Anthony Gallo Reference 3 S.A. Amp - Manual (Page 2)

The upper ‘speaker in’ terminals are conventional inputs. They connect the incoming full-range amplifier
signal to the entire speaker. The 10” side-firing woofer, dual 4” mids and our unique 300° dispersion CDT² tweeter
are all operated together from this one input. To enjoy music, that’s all you need. You never have to use the second
input at all. But what if you wanted true subwoofer bass without a separate subwoofer? That’s where the ‘sub in’
terminals enter the picture.
They connect directly and separately to the woofer’s 2
nd
voice coil. That’s because our 10” woofers in the
Reference³ speakers are outfitted with two voice coils. Those can be independently amplified or bi-amped. As you
would assume, the 1
st
or main voice coil is driven from your main stereo amplifier via the ‘speaker in’ input like
any other ordinary speaker. The 2
nd
voice coil can be driven with a second ‘bi-amp’ amplifier. This ‘twin drive’
scheme extends the speaker’s reach into true 22Hz subwoofer territory. Hence this input is labeled ‘sub in’. But
why do you need the SA for that? Wouldn’t any other amplifier (or two additional channels on a multi-channel
amp) do the trick? Not exactly. Here’s why.
Remember that we just mentioned how this input drives the 2
nd
voice coil directly? That means this lower
input bypasses the crossover behind the ‘speaker in’ upper inputs. That crossover network inside the speaker
chassis sends frequencies below 150Hz to the woofer and everything above 150Hz to the midranges and tweeter.
The ‘sub in’ terminals of our Reference³ don’t use any crossover.
Why not? Because the ‘sub out’ or ‘0.1 out’ of a surround sound receiver or preamp/processor (pre-pro)
already comes with its own low-pass crossover. That’s usually fixed to the THX standard of 80Hz. More on that
hookup scheme from a pre-pro or multi-channel receiver in a moment. For right now, let’s stay with a stereo
system which will use a preamp or integrated amplifier instead.
This preamp/integrated (via a second pair of pre-outs or a Y-adaptor) would send a full-range signal to
whatever amplifier would power the Reference³s’ 2
nd
voice coil if you didn’t have the SA. Can you imagine what
would happen? Without a crossover on the 2
nd
voice coil, the woofer would now receive frequencies way above
150Hz, in the range the midranges and tweeter already reproduce. This would wreck havoc with our speaker’s
carefully calibrated tonal balance. You would hear murky thickness from the mid-bass on up, as though you had
maxed out a bass tone control while cutting the matching treble control to zero. Not good.
What you need to use these ‘sub in’ inputs properly and as intended are two additional features besides just
another amplifier. You need an adjustable low-pass filter (crossover) to restrict the 2
nd
voice coil signal to the
proper frequency range below 150Hz. You also need an independent attenuator for this second input to match the
amount of low-frequency support beneath what your main amplifier already provides. This allows adjustments so
that the full-range response plus bass augmentation of your Reference³ speakers add up to a flat and linear
frequency response in your room.
And that is exactly why our SA isn’t merely an amplifier but includes a continuously variable low-pass
crossover and gain/volume functions. It even adds phase and EQ boost facilities which we’ll visit in a moment. For
now, let’s inspect the front panel. Except for the gain controls (one per channel), all other front-panel adjustments
of the SA are recessed so that kids or curious visitors can’t twirl with the knobs and undo the calibration you (or a
dealer or installer) have spent time on setting up to your satisfaction. Simply use a slotted screwdriver to make the
adjustments - the controls move very easily. Let’s explore all controls in detail now and how to set them up: