When is a Watt, not a Watt

[4-string-thing]

[quote name='Bill Fitzmaurice' timestamp='1446302135' post='2898466']
The volume control acts like a water valve. One may configure a valve to be fully open with 1/4 turn, 1/2 turn. 3/4 turn or for that matter with ten turns.
[/quote]

Understood, maybe he should have used this analogy in Spinal Tap?

Any explanation why my 575w Ashdown Head is (seems) no louder than my 125w Acoustic head through the same cab?

[Bill Fitzmaurice]

[quote name='4-string-thing' timestamp='1446306541' post='2898501']
Any explanation why my 575w Ashdown Head is (seems) no louder than my 125w Acoustic head through the same cab?
[/quote]To sound twice as loud as 125w you'd need 1250w. There's also the matter of maximum driver excursion. Once that's reached more power applied won't make it louder, it will only add distortion. If your cab is loaded with 40 year old drivers chances are they run out of excursion around 40-50 watts each.

[4-string-thing]

[quote name='Bill Fitzmaurice' timestamp='1446308539' post='2898515']
To sound twice as loud as 125w you'd need 1250w. There's also the matter of maximum driver excursion. Once that's reached more power applied won't make it louder, it will only add distortion. If your cab is loaded with 40 year old drivers chances are they run out of excursion around 40-50 watts each.
[/quote]

I understand that Bill, I know that to get double the loudness, you need x10 the wattage. What I don't understand is why x4 the power makes no noticable difference. At the time I was doing the A/B comparison, I had replaced the original units with 300w Eminence drivers as I didn't want to risk the originals with the higher output from the Ashdown.

[Phil Starr]

[quote name='4-string-thing' timestamp='1446291071' post='2898357'] I find this quite fascinating, my old Acoustic 220 is only rated at 180w at 2 ohms and only 125 through my 4ohm 2x15 cab. Yet, it as "loud" as my (modern) 575w Ashdown head through the same cab. The cab, which is also a 40 year old Acoustic 402 has a label on the back warning that sound levels may exceed 120 decibels. 120 db from a 125w amp..... Maybe thats just marketing hype too? All I know is, that amp has always been loud enough to cope with most bands I've ever been in (except one who were just ridiculous when it came to levels) And that it got no louder after about 3 on the volume pot! With regard to Phils comments about lumens per watt etc, when I worked for an electrical wholesaler selling LED lamps, people always thought cool white lamps were brighter than warm white, despite the same output. They may "look" brighter, in the same way that some amps may "sound" louder despite the wattages being the same? [/quote]

There's a bit of truth in the cool white/warm white analogy. It may explain some of the perceived differences between your amps. Our ears are much more sensitive to mid-range frequencies than extreme bass or treble, they are after all the human voice frequencies. The difference can be more than 12db. I don't know the acoustic amp but I used to have a MAG 600 and it was far from flat with the mids pulled back, even with the controls set for level. If the Acoustic was more mid prominent it would sound louder.

If anyone is interested try this. http://plasticity.szynalski.com/tone-generator.htm

Use headphones and turn the volume down. You have been warned!! Change the frequency to 2000Hz and turn the volume up so you can hear the tone. Drag the frequency down to 40Hz which is around bottom E and it will get quieter, maybe so quiet you can't hear it any more. The volume hasn't changed it's your ears that aren't working as well with the bass.

[Bill Fitzmaurice]

[quote name='4-string-thing' timestamp='1446309701' post='2898522']
What I don't understand is why x4 the power makes no noticable difference.
[/quote]Just because the Ashdown claims 4x more power that doesn't mean you were getting it. You'd only know for sure by measuring the output voltage of the two.

[Mykesbass]

[quote name='Phil Starr' timestamp='1446315882' post='2898569']
There's a bit of truth in the cool white/warm white analogy. It may explain some of the perceived differences between your amps. Our ears are much more sensitive to mid-range frequencies than extreme bass or treble, they are after all the human voice frequencies. The difference can be more than 12db. I don't know the acoustic amp but I used to have a MAG 600 and it was far from flat with the mids pulled back, even with the controls set for level. If the Acoustic was more mid prominent it would sound louder.

If anyone is interested try this. [url="http://plasticity.szynalski.com/tone-generator.htm"]http://plasticity.sz...e-generator.htm[/url]

Use headphones and turn the volume down. You have been warned!! Change the frequency to 2000Hz and turn the volume up so you can hear the tone. Drag the frequency down to 40Hz which is around bottom E and it will get quieter, maybe so quiet you can't hear it any more. The volume hasn't changed it's your ears that aren't working as well with the bass.
[/quote]

Just tried that link, but it seems to go against your third sentence, as I found around 7000 Hz by far the loudest. almost painful at a volume where the mid range sounded pretty quiet.

