Ellipticor-A50-mkII

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ScanSpeak Ellipticor-A50-mkII
Copyright 2023 © Troels Gravesen

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DRIVERS CROSSOVER CABINET MEASUREMENTS
SPEAKER-KIT CROSSOVER LAYOUT WORKSHOP PICS

This is the combined presentation of the Ellipticor-A50 and Ellipticor-A50-II, now Ellipticor-A50-mkII. There are changes to the crossover as the first iteration was more than two years ago and it turned out - as often is the case - that we could get the same for less. Those who have built the Ellipticor-A50 and Ellipticor-A50-II need not worry. Stick to what you have.
Go to picture gallery of speakers made for ScanSpeak exhibitions.
Download mkI versions here: ScanSpeak-Ellipticor-A50 (pdf 23 MB) and ScanSpeak-Ellipticor-II (pdf 35MB)

2020:
ScanSpeak Ellipticor-A50 is a loudspeaker created to celebrate 50 years of service in speaker driver manufacturing. Since 1970 speaker drivers have been produced under the ScanSpeak brand name and countless models, from economy drivers to some of the most sophisticated and expensive transducers the hifi market has seen, has been produced. The ScanSpeak history here by Claus Futtrup.
The construction here is based on further expansion of the Ellipticor series and you will find new models never seen before, like a 15" bass driver with elliptical voice coil, a large elliptical midrange dome with double spider and exceptional flat frequency response - and icing of the cake - a 24 mm elliptical dome ensuring delicate handling of overtone structure. All ingredients for making state of the art speaker constructions - if we do well! The crossover is the heart of any speaker construction and can be tuned to personal taste and specific acoustic conditions, and a four-driver speaker can be put together in countless ways and here's my take on these new and exiting drivers.
What was meant to be a springtime celebration at Munich High End Show, May 2020, was delayed until 2022 due to corona virus and all the things that followed, like delays in shipping, etc. Writing these preliminary lines here in April 2020, where the pandemic has affected almost all parts of the world in ways we haven't seen since the Spanish flu a century ago, is really strange. This is going to impact our lives years ahead, but here and now, the sick must be nursed, children must be taken care of, schools must operate under restrictions, food must be produced - and speakers must be built.
And I have to admit that due to corona, I've had a lot more time to try out a large number of crossovers designs and not necessarily play the safe card, as we sometimes do, when time is limited as an introduction at Munich 2020 would have been.
Most of my regular readers will know I hate describing sound as we will never know how it sounds before we hear it ourselves. If I wrote a book on this speaker - you'd still not know. I've often been thinking all speakers should have a front grill as so many listen with their eyes rather than ears. As soon as our eyes sees something our brains are working overtime to form an opinion. Vision rules! Some thoughts here. This prototype cabinets here do feature a front grill and it impacts performance very little - if anything at all.

When I visited the ScanSpeak factory in February 2020 to sign a NDA, I heard an initial set-up of the 15" bass driver on an open baffle and I was immediately struck by the featherlight and responsive bass. By simulation this 15" doesn't go particularly deep, it's not a subwoofer - but for sure this 15" can play deep bass. I remember my first visitor jumping the seat when I put on my 45 rpm Tin Pan Alley by Stevie Ray Vaughan and turned up the volume. The classic hifi-show LP/track that makes professional reviewers run away. It is chokingly dynamic. Fortunately my first open baffle experience at ScanSpeak was transferable to a vented solution here at home.

Doing measurement on the D8404 mid-dome and seeing how deep it goes, I realised the 21WE didn't have to go very high, actually only handling the ~80-300 Hz range, thus a 3½-way system might be feasible, and this was what I was most excited about with regard to the bass section, when setting up the system. Would this go well? Given the low point of crossover from the 21WE to the D8404 I wasn't happy about having a high-pass filter on the 21WE. Given its limited cabinet volume it makes F3 = 66 Hz, so it really doesn't do deep bass and also given its closed box, has all the advantages of dynamics in handling upper-bass and lower-midrange. The 21WE has phenomenal dynamic headroom and regardless of source material I've never been able to overload the driver from a 3½-way configuration. So, with the 38WE doing deep bass in a vented box, the 21WE adds punch in its closed box. The best of both worlds.

I goes without saying the elliptical midrange dome is the key component in this speaker as it handles the overall most important frequency range, from middle-midrange and lower- to middle-treble, say ~300-5000 Hz, some four octaves. Quite frankly, I had no idea what to expect from such a driver and I was more than exited after some 120 hours of cabinet work to finally put together my initial simulated crossover and hear what it does.
I ran the 21WE/D8404/D2404 from my 32 wpc EAR-861 and had my Hypex UcD400 power amp run the 15" bass driver - and was blown away. Half the night I put on record after record to experience what this mid-dome did, because it does something very differently - and to my ears better than anything I've ever heard. I guess one of the things it does - or does not - is start beaming in the same way any conventional cone driver does, even small drivers will at some point start beaming and it may not sound bad at all, just different and with a certain sonic character. The D8404 allows an unprecedented window to the music and I've never had the spatial information so clear in that sense you do not have to concentrate on listening for that quality, it is just there. It has presence and transparency - and at the same time is smooth on the ear. I'm amazed such a small driver can go so low with such power and lack of distortion - and even from a simple low-pass crossover.

