Why Does It Have To Be 50hz

[Kicker Guy]

CD with a sine-wave test tone recorded at 0dB reference level in the frequency range to be amplified (ex. 50Hz for a subwoofer amplifier, 1 KHz for a midrange application). Do not use attenuated test tones (-10dB, -20dB, etc.).

As long as your in the range of the speaker it doesn't matter what tone you use.

[ISO]

If you deal with an amp that has a flat frequincie response and you make sure all crossovers are off and any other signal processing are shut down you should be able to set your gain at any frequency. In theory.

Make sure there is no load on the amp.

I myself out of all the tones 50 hertz just feels rite after all these years. I still use 60 alot though too. With amps that don't have a flat frequency response, I try and find out what frequnecy it peaks at in the response and set it at that frequency.

Oh wait I do my shit by ear.

Man get a high quality recorded rap album. Fire everything up and stand there with your amp and subs and you will probbly beable to set your gains pretty well.

When ever the bass just starts to sound weird start to back off on the gain untill it sounds better.

It will take practice.

[MickyMcD]

I agree, it's spot on. Why d'you think the make tweeters small.

Theoretically you could put 20kHz out of a sub, but the ability to control such a thing would be and incredible feat...

50Hz just gives the spot on calibration for the gain setting guide. If it were 55 it's be different but only marginally i believe.

Excuse me?

The reason hi-range drivers are small is because they pull more current? And it would be an incredible feat to control a woofer at high frequencies?

I'm not even going to start a rant before I ask this; where did you come across this information, and why did you believe it?

Cheers,

Mick

P.S. On side note, fuck it. Right, well let's start. No, a higher frequency waveform does not 'draw' more current. To be straight, I can get 20volts at my output terminals whether it be 20 hertz or 20,000. No matter the frequency, 20 volts is still 20 volts. An amplifier amplifies (funnily enough) so it will amplify any frequency within range that you feed to the input terminals. The reason 50hz is used is because it falls exactly on a harmonic, and also falls at one of the 'standard' 1/8 octave regions. Not only that, but it provides a mean average of low frequency output power. A proper, 100% show of output power is used through white noise.

The reason a high frequency driver is smaller is to keep moving mass low, sensitivity high and transient response high. And for the record, it is much harder to get 20khz out of any cone based loudspeaker than to 'control' it's movement. Christ man, what movement? Any cone based loudspeaker is barely tickled by high frequency programme. You'll cook coils before you even begin noticable linear cone movement. Take the Peavey 22xt and 44xt drivers. One is a two inch, titanium compression driver. The other is a four inch titanium compression driver. The four inch model sees reduced overall programme effeciency and a roll off of 12db/octave almost half an octave before the 22xt's roll off. But, it does get a hell of a lot louder, and sees response well into the midrange frequencies from using a high mass driver.

[Decaf]

i love ur responses.. so matter of fact

cheers to someone who knows!!!

[Eskii]

I'm just putting ideas out there.

but the way i see it is power = energy/time. with energy being the kinetic energy ((1/2)(mass)(velocity)^2 to move the sub plus shear force from the cone moving through air (volume flow rate x time)

velocity being 2 way excursion times (1/frequency)

mass is the cone mass

volume flow rate is how much of the cone area is moved per second

time is (1/frequency)

...

But maybe you're right and i been studyin too much today...

I'll ask a lecturer tomorrow, i'm pretty interested actually!!!

[MickyMcD]

Right, but what you just posted, if read correctly, doesn't match what you posted before. Your last post mentions 'sheer force from the cone moving through the air.' That is indicative of a higher power level towards something that is moving. A low frequency driver with 20mm of linear motion, by your reasoning, has more power than a high frequency driver moving .02mm....which is correct...

....but your first post explains you believe high frequency devices have more power? As we say.....lolwut?

Another thing is the equations below do work for most things, but keep in mind a loudspeaker is a passive inductive reactive load (ain't that a mouthful?) being driven by a variable voltage supply. It's motion is dependant on what the amplifier is doing.

And now for my own Big Three - Resonance, Resistance and Effeciency. A loudspeaker almost always has a non linear resistance, that is it is constantly changing depending on frequency. Driver X may have a resistance of 2.14ohm @ 34hz, but a resistance of 32ohm@80hz. In most cases, low frequency drivers have the lowest resistance at their natural resonance point, which is quite often a very low frequency. The closer you are to that point, the less resistance encountered, the more power out of your amplifier.

