Ellipticor-2F8

In hindsight, my ATELL-3 was a keeper, but I was desperate for space and had to let it go. Actually I may have to lend these to friends to have some space at home.... Anyway, since then I wanted to make a semi-active version together with a fully passive version, thus the 8 Ohms Ellipticor 18WE/8542T00 for mid-bass in order to keep final system impedance relatively high.
With the Viawave ribbon tweeter not being available I decided on the Ellipticor D2404/552000, being more expensive - but doing so well in my Ellipticor-A50 it had to be this tweeter.
With the Hypex module running the bass, the MT-section impedance stays above 7.1 Ohms - and you have almost infinite options for room-adaption, something very much in demand as room acoustics leaves a lot to be desired for most.
My 32 wpc EAR-861 runs the fully passive version from its 8 Ohm tabs without trouble.
I also wanted to use the magnificent Faital 10RS350 for bass as it does the same as the AudioTechnology 10C77 - and at around a third of the price. If you're a strong believer in high cost equals better performance, the AudioTechnology 10C77-25-10-KAP or the ScanSpeak 28W/4878T01 can be used, but only with the Hypex module as I don't have the drivers and can't ensure proper function from the passive Faital bass crossover.

Now, why should you build a speaker like this? Well, first of all it isn't big. Everything is relative, but it's not large like the Ellipticor-3 or the SEAS CNO-4, speakers similar in design, but building on 2½-way philosophy. The ScanSpeak 7" Ellipticor driver has a phenomenal power handling and can be pushed extremely hard before distortion sets in.
So, you need a modest sized speaker, that all the same can produce a significant soundstage and create some potent bass. You want the benefits of a basically 2-way system in terms of simple crossover with no high-pass filter to the midrange. It has its benefits, but also its limitations in terms of fullness and power handling. Building the Hypex version you get the benefits of almost infinite room adaption, which is by far the most common problem due to inadequate room acoustics and not least speaker placement.
You may furthermore like this design because you have a smaller, but good sounding amplifier that together with the Hypex module can do stuff it couldn't do alone. 20-30 watts is enough to drive the MT section.
The cabinets, as seen here, are seriously heavy due to the reinforced bass cabinet, which allows uncoloured sound. What you hear comes from the drivers, not from resonating cabinets.

The Faital bass driver has a rigid spider and needs some massage. Press the cone to the bottom and pull the cone as far out as possible until you hear the spider making a slight crackling noise. And DON'T stick your fingers through the cone!! Gentle but firm!

The crossover follows a textbook LR2 topology and initially I ran the 18WE from a single coil - and nothing else, just as I did with the ATELL. Here I wanted to smooth the 18WE roll-off a little more, hence C2/R3. This removes a slight peak around 4 kHz.
The bass crossover is very close to the ATELL crossover, only here 1st order and the impedance flattening circuit was added, something I omitted in the ATELL design. Obviously the Hypex version is void all of this and the low-pass section just mimics the passive low-pass function and cuts 1st order around 150 Hz. In addition to this a 4 dB boost at 40 Hz and an LR2 high-pass filter at 15 Hz for vinyl fans. The bass is deep and powerful and can obviously be adjusted to almost any room condition.
From a lot of builders' respons, I can see many have problems with bass boost below 100 Hz and also most likely have a dip around 150 Hz due to speaker placement. This often comes from corner placement with equal distance to side- and front wall. I many cases builders cannot place the speakers symmetrically and one speaker may have a lot of room-gain - the other a lot less. Most people cannot do much about it as speakers must be where they are and there is no way we can adjust this with passive means. Only the Hypex can do that - and easily. Go to Hypex info here.

For the cabinets I used 20.5 mm Baltic birch and for the front panel 25 mm. 20 mm is OK. The mid-tweeter front was made from 25 mm black MDF (HDF).
For the mid-tweeter brace I use 15 mm BB, use 15-20 mm.
I had 3 mm space between the two panels separating the bass and mid cabinet.

The cabinet is in many ways similar to the ATELL-3, so go there to get more ideas of cabinet construction.

Use a clean sheet of MDF and draw up the shape of the cabinet to align the panels properly as seen below.

Making the rear panel fit the shape and rebate is the most troublesome - in Baltic birch.
Using MDF and filler - piece of cake.

Route for the midrange port, bass driver and Hypex module.
The Hypex compartment can be use for the crossover if fully passive is wanted - for bi-amping! If so, place the bass crossover in the bass compartment and the mid-tweeter crossover in the Hypex compartment.

Left: Hypex compartment in place. Right: Bass cabinet bracing.
Make holes as seen on photo.

Make sure you have some gab between the decor ring and and the rebate, otherwise you won't be able to remove it.
I took a router diameter some +0.5 mm to make sure I can lift the ring with a wrench or similar (the ring has magnets).

Chamfer driver holes properly!
MDF/HDF and screws are not best buds. After drilling the screw holes, I filled the holes with thin epoxy glue. The fibre material will suck up the epoxy and provide a firm grip for the screws.

Faceting the front panels. Set table saw to 30 deg.
Set your gliding table guide at an angle of 3 deg.
The exact angles are 29.7 deg. vertical and 3.05 deg. horizontal.
Do test cuts to make sure it works correctly - and adjust to your conditions.
At the top 35 mm wide and 20 mm deep.
And remember, all this can be done by hand: Chisel/planer and sandpaper.

The finished front panels.

The bass cabinet was added 10 mm HDF to strengthen panels and reduce volume.
Now we have around 39 litre net volume. The damping materials will add in the area of 10% extra volume.
Use vinyl glue for the panels, bitumen pads and felt material.

