我朋友用呢隻
TrueRTA 3.2
聽講check完之後, 係用人手執執間房, 令到接收到既signal (20hz~20KHz)都係一樣
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Duntech Audio 寫:
In the early days of hi-fi, when two loudspeakers which "measured the same" sounded entirely different, the popular notion (even amongst early designers) was that loudspeaker measurements were completely meaningless ...
It was not until the late Richard Heyser ...
His great breakthroughs related to the effects of phase upon the sound of a loudspeaker ...
This brings us to the next important loudspeaker measurement which is called the Waterfall plot (or Cumulative Spectral Decay to scientists and engineers).
This plot displays how loud the speaker is at all frequencies ... at each instant in time.
These plots are shown one after each other, like cards in a deck.
The effect is like looking at a cliff face. The steeper the cliff the better.
Arthur C Ludwig Sr 寫:
When the sound system tries to play a note that suddenly stops, the sound does not suddenly stop.
The main effect is that sound echoes around the room for 1/3 second or so.
The loudspeaker enclosure walls, driver cone, etc. also continue to vibrate for a fraction of a second.
The waterfall plot shows the relative frequency response of this lingering sound, as it decays. Room resonances persist the longest. ...
Why do we care about any of this?
For two reasons:
(1) the change in the shape of the frequency response of the decaying sound adds coloration not present in the original music, and
(2) resonances at the higher frequencies can also affect the transient response.
An ideal waterfall plot would show a sequence of curves that are all smooth and flat across the frequency band, and that drop uniformly in amplitude to near zero in 1/3 second or so.
A more rapid decay at higher frequencies may be preferable for good transient response.
The waterfall plot is useful in identifying unwanted resonances, and sometimes something can be done to eliminate or reduce them. ...
距自己 寫:
... Now retired, I have had a very enjoyable 35-year career working at the NASA Jet Propulsion Lab (during the Apollo era),
as a visiting professor at the Technical University of Denmark,
and with a great group of engineers at Toyon, a small research firm in Santa Barbara.
My specialties are electromagnetics, signal processing, and systems engineering. ...