Platon Measurements

Comparision between Aurasound NSW2-326-8AT and Peerless P830970.

Conditions:

  • Both drivers are mounted in identical pipe constructions with identical stuffing.
  • Measurements are valid down to 170Hz (5.9ms gate). Mic distance 1m.
  • No equalization applied. Only a LR4 HP @100Hz against accidents.
  • Measurements taken vertically on axis and horizontally at 5° increments from 0°...+90° and at 180°.
  • Excitation: periodic noise.
  • From the first diagrams below it seems the Aura has a higher sensitivity than the Peerless. This is not the case. See the extra diagram further down.

Polar Response:

The Aura has wider dispersion but the Peerless has a more uniform off-axis behavior (compare e.g. the 75° and 90° responses around 2...3KHz).

Other measurements:

These are both pipes measured from the back (180°) !
Responses are normalized at 1 KHz.
The Peerless (black line) starts to roll off a little earlier but the descent is again pretty uniform. It follows closely a 2nd order LP response while the Aura (red line) is very similar to a 3rd order response.
Either way, you would never see such a beneficial behavior with a regular box speaker.

Comparison 90° and 180° responses:

This is a comparison of the 90° and 180° responses. It is amazing how similar they are in both cases, even in level, which has not been adjusted in any way. Here it becomes really clear why this speaker can be considered an omni.

Sensitivity: The Peerless is 3.6dB louder (@1KHz) in this setup.

Interim Conclusions:

  • The Aura scores with wider dispersion but the Peerless has a well controlled and uniform off-axis behavior. It needs to be verified how the dispersion pattern of the Peerless mates with the Seas woofer section of my design approach.
  • The Peerless’ >3 dB extra in sensitivity are beneficial.
  • The Peerless has better distortion ratings (not visible here). Ref. Hobby Hifi magazine 2/2006 (Aura) and 4/2009 (Peerless). The diagrams there are visually similar but the Aura was measured @80dB sound pressure and the Peerless @90dB.
  • The Aura has a greater xmax (+-1.8mm vs. +-1.45mm). But this is no real advantage when operated only 1KHz and up.
  • The wider bandwidth of the Peerless is nice from an engineering point of view but is most likely no striking audible advantage over the Aura.

For the folks out there, who would like to build a Pluto but have problems with obtaining the Aura, which is not easily available in all countries:
The Peerless is obviously no drop-in replacement for the Aura. It requires different equalization, leveling and mounting. All this is no rocket science but probably needs skills beyond rookie level, especially the equalization. This has to be applied with great care because as you can see, it is only required on axis and theoretically less and less off axis (aka diffraction- / baffle step correction).

Last updated 27-Mar-2017