4x12s and low wattage amps Q

[006]

Something I wasn't aware of and/or have never run into really so I'm looking for some clarification. I went to the local music shop to pick up some strings and I noticed they had a Tiny Terror in the guitar room, as well as a Mesa oversized 4x12. The TT was hooked up to the matching 1x12 so I went to the guy at the counter and asked if I could hook the TT up to the Mesa cab since I have the same one at home. He said "you could but I wouldn't recommend it, it's only like 15 watts so you'd actually be doing some damage to the coils in the 4x12. You'd be better off with a 1x12 or a 2x12 max unless you want to replace speakers once a year if you will be using it heavily." Again, I've never heard of this. So I told him "alright, nvm then" and I bought the strings and left.

Can anybody confirm his statement or this bogus info? I've worked in car audio and that never came up and we had people getting like 300w amps to push speakers that were rated at 1,200w all the time. I've been thinking maybe he told me that because he thought I would buy the TT and believe him so I might buy a 2x12 or the matching Orange 1x12 that it was hooked up to. I have plans to get a TT in the future, after a Krank Rev Jr, and I will be using them both through my Mesa 4x12 for studio use... but if it's true that I will be jacking my speakers up then I will also look into a 2x12, maybe an iso cab or something along those lines.

~006

 

[Torniojaws]

In live audio PA systems, the power amp is always recommended to be a lot more powerful than the speakers' *capability (double or more). I think the same would apply to guitar amps. But then again, the difference between 100 W and a 10 W amps is only halved output (*), so it should not matter much at all. Orange even advertises the Tiny Terror with their 4x12" cabs.

 

[006]

See, I've always felt it was better to have a high powered amp and lower wattage speakers, like a 120w amp and a 60w speaker, and just don't turn the amp all the way up. This would deliver a cleaner signal with better headroom as well as drive the speaker nicely to get the breakup you wanted. I felt that was true with car audio as well, but people care more about speakers than the amps for some reason in cars most of the time. Which beats me because the amp will deliver a noisy pushed ass signal to those nice clean speakers but WHATEVER.

Ok so the general idea, though, is that it should be fine?

~006

 

[Wolfeman]

I have a 4x12 that I run my Epi Valve Jr. and my 5 watt homebrews thru..... Never caused me any issues....

 

[Metaltastic]

Yeah, at NAMM they were demo'ing the Tiny Terror through a 4x12 (not to mention in that famous video "can you play metal with a TT?" I call bullshit on that dude.

 

[colonel kurtz]

i'm calling bullshit also...the only way i could see the speakers being damaged is if the amp clips really hard, and hits the drivers with square sine waves, but i don't see that being as much of a problem with a guitar amp as say a power amp in a car or PA system

 

[MetalJonesy]

id have to agree with it being a load of crap, my krank rev jr works great through my 4x12. Anyway both orange and krank say that you can use these things to power 4x12s anyway!

 

[Razorjack]

I know for a fact that the guy is talking shit. Go back and explain to him that wattage works on a 10 base logarithm, so that 15 watt amp can pump out over half of what a 100 watt amp can (probably a little more actually, since it's class A).

I used to run a tiny terror into two Orange PPC412's as part of my display at the store and the guys from Orange never had a problem with it when they came to visit.

Of course, it is possible to undercook speaker coils but it's not a real problem unless you are (for example) running a PA system capable of handling 10,000 watts with a 100 watt solid state power amp being pushed to it's limits.

 

[viggen666]

total bullshit, this whole "underpowering speakers can be dangerous" thing doesn't apply to tube amps, you can run that TT on 10 all day thru that mesa cab and not have a single problem.

 

[Omega_Void]

the difference between 100 W and a 10 W amps is only halved power

wattage works on a 10 base logarithm, so that 15 watt amp can pump out over half of what a 100 watt amp can

No, guys!

10-watt amp is one tenth the power of a 100 watt amp - Wattage is a direct measurement of power.

10 times the wattage doubles the percieved loudness (all other things being equal).

Here's how it stacks up in dB:

Double power = gain of 3dB
Double signal (voltage) level = 6dB
Double perceived volume = 10dB SPL

 

[Omega_Void]

(probably a little more actually, since it's class A).

And what's that about? "Class A Watts" aren't any louder than "Class AB Watts". Poweramp Wattage is the RMS of a 400Hz sinewave into a resistive load when the peak is at the point of clipping - regardless of the amp topology!

Did you learn everything you know about guitar amps from a salesman?

