Ellipticor One
Copyright 2017 © Troels Gravesen

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DRIVERS   CROSSOVER    CABINET    MEASUREMENTS    SPEAKER-KIT     CROSSOVER LAYOUT   SETTING UP SPEAKERS

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!

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. 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 crossovers. What goes and what doesn't? Initial crossovers tend to be complicated as we want to make the drivers work nothing less than perfect.

Both drivers are easy. They are 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. Check Ellipticor-4.


       

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 allowing high resolution and 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 paper cones are history for high-end drivers, try these. I'm sure you won't be disappointed.
Speaking of 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 iron 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, sandwhiches 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 know the all too common ~1 kHz dip in frequency response from many 6" drivers due to part of the rubber surround starting moving in opposite direction to the cone. At a certain frequency the rubber surround 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.

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

Basics:
2-way speaker from 6" + 1.5" drivers.
System sensitivity: 89 dB/2.8V, 1 meter.
Impedance: 4-8 Ohms, minimum 4 Ohms @ 200 Hz.
Point of crossover: 1900 Hz.
Power requirement: 25+ watts/channel.
Power handling: See 18WE specs and please read this: http://www.troelsgravesen.dk/power-handling.htm, and remember any burned driver is a misused driver.

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


Speakers at ScanSpeak demo room in Videbaek, 2017. External crossovers on the floor. 


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

 


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Generally I find it pathetic when people post images of unpacking something they've just bought... You're welcome, call me pathetic. Unpacking the Ellipticor drivers is like unpacking an iPhone times four. First of all I'm sure these drivers will reach you in good condition no matter what brutal shipping company you're using. Next there's the feel-good factor. Buying expensive stuff requires proper wrapping so that un-wrapping is a part of the overall positive experience. I'm sure the ScanSpeak guys did a lot of thinking making sure you will have pleasant time un-packing these gems.


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CROSSOVER
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The crossover has undergone considerable changes since the Munich show. Having only a short time to prepare a crossover, you tend to wear belt and suspenders. However, the voicing was as I wanted it to be, thus the long winter months allowed the time to fine-tune a simpler crossover delivering the same tonal balance with fewer components, thus two correction circuits have been eliminated and frequency response could be maintained within +/- 0.5 dB of the Munich crossover. The point of crossover has been lowered some 300 Hz, from 2200 Hz to 1900 Hz. Subjectively the new crossover delivers a little more presence, and little more vivid presentation.


The final crossovers.


Driver details


Tweeter details.


Mid-bass details.


The ring covering mounting screws can be had in different colours.


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

The cabinet dimensions make a net volume of 15.8 litre, minus port, crossover and drivers, plus added volume generated by damping materials. With a Fb = 45 Hz we need a port of Ø50 x 100 mm length.

Check out this file regarding construction tips: http://www.troelsgravesen.dk/tips.htm

 

The material used is black MDF, or rather HDF as the density is around 0.85. Obviously you can use ordinary MDF or Baltic birch to your liking. Hardwood may be suitable too. In any case, I suggest 4 mm bitumen pads on all internal panels (included in kit).


Do not forget to chamfer 18WE driver hole! The speaker needs breathing and like any other speaker, the energy coming from the rear of the cone is exactly the same as coming from the front.

Routing for the drivers can be tricky in case you have the the cabinets spray painted as I did. Coming back, the rebates were too small for accepting the cover rings and I had to sand the rebates with a Dremel rotary sander. If you squeeze the rings in place you will most likely never get them off again. I did so and had to drill a hole in the ring - and order new ones! Make sure you have at least 100 um around the rings. It should be easy to rotate the rings to get off the neodym grip.


Place the crossover on rear panel and cover with 1 layer of felt.


Add two layers of acoustilux on top of crossover.

Cabinet damping:
Add felt to all internal panels except front and rear panel behind midbass driver (room for crossover)
Add two layers of acoustilux on top of cabinet.
Add felt and acoustilux on top of crossover as seen above.

 

Setting up the speakers
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It goes without saying that setting up the speakers correctly is pivotal for getting the best from this expensive kit. There are loads of sites on the web to help you out, and here's one: http://www.cardas.com/room_setup_main.php


This one fits my room the best. The numbers mean of if you have the speakers 1 meter from the front wall (the wall behind the speakers) you have an optimal distance of 1.62 meters to the end walls of the room. If you have the speakers 0.8 meter from the front wall, then 0.8 x 1.62 = 1.3 meters to the end wall.
If you have the speakers on the end wall, the distances are the same, only visa versa, 1 meter to side walls and 1.6 meters to front wall. I'm sure not everyone can fulfill these guidelines.

The stands I use are of 52 cm height and I have made wedges of 4º to tilt the speakers suitable for my listening position in my sofa. Optimal listening height is somewhere between midbass and tweeter. You may obviously choose another stand height, but take care not having the same distance from the 18WE driver to the floor and to the front wall. Symmetry here is bad! The 52 cm stand height and wedges makes some 68 cm height above the floor of the 18WE. If you have the same distance to the front wall, you may have a -6dB dip at around 160 Hz, so take care. Download excel file here to find your placement from cells B25-26-27.
Further I have 180 cm from one end wall and 200 cm from the other.

The 18WE is no more tricky than any other speaker, but I want you to have the best possible sound from your investment. The room is always half the system.


MEASUREMENTS
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Tweeter response on a 60 x 100 cm baffle.


D3404/552000 CSD.


18WE/4542T00 response on a 60 x 100 cm baffle. Who could ask for more?


18WE/4542T00 waterfall plot, 25 dB scaling.

 



Frequency response of left and right speaker.



Response of drivers driven from crossover and summed response.


Impedance plot of speaker. Minimum at ~200 Hz is 4.0 Ohms.


Horizontal dispersion @ 0, 10, 20 and 30 deg.


SPEAKER-KIT
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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):

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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There are three tweeter level options. My preferred, and +/- 1 dB.


You can expand the board a little and have the tweeter coil horizontal.
Make sure you can have the board through the driver hole and have room for binding posts and terminal block.

Speaker wiring

 

Speaker wiring with tweeter attenuation selector


Place the terminal block on the rear side of the cabinet.