Are power ratings BS?

[ezstep]

... 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.

I have NEVER heard of this in my life. (And I am old!) You keep teaching me new tricks - leave an old dog alone. Seriously, can you explain a little?

 

[Mike Marshall]

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.

This will offend many here but hearing is believing. I have tried numerous class D heads that boast 800 watts and have found them unsuitable for me because of lack of headroom. Recently I tried a 800 watt class D and found that it had less usable volume than my 1961 Bassman head rated at 50 watts. I had read numerous forums about this head and people were talking about it's power favorably. I did not experience what they spoke about. The class D was very weak at 8 OHM's it would have to be run at 4 it would be lacking playing outside to large crowds. I have noticed both Demeter and Jule have amps rated at 1600 or more is this because the 800 really doesn't cut it?

 

[AlexanderB]

I have NEVER heard of this in my life. (And I am old!) You keep teaching me new tricks - leave an old dog alone. Seriously, can you explain a little?

That is well known in some circuits (no pun intended!) and goes back to Newton laws...
If the same amount of force (the output from the amp) is applied in a voice coil that has a larger part of its length INSIDE the magnet gap, the resulting output will be larger.

So a long VC will have a higher potential max volume (SPL) than a shorter VC, but at the expense of lower sensitivity. (All else being equal).

A high frequency driver has virtually zero Xmax, and very high sensitivity (105 dB or more), where a true subwoofer might have 100 times higher xmax (like 12mm) and 100 times (-20 dB) lower sensitivity.

Again, not quite apples to apples, but the principle is the same...

 

[yberwaffe]

This will offend many here but hearing is believing. I have tried numerous class D heads that boast 800 watts and have found them unsuitable for me because of lack of headroom. Recently I tried a 800 watt class D and found that it had less usable volume than my 1961 Bassman head rated at 50 watts. I had read numerous forums about this head and people were talking about it's power favorably. I did not experience what they spoke about. The class D was very weak at 8 OHM's it would have to be run at 4 it would be lacking playing outside to large crowds. I have noticed both Demeter and Jule have amps rated at 1600 or more is this because the 800 really doesn't cut it?

Hipster bass player detected ;-)
What amp was the one you refered to ?

 

[agedhorse]

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.

Any amp that is certified to international safety standards must have either the current or power consumption listed on the back based on the minimum of 1/8-rated audio power or sometimes greater if the amp is marketed under that condition.

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.

This is a good point that I forgot to mention.

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).

This is also a good point that I did not mention.

 

[Coolhandjjl]

...Are transistor watts louder than class D watts?...

Here's an overly simplistic explanation of how amplification works: Nothing is really amplified per se. That would violate the first law law of thermodynamics. An amp is plugged into the wall outlet- that's where all the power comes from. It's not invented out of clean air. The device that allows us to use a tiny amount of power (your instrument) to control a larger amount of power (from the wall outlet) has to be either a tube or a transistor.

 

[Nevada Pete]

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.

It was until Mesa released their WD800. Any of the D800 series Mesa bass heads will get the job done. In an exemplary manner.

 

[dBChad]

Wattage rating is deceptive at best in predicting how loud an amp will be. In the close cousin community of skinny, close-together strings (guitars), players often balk in amazement on how a Vox AC30 and a Mesa Triple Rectifier can 1. both be on stage together and each be heard clearly, and 2. be loud beyond the physical threshold of pain. There are several reasons why this happens, and most of this will be true for your two amps as well.

1. Power ratings for both amps are rounded averages. Imperial measurement would show around 44w RMS for a Vox and 144w RMS for the Mesa.

2. A multiple of watts does not equal the same multiple in sound pressure level (144w is not going to be close to 3x as loud as a 44w amp. Actual measured difference in volume will be marginal). Ceteris paribus, to double sound pressure level requires 10x the output power.