[Chienmortbb]

[quote name='Mykesbass' timestamp='1446326126' post='2898649']
Just tried that link, but it seems to go against your third sentence, as I found around 7000 Hz by far the loudest. almost painful at a volume where the mid range sounded pretty quiet.
[/quote]What phones were you using?

Edited October 31, 2015 by Chienmortbb

[Phil Starr]

[quote name='Mykesbass' timestamp='1446326126' post='2898649']
Just tried that link, but it seems to go against your third sentence, as I found around 7000 Hz by far the loudest. almost painful at a volume where the mid range sounded pretty quiet.
[/quote]

7000 isn't really between 2000 and 40Hz I trust if you continue going up the sound level fades out again above 10,000Hz. this is also age dependant and to a certain extent an individual thing but here are the curves averaged out for the population. https://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves

[Mykesbass]

[quote name='Chienmortbb' timestamp='1446328427' post='2898662']
What phones were you using?
[/quote]

Just some Sennheiser in ears.

[Mykesbass]

[quote name='Phil Starr' timestamp='1446329015' post='2898666']
7000 isn't really between 2000 and 40Hz I trust if you continue going up the sound level fades out again above 10,000Hz. this is also age dependant and to a certain extent an individual thing but here are the curves averaged out for the population. [url="https://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves"]https://en.wikipedia...93Munson_curves[/url]
[/quote]

Yes, taken, and I'm only asking as I find this very interesting. Yes, over 7000 it does start to fade, but my point was, contrary to your statement, that treble seems louder than mid to me. Between 2000 and say 300 there was no real noticeable difference, but over 2000 up to 7000 it seemed to increase substantially.

[Chienmortbb]

The OP asked when is a WATt not a WATt. Try this:

What is a Watt
In terms of DC direct current then the measurement of one watt is easy.

One watt is 1 Volt across 1 Ohm.

For AC one watt is 1 Volt RMS across 1 Ohm.

Why 1 Volt RMS?

Heat!

To get the same amount of energy in the form of heat, into a 1 Ohm resistor as 1 V DC you need 1 Volt RMS.

So how does this affect my amp?

Well for years amplifiers were measured in terms of watts RMS. Now this is slightly wrong as there is no such thing as a watt RMS. It is a Watt or at least the equivalent of a watt.

So our 1 watt is fixed, no quibbles! 1 Watt is one watt. What idiot told the marketing department about peak and peak to peak.

If we look at the peak voltage at 1 watt we get 1.414V peak.

Using Ohms law, I = V/R where I is current in Amperes and R is resistance in Ohms.
Note! There is no such thing as Amperage or Ohmage!


Now we have a voltage of 1.414 Volts and a current of 1.414 Amps. (short form of Amperes) and as Power = Volts X Amperes then our peak power is 2 watts.

If you take peak to peak values, the power would be 8 watts,

Transfer that to an amplifier and marketing might call a 500 Watt amp 1000 or 4000 Watts. If you think this is exaggerated. The Burgera Veyron thread should put you right. Of course it is not as simple as that but that is another story.

Edited October 31, 2015 by Chienmortbb

[xgsjx]

[quote name='Chienmortbb' timestamp='1446330522' post='2898681']
...
Note! There is no such thing as Ohmage!
[/quote]
Now that's not quite true...

It's just spelt differently & means something completely different.

[spoiler]Homage[/spoiler]

[Phil Starr]

[quote name='Mykesbass' timestamp='1446329591' post='2898670']
Yes, taken, and I'm only asking as I find this very interesting. Yes, over 7000 it does start to fade, but my point was, contrary to your statement, that treble seems louder than mid to me. Between 2000 and say 300 there was no real noticeable difference, but over 2000 up to 7000 it seemed to increase substantially.
[/quote]
there isn't really a definition of bass/middle/treble in truth. For most people the peak in hearing sensitivity is 3-4,000Hz as you see on the curves I linked to. If you are using the sort of Sennheiser in ears I use with my iPod then there are some very sharp resonances that you may be hearing, at the computer I use some fairly pricey Sennheiser HD595's.

Funnily enough I was wondering if I ought to pm you to check for hearing loss problems but then thought 'he's using in-ears' I used to do this frequency test with students when I taught physics, and in those days my hearing followed the equal loudness curves curves in textbook fashion. Now there are all sorts of lumps and bumps in my hearing with age related hearing loss.

