my subs + jackhammer song

[91_4_door]

http://videos.streetfire.net/video/C1C474FB-65A9-4D5D-AF94-5617A9C97499.htm

turn your speakers up!!



can someone tell me why i have more bass at the back of my box?

[mrmidnight]

its not more bass, its clearer bass, caused by the doppler effect

[91_4_door]

its not more bass, its clearer bass, caused by the doppler effect

huh?

[mrmidnight]

Things sound different from different angles.

Doppler effect

From Wikipedia, the free encyclopedia


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The Doppler effect, named after Christian Andreas Doppler (http://en.wikipedia.org/wiki/Christian_Andreas_Doppler), is the apparent change in frequency (http://en.wikipedia.org/wiki/Frequency) or wavelength (http://en.wikipedia.org/wiki/Wavelength) of a wave (http://en.wikipedia.org/wiki/Wave) that is perceived by an observer moving relative to the source of the waves. For waves, such as sound (http://en.wikipedia.org/wiki/Sound) waves, that propagate in a wave medium, the velocity of the observer and the source are reckoned relative to the medium in which the waves are transmitted. The total Doppler effect may therefore result from either motion of the source or motion of the observer. Each of these effects is analyzed separately. For waves which do not require a medium, such as light or gravity in special relativity (http://en.wikipedia.org/wiki/Special_relativity) only the relative difference in velocity between the observer and the source needs to be considered.

Doppler first proposed the effect in 1842 (http://en.wikipedia.org/wiki/1842) in the monograph Über das farbige Licht der Doppelsterne und einige andere Gestirne des Himmels (On the colored light of the binary star and other stars). The hypothesis was tested for sound waves by the Dutch (http://en.wikipedia.org/wiki/Netherlands) scientist Christoph Hendrik Diederik Buys Ballot (http://en.wikipedia.org/wiki/C.H.D._Buys_Ballot) in 1845 (http://en.wikipedia.org/wiki/1845). He confirmed that the sound's pitch was higher as the sound source approached him, and lower as the sound source receded from him. Hippolyte Fizeau (http://en.wikipedia.org/wiki/Hippolyte_Fizeau) discovered independently the same phenomenon on electromagnetic waves (http://en.wikipedia.org/wiki/Electromagnetic_wave) in 1848 (http://en.wikipedia.org/wiki/1848) (in France (http://en.wikipedia.org/wiki/France), the effect is sometimes called "effet Doppler-Fizeau").

It is important to realize that the frequency of the sounds that the source emits does not actually change. To understand what happens, consider the following analogy. Someone throws one ball every second in your direction. Assume that balls travel with constant velocity. If the thrower is stationary, you will receive one ball every second. However, if he is moving towards you, you will receive balls more frequently than that because there will be less spacing between the balls. The converse is true if the person is moving away from you. So it is actually the wavelength which is affected; as a consequence, the perceived frequency is also affected.

If the moving source is emitting waves through a medium with an actual frequency f0, then an observer stationary relative to the medium detects waves with a frequency f given by:

http://upload.wikimedia.org/math/3/9/5/3952efabb703e6e056518dfede90e6b7.png where v is the speed of the waves in the medium and vs, r is the speed of the source with respect to the medium (positive if moving away from the observer, negative if moving towards the observer), radial to the observer.

A similar analysis for a moving observer and a stationary source yields the observed frequency (the observer's velocity being represented as vo):

http://upload.wikimedia.org/math/7/2/b/72bbb1ecbd3cfff7f16e590e8f5dc6c4.png where the same convention applies : vo is positive if the observer is moving away from the source, and negative if the observer is moving towards the source.

These can be generalized into a single vector equation. Take the coordinate system to be at rest with respect to the medium, whose speed of sound is c. There is a source s moving with velocity http://upload.wikimedia.org/math/2/f/9/2f9ce856bbd1a0b07000ec437842e489.png and emitting waves with a frequency fs. There is a detector r moving with velocity http://upload.wikimedia.org/math/9/6/5/9659f3a3a001a4982730117a73abaa83.png, and the unit vector from s to r is http://upload.wikimedia.org/math/5/2/d/52d5bf7c5d418ba77b18c203f494e09b.png (i.e. http://upload.wikimedia.org/math/c/f/1/cf139a29b54e24ee77faf03eb6d71054.png). Then the frequency fr at the detector is found from

http://upload.wikimedia.org/math/1/9/4/1949087d28e74b57da56f52cc17e2829.png If http://upload.wikimedia.org/math/9/5/c/95c888aeff4cf818787b3cefdb64c6a1.png, then the change in frequency depends mostly on the relative velocity of the source and detector:

http://upload.wikimedia.org/math/c/b/f/cbf559a7831c3641030f9824d7390ce4.png The first attempt to extend Doppler's analysis to light (http://en.wikipedia.org/wiki/Light) waves was soon made by Fizeau (http://en.wikipedia.org/wiki/Armand-Hippolyte_Fizeau). In fact, light waves do not require a medium to propagate and the correct understanding of the Doppler effect for light requires the use of the Special Theory of Relativity (http://en.wikipedia.org/wiki/Special_relativity). See relativistic Doppler effect (http://en.wikipedia.org/wiki/Relativistic_Doppler_effect).

