dampening factor?

[ambyrell1 11]

what is a good number, and what does this mean?

[KU40 173]

It is the amplifier's ability to control the cone movement of the speaker, such as starting and stopping. More technically it's the ratio between load impedance and source impedance of the amp. Really it isn't all that important and you probably couldn't tell a difference between any number. There's basically no difference above 50, and really not much even above 20.

[Thumpper 266]

Loudspeakers have a mind of their own. You send them a signal

and they add their own twist to it. They keep on vibrating after the

signal has stopped, due to inertia. That’s called “ringing” or “time

smearing.”

In other words, the speaker produces sound waves that are not part

of the original signal.

Suppose the incoming signal is a “tight” kick drum with a short

attack and decay in its signal envelope. When the kick-drum signal

stops, the speaker continues to vibrate. The cone bounces back and

forth in its suspension. So that nice, snappy kick drum turns into

a boomy throb.

Fortunately, a power amplifi er can exert control over the loudspeaker

and reduce ringing. Damping is the ability of a power

amplifi er to control loudspeaker motion. It’s measured in

Damping Factor, which is load impedance divided by amplifier

output impedance.

Let’s explain.

If the speaker impedance is 8 ohms, and the amplifi er output

impedance is 0.01 ohms, the damping factor is 800. That’s a

simplication. Since the speaker impedance and amplifi er output

impedance vary with frequency, so does the damping factor. Also,

the impedance of the speaker cable affects damping. Thick cables

(with low AWG) allow more damping than thin cables with (high

AWG).

The lower the amplifi er’s output impedance, the higher the damping

factor, and the tighter the sound is. A damping factor of 1000 or

greater is considered high. High damping factor equals tight bass.

How It Works

How does an amplifi er control speaker motion? When the loudspeaker

cone vibrates, it acts like a microphone, generating a signal

from its voice coil. This signal generated by the speaker is called

back EMF (back Electro Motive Force). It creates a current which

travels through the speaker cable back into the amplifi er output, then

returns to the speaker. Since back EMF is in opposite polarity with

the speaker’s motion, back EMF impedes or damps the speaker’s

ringing.

The smaller the amp’s output impedance, the greater is the effect

of back EMF on the speaker’s motion. An amplifi er with low output

impedance short-circuits the back EMF, so the back EMF drives the

loudspeaker with a relatively strong current that works against the

speaker’s motion. When the speaker cone moves out, the back EMF

pulls the speaker in, and vice versa.

In short, the loudspeaker damps itself through the amplifi er output

circuitry. The lower the impedance of that output circuitry, the more

the back EMF can control the speaker’s ringing.

To prove it to yourself, take a woofer that is not connected to

anything. Put your ear next to the cone and tap on it. You might

hear a low-pitched “bongggg” if the speaker itself is poorly damped.

Now short the speaker terminals and tap again. You should hear a

tighter thump.

Damping factor varies with frequency. As you might suspect, damping

factor is most important at low frequencies, say 10 Hz to 400

Hz.

Bottom Line......

Amps with a high effective Damping Factor

deliver clean, tight kick drum and bass.

..................................................................................

here is an article from Richard Clark on Damping Factor

http://www.monstercable.com/mpc/stable/tech/A2412_Damping_Factor_Article.pdf

[djphilly 11]

very nice explinations

[ambyrell1 11]

my amp is >250 dampening factor is this good?

[Aaron Clinton 2,372]

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