1. ## Re: 4 18s in a wall, 94 astro

Originally Posted by sub2weeker
and what kinda degree do you have?, did you even graduate? or are u a mindless puppet, A gelatinous tape worm? a sicofante that follows the crowd to be cool. dont pop in without any evidence or theory to back it up.
I'm studying electrical engineering, bud.

2. ## Re: 4 18s in a wall, 94 astro

Originally Posted by PV Audio
I'm studying electrical engineering, bud.
then SURELY..... you would understand this concept. and studying it dont mean nothing if you dont have the common sense to understand common properties and physics .

3. ## Re: 4 18s in a wall, 94 astro

Originally Posted by sub2weeker
then SURELY..... you would understand this concept. and studying it dont mean nothing if you dont have the common sense to understand common properties and physics .

4. ## Re: 4 18s in a wall, 94 astro

Originally Posted by sub2weeker
then SURELY..... you would understand this concept. and studying it dont mean nothing if you dont have the common sense to understand common properties and physics .
You really want to be right, but you just aren't. The TL measures the peak SPL from your vehicle. If you play a tone at 130db at 20khz and a tone at 130db at 20hz, then the net result will be 130dB. Which frequency it will measure I can't be sure since I don't know the mechanics of the TL, but it won't be over 130db. Why? Because of the simple physics you're talking about. To have constructive interference, aka, additive output, the output waveforms must be in phase and at the same frequency. Multiplication of waveforms is a different entity entirely and that isn't up for discussion, and even then, it wouldn't yield the results you're talking about.

Loudspeakers are very simple devices that follow very simple physics. Signals combine differently when they are in phase than when they are not. You can have what is called correlated and uncorrelated sound sources. When two output waveforms are in exact phase and frequency, they are correlated and combine as scalar quantities. This normally yields you 6dB of output. When two output waveforms are not in perfect phase BUT the same frequency, they yield between 3 and 6dB of output, OR the RMS (root mean square) value of the 6db gain. This is basic physics from the fundamentals of audio filter theory and is why what you're saying is completely false. When you take two signals which will always be out of phase and of different frequencies as they are playing different source material, the output does NOT add together. If you don't believe this: pg. 111 of the Loudspeaker Design Cookbook by Vance Dickason, 6th edition. It was originally derived from a paper by A.N. Thiele as well.

Think about this: when you're in a car demoing or at a concert and want to talk to someone, what do you have to do? You have to yell. Why? Because the output from your vocal chords does not add to the output of the music and as such, you need to speak at a greater amplitude than the background noise. The overall loudness is not getting any louder by you talking because your voice and the background noise are completely uncorrelated and are canceling due to the issues I said above. You need output greater than the noise threshold for it to be audible, so you yelling at 130db to your friend in a 125db car still registers as 130db to your friend's ears because that's the necessary loudness level for him to pick up what you're saying.

Ouch

6. ## Re: 4 18s in a wall, 94 astro

How are you possibly 33 and acting so immature? I mean really, I'm always up for a good debate, but someone who is in his 30s should be nowhere near as childish as you are.

7. ## Re: 4 18s in a wall, 94 astro

Originally Posted by sub2weeker
Sound is required by the law of physics to ADD UP, just like adding any other measureable propertys.
i guess measuring a 1/2in and 3/4 inch gives you a 3/4 because 3/4 is bigger?
or a gallon of milk + a gallon of water = a gallon of milk because the milk is dense?.
a harley drives by with screaming *** pipes and bus roars by, oh,i didnt even hear that harley because the bus was so loud.
You clearly don't know anything about physics because this is not true. If you wire your two subs out of phase with one another, you will be quieter than having just one.

8. ## Re: 4 18s in a wall, 94 astro

Originally Posted by JBGabriel
I have never ran fuses. And I have never had a problem. If you install correctly than there is little chance of a short. That said I ALWAYS do other peoples installs with proper fusing...
You installing correctly is irrelevant when you get t-boned at an intersection and short out your 3000.1 and end up dying in a car fire.

9. ## Re: 4 18s in a wall, 94 astro

Actually, I disagree on some points.

Here's an easy example. Think of the Beats phenomenon. You have 2 waves that are similar in frequency(f) and are equal in amplitude(A). At points they will cancel out completely, and at other points they will have a cumulative amplitude of 2A, with a peak to peak beat frequency of |f1-f2|. This can be applied to any two frequencies, and many more actually, but it isn't as easy. This operation is the basic principal of AM transmission.

Regardless of the frequency, it will shift in and out of phase with another signal.

Wave and signal can be used synonymously as long as both of them are sinusoidal.

10. ## Re: 4 18s in a wall, 94 astro

Originally Posted by stevew007
I dont like it because it's just a twist of the wrist to give or take 10db. Ive lost to people with a 1000 watt amp and 1 12 in a sealed box by 5 db because the guy forgot to turn the meter down before he went through.I will say that most the problems that come from the AC is the judges fault
Just reread my post and I didn't word it properly. I was referring to the TL in the first part about being the most consistent and widely used.

We've had the same issues at local shows with the AC160. Trunk car with 2 12's puts up a 168, then they readjust and a bunch of us with walls all did a 135 as it wouldn't go any higher

x50 on building a street driven vehicle with fuses as no one plans for a crash but they happen and I'd rather not do a free fireworks show for anyone around when it happens

11. ## Re: 4 18s in a wall, 94 astro

Originally Posted by PV Audio
You installing correctly is irrelevant when you get t-boned at an intersection and short out your 3000.1 and end up dying in a car fire.
lulz....

12. ## Re: 4 18s in a wall, 94 astro

Originally Posted by PV Audio
How are you possibly 33 and acting so immature? I mean really, I'm always up for a good debate, but someone who is in his 30s should be nowhere near as childish as you are.
He's been in the game for 20+ years

Pressure > khz

I've always forseen the TL to be more of a pressure gauge like those on air compressors and the like to measure the PSI not audible loudness to the ear.

There's a video on ROE somewhere, where a guy screamed at the top of his lungs into a mic and it only measured like 140s. Then blew into it and it did like 170's IIRC.

13. ## Re: 4 18s in a wall, 94 astro

Originally Posted by MakeshiftAudio
Actually, I disagree on some points.

Here's an easy example. Think of the Beats phenomenon. You have 2 waves that are similar in frequency(f) and are equal in amplitude(A). At points they will cancel out completely, and at other points they will have a cumulative amplitude of 2A, with a peak to peak beat frequency of |f1-f2|. This can be applied to any two frequencies, and many more actually, but it isn't as easy. This operation is the basic principal of AM transmission.

Regardless of the frequency, it will shift in and out of phase with another signal.

Wave and signal can be used synonymously as long as both of them are sinusoidal.
That's entirely true, but a beat is usually two tones of <15hz difference and as such those two tones will have very close fundamental periods. Tones many thousands of hertz apart don't so I'm not sure if that same phenomenon applies.

And AM transmission is multiplying two frequencies together, not adding them together:
x(t) = A*[1+m*cos(2*pi*fm*t]*cos(2*pi*fc*t)
where m is the modulation index, fm is the frequency of the modulated signal and fc is the frequency of the carrier signal (don't ask me how I remember this from lab ). Now I could be wrong, and please correct me if I am, but I don't think that playing two tones of different frequencies yields a modulated output signal. And either way, the output amplitude is still the amplitude of larger signal:

14. ## Re: 4 18s in a wall, 94 astro

Originally Posted by TnT_Sounds
He's been in the game for 20+ years

Pressure > khz

I've always forseen the TL to be more of a pressure gauge like those on air compressors and the like to measure the PSI not audible loudness to the ear.

There's a video on ROE somewhere, where a guy screamed at the top of his lungs into a mic and it only measured like 140s. Then blew into it and it did like 170's IIRC.
That is because it's just measuring pure sound pressure in dB, which is why as I said, there are weightings to reflect how the human ear perceives loudness. Higher frequencies seem to be much louder to us than low frequencies. If someone played a 140dB tone at 25hz a few feet away from you, you really wouldn't be bothered by it. If they played the same one at 5000hz, you would be running out of the room.

15. ## Re: 4 18s in a wall, 94 astro

Originally Posted by PV Audio
That is because it's just measuring pure sound pressure in dB, which is why as I said, there are weightings to reflect how the human ear perceives loudness. Higher frequencies seem to be much louder to us than low frequencies. If someone played a 140dB tone at 25hz a few feet away from you, you really wouldn't be bothered by it. If they played the same one at 5000hz, you would be running out of the room.
Seems viable to me. Thanks for the info.

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