Ellipticor One
Copyright 2017 © Troels Gravesen

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DRAFT PRESENTATION

The final construction will probably be ready around August 1st 2017

The construction here displays new drivers never seen before and to be honest, it's a daunting task being the first to put these drivers together and see what has become of a serious investment in time and money. Both mid-woofer and tweeter feature elliptical voice coils, something - to my knowledge - never tried before.
We have seen oval* speaker cones, even square cones, but all with a round voice coils. I can only imagine the trouble ahead of these units in terms of manufacturing oval voice coils, oval magnet parts, machines that can add glue in ovals and many other issues in manufacturing. Round is so easy.
And no, they are not going to be cheap! We're talking close to 700 EUR for the 18WE driver - and this without VAT.

This ellipse project was started at ScanSpeak a few years ago by Birger Jørgensen, who sadly passed away last year. The project was brought to maturity by Dennis Hansen and Simon Møller Nielsen, and I was handed the drivers to make a 2-way stand-mount for the Munich High End Exhibition 2017 for the presentation of the drivers. Quite a challenge as it often takes considerable time to get to really know a driver, know its strengths and weaknesses, because all drivers have compromises, and we have to learn how to handle a driver with regard to cabinets and not least crossovers. What goes and what doesn't?

Both drivers here are easy. They are both extremely broad-banded and display no serious break-up modes that require any particular damping. They are kind of drivers you quickly make friends with and they generously feed your imagination for future constructions, e.g. 3-ways, 4-ways, and who knows? And not only that, they allow you to think in terms of high-efficiency systems, 90+ dB.

It's not often a "6+1" keeps me up half the night. In fact, I don't remember any such speaker that did. I didn't even care to pull in my subwoofer to assist in the lower octave, because obviously any 6" driver just doesn't move much air below 40 Hz unless we settle for a sensitivity around ~82 dB, and this speaker is tuned for some 89-90 dB sensitivity.
If low-level detail has much meaning, these drivers may display what it means - if you have a front end that allows you high resolution and a low noise floor. I surely haven't heard all 6+1s in the world, but I'll stick my neck out and be ready for any challenge you may suggest. And should you think coated paper cones are history for high-end drivers, try these. I'm sure you won't be disappointed.
Speaking of coated paper cones, I couldn't help thinking of the venerable Vifa C17, but this is also where every comparison stops. This 18WE driver features almost everything the C17 does not - and it pays off. Due to generous cladding of magnet parts with copper, proper balancing of suspensions and the overall open magnet structure we see a whopping Qm og 6.5. Nice! 
Making a good cone is an art of balancing stiffness and self-damping and we have seen a lot of new exiting cones over the last 2 decades, like carbon composites and ceramics. Add to this some marketing spices in form of special coatings and technologies, and we're done. Some materials appear to persist without much variation like mineral (talk) filled polypropylene and paper pulp, the latter added all sorts of ingredients, from reed and cotton to papyrus or even more exotic organic polymers.

The aim of elliptical voice coils is obviously to break symmetry. The force applied to the cone through the voice coils usually sees the same distance from the edge of the voice coil to the surround, thus inevitable break-up modes occur and we may have high-Q resonances disturbing frequency response and phase performance.
Apart from the basic resonance of the moving system, Fs, public enemy #1 for speaker designers is resonance. These ScanSpeak guys listen for resonances all the time and through design of coils, cones, suspensions, etc., they try to minimise resonance. From a cumulative spectral decay plot we can see where in the frequency band we have resonance/stored energy. Most common is cone break-up and resonances in the cone rubber/foam surround. We all know the all too common ~1 kHz dip in frequency response from many 6" drivers due to parts of the rubber surround starting moving in opposite direction to the cone. At a certain frequency the rubber holds too much mass and rigidity is too low and the cone may move outwards while the rubber moves inwards, thus the two parts are in opposite phase and we have a dip in response. Add to this the air flow around the half-roll rubber surround and we have a complex sum of issues to address - and balance.
Dips can be hard to hear unless severe, where peaks from dedicated cone break-up are more easily detected. And by the way, if a peak is not superseding a dip, the peak may be fairly good-natured and ear-friendly.
The driver here features a coating round the edge of the cone adding mass and elasticity to the inner part of the rubber surround in order to reduce the disturbance in the 1 kHz area.

Short review here from the Munich presentation: http://www.soundstageglobal.com. Maybe the reviewer should look into the DIY community and see what wonderful things we can do that would make commercial designers drool. Like well-braced bitumen clad epoxy glued cabinets made from 25 mm high-density fiberboard and quality crossover components that would sky-rocket commercial prices. :-)

*: An ellipse is an oval, but an oval is not necessarily an ellipse.


 


Final speakers were made from 25 mm HDF, damped with bitumen pads and spray laquered.


Speakers at ScanSpeak demo room in Videbaek. External crossovers on the floor.

 


DRIVERS
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Click images to view large

Download specs here: 18WE/4542T00     D3404/552000

Recommended retail price ex VAT:
18WE/4542T00: 691 EUR/pcs
D3404/552000: 464 EUR/pcs


CROSSOVER
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The performance of the drivers - and the given baffle - allows an almost perfect LR2 topology, far beyond the target point of crossover. Grey lines are target LR2 curves. This is rarely seen as we usually may have an LR2 profile some one octave below and above point of crossover followed by a gradual increase in roll-off. This may count for some of the exceptional transparency of the construction.

Driver details


Tweeter details


Midbass details


The ring covering mounting screws can be had in different colours. To the right the outboard crossover.
Crossover is mounted on two boards and can be placed inside cabinet on rear panel. 


CABINET
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Cabinets made from 25 mm black HDF throughout. Epoxy glue was used (WEST SYSTEM 104).

 

 

MEASUREMENTS
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SPL of drivers w/wo crossover.


SPL @ 2.8V/1 meter for left and right speaker.


Tweeter dispersion vertically, 0-10-20-30-40 deg. off-axis.
Response measured on 60 x 100 cm baffle.


Tweeter dispersion horizontally, 0-10-20-30-40 deg. off-axis.
Due to the elliptical shape of the dome dispersion is not the same vertically and horizontally, although not that different.
One may argue the tweeter should be mounted horizontally, but sonically it doesn't change much, if anything.


Cumulative spectral decay from 18WE driver in actual cabinet. Unusually calm in the ~5-8 kHz trouble zone.

 

More measurements to come.


SPEAKER-KIT
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To come

Probably ready by August 1st 2017

You can buy the kit with or without the drivers - or some of the drivers if you already have some.
Please ask Jantzen Audio for options.

All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.

Download Complete Kit Sale Presentations (pdf file): To come

All technical questions to troels.gravesen@hotmail.com

All questions regarding purchase of kits, please mail Jantzen Audio at contact@jantzen-audio.com


CROSSOVER-LAYOUT
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Crossover layout for tweeter and midbass. Make in two sections allowing mounting on rear panel through driver hole.

 

 

 

Speaker wiring