases the amp/speaker combo is too small for the task at hand so it's run at it's limits. It's far better to have enough power in both to give you adequate headroom so you don't need to push it too hard.

The rest is up to your ears because you can EQ boost a lot of low frequencies so you can get to the limits a lot quicker.

 

[two fingers]

I am not disputing your claim but distortion aggravates ears more quickly than clean power so as to perceive it is loud and a need to turn down even in actuality it is low in decibels; where as clean power may be much higher in Decibels and not sound to loud but comfortable. Hence how a 3watt AM radio in Car can sound loud, Distortion Pedals that give off loud distorted sound at low volumes for smaller places, Etc.

1) O know the difference between clean and distorted tones. I've been doing this for over 35 years... including some sound guy duties.

2) Nothing you saod has anything to do with damaging speakers by "under powering" them....which was the topic at hand.

 

[dbase]

Ive seen where my guitar player played thru my Ampeg B15 bass amp and blow out the speaker. Higher voltages can burn out the voice coil.

 

[Samatza]

I think reading through this again that the OP is really asking why you don’t see lower powered heads with much higher powered speaker.

This rather than running a smaller head flat out. I guess the reason then is more of practicality. I use a 700W head with a 300W speaker for small gigs but if I need more volume I add more speakers.

So mostly if you say would run a 200W head at normal levels but plugged it into an 800W speaker you’d be fine.

I suppose the second reason is economics. If I buy a lower powered amp I probably wouldn’t buy a more expensive, higher powered speaker to use it with.

 

[lowendrv]

AMPS FAQ!! Info on OHMS, Allsize RIGS-OverUnderPowerCabs DIY TechTalk-Links

 

[Mushroo]

All amps drop to 0 watts when you stop playing.

If your theory were correct then our cabs would explode every time there is a rest in the music!

So (obviously) it is a totally false assumption.

 

[chadds]

All amps drop to 0 watts when you stop playing.

If your theory were correct then our cabs would explode every time there is a rest in the music!

So (obviously) it is a totally false assumption.

Wait that would be thrilling!

 

[Tommy Sparks]

No issues at all under powering a cab.
I do it every time I play and you probably do too. If you were powering the cab to 100% of the watt rating it probably won’t last that long.

 

[JeezyMcNuggles]

Just thought I'd throw this one out there, and see what the general consensus is. I've heard many differing and often conflicting ideas on this topic, over the years. Do you see any issue in under-powering a cab ?

Example: Say I have Neo 212 cab, that's rated at 1000 watts RMS @ 4ohms, not "peak", "program" or "musical" watts, as often spun by marketers. Real continuous RMS watts.
Now say I match it with a class-D head, that does 300w @ 4ohms, or even 500w @ 4ohms. What's the downside ? Is there a downside ? Is it bad for the cab in some way ? Will the cab not perform optimally, unless it's driven hard ?

I see a lot of rigs, the other way round... a 500w head (or more) into a cab that's rated @ 300w RMS. Obviously, it just takes a little common sense, with the volume knob. I rarely see rigs where the cab capacity is significantly above the output of the amp.

What say ye ?

You could power that cab with this

Speakers don't give power, they take it.