some ideas about attenuator, power scaling etc from Fletcher Munson curve

[kldguitar]

At present, many people like their amp with attenuator, power scaling, or they have to buy smaller amp , so they can use amp in different place.Let us watch Fletcher Munson curve , we can found many interesting things which tell us how to know about guitar amp.

If you drive 100 watts worth of speakers with 60 mW, it will sound thin and fizzy. This is not the fault of the power attenuator; the speakers aren't designed to respond correctly with such low wattage. Try reducing your cab wattage capacity when attenuating down to the milliwatt (TV) level.
At same way if you drive 5 watts speaker and wish it have same sound as you drive 100watts speaker, It is impossible. Why is it? Please watch
From Fletcher Munson curve

We can know.
1. The high intensity is, the flat curve is. It means that peoples are sensitive to bass and high freq harmonics during high intensity sound. So the higher intensity sound will have more dynamic depth . Although smaller amp maybe have same harmonics, but people can not feel it. Please compare 60dB curve with 100dB curve. In 60 dB, only 700HZ-2000HZ, feeling is 60(phon), below 700HZ, it is below 50(phon). Harmonics and resonances drop off dramatically as volume is decreased.
2. If smaller amp want to have same dynamic depth as bigger amp, The bass and high freq of sound must have more compensation.
3. When we use attenuator or change power of amp( include VVR ,or power scaling), the feeling of sound will be changed, so we must compensate bass and hi freq . High freq sound is sensitive than bass sound.
4. Fletcher Munson curve, we can know each kind of amp need compensate bass and high freq, the freq curve of amp cann’t be flat, they must high in bass and hi freq. but How and where ,it is know-how.
5. Hi freq is more sensitive than bass freq . Hi freq sound arrive to same feeling need lower intensity than bass freq sound.

[Chuck H]

Thanks KLD. This is a useful post.

[J M Fahey]

the speakers aren't designed to respond correctly with such low wattage.

Not true.
It's an *ear* problem, not a *speaker* problem.

The high intensity is, the flat curve is.

should read: "The higher intensity is, the flatter curve is."

So the higher intensity sound will have more dynamic depth .

We are not talking *dynamics* here, but perceived low and high frequency levels, relative to mid-frequency sounds.

the freq curve of amp cann’t be flat

You should say: " the attenuator's frequency response shouldn't be flat, but depending on attenuation, following Fletcher Munson's curves"
And so on.
I suggest next time you just post the link to the approppriate Wikipedia page.

Grammatical correction fees sent by separate personal e-mail.











Just kidding, if you had to pay for the information you got here, US would be China's creditor

[Chuck H]

Hey, contributing posts from KLD are rare (so I like to encourage them). I know what was meant without the corrections. DON'T PISS IN THE CHEERIOS

[kldguitar]

let me explain more about
1. when one speaker designed for 100w amp is driven by 60 mw, speaker cann't work in normal , The sound became thin and fizzy.
2. From Fletcher Munson curve. We will know that the smaller amp need different FREQ curve with larger amp. It need more bass and treble freq . It is basis of design smaller amp.
3. We can think amp as filter,different filter combine together,so the parameters of filter is more important than circuit. We can use different circuit obtain same FREQ curve,(same tone)

[kg]

let me explain more about
1. when one speaker designed for 100w amp is driven by 60 mw, speaker cann't work in normal , The sound became thin and fizzy.

well, thin and fizzy... that sounds to me like a subjective interpretation of the sound, not an objective one.

does the frequency response of a speaker system have highs and lows accentuated or boosted at low power levels?

if you plot the system's response vs. input power, does it show this boost?

if not, then you are observing a PERCEPTUAL issue.

[Steve Conner]

The Fletcher-Munson curve explains the existence of the bass-heavy "woofie drone tone" beloved of bedroom shredders.

[J M Fahey]

d

oes the frequency response of a speaker system have highs and lows accentuated or boosted at low power levels?

Neither accentuated nor attenuated.
In fact, published speaker frequency response curves are usually (just not to say "always") at 1W power input, *because* they are representative of the speaker sound at higher and lower power, meaning frequency response does not change with power, the contrary of what was stated.
The grammatical corrections were meant more as a joke, as was clearly shown at the post's end, although they were gross enough as to make the subject difficult to understand for the beginner.
Pros, of course, understand it even if garbled.
The *technical* correction was not a joke.

if you plot the system's response vs. input power, does it show this boost?

No, definitely, as stated above.

if not, then you are observing a PERCEPTUAL issue.

Agree, I said the same in other words.

[kldguitar]

in fact, we must think about distortion of speaker. The distortions of guitar amp are from preamp, power amp, and speaker, when one 100w speaker was driven by 60 mw, no distortion . otherwise,if you think speaker as line components, you are right, 100w is same as 1w, but in fact, real line component do not exist

[Koreth]

That would probably depend on the speaker being used. Those guys who use 100W half-stacks to drive a quad of 25W greenbacks are very likely looking for the coloration a speaker on the verge of catching fire adds to the sound. But I doubt those especially high power handling speakers such as an EVM-12L with its 300W rating change their voicing very much whether driven with 1W or 100W of power.

[trobbins]

Do I interpret that the intent of the topic is more related to those that add in VVR, or need to operate at very low volume levels, but are still aiming for 'typical' perceived sound character. There are a myriad of electronic and speaker related influences on sound character due to VVR or very low vol levels, and yes one additional factor for the player to appreciate is to readjust their favorite tone settings relative to the sound level used. Even moving your rig in to a 'bedroom' can have more acoustic influences than you thought with respect to reverb and bass response and typical listening distance and position.

[DougH]

This is why I use some presence and resonance if I'm using a lot of attenuation, but keep those turned down otherwise. Of course it's all about perception, the point of F&M is to show how our ears perceive freq response at different SPLs.