A stationary microphone records moving police sirens at different pitches depending on their relative direction.


[edit (http://en.wikipedia.org/w/index.php?title=Doppler_effect&action=edit&section=2)]


Everyday

The siren (http://en.wikipedia.org/wiki/Siren_%28noisemaker%29) on a passing emergency vehicle (http://en.wikipedia.org/wiki/Emergency_vehicle) will start out higher than its stationary pitch, slide down as it passes, and continue lower than its stationary pitch as it recedes from the observer. Astronomer John Dobson (http://en.wikipedia.org/wiki/John_Dobson_%28astronomer%29) explained the effect thus:

"The reason the siren slides is because it doesn't hit you." In other words, if the siren approached you directly, the pitch would remain constant (as vs, r is only the radial component) until the vehicle hit you, and then immediately jump to a new lower pitch. The difference between the higher pitch and rest pitch would be the same as the lower pitch and rest pitch. Because the vehicle passes by you, the radial velocity does not remain constant, but instead varies as a function of the angle between your line of sight and the siren's velocity:

http://upload.wikimedia.org/math/a/5/c/a5c78ad8fd2d6bb51f6f143b2fec0bf8.png where vs is the velocity of the object (source of waves) with respect to the medium, and θ is the angle between the object's forward velocity and the line of sight from the object to the observer.

[edit (http://en.wikipedia.org/w/index.php?title=Doppler_effect&action=edit&section=3)]




Radar

Main article: Doppler radar (http://en.wikipedia.org/wiki/Doppler_radar)

The Doppler effect is also used in some forms of radar (http://en.wikipedia.org/wiki/Radar) to measure the velocity of detected objects. A radar beam is fired at a moving target - a car, for example, as radar is often used by police (http://en.wikipedia.org/wiki/Police) to detect speeding motorists - as it recedes from the radar source. Each successive wave has to travel further to reach the car, before being reflected and re-detected near the source. As each wave has to move further, the gap between each wave increases, increasing the wavelength. In some situations, the radar beam is fired at the moving car as it approaches, in which case each successive wave travels a lesser distance, decreasing the wavelength. In either situation, calculations from the Doppler effect accurately determine the car's velocity.

The Proximity fuze (http://en.wikipedia.org/wiki/Proximity_fuze) which was developed during World War II (http://en.wikipedia.org/wiki/World_War_II) also relies on Doppler radar.

[edit (http://en.wikipedia.org/w/index.php?title=Doppler_effect&action=edit&section=6)]

[91_4_door]

oh. lol

[CitizenLame]

91 are those subs in the right cubic foot enclosures and are they seperated from one another? Your suspension sounds way off.

[91_4_door]

91 are those subs in the right cubic foot enclosures and are they seperated from one another? Your suspension sounds way off.

box is right yes, no they are not seperated. i was running in series when i made that video. now im running paralell and seems to sound alot better.:)

[CitizenLame]

They should be seperated, and that's what I'm hearing. Subs don't move exactly the same as each other even on the same frequency. So when they are open in the same box together they resonate off of the refracted sound waves inside the box and end up having that sound I'm hearing. And how can your cubic feet be right and the subs not be seperated? If your sub needs 3 cubic feet (just using as an example, I know that's huge) for suspension that's 3 cubic feet per sub, or a 6 cubic foot box with a seperated wall making it 2 individual boxes in 1. Not a single 3 cubic foot box with 2 subs put into it.

[91_4_door]

since im running a sealed enclosure, i only partly agree with you. it is NOT NECESSARY to have two separate chambers for two subs, it is BEST to take this approach for two reasons: First, if one of the subs dies, then the volume of the box will be "twice" as big, as seen by the sub that is still working. This could cause problems and even damage the other sub.


Sealed enclosures need to be big to be loud(meaning box,speakers, and amplifiers).hence the reason i didnt seperate.

[CitizenLame]

You might want to re-read what you wrote. You say you're going to give "two reasons" on why that's the best approach and you only give one reason on why it's a bad approach to take.


And "Sealed enclosures need to be big to be loud" is a very misguided statement. If your sub is designed to be in a 1.25 cubic foot sealed enclosure then you should have it in a 1.25 CF sealed enclosure isolated from other subs.

I've done this for about 10 years now so I know a thing or two. I wouldn't be hearing the distortion in your subs if your way was "the best way" to go.

[91_4_door]

if all your concerned with is distortion, then ill tell you i had my bass level on my HU at +7 just for the video(it was supposed to be an excursion video). That could be why you heard what you heard. If you would like ill do it again at my nomal bass setting of -3 and see if you still hear it.

Btw, i wasnt trying to say you were wrong or that i know more, because im sure i dont since this is my first big system so dont go on the defense.