Are power ratings BS?

[plf]

Hey, all,

So here’s my situation. I had to leave my rig at my folks’ house after a move from Philadelphia to Idaho, and I’m looking to get an amp. Before, I had a Peavey TKO 75 from (guessing here) the 80’s or early 90’s. I also had a rig involving a newer 210 Rumble cab and a Markbass Big Bang (500W, 350 of which ran into the Rumble cab).

Here’s the quandary. These rigs had NO noticeable difference in volume, despite a 4x or more difference in wattage. I’ve played a number of rigs in my search, and the Peavey seems to be as loud as all of the fancy X00 watt heads I try. What’s the deal here? Are transistor watts louder than class D watts? Is the Peavey speaker that much more efficient? Is it the horrific weight of the Peavey that makes it louder? I’m trying to figure out what to get, but I’m starting to feel like wattage ratings are meaningless.

 

[Killed_by_Death]

Class D heads also use transistors.

 

[yberwaffe]

The effiency of the speakers makes a big difference.
Try the amps with the same cabinet.

 

[agedhorse]

Good question with several answers that are contributing to what you are hearing. I am going to describe them in a list format because this subject comes up a lot and I get a number of PMs asking for more information, especially about WHY.

1. In general, power is power and when it's specified in the same units (ie. watts "RMS" which is the same as watts based on RMS voltage x RMS current), there's no difference. That said, there are some manufacturers that use different units, or do not specify the units, which can lead to great confusion. For clarification, there is also a unit of measurement in amplifiers called "peak power" which should be specified as watts (peak), which is generally 2x the RMS rated power. There is also a 20msec burst power which can vary by as much as 50% over the "continuous RMS" power. Combine the two and you can end up with peak burst power being as much as 4x the continuous RMS power. Continuous for the purpose of a bass guitar would be for a period of seconds rather than thousandths of a second.

2. Speakers in older combos and cabinets were much more often specified with less low frequency extension which allowed them to be higher sensitivity. Also, since they didn't have to handle as much power, the voice coil winding height didn't have to have as much overhang which also increased sensitivity. This certainly can explain a large amount of what you are experiencing, but at a significant sacrifice to the deeper low end extension and higher power handling that today's player seeks.

3. By limiting an amplifier's low frequency extension, this too can increase the effective efficiency. With many of the older, lower powered amps, the low frequency started rolling off between 40 and 70Hz which is not a bad compromise when you have limited power, and matches well with the typical speakers of the day. Since a bass guitar's lowest notes are more harmonics than fundamental, it's a passable compromise.

4. Today's (better quality) amps have much better low frequency extension, which takes more power to execute. Today's speakers also have better low frequency extension, which sounds "better" and more full, rich, round (insert adjective here) but this comes at a sacrifice to efficiency too.

So, yes, what you are experiencing makes sense, and this is WHY it makes sense.

Hope this helps

 

[el jeffe bass]

Thank you @agedhorse for a clear, concise explanation.

 

[Oren Hudson]

Part of it is makers ratings. One than once, some of them have been found to be incorrect. I learned a long time ago to not be as swayed by the statistics but rather, let my ears be the guide.

 

[plf]

@agedhorse that makes a lot of sense! it’s always been my impression that the older, less hi-fi/ full-frequency amps sound way louder at comparable wattage. The Markbass head mentioned above does have a lower bottom end, while the Peavey has a tighter/ more rolled off low bass.

So is there a more accurate way to measure this kind of stuff? dbs at a given frequency, maybe?

 

[plf]

@Oren Hudson Really? I guess I shouldn’t be surprised. Any idea who the worst offenders are, and whose reported power handling is more or less accurate?

 

[Foz]

correct... next question.

 

[Stumbo]

3. By limiting an amplifier's low frequency extension, this too can increase the effective efficiency. With many of the older, lower powered amps, the low frequency started rolling off between 40 and 70Hz which is not a bad compromise when you have limited power, and matches well with the typical speakers of the day. Since a bass guitar's lowest notes are more harmonics than fundamental, it's a passable compromise.

Is why a HPF helps out less powerful amps/cabs?

 

[agedhorse]

Accurate ways to measure, sure but not really practical as a DIY project.

Accurate, clear specs are helpful but a manufacturer's reputation is another way to gain confidence. Choose a manufacturer that has a solid reputation, you have quite a few to choose from.

 

[SteveCS]

Good question with several answers that are contributing to what you are hearing. I am going to describe them in a list format because this subject comes up a lot and I get a number of PMs asking for more information, especially about WHY.

1. In general, power is power and when it's specified in the same units (ie. watts "RMS" which is the same as watts based on RMS voltage x RMS current), there's no difference. That said, there are some manufacturers that use different units, or do not specify the units, which can lead to great confusion. For clarification, there is also a unit of measurement in amplifiers called "peak power" which should be specified as watts (peak), which is generally 2x the RMS rated power. There is also a 20msec burst power which can vary by as much as 50% over the "continuous RMS" power. Combine the two and you can end up with peak burst power being as much as 4x the continuous RMS power. Continuous for the purpose of a bass guitar would be for a period of seconds rather than thousandths of a second.

