Common amp myths

[Navybass]

How do you define "equal volume setting?"

I guess it would be defined as same voltage and current going to the same load.

You really can't go by the knob settings because of the variables such as potentiometer tollerance differences, knobs numbers could be off a bit.

I know, no one would actually get in there and measure things to be that exact. There will always be variables there.

 

[joebingo]

No. "Proximity effect" applies to directional microphones, not headphones.

Headphones work like small loudspeakers because that's what they are. Sound waves are waves of alternating compression and rarefaction, and low frequencies don't need space or distance to "develop."

Then why do headphones get bassier the closer they are to your ears?

I understand that headphones are miniature loudspeakers, but loudspeakers and microphones are the exact same thing in principle. A diaphragm, coil and a magnet.

I also know that bass frequencies don't need distance to "develop", they need distance to finish though. For a 100Hz sine wave, the wavelength is 3.43 meters, or thereabouts.

How do you define "equal volume setting?"

I would imagine that he would define it as any number between 1 and 10, when going through the exact same cab.

 

[Richard Lindsey]

Yes, the analogy is flawed. That was my point. It's a meaningless analogy because it doesn't address what actually blows the speakers, it just explains it away by suggesting that waves of different types are the same just because of the shape. It's much the same as saying that you shouldn't listen to Van Halen because the recording of the guitar distortion is bad for your speakers.

Well, it's not really meaningless, because it does address the basic error in this particular myth, which is precisely that the shape of the wave, in and of itself, can damage the speakers. The error is in believing that a square wave, simply because it is a square wave, is inherently damaging to speakers. You may not believe that, but I can assure you that many people who have posted here do believe it, and that's why JimmyM listed it as a myth. If this myth were true--that is, if the mere shape of the wave that hits the speakers, irrespective of anything else, were enough to cause damage--then a square wave from a synthesizer, or a fuzz box, would be just as likely to damage a speaker as a square wave produced by an amp in heavy clipping (assuming the amp is even getting to the point of producing a true square wave).

 

[jmac]

How do you define "equal volume setting?"

To quote Dr. Lanning, "That, detective, is the right question. Program terminated."

 

[slyjoe]

Then why do headphones get bassier the closer they are to your ears?

I understand that headphones are miniature loudspeakers, but loudspeakers and microphones are the exact same thing in principle. A diaphragm, coil and a magnet.

One is converting electrical energy to mechanical. The other is converting mechanical energy to electrical.

I also know that bass frequencies don't need distance to "develop", they need distance to finish though. For a 100Hz sine wave, the wavelength is 3.43 meters, or thereabouts.

Why do they need distance to "finish"? The wavelength doesn't determine the speed of propagation.

 

[Bob Lee (QSC)]

Yes, the analogy is flawed. That was my point. It's a meaningless analogy because it doesn't address what actually blows the speakers, it just explains it away by suggesting that waves of different types are the same just because of the shape.

No, Jimmy was refuting the myth that square waves themselves are dangerous to loudspeakers--and only that myth--by pointing out examples of them not harming loudspeakers.

It's much the same as saying that you shouldn't listen to Van Halen because the recording of the guitar distortion is bad for your speakers.

Essentially, he was refuting that as well, but some might not get the parallel between guitar distortion and square waves.

 

[Scott in Dallas]

Well, it's not really meaningless, because it does address the basic error in this particular myth, which is precisely that the shape of the wave, in and of itself, can damage the speakers. The error is in believing that a square wave, simply because it is a square wave, is inherently damaging to speakers. You may not believe that, but I can assure you that many people who have posted here do believe it, and that's why JimmyM listed it as a myth. If this myth were true--that is, if the mere shape of the wave that hits the speakers, irrespective of anything else, were enough to cause damage--then a square wave from a synthesizer, or a fuzz box, would be just as likely to damage a speaker as a square wave produced by an amp in heavy clipping (assuming the amp is even getting to the point of producing a true square wave).

I agree, but taken by itself, there is a danger of someone thinking that there is no square wave, even one produced by an amp in heavy clipping, that can damage their speaker if its rating is more than the rated wattage of the amplifier.

 

[billfitzmaurice]

Headphones work because of the proximity effect....

Not even close. A blurb on Wikipedia is not a substitute for an audio engineering textbook, dozens of which written over the course of the last sixty or so years have examined this issue in great depth.

This is not a phase issue. If it was to do with boundaries, I wouldn't be able to hear myself at any point in the room.

It has everything to do with boundaries. Otherwise it would sound the same everywhere in the room. It's also why your rig sounds different in every room. Sometimes only by a little, sometimes by a lot, but never exactly the same. Since your axe and rig aren't different the only explanation why they sound different in different rooms is the room itself.

Then why do headphones get bassier the closer they are to your ears?

