Subjective loudness

[Rob H]

How loud is a WATT to me?

Quote from the web:
"Doubling the power output (watts) will result in a 3 dB increase in loudness. A ten times increase to the power output will result in a 10 dB increase, or sound that is twice as loud."

So, a 1watt amp sounds half as loud as a 10watt amp.
1.5watt , half of 15watt.
2watt, half of 20watt........
No help there!

I'm trying to hear an approximate 1W through 5W volume levels to choose output tubes. I have ECL80s, 6AK6s, 6MB8s, El91s, etc.

So, if I fed my amp input with a, say, 5khz sine wave and compared the Vrms on the speaker at different  volume pot settings, I could use         P=v²/r to answer the question of how loud 'to me'  is 1W, 2W, etc.  It's been bugging me.

Any easier ways?

Thanks

[shooter]

 
yep, the ears work well for what's loud, the calculator works well for passing tests

[Rob H]

How loud is a WATT to me, or you?

Quote from the web:
"Doubling the power output (watts) will result in a 3 dB increase in loudness. A ten times increase to the power output will result in a 10 dB increase, or sound that is twice as loud."

So, a 1watt amp sounds half as loud as a 10watt amp.
1.5watt , half of 15watt.
2watt, half of 20watt........
No help there!

I'm trying to hear an approximate 1W through 5W volume levels to choose output tubes.
So, if I feed my amp input with a, say, 5khz sine wave of known voltage and compare the Vrms on the speaker at different  volume pot settings, I could use P=v²/r to answer the question of how loud 'to me'  is 1W, 2W, etc.  I know it's not perfect.

Any other ideas?

Thanks

[Williamblake]

I can tell you 3W is plenty loud. Even on a speaker attenuator with -20dB it still is.

[Rob H]

You're saying that a 3w amp with -20db attenuation is still loud? Question, not argument.
Then a 1w or 1.5w op would be plenty loud for the den, louder than getting rough with an acoustic too?

[Rob H]

You're right. It's like trying to see around the corner before I get to it. Easier to pull the trigger. Guess ill go with a 1watt and see how it sounds.

Thanks

[PRR]

Get a functional handy tube near the one Watt point and adjust the supply voltage down until the baby stops crying. 6AU6 is good for a third Watt and real cheap.

[glass54]

Hi Rob
For your Sanity, don't use 5kHz, settle for something more soothing like 800Hz. 
Be aware that the power band of your guitar amp/speaker combination rolls off well at 5kHz or so.
Most reference work is done with 1kHz, but with Guitar amps, its good to know whats happening at 100Hz and 5kHz as well.
Regards
Mirek

[thetragichero]

6AU6 is good for a third Watt and real cheap.

shhhhh these are one of my favorite preamp tubes. get that 'vox-y' pentode preamp sound for a TON less than an ef86

[HotBluePlates]

How loud is a WATT to me?

How sensitive is your speaker?

     The small-magnet Jensen C12R makes 92.3dB SPL with 1 watt applied.

     The heavy-magnet Celestion Alnico Cream makes 100dB SPL with 1 watt applied.


The Celestion is as loud with 1 watt as the Jensen would be if you applied 5.9 watts, nearly 6x the power.  A vacuum cleaner is about 80dB SPL so if you're looking for "quiet distortion" you might want to shoot for 1/10th to 1/3rd watt, as with PRR's 6AU6 amp.

[ac427v]

The frequency of the signal and efficiency of the speaker at each frequency are essential parts of your answer. Glass54 posted about that.     RANT WARNING.
Speaker efficiency is measured at 1000 Hz. That specification does not match the sound a guitar produces. An open low E string has a fundamental frequency of 82Hz. Even the high E guitar string, fretted at the 12th fret, only has a fundamental frequency of 660 Hz. Posted efficiency numbers are almost an octave above that. So they have limited value in determining how loud and truthful an amp will sound. The graph of speaker response show acoustic output (sound volume) at fundamental guitar frequencies is far less than it is at 1000 HZ.

Many players love the sound of a five watt amp played through an 8 inch speaker. An amazing level of detail is heard in the high harmonics it easily produces at loud volume. But the fundamental tone (the bass part of the note) is missing. Great for slide guitar (Layla anyone?) or a quiet practice amp. But not for most of my playing. I find that I need 12 or so watts and a decent speaker to get tone in a medium sized quiet room. Your preferences may be different but I say test out your needs with several existing amps before designing and building another low watt amp.

[shooter]

Many players love the sound of a five watt amp played through an 8 inch speaker.

...and the rest like a 5W amp, dimed, driving a Marshall 4X12 cab. 

[HotBluePlates]

RANT WARNING.
Speaker efficiency is measured at 1000 Hz. That specification does not match the sound a guitar produces. An open low E string has a fundamental frequency of 82Hz. Even the high E guitar string, fretted at the 12th fret, only has a fundamental frequency of 660 Hz. Posted efficiency numbers are almost an octave above that. So they have limited value in determining how loud and truthful an amp will sound. ...

You're not "wrong."

But I have a 1962 Reverberocket with a Jensen C12R.  Turn it up near half, and it's a nice pleasant volume.  If I plug the same amp into my 2x12 cab with some 1960s Celestion alnico speakers, it's really f##$ing loud!!

I don't have claimed/measured sensitivity specs for either of these 1960s speakers.  But the same-power yields very different loudness, which is worth pointing out.  Even if we're uncertain of the accuracy/precision/applicability of the sensitivity figures...

[pdf64]

… Speaker efficiency is measured at 1000 Hz…

WGS advise that their sensitivity info is at 1kHz, goodness knows why
But Eminence, Celestion, Jensen and EV sensitivity info is either stated, or appears, to be an average over an appropriate frequency range. Which seems a much more useful metric.

[ac427v]

My post is based on an n of 1. So take it with a grain of salt. My home built vibrochamp was capable of very loud distorted music with 10 inch Eminence Cannabis Rex in an open back cabinet. I could also get clean music at lower volume except when playing chords with notes from the lowest half octave of a 6 string guitar. Those notes distorted at almost any volume.  I reduced coupling cap values and got a much cleaner, tighter tone but missed hearing the fundamental tones on those lower notes. In my brief experience, 5 watts could play very loud but not in a musical way.

I rebuilt it as a Princeton Reverb and found full frequency tonal bliss at bedroom volumes.YMMV