To sum it all up, you can test your amplifiers on any god-damn frequency you want. Hell, be a professional and test on white noise to set it up properly. Again, 20volts is 20volts. It's a fuggin variable voltage supply, it's not hard to get what you want out of it. But pushing low frequencies requires more power than high frequencies becuase of driver impedance, effeciency, the way humans hear, cabinet resonances, linear motion, material suspension.........

Cheers,

Mick

P.S. FUCK YES AUSTRALIA

[tacomabanga1986]

the only reason i put that it takes more power to make a higher freq tone than a lower one is it takes more power to drive a speaker faster than it does to move it slower, and an amp does is take a dc current and convert it to an ac current at a higher amprage to a alternating freq, its just physics, and yes it does take more power to do a higher htz tone than it does a lower htz tone cause when i had my other 15's in my truck when the bass hit high notes the lights would dim but i could play low bass all night long and get no dimming at all thus for more power to make a higher freq than a lower one, thats why most sub amps are class d and mids n highs are class a/b and thats why class a/b's get hotter cause it takes more current to make higher freqs than it does lower ones, i hope i made myself clear im not a noob at this stuff cause ive seen it done in electronics class

[MickyMcD]

the only reason i put that it takes more power to make a higher freq tone than a lower one is it takes more power to drive a speaker faster than it does to move it slower, and an amp does is take a dc current and convert it to an ac current at a higher amprage to a alternating freq, its just physics, and yes it does take more power to do a higher htz tone than it does a lower htz tone cause when i had my other 15's in my truck when the bass hit high notes the lights would dim but i could play low bass all night long and get no dimming at all thus for more power to make a higher freq than a lower one, thats why most sub amps are class d and mids n highs are class a/b and thats why class a/b's get hotter cause it takes more current to make higher freqs than it does lower ones, i hope i made myself clear im not a noob at this stuff cause ive seen it done in electronics class

Ah christ. Look, it doesn't take any more current to make any frequency. 20volt output at the terminals is 20 fucking volts, no matter the frequency. If I knew how to upload video's and had the time, I'd grab some footage of my rack at work. The low frequency amplifier is pumping close to 70 volts a side, the midrange close to 40 volts and the high range a mere 20 volts. However, this is from acoustically flat white noise with no compression or equalisation. Now, my PV3800 draws 9 amperes of current, my C-T410 draws 4.6 and the M700 draws 2 amperes at 240volt. Which ones do you think handle low, mid and high frequency?

And no, Class A/B amplifiers do not get hot because it takes more current to amplify high frequencies. Class A, A/B, C, G, H and A/B+B hybrids generate heat becuase they are inefficient power suckers. Because of the transistor arrangement (push-pull) and the power supplies necessary to sustain negative feedback amplification, traditional analogue amplifiers generate heat through power loss and transformer saturation. Class D and tD function on what is called Pulse Width Modulation, or 'digital.' In this amplification, a high frequency oscillator feeds the amplification circuit a constant triangular wave on which the incoming signal is referenced to. The signal is then converted to varying amplitude ons and offs (1's and 0's) that vary in resolution depending on the reference oscillator's frequency. The comperated signal is then demodulated (who comes up with these words? No-one with a speech impediment I bet) in which the triangular reference wave is removed and BA-DA! A high power signal is present at the output terminals.

This process is damn effecient, sometimes up to 90%, a far cry from the 40-60% effeciency of other amplifier topologies. If my amplifier is 40% effecient, where does the rest of the energy go........you guessed it, HEAT!

This is what has people confused; A high frequency waveform contains more energy in joules during the same period as a low frequency waveform if both amplitude and period stay constant. But GENERATING A HIGH FREQUENCY WITH CONE, DIAPHRAGM AND ELECTRET BASED LOUDSPEAKERS REQUIRES LESS ELECTRICAL ENERGY THAN LOW FREQUENCY.

And that, ladies and gentlemen, concludes today's rant and rebuts the point that low frequency amplification is a taxing task, and the amplification unit will draw more current generating a low frequency waveform of the same amplitude through a loudspeaker than a higher frequency waveform.

But for christ's sake, the difference in power draw between 50 and 60hz is negligable at best. If you are that worried, upgrade your charging system.

[Decaf]

pwn'd

good stuff.... learned lots from this post

[Eskii]

Okies, i'll let ya have a little victory.

But get back to me after ya finished high skool