- Efficiency
-
This is the volume level a speaker produces, usually fed with 1 W,
measured at a distance of 1 m (in the metric part of the world ;-).
It is measured in dB[A] (somebody correct me if I am wrong).
90 dB/1W/1m is a fair efficiency,
96 dB/1W/1m is a good value for a PA system,
less than 90 is IMO unacceptable for PA use.
Here horn speakers (broadband horns like HILTONs and highband horns
from PA systems) stand out. A good midrange horn can reach over
100 dB/1W/1m.
Speaker efficiency is a function of frequency. A usual HIFI speaker
system has it's rated efficiency in a range of roughly 50 Hz to 20 kHz.
If efficiency is constant in this range, the speaker sounds 'even'
(would this word be appropriate here?) - no sharp or missing high notes,
a strong but clean bass.
The low cut-off frequency depends on the speaker design and on the size.
There is not much a small coulumn speaker like in the YAK (with 6"x9"
size) can do below 100 Hz compared to a 15" PA speaker, that maybe can do
even 45 Hz rather well.
Compared to the fact, that most men can sing a lowest note (A') at about
110 Hz and some can go down to 50-60 Hz, this limit can really hurt.
- speaker power
-
This mainly states how much power the speaker can carry before overheating
it's coil. A usual rating could be 150W continous, 600 W peak (for a
small PA speaker). This does not mean "undistorted", it means "without
blowing."
- maximum speaker power with stated distortion
-
How much power a speaker can handle without distorting and becoming
nonlinear, is a complicated thing, and - very important -
is a function of the frequency.
It is fairly easy to handle the
maximum speaker power
at 1 kHz, but doing that at low frequencys requires big speakers.
I doubt that a YAK can handle more than 75 W at 200 Hz without distortion.
- Amplifier power
-
The power an amplifier can handle depends on physics, the number
you hear depends on interpretation.
There is a peak rate, a continous rate, a burst rate ....
so ask for which power rating is used.
The Hilton 201 amplifier integrated circuit is listed for less
than 75 W continous, the same IC is used in the 300B, so
take the numbers you get from callers and suppliers with a grain
of salt.
An amplifier should never, never clip, i.e. run into it's hard
limits, because this can easily kill highrange systems in
more-way-speakers. Speakers need amplifier
headroom for survival.
So a recommendation often heared is that the amplifier could
have a slightly higher rating than the speaker, but not less.
- The power needed
-
What do we need?
Not power per se. We need a certain volume level at a certain distance
from the stage. So an efficient speaker requires only a small
amplifier.
I found the Director rather efficient, but most PA speakers are
far better. (I can check that, if somebody is interested.)
- The impression of volume
-
I heared very different things on how the subjective volume
impression is made. I came across different models on how
to weight the spectrum of the 'noise' and so on.
From personal view, I found that i feel music as "loud" or
"too loud", if it becomes distorted, either because the speaker
is at it's end or my ears are.
- Loudness correction
-
As the ear is somewhat nonlinear regarding volume,
basses and trebles are often boosted at low volume levels for creating
a rather 'even' impression. This is done in the Hiltons with
special volume controls. If it is done wrong, the impression
becomes uneven, either too little basses, or to much.
- headroom
-
Headroom is a term for how much a system can handle over the=20
normal load. A typical headroom for a sound mixer is 20dB,
that is: the normal voltage level is 1/10 of what the system
can do. For a speaker this would mean to run a 100 W speaker
at about 1 W average load.
With enough headroom a loud signal (i.e. drum solo in the
middle break of "rocking in rosalies boat") will be transferred without
distortion (even if someone drops the mike...). This is necessary
for a clean sound.
A well made sound system still has some headroom when it is
at full operation volume.
I found that most Hilton/Yak setups at special dances don't.