3. Amp/speaker combinations tuned where average human hearing is more sensitive will be perceived as being louder at less power ratings than frequencies outside this range. In my Vox/Mesa example, the Vox is tuned brighter while the Mesa is tuned darker (generally speaking). This puts the Vox closer the more sensitive frequency range, and also clears room in the mix for each other.

In my experience, adding speaker volume (more drivers) is a better way to add perceptible volume than adding watts. Voice coils need to move further to reproduce low frequencies, which is where power becomes an advantage, but power needs to be increased in orders of magnitude to add significant volume.

Hope that helps

 

[Mike Marshall]

Hipster bass player detected ;-)
What amp was the one you refered to ?

I do not want to name the Amp I tried because it is my experience alone and my needs may be totally different than another persons needs. Also the manufacture is a company I respect who has made some fine products.

 

[KevInDaBassment]

2. A multiple of watts does not equal the same multiple in sound pressure level (144w is not going to be close to 3x as loud as a 44w amp. Actual measured difference in volume will be marginal). Ceteris paribus, to double sound pressure level requires 10x the output power.

In my experience, adding speaker volume (more drivers) is a better way to add perceptible volume than adding watts. Voice coils need to move further to reproduce low frequencies, which is where power becomes an advantage, but power needs to be increased in orders of magnitude to add significant volume.

All good points, but those two are VERY big points in the OPs question...really wish someone would have sat me down and explained that to me when I was starting off on bass guitar. I'd also add that more speakers as opposed to just larger speakers also makes a substantial difference.

 

[seamonkey]

There are No standards for musical instrument amplifier power ratings.
It's unfortunate that at least a few major manufacturers don't get together and do some voluntary standards but it hasn't happened yet.
Government intervention isn't going to happen in the US, but maybe Europe will step in as they have done for even automotive audio standards. We'll see.

 

[StatesideRambler]

Then there’s the tidbit about the sensitivity of the human ear varying with frequency. 500W driving a 1000 Hz or 300 Hz tone will seem a lot louder than the same 500W driving a 60 Hz or 80 Hz signal.

 

[Stumbo]

I do not want to name the Amp I tried because it is my experience alone and my needs may be totally different than another persons needs. Also the manufacture is a company I respect who has made some fine products.

Until you name the manufacturer, it's all gossip.

 

[plf]

@Mike Marshall I’m glad I’m not the only one who has noticed that... A lot of the class D amps I’ve tried (specifically thinking of a friend’s Ampeg PF500 I used to rehearse with, the aforementioned Markbass, various others) sound pretty, but not that loud. Hm, I may be talking myself into an indestructible old Peavey...

 

[beans-on-toast]

When it comes to wattage, every manufacturer has their own version of the truth.

Do you report wattage over a frequency range with less then a certain specified THD. Do all your production amps meet this spec. Do you report wattage at a level with more dirt in it, but still useful for a musician. Does the marketing department dictate what the specifications are after the product is designed.

 

[yberwaffe]

For Hi-Fi amps they usually measure at 1kHz and allows for a ceartin, but specified, amount of distortion.
I have no idea how thay rate bass/guitar amp, but I suspect they are using a hefty amount of poetic freedom.

 

[agedhorse]

For Hi-Fi amps they usually measure at 1kHz and allows for a ceartin, but specified, amount of distortion.
I have no idea how thay rate bass/guitar amp, but I suspect they are using a hefty amount of poetic freedom.

Some manufacturers clearly describe their power rating conditions if you know what to look for and what they mean.

 

[beans-on-toast]

I would hope that you could compare product specs of amps from the same manufacturer.

Look at specs as a general guideline. Is it a loud amp, a really loud amp, or a really really loud amp. The tone that best appeals to you isn’t on a spec sheet. That you have to hear.

 

[gazzatriumph]

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

I was going to say the exactly the same thing

 

[NoSlapForYou]

I was thinking about this the other day as I was playing a 1000-watt solid state Ampeg and noticing that it wasn't as loud as a V-4B (100 watts) I had played a few weeks earlier. I was wondering if something was wrong with the solid state amp or it was that I was using a different cabinet.