The mid-tweeter cabinet was added 4 mm bitumen pads on all sides except rear panel, where the passive crossover will be placed. Before you glue the bass front panel, make sure to drill a whole for wires from terminals to mid-tweeter section. Seal wire hole with Superfix or similar.

Cover all internal panels with felt except for mid-tweeter rear panel (right).
My mid-tweeter front panel was made detachable, as I have plans for more versions. Don't ask, please!

Before finishing the cabinets I couldn't help setting up the speakers to do the final measurements, simulations and prototype crossovers. The dynamic headroom of these 18WE drivers is phenomenal. Even the Tin Pan Alley came through at thunderous levels - with deep potent bass.

Left: Mounting the bottom frame, here in solid oak. Right: Wiring the bass driver.
Place 1 pcs 50 x 50 cm acoustilux at top of the bass cabinet.
Place 2 pcs 40 x 50 cm acoustilux on sides of bottom of bass cabinet leaving two layers at the back.

Add 1 pcs 20 x 50 cm at top of MT cabinet.
Add 1 pcs 20 x 20 cm on top of crossover.
Add 1 pcs 20 x 50 cm at bottom and sides of MT cabinet.

Mounting the Ellipticor driver is a bit tricky.
Make sure you have some space around the driver for the decor ring to move freely! Use some foil to make sure you keep some space when adding the screws. If not, you will never be able to remove the decor ring.
I used some countersunk screws found at the local Bauhaus, 4 x 20 mm.
I'd say that 6 screws for a small tweeter like this is overkill, but that's what the ScanSpeak people decided.

The almost finished speakers in my workshop. Hypex modules on their way and my stock FA501s running the bass.
This is the time you lean back and see of the final results resembles what you had in mind when starting contemplating the whole project. Pretty close to what I had in mind.

Mounting the Hypex module.
Combine read and blue = PLUS
Combine grey and black = MINUS.

As can be seen I reversed the polarity of the bass driver at the high-level input.

Go to Hypex programming here.

A few comments on MEASUREMENTS before you start interpreting the readings below.
First of all, if we think measurements will tell us how a speaker sounds, we're wrong. The perception of sound is way too subjective to be reflected in any measurements we can perform. A loudspeaker system is meant to give us a satisfying idea of an acoustic event and for some people a pair of 5 USD ear-plugs are enough, others spend 200 kUSD on a truly full-range pair of speakers - and the latter may not be happier than the former.
Measurements may give us an idea of tonal balance of a system, i.e. too much or too little energy in certain areas, although dispersion characteristics play a vital role here. A two-way 7+1 and a three-way 7+4+1 may display similar horizontal dispersion, yet sound very different. Measurements may tell us about bass extension if far-field measurements are merged with near-field measurements. In addition to this, ports may contribute to bass extension. Most of we diy'ers do not have access to an anechoic room for full-range measurements from 20-20000 Hz.
What cannot be seen is what kind of bass performance we get in a given room. Bass performance is highly dependent on in-room placement of your speaker and the same speaker can be boomy in one place and lean in another. Actual SPL level at 1 meter distance and 2.8V input is useful for en estimate of system sensitivity and combined with the impedance profile may give an idea of how powerful an amplifier is needed to drive the speaker to adequate levels.
What measurements do not tell is the very sound of the speaker unless displaying serious linear distortion. The level of transparency, the ability to resolve micro-details, the "speed" of the bass, etc., cannot be derived from these data. Distortion measurements rarely tell much unless seriously bad, and most modern drivers display low distortion within their specified operating range.
Many people put way too much into these graphs and my comments here are only meant as warning against over-interpretation. There are more to good sound than what can be extracted from a few graphs. Every graph needs interpretation in terms of what it means sonically and how it impacts our choice of mating drivers, cabinet and crossover design.
What measurements certainly do not tell is the sonic signature of the speaker, because speaker cones made from polypropylene, aluminum, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of adding spices to the stew. Nor do measurements tell what impact the quality of the crossover components add to the sound, from state of the art components to the cheapest of coils and caps, they all measure the same if values are correct, yet sound very different.

Frequency response of 18WE and D2404 measured at 0.5 meter distance at a point between drivers.
The 2404 has a slight increase in response above 10 kHz, but I decided not to do anything about it as it will even out when we look at horizontal dispersion. See below.

Combined impedance of bass module and MT section. Overall an easy load and my bridged EAR-861 has no trouble running the fully passive version.
Minimum impedance around 4.5 Ohms in critical area (20-100 Hz).

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

Short introduction to programming the Hypex module:

Further info on Hypex programming here.

Update firmware before installing the software.

Download FA Update Tutorial V0300.pdf

Download Ellipticor-2F software here. zip file, unpack and place the Folder in the FilterData folder the HFD software has created under Documents.

Turn on your FA251 and connect to PC via USB cable.
Update firmware. See above.
Set all presets, 1-2-3, to AnalogueSUB input.
Set volume to 0 dB.
Click Device setting:

Set driver impedance to 8 Ohms.
Set volume start to 0 dB.
All other settings as seen above.
Click Update limiter.
Undo window and you're back to this:

Click Filter design and you have this:

Click New FA251.

Click Open:

This will open the FilterData folder in your Documents folder.

Click the file Ellipticor-2F8 and press Ok and you will have this:

1st order @ 150 Hz and further low-pass LR2 at 1000 Hz to remove any peaks above this.

Upload all presets and you're done.
Set the volume control on the Hypex panel as 12 o'clock.
Preset 1-2-3 has 8, 10 and 12 dB gain and usually 10 dB will do, but try it out.
Use preset 1 or 3 if 2 is too much or too little.