 

[cobhc]

No, guys!

10-watt amp is one tenth the power of a 100 watt amp - Wattage is a direct measurement of power.

10 times the wattage doubles the percieved loudness (all other things being equal).

Here's how it stacks up in dB:

Double power = gain of 3dB
Double peak level = 6dB
Double perceived volume = 10dB

Edit: - I'm a n00b. Ignore me

 

[Wolfeman]

X% louder = 2^log10(P2/P1) * 100%

 

[Metaltastic]

Paging JBroll...not to say some of you guys aren't right, but so he can confirm it with his characteristic ownage...

 

[AdamWathan]

I hope you're taking the piss! Or else delivering a late April Fool. Everywhere you will read up on this, you will see that a 10W amp is half the volume of a 100W amp. It's not just simple maths here. It is as Razorjack mentioned logarithmic.

Also Class A amps can sound louder, because they amplify both the peaks and the dips in the signal, where as a Class B amp for example only amplifies the peaks or the dips, never both simultaneously. Whether this is a significant change is debateable, but it certainly has the potential to be louder.

No he's right. You aren't reading his post carefully enough. 50 watts is half the power of 100 watts. But just because it's half the power doesn't mean it's half the volume. Loudness is based on a logarithmic scale, power isn't.

100 watts is twice as loud as 10 watts yes, but 100 watts is ten times the power of 10 watts.

This is just me regurgitating what Omega Void already said, so read it over again... He definitely knows his shit...

 

[cobhc]

Sorry, you are correct. I just assumed we were talking about volume here, not raw wattage. Sorry Omega, didn't mean to sound harsh with that post anyway, I was in a bad mood.

I feel like a twat now, but being put in your place once in a while, and being made to feel small, is surely good character building, right?

 

[Omega_Void]

Also Class A amps can sound louder, because they amplify both the peaks and the dips in the signal, where as a Class B amp for example only amplifies the peaks or the dips, never both simultaneously. Whether this is a significant change is debateable, but it certainly has the potential to be louder.

Class A amps don't amplify "peaks and dips" simultaneously - that would require both a positive and a negative voltage to exist simultaeously in the input signal, which ain't possible.

If one amp sounds louder than another of the same wattage this could be because:

- Greater harmonic distortion causing the tone to be thicker...
- More overdrive used (since the Wattage is merely a measurement of how high peaks can be without clipping, more overdrive gives higher RMS)...
- Greater output impedance causing bigger peaks in the response at the speaker's resonant frequency (bass) and in the high range as the inductance of the voice coil becomes more significant than its resistance....
- High presence knob setting...
- more high frequency in the input signal (since perceived loudness increases with frequency)...

The list goes on. Class of operation is, however, one thing which is not relevant!

Oh, and note that Wattage rating is independant of the amp's gain - one 50W amp could well put out more Wattage than another with both amps' level on 6. All that would mean is it will clip sooner.

 

[Omega_Void]

I feel like a twat now, but being put in your place once in a while, and being made to feel small, is surely good character building, right?

Nope, it happens to me all the time and I'm still a cunt.

 

[Razorjack]

And what's that about? "Class A Watts" aren't any louder than "Class AB Watts". Poweramp Wattage is the RMS of a 400Hz sinewave into a resistive load when the peak is at the point of clipping - regardless of the amp topology!

Did you learn everything you know about guitar amps from a salesman?

I WAS a salesman, does that invalidate my knowledge or the BSc in Acoustics that I have?

Just to clarify, I was talking about perceived volume and not power (I know, the term "pumps out" is rather vague).

The Class A comment comes from the trend for some small wattage Class A amps, especially those based on el84's, to be designed to clip early and have a lot of harmonic distortion. Both of which, as you yourself stated, contribute to higher output (be that perceived or power).

 

[Morgan138]

The idea that "underpowering" speakers can damage them is a total myth; if it were true you'd be damaging your cab everytime you switched channels to play a quiet guitar part.

What IS bad for speakers is running cranked solid state power amps into them, even if the amps aren't powerful enough to blow the speakers. This is because when SS poweramps distort they produce square wave distortion, and square wave distortion can damage speakers even at low power levels.

So I'm guessing the myth came about because people would buy speakers that were the right wattage for their needs, and then run smaller power amps that wouldn't get loud enough without distorting. Like if the car people at your job were buying 300 watt amps and 1,200 watt speakers but expecting to get 1,200 watts' worth of volume out of the rig instead of 300, maybe?