The AT4073a lives on as an upgraded model, BP4073

Steve:

The specs, features and pickup pattern are a lot different on the BP4073 from the 4073a.

I don't know why AT has to try to confuse everybody with using almost the same name on different products.

There are still some new 4073a mics for sale too I just saw.

They're not THAT far different and what has changed makes the BP4073 look significantly improved at about the same price.

AT changed many of its mics. Isn't one of the main reasons the mics were "upgraded" was to make them legal to sell in Europe under the new laws? Or is this not accurate.

4073a SPECIFICATIONS
ELEMENT Externally polarized (DC bias) condenser
POLAR PATTERN Line + gradient
FREQUENCY RESPONSE 30-20,000 Hz
LOW FREQUENCY ROLL-OFF 150 Hz, 12 dB/octave
OPEN CIRCUIT SENSITIVITY -23 dB (70.8 mV) re 1V at 1 Pa
IMPEDANCE 100 ohms
MAXIMUM INPUT SOUND LEVEL 126 dB SPL, 1 kHz at 1% T.H.D.
NOISE 14 dB SPL
DYNAMIC RANGE (typical) 112 dB, 1 kHz at Max SPL
SIGNAL-TO-NOISE RATIO 80 dB, 1 kHz at 1 Pa
PHANTOM POWER REQUIREMENTS 11-52V DC, 3.2 mA typical
SWITCH Flat, roll-off
WEIGHT 4.0 oz (114 g)
DIMENSIONS 9.13" (232.0 mm) long,
0.83" (21.0 mm) diameter
OUTPUT CONNECTOR Integral 3-pin XLRM-type
ACCESSORIES FURNISHED AT8405a stand clamp for 5/8"-27 threaded stands; AT8134 windscreen; protective carrying case

BP4073 SPECIFICATIONS
ELEMENT Externally polarized (DC bias) capacitor
POLAR PATTERN Line + gradient
FREQUENCY RESPONSE 20-20,000 Hz
LOW FREQUENCY ROLL-OFF 80 Hz, 12 dB/octave
OPEN CIRCUIT SENSITIVITY -29 dB (35.5 mV) re 1V at 1 Pa
IMPEDANCE 50 ohms
MAXIMUM INPUT SOUND LEVEL 141 dB SPL, 1 kHz at 1% T.H.D.;
151 dB SPL, with 10 dB pad (nominal)
NOISE 13 dB SPL
DYNAMIC RANGE (typical) 128 dB, 1 kHz at Max SPL
SIGNAL-TO-NOISE RATIO 81 dB, 1 kHz at 1 Pa
PHANTOM POWER REQUIREMENTS 48V DC, 4.8 mA typical
SWITCHES Flat, roll-off; 10 dB pad (nominal)
WEIGHT 99 g (3.5 oz)
DIMENSIONS 233.0 mm (9.17") long,
21.0 mm (0.83") maximum body diameter
OUTPUT CONNECTOR Integral 3-pin XLRM-type
ACCESSORIES FURNISHED AT8405a stand clamp for 5/8"-27 threaded stands; 5/8"-27 to 3/8"-16 threaded adapter; AT8144 windscreen; two O-Rings; protective carrying case

Those two polar patterns are pretty close - the reason the AT4073 looks lopside is they graphed 6 frequencies, putting the lower three on the left side of the graph and the higher three on the right so the graph didn't get so muddied up. For the complete pattern, take the left side and flip it to superimpose its mirror-image over the right and vice-versa.

In terms of the numbers, the only really signifigant differences on the BP version are its 15dB higher maximum SPL, the 6dB lower sensitivity, and the lower shelving point of its HPF.

Hey Steve, would say that with 6 dB lower sensitivity and only 1 dB better S/N ratio that the new mic effectively has more noise (to achieve the same signal), or is that already factored in? I don't really know what "1 kHz at 1 Pa" means.

The mic's internal noise, its EIN, is the equivalent to the signal that would be produced by exposing the mic to a 1 kHz tone @ 13dB SPL were there no internal noise. The mic also achieves its rated output when exposed to a 1kHz tone at volume that generates 1 Pascal of overpressure, about 94 dB SPL. Thus at rated output the signal+noise to noise ratio is 94 - 13, or 81dB. The dynamic range is the Maximum SPL, 141dB, minus the EIN, 13dB, or 128dB SPL and describes the range between the softest sound the mic can detect and loudest it can handle without distortion. The older mic has 1 dB more internal noise, hardly noticable.