|
Termyn8or -> RE: Quieter TV commercials (12/20/2009 2:03:10 AM)
|
Poly V, I'll try to field that as quickly as possible.
The AC coming into the house is 120V RMS. The peak value is 160V. When they talk RMS it is the average in a way. It is peak 160V, not 160V all the time. And that is just a sine wave.
Audio is not a sine wave unless it is off a synth or something set to do it. No instrument known produces a sine wave. Some come close, but still no, they don't. The voltage varies rapidly and the whole envelope not only rises and falls, so do the low parts.
Now there are different waveforms than a sine wave. Let's take the example of a muted trumpet. Not very loud huh ? But it has this high tonal quality, whether you like it or not, there is alot of harmonics in it. If you analyse and measure the output it has a very high peak value and a very low RMS value. So to most people it is not that loud, but to really reproduce it accuarately would require some really gnarly tweeters and horns and about 1.5 kilowatts per channel. So forever they have been clipping and/or compressing music for recording or transmission. There is simply no way around it.
A true sine wave is based on a circle, in fact is a circle. However when viewed on a scope it is plotted against linear time and can be hard to recognize. It's peak vs RMS value is pegged at 0.70711 which happens to be a coincidence in geometry as well, being a sine and cosine of a 45 degree angle. However in sound it varies greatly. In the case of an overdriven solid state amp rum off a synth or keyboard, RMS can be near 100% of the peak value rather than 70.711%. In the case of the muted trumpet it can be as low as 5%, or expressed as a factor of 0.05.
Speaker impedance is a whole different story. First of all eight ohms is a joke. The impedance varies so widely with frequency it is less useful than EPA estimates of gas mileage. In the very best sounding speakers, the inductance of the drivers is calculated to null the effect of the cone being smaller that the wave emitted. They don't make many speakers like that anymore. However speaker impedance does have an effect on dynamic range. This is because when the cone excursion is greater it is moving out of it's optimum magnetic field. Put in more pwer, but don't get the equivalent sound. It is transformed into third and other odd order harmonics. These have been found to be pallatable to the human ear in reasonable quantities and this has been used to lie about the specs on audio equipment for a long time.
In TVs. Now a normal sine wave of 6.3 V RMS would have a peak value of about 8.9V. However in a regular TV the filament voltage is 6.3V RMS, yet it is 22V P-P. how is this possible ? It is not a sine wave. It is a half sine wave with the duration (tuning) of about 70Khz but with a rate of 15Khz. But nonetheless they take a winding and supply that 6.3V RMS because that is really the equivalent heating power for the filaments of the CRT.
When it comes to sound, very few people understand how subjective it is. I don't mean how high you turn the bass and treble, I mean the loudness percieved. With all these other factors our ears also adjust to the sound level. Working in a factory with loud noises might be bad, but hearing gunshots is worse. The ears can adjust, and they do. If you keep everything the same and buy an amp with twice the power, that is barely discernable as an increase in volume. To get what is percieved as twice as loud you need ten times the power. But don't forget that the sound will carry ten times as far to your neighbors. Take it from someone who has actually been thrown in jail for a loud stereo. Story available on request, and I actually had a good time !
A local audio or TV shop might be a good stop for you. See if they have a scope. Just ask them to show you some various audio waveforms on the scope and you will gain alot more understanding of the subject, and why it is so hard to explain sometimes.
Incidentally, all this boom boom shit you hear out of people's cars, I started that. I built my own amp. Later I sold a few and in every case when they brought them back bitching that it didn't work, turns out it had blown the speakers. I told them the thing had real power. Basically thirty watts a channel in a car into eight ohms. Two thrty amp fuses (for the peaks). Still you needed new fuses about every other month. I am talking early eighties here. My amps were boss.
Impedance on speakers also varies. Mine are damnear a short circuit, but the sound is awesome. The problem is that even at low listening levels I have to use a fan on the amp. Remember the smell of an iron that gets too hot ? I have smelled that out of my amp. Well it's not really mine I just took it from work. The boss gave me most of the speaker wire he had but I need more. I need 135 feet of it to complete my system, but it is not high on my list of priorities right now. One nice thing about the situation though, if I burn ,,,,, wait, when I burn this amp up I am out nothing. I'll just take it back and either get another one or they'll have the kid fix it.
Buying new is not an option, all the new shit is junk. Eventually I won't be able to get what I want at all, and when that time comes watch out. I might show the world that this old Man still has something, and put the US back on the map for the best amps in the world. I am into power. I have many ideas for which the time is not yet right. Like a 1,200 watt powered subwoofwer with the ultimate in efficiency and everyhing. Preamps with features that, once you understand how to use them you will wonder how you got along without them all those years. Asians beat us in certain areas, but whe you are facing an adversary, you do not stand face to face. You sidestep.
I'd like to see this become my niche. I CAN do better than this fucking junk they sell today, easily. I could probablhy borrow about a million bucks, but the way people are today I can't purport this to be a viable investment. Maybe when people get real I might take a stab at it, if I am still among the living.
T
|
|
|
|
