The First Watt is a transconductance amplifier i.e. it maintains a constant output current for a given input voltage. This is in contrast to almost all other amps that are voltage amplifiers, they maintain a constant output voltage for a given input voltage.
The passive crossover networks in conventional multiple driver speakers are at least in part in series with the driver and are designed to act as voltage dividers. They will not provide the frequency response they were designed for when driven by a current source. For instance, a simple high pass filter puts a cap in series with a tweeter to decrease current and therefore power to the tweeter at low frequencies. This is ineffective with a transconductance amp as it will increase it's output voltage at low frequencies to overcome the increase in impedance and deliver within it's limits the same current and power to the tweeter at all frequencies. Of course the amp will reach it's voltage limit at some point and not be able to compensate any further (it will be clipping the current), but the tweeter will still operate well below it's designed cutoff frequency.
These effects would not be subtle, and if one prefered the resulting gross distortions in the frequency response of the speaker then I suppose it could be considered compatible.
The frequency shaping network for this amp should be a current divider in parallel with the driver. The tweeter in this case would have an inductor in parallel with the driver instead of a capacitor in series.
The passive crossover networks in conventional multiple driver speakers are at least in part in series with the driver and are designed to act as voltage dividers. They will not provide the frequency response they were designed for when driven by a current source. For instance, a simple high pass filter puts a cap in series with a tweeter to decrease current and therefore power to the tweeter at low frequencies. This is ineffective with a transconductance amp as it will increase it's output voltage at low frequencies to overcome the increase in impedance and deliver within it's limits the same current and power to the tweeter at all frequencies. Of course the amp will reach it's voltage limit at some point and not be able to compensate any further (it will be clipping the current), but the tweeter will still operate well below it's designed cutoff frequency.
These effects would not be subtle, and if one prefered the resulting gross distortions in the frequency response of the speaker then I suppose it could be considered compatible.
The frequency shaping network for this amp should be a current divider in parallel with the driver. The tweeter in this case would have an inductor in parallel with the driver instead of a capacitor in series.