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April 2011 - Elsinore Mk5 - some details below are obsolete.           

ALTERNATIVE DRIVER - PEERLESS HDS 830875

The driver on the left is 830874 with PPB Cone and on the right is 830875  with Nomex Cone

Note the crossover below, it shows that only one component value needs to be changed. This is strangely in the Tweeter part of the crossover and not the MidBass and Bass. This may seem odd, but is easily explained.

The two drivers have virtually the same amplitude response (or frequency response). While the main cone material is changed, in all other aspects the drivers are the same. The main difference is that the Nomex is slightly lower mass and as such is 0.8dB more efficient according to Peerless. Our measurements show it to be effectively 1dB - hence the increase in the Tweeter's output is maintained by reducing its padding resistor from 1R8 to 1R. The overall system sensitivity is also up by 1dB - a nice thing.

The main question that should be asked is this: How can these two drivers be so similar that no other crossover change is required? One: The driver's Thiele-Small parameters are so close that the box alignment is left unchanged. Two: The acoustic response is very similar - stunningly similar. Note the overall profile of both cones are the same. The inverted dust cap is actually also PPB in the Nomex version, albeit the diameter is slightly smaller. As long as the cone works as a piston - using the same driver motor assembly and basket (the heavy duty cast frame that holds it together), we would expect they have the same response up to about 1500 Hertz. Such is the case and has been confirmed by measurement. Please note the plots below which are high resolution 1/6th Octave RTA type (four times the resolution of 1/3rd RTA), mounted on an IEC type baffle that largely eliminates diffraction effects above 100 Hertz.

PPB Cone

Nomex Cone

(largely ignore identical peaks at 200 Hertz as a measurement artefact)

As you can see, the Nomex output is about 1dB higher, but the general response very similar. The peak around 4KHz is a bit broader. As discussed elsewhere, this is not a cone resonance but a build-up of energy largely to do with the shape of the inverted dust-cap and cone profile. Note, the material of the dust-cap is both made of PPB.

The shift in the response at any frequency is less than can be considered correctable by the crossover. The LCR trap that is designed to deal with 4KHz energy build-up (see L3, R2 and C1 components) is quite capable of dealing with both situations and the amplitude response change is minimal through that area. The summed driver response is about 7-8dB down as the Tweeter is taking over - that helps too.

The explanation, partly given above, is that the two driver's pistons response is the same and above that the inverted cone becomes dominant (above piston range) is the same material and shape. The minor change around 4Khz is that the Nomex version's PPB dust-cap is a bit smaller in diameter. Of greatest interest here is that the roll-off above the peak is practically identical. Then the total system response is largely maintained by increasing the Tweeter's output by near 1dB.

(None of this would be possible if the electrical parameters are identical. They are, in fact the only deviation is in the 10-20KHz range, indicating that the eddy currents are slightly different. But being so high in frequency have no import, besides the difference will be swamped by the inductance in the crossover.)

We would thus expect the overall tonal balance to be the same, and so it proved to be. The Nomex are just a little less rich than the PPB which comparatively do have a quite attractive lushness here, but not overtly so. The Nomex are also a bit faster (and possibly a bit more detailed?). The tonal balance is not significantly different - as expected. But where perhaps I am leaning towards the Nomex is that they just seem to sound that touch bit more real - a difficult to define matter I know, but what sways me is that the Nomex does voice better, IMHO. But there will be those who will prefer the PPB and there should be no criticism on that score.

Both versions of the Elsinores are hard to beat in terms of sheer value for money, as they are intended to compete with speakers that are in a price range that most of us are not able to afford. The bottom line, as far as I am concerned, IF you are not able to source one driver, then don't hesitate to get the other if available. As the Danes say, Basta!


THE CROSSOVER

(note the red underlined components changes)

Note: Crossover & Values of Components are Subject to Change - date 5th November 2006

 

Here below are the two above combined plots:

Note that lateral lines show a consistent 1dB increase in Black (Nomex)

 

Send mail to joeras@vacuumstate.com with questions or comments about this web site.
Copyright 2003-10 Joe Rasmussen & JLTi
Last modified: Monday June 08, 2015

Just had a terrible thought. If "intelligent design" is unscientific, then who will design our audio equipment?