窮人睇concert....之音魂不散

xover

tomtomsuccess 發表於 2012-12-1 12:31

幾時摩下對天龍

tomtomsuccess

玩緊北星呀

xover

tomtomsuccess 發表於 2012-12-2 00:37
玩緊北星呀

正吾正

xover

果然不出我所料...TOA原本之Nippon Chemicon..因年事己高,再加上本身聲底太清...所以音像較前, noise level較大...
換心手術後之TOA,有如換机一樣...聲濃厚而殘響多...聲音密度較Nippon Chemicon高出好多而膛音十分豐富...
人聲立体感特強....而最重要既係....Noise Level低至完全dead silence...

xover

~~Damping Factor~~

In Power amplifiers, it is a measure of the output Impedance of the device. Expressed as a number arrived at by dividing the Impedance into 8 ohms. For example, an Amplifier with an output Impedance of 0.04 ohms would have a Damping factor of 8/.04=200. This, and higher numbers are common for solid state amps. Tube amplifiers have much higher output impedances and lower Damping factors. In practice, the output Impedance of the Amplifier has almost no effect on Loudspeaker Damping, but it can have a significant effect on the Frequency response of loudspeakers, most of which have Frequency-dependent impedances. Within reason, higher numbers are better.

tomtomsuccess

大師呀, 拜呀.

xover

Damping factor is another way of expressing an amplifier''s output impedance. It''s the speaker load impedance divided by the amplifier output impedance. But since both these impedances (the speaker''s especially) vary with frequency, the standard damping-factor specification is simplified to 8 ohms divided by the amplifier''s output impedance at 50 Hz. If the damping factor gets low enough, the amplifier''s frequency response will start to pull toward the shape of the speaker''s impedance curve, but you''re not likely to encounter such a situation except possibly with an amp with a transformer-coupled output, such as a tube model. (A very long run of high-gauge cable might affect high-frequency response in some instances, since the cable impedance adds to the amplifier output impedance, which will almost always be higher at high frequencies than at low to be begin with.)

xover

tomtomsuccess 發表於 2012-12-4 11:17
大師呀, 拜呀.

妖~~

xover

Damping factor is one of the most mis-understood parameters used when talking about speakers and amplifiers. It exists a lot of misconceptions around this item and many people deliberatly misunderstand or mix up the effects damping factor can have on the performance of a amplifier speaker combination. Amplifiers are advertised as having a damping factor of 100 or even 1000 and people are led to believe that the higher damping factor the better the speakers will dampened.

Definition of Damping factor

Damping factor is defined as the quote between the nominal speaker impedance Zs and the amplifier output impedance Za, as an example if we have a speaker with nominal impedance 8 ohm and an amplifier with an output impedance of 0.5 ohm the damping factor would be 8/0.5 = 16.

Suggested effect of damping factor as defined above

An electrodynamic speaker consist of a coil moving in the field of a magnet. A speaker can convert electric current to movement, (the coil and the attached membrane will move when a voltage is applied to the coil), but also a voltage will be generated in the coil when the the membrane is moved physically for instance by hand. If a transient voltage is applied to a speaker the speaker membrane will try to move in accordance with the transient voltage and then stop, but because of the mass of the membrane it will continue to move after that the applied voltage is removed, a voltage is then generated by this movement.

The theory about the need for high damping factor is that if this generated voltage would be short circuited by an amplifier with low output impedance, (high damping factor) the transient response of the speaker will be improved as the effect of short circuiting the voltage would generate a high current in the coil and that would generate a physical force that would stop the speaker membrane moving. If however the amplifier had high output impedance, (bad damping factor) the voltage would not be dampened completely and the speaker would continue ringing after a transient was applied.

Unfortunately the amplifier output impedance has not so much effect on the transient response of a speaker. It is true that the effect described above exist, it is easy to check this by comparing how a speaker element reacts wether the terminals is open or short circuited. Try this on a woofer element and tap the membrane with a finger, if the terminals is shortcircuited the sound is more dull then when the terminals are open, indicating that the effect of controlling the membrane exists.

Real effect of amplifier damping factor on speaker transient response

So the effect of transient damping exists so why is damping factor a very misunderstood concept?
One factor is deliberatly forgotten in the description above i.e. speaker internal resistance Rs. A normal electrodynamic speaker has a internal resistance that is usually ~Zs/1.2 so an 8 ohm speaker have an internal resistance of ~6.7 ohm. Even if the speaker is completely short circuited externally it will still have the internal resistance that will determine how well it is dampened!

Lester

xover 發表於 2012-12-4 11:22
Damping factor is one of the most mis-understood parameters used when talking about speakers and amp ...

即係買大ohm spk 有著數? {:9_404:}