Edited November 1, 2015 by Phil Starr

[Merton]

Speaking of frequency-related hearing loss I tried that little slider and can hear nothing below about 35 Hz and nothing above 12kHz. I swear I did a similar test last year and still got to around 15 kHz, maybe my memory is also going :/

[Chienmortbb]

[quote name='Merton' timestamp='1446374376' post='2898808']
Speaking of frequency-related hearing loss I tried that little slider and can hear nothing below about 35 Hz and nothing above 12kHz. I swear I did a similar test last year and still got to around 15 kHz, maybe my memory is also going :/
[/quote]You are lucky mine cars out at 10KHz

[Marvin]

Mine drops away at 8khz with nothing after about 13.5khz

[Chienmortbb]

[quote name='xgsjx' timestamp='1446341314' post='2898722']
Now that's not quite true...

It's just spelt differently & means something completely different.

[spoiler]Homage[/spoiler]
[/quote]I give homage to you. Are you Wictionary in disguise?

[deepbass5]

This is basically how we hear, which is why we often dial in a to even things out, and need bigger amps than guitarists

Edited November 1, 2015 by deepbass5

[Phil Starr]

Ma[quote name='Merton' timestamp='1446374376' post='2898808']
Speaking of frequency-related hearing loss I tried that little slider and can hear nothing below about 35 Hz and nothing above 12kHz. I swear I did a similar test last year and still got to around 15 kHz, maybe my memory is also going :/
[/quote]
[quote name='Chienmortbb' timestamp='1446378282' post='2898852']
You are lucky mine cars out at 10KHz
[/quote]
[quote name='Marvin' timestamp='1446388222' post='2898960']
Mine drops away at 8khz with nothing after about 13.5khz
[/quote]

Makes me feel better about my hearing Seriously though it might be the gear you are using, Proper over ear headphones are usually quite good but computer speakers or in-ears not so much.

I use this test at least once a year http://www.actiononhearingloss.org.uk/your-hearing/look-after-your-hearing/check-your-hearing/take-the-check.aspx it does test your ears but there could be problems with the auditory nerves which won't show up in this test.

Should wear ear defenders really but it is so hard to mix with them in.

[Mykesbass]

[quote name='Phil Starr' timestamp='1446374152' post='2898805']
there isn't really a definition of bass/middle/treble in truth. For most people the peak in hearing sensitivity is 3-4,000Hz as you see on the curves I linked to. If you are using the sort of Sennheiser in ears I use with my iPod then there are some very sharp resonances that you may be hearing, at the computer I use some fairly pricey Sennheiser HD595's.

Funnily enough I was wondering if I ought to pm you to check for hearing loss problems but then thought 'he's using in-ears' I used to do this frequency test with students when I taught physics, and in those days my hearing followed the equal loudness curves curves in textbook fashion. Now there are all sorts of lumps and bumps in my hearing with age related hearing loss.
[/quote]

Wow, just tried again with some cheap Sony, big, over ear jobbies, the difference is quite striking. Peak sensitivity is still above average, but with the new headphones on there is a series of moderate peaks and troughs with a much wider range at similar volume.

Perhaps this upper sensitivity explains why I hate Vox guitar amps and those horrid riveted cymbals

Thanks for your time on this one Phil.

[Japhet]

Back to the topic (cough)......why is it that a 200 Watt valve amp outperforms a 600Watt class D? I suspect manufacturers are prone to exaggeration, but is there any scientific explanation?

[Mykesbass]

[quote name='Japhet' timestamp='1446458986' post='2899428']
Back to the topic (cough)......why is it that a 200 Watt valve amp outperforms a 600Watt class D? I suspect manufacturers are prone to exaggeration, but is there any scientific explanation?
[/quote]

Hasn't really strayed off topic, I think the discussion has shown that watts do not equate directly to loudness, and that will probably be partly the answer to your question as well!

[Bill Fitzmaurice]

[quote name='Japhet' timestamp='1446458986' post='2899428']
why is it that a 200 Watt valve amp outperforms a 600Watt class D?
[/quote]Signal compression. Valves do, SS doesn't.

[Chienmortbb]

Bill is right 600W solid state is usually quoted into 4 Ohms and the will give you 300W into * Ohms providing the watts are not "marketing watts".

Add the increased power due too compression in he valve amp and there will be little difference. If it is a Behringer or Bugera, the Valve head will be louder.

However set the valve head to 4 ohms and the 600W SS into 4 ohms will be louder but not by much.

Of course the issue here is that compression is distortion and any amp will be louder with distortion. So if you want a loud SS head add a little fuzz an pitch of compassion and your there (don't forget the lead weights top if you want a "vintage" valve sound).

Edited November 2, 2015 by Chienmortbb

[JPJ]

I have nothing to add here other than to say its threads like this that keep me coming back to this site time and again. Some excellent knowledge imparted here. Thanks chaps (and chapesses)