2. Speakers in older combos and cabinets were much more often specified with less low frequency extension which allowed them to be higher sensitivity. Also, since they didn't have to handle as much power, the voice coil winding height didn't have to have as much overhang which also increased sensitivity. This certainly can explain a large amount of what you are experiencing, but at a significant sacrifice to the deeper low end extension and higher power handling that today's player seeks.

3. By limiting an amplifier's low frequency extension, this too can increase the effective efficiency. With many of the older, lower powered amps, the low frequency started rolling off between 40 and 70Hz which is not a bad compromise when you have limited power, and matches well with the typical speakers of the day. Since a bass guitar's lowest notes are more harmonics than fundamental, it's a passable compromise.

4. Today's (better quality) amps have much better low frequency extension, which takes more power to execute. Today's speakers also have better low frequency extension, which sounds "better" and more full, rich, round (insert adjective here) but this comes at a sacrifice to efficiency too.

So, yes, what you are experiencing makes sense, and this is WHY it makes sense.

Hope this helps

More gold dust! My short-form takeaway is that the additional power is not translated into higher output 'volume' but is used to improve the quality of the sound - greater dynamic range, better low-frequency extension, faster clean transients and greater detail with lower distortion. At least that's what my ears tell me.

 

[Samatza]

In the early days basses were 4 string and amps and cabs were more in tune with guitars than basses.
These days I'm amazed at the low frequency extension and clarity that these smaller amps can provide and they weigh a lot less.
When I got my first combo amp it was a Washburn 60W with a single 15" speaker, it was respectably loud but as soon as I got my first 5 string I had to change the amp, it just didn't like those lower notes.
Those low frequencies chew up a lot of power so you need to understand that a lot of those additional watts go into the low frequency extension that newer amps are capable of reproducing.

 

[yberwaffe]

Don't forget that manufacturers sometime prints the power IN to the amp instead of OUT from the amp.
Less of a problem in case of the modern D-class amps as they are more efficient.

 

[AlexanderB]

Good question with several answers that are contributing to what you are hearing. I am going to describe them in a list format because this subject comes up a lot and I get a number of PMs asking for more information, especially about WHY.

1. In general, power is power and when it's specified in the same units (ie. watts "RMS" which is the same as watts based on RMS voltage x RMS current), there's no difference. That said, there are some manufacturers that use different units, or do not specify the units, which can lead to great confusion. For clarification, there is also a unit of measurement in amplifiers called "peak power" which should be specified as watts (peak), which is generally 2x the RMS rated power. There is also a 20msec burst power which can vary by as much as 50% over the "continuous RMS" power. Combine the two and you can end up with peak burst power being as much as 4x the continuous RMS power. Continuous for the purpose of a bass guitar would be for a period of seconds rather than thousandths of a second.

2. Speakers in older combos and cabinets were much more often specified with less low frequency extension which allowed them to be higher sensitivity. Also, since they didn't have to handle as much power, the voice coil winding height didn't have to have as much overhang which also increased sensitivity. This certainly can explain a large amount of what you are experiencing, but at a significant sacrifice to the deeper low end extension and higher power handling that today's player seeks.

3. By limiting an amplifier's low frequency extension, this too can increase the effective efficiency. With many of the older, lower powered amps, the low frequency started rolling off between 40 and 70Hz which is not a bad compromise when you have limited power, and matches well with the typical speakers of the day. Since a bass guitar's lowest notes are more harmonics than fundamental, it's a passable compromise.

4. Today's (better quality) amps have much better low frequency extension, which takes more power to execute. Today's speakers also have better low frequency extension, which sounds "better" and more full, rich, round (insert adjective here) but this comes at a sacrifice to efficiency too.

So, yes, what you are experiencing makes sense, and this is WHY it makes sense.

Hope this helps

In addition to the above technical/factual contributors, there is also a psycho acoustic dimension (actually fuelled by the technical shortcomings of older gear).
As "less accurate" (in this case the old amp) gear is used, the resulting distortion will make our ears perceive the sound as "louder", even though it may not MEASURE any louder.
A small transistor radio might be perceived as painfully loud, but the exact same level on a good hifi kit might be considered way too soft.

So, middy, honky, distorting, old Peavey gear (and I have heard some...) might seem "loud", but you will have to sacrifice a lot of the original signal to get there!

 

[yodedude2]

also bear in mind that volume knobs are not necessarily linear. this means that 'halfway up' on the volume could be 30% available gain on one amp, 50% available gain on another, and 90% available gain on a third.

 

[MaxSpinrun]

Thank you @agedhorse for a clear, concise explanation.

Yes thank you also @agedhorse for that excellent explanation! Very clear and to the point. Your explanations always help me get a better understanding of the TRUTH the real nuts and bolts of the matter being discussed.

 

[MaxSpinrun]

Accurate ways to measure, sure but not really practical as a DIY project.

Accurate, clear specs are helpful but a manufacturer's reputation is another way to gain confidence. Choose a manufacturer that has a solid reputation, you have quite a few to choose from.

Exactly! That is why I chose the Mesa D800+! Mesa has a great reputation for quality and service. This head is the most full featured amp out there IMHO.

 

[ardgedee]

Increasing wattage does less than you might think. In a system where only the amplifier is changed, four times the wattage will only contribute 6 dB more headroom. A change in speakers can have a greater perceived effect (for reasons agedhorse outlines above).

 

[lug]

Amps that seem louder actually have a volume control that goes to eleven but someone probably put the wrong knob on.