The smaller the vessel being pressurized the less energy required to pressurize it to a given point. By the same token, with equal force applied a smaller vessel will attain a higher pressure level than a larger one. SPL stands for Sound Pressure Level. It measures changes in air pressure caused by the presence of sound. The less air the driver has to push the higher the SPL.
Precisely the same phenomenon occurs with the bass levels in a sealed room, via the effect known as Cabin Gain. Cabin Gain is the reason why auto sound competitions can get bass SPL readings unattainable outside of a small sealed vehicle. A vehicle which, BTW, is far too small to allow a low frequency wave to 'develop'.

 

[MtManiac]

For a 100Hz sine wave, the wavelength is 3.43 meters, or thereabouts.

I always thought of a sound wave as path along which energy travels, but at any point along the path, if the energy is interrupted in its travels, in this case if the sound is heard, the energy is still the same energy - it dissipates in volume as it travels, but it exists only at a given point along the sound wave. In other words, you do not hear the sound wave, you hear the energy that is traveling along that sound wave. So the frequency of the wave doesn't affect how close or how far you should be from the source before you hear it, the frequency relates more to how far in a straight line the energy is capable of traveling before it totally dissipates. Low frequencey sounds travel farther - if we think of a sound wave as a hose, where the length of the hose is analogous to the wattage at which a sound is amplified, for a high frequency sound the hose would be scrunched up, with many very short waves, so the hose would not stretch out as far from the source. Low frequency sounds will stretch the hose farther, because it isn't as scrunched up. If you pour water through the hose (i.e. sound traveling along the wave form), the same amount of water comes out the end regardless of how long the hose is or how scrunched up it is.

 

[Bob Lee (QSC)]

The Wikipedia article explains correctly that "proximity effect" is a phenomenon that affects directional mics. It correctly does not claim that it is a headphone phenomenon. joebingo interprets the article incorrectly.

 

[JimmyM]

Bro, you might want to get a little less personally involved with all the coloring that strays outside the lines. Keeping a forum "in line" is like hearding cats anyway... it's just a discussion, and most of us are into this for some kind of fun.

Exactly. Geez, it's not life or death...it's a thread on Talkbass.

 

[JimmyM]

The Wikipedia article explains correctly that "proximity effect" is a phenomenon that affects directional mics. It correctly does not claim that it is a headphone phenomenon. joebingo interprets the article incorrectly.

I think that goes to another thing I've heard that people compare speakers to mics...I have heard many people say that mics and speakers are the same thing only reversed. Not knowing enough about it, I can't comment intelligently on it, but it seems kind of flawed thinking to me.

 

[JimmyM]

That's sort of like saying, "if snakes are dangerous, how come a picture of a snake won't bite you?"

So you're saying that an analog synth is the equivalent of a picture of a square wave? Are you saying it won't produce a real square wave?

 

[Jonyak]

I think that goes to another thing I've heard that people compare speakers to mics...I have heard many people say that mics and speakers are the same thing only reversed. Not knowing enough about it, I can't comment intelligently on it, but it seems kind of flawed thinking to me.

nope they are the same thing on a basic level.

you can use headphones as a mic.. a bad bad mic, but a mic nonetheless...

try it sometime. plug a set of headphones into a mic line and record with them. it works. I have done it.

 

[deggial]

I think that goes to another thing I've heard that people compare speakers to mics...I have heard many people say that mics and speakers are the same thing only reversed. Not knowing enough about it, I can't comment intelligently on it, but it seems kind of flawed thinking to me.

There is some truth to that. You could actually connect your computer speakers in the microphone input and record through them. However, not being constructed for that specific purpose, expect the sound quality to be poor.

 

[shakerattleroll]

 

[chadds]

Exactly. Geez, it's not life or death...it's a thread on Talkbass.

It isn't? I thought everything on the net is true.

 

[joebingo]

The Wikipedia article explains correctly that "proximity effect" is a phenomenon that affects directional mics. It correctly does not claim that it is a headphone phenomenon. joebingo interprets the article incorrectly.

I'll admit defeat on this - I was being stubborn with my small understanding of physics. Sorry guys.

I'm still wondering though, why do headphones sound bassier the closer they are to your ear, if it's not the proximity effect?

 

[seamonkey]

I think that goes to another thing I've heard that people compare speakers to mics...I have heard many people say that mics and speakers are the same thing only reversed. Not knowing enough about it, I can't comment intelligently on it, but it seems kind of flawed thinking to me.

Yamaha sells this - it's a speaker as a mic. It probably has a small transformer to bring the impedance up to 600Ω

 

[derrenleepoole]

Yamaha sells this - it's a speaker as a mic. It probably has a small transformer to bring the impedance up to 600Ω

That is so cool