Go to site with gallery of the speakers made for ScanSpeak

Finishing the Ellipticor-A50, I had a version planned for myself, a smaller pyramid version, better suited in size for our living room - and with a smaller 28W woofer. So, a mockup was made and from measurements and simulations it soon became very clear it just didn't work. The D8404 on a narrow baffle had some + 4 dB @ 1 kHz and there was no way I was going to spoil the simplicity of the A50 crossover by equalising in this area, in particular for this key driver covering some four octaves.
What I had planned - and did work - was having the bass driver driven from a Hypex FA251 plate-amp/DSP, thus eliminating the passive bass crossover. I had this tested with the first A50, but the ScanSpeak people wanted a fully passive version, which I fully understand having a simple set-up for shows, etc. I also have to say the passive version plays wonderful with the Gryphon amps in Videbaek.

For my own version I also wanted an even more classic design, thus 25 mm Baltic birch.

Sound?

Finishing my own Ellipticor-A50s called for some celebration and I went to our local vinyl pusher and picked up these records. Not all stellar recordings but featuring artists I have enjoyed for decades. I addition to these records I obviously went through my current selection of records I use for testing loudspeakers. See some of the latest speaker constructions. For some reason I also picked up an old and worn copy of Double Fantasy/John Lennon-Yoko Ono. I mostly know this album from CD and hadn't heard it for many years. I don't think I had ever really heard this album before this speaker. Even Yoko's high pitched voice came through tolerable which is - again - a credit to the D84 dome.

Basics:
4-driver speaker, 3½-way configuration.
Dimensions: 45 x 45 x 105 cm, WxDxH. H + base panel and feet.
System sensitivity: 91-92 dB/2.8V/1 meter.
Impedance: 4-8 Ohms for MMT section.
Point of crossover: 80, 340 and 4000 Hz.
Power requirement: 20+ watts/channel.

Useful links (Please follow all links before e-mailing!):
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
http://www.troelsgravesen.dk/Inverted-Polarity.htm
http://www.troelsgravesen.dk/choices.htm
http://www.troelsgravesen.dk/power-handling.htm

DRIVERS
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D2404/552000.

D8404/552000

21WE/8542T00

38WE/8582T00
Click images to view large

Download driver specs: D2404/552000 D8404/552000 21WE/8542-T00 38WE/8582T00

The Hypex modules

The Hypex FUSION FA251 module.
If you can't live with the FA251, ask for FA501. The FA251 is more than enough for driving the 38WE bass.
The Hypex version allows bass lift of 4-5 dB @ 40 Hz for preset 2 and 3. Preset 1 is flat.
In general the Hypex version allows infinite room adaption.
Also incorporated in file is a high-pass filter @ 20 Hz for vinyl aficionados.

Go to Hypex page here.

Download software here (zip file)

CROSSOVER
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Like the ATELL-3 and Ellipticor-3, there is no high-pass filter to the 21WE midrange cone driver. This driver can handle a lot of power and with its relatively small closed cabinet, it has a natural 1st order roll-off below 80 Hz, where the 38WE takes over through the passive crossover or powered by the Hypex module.

CABINET
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Click image to view large.
Cabinets were made from 15, 20 and 25 mm Baltic birch.
Use 12-15 mm for the Hypex box. I used 12 mm.

Ready made/flat-pack cabinets now available from EBEL Holztechnik, Germany:
https://www.ebelholztechnik.de/galerien/index.php/category/411-ellipticor_a50_mk_ll

Placement of crossovers on rear panel. Mount though D8404 and 38WE holes.

Port. See images below in workshop pics.

Workshop images

I started making the midrange cabinet/braces. Rear panel of midrange cabinet glued in place while placed in cabinet to make a sure fit.

Routing for drivers. Chamfer 21WE hole slightly.

Sometimes I have glued the whole thing in one operation, but a cabinet large as this is enormously stressful as we only have less than 15 minutes to get it all inplace. This time I started gluing the left side panel and rear panel, making absolutely sure it is 90 deg. Next I glued the braces/midrange cabinet in place. After this the top panel followed by the bottom panel. At this stage I glued the port panels/fillets in place, only leaving the right side panel and front panel to be glued in one operation.

Testing drivers on front panel. Right: Gluing upper panel.

Sometimes a rectangular box like this may be slightly skewed when you have glued rear, braces top and bottom panel and you need to pull the whole structure to make the front panel fit exactly. Fortunately we have driver holes to add pressure.

Making all the felt sheets needed. Gluing the right side panel and front panel in one operation.

View video of felt damping.

Making the Hypex enclosure from 12 mm plywood.

Two frames of 450 x 450 mm were made from 30 mm solid oak.
Adjustable feet, read here.

Further damping:

Left: Bass section, add acoustilux. Fasten with staples or dots of glue.
Right: Fill midrange (21WE) cabinet with 200 grams of sheeps wool.

Top cabinet: Fold a piece of 150 x 50 cm acoustilux and cover rear panel (over the crossover) and on top of cabinet.
Not shown: Add a piece of acoustilux on rear panel behind midrange (21WE) cabinet.

Workshop test during crossover development.

Here the final speakers.

Some thoughts on mounting Ellipticor mid-dome and tweeters:

Using countersunk screws will eventually skew the drivers a tiny bit and if you have to press the decor ring into place - you are never going to get it up again!
So, add some foil around the driver when fastening the screws. This way you will leave some 0.1-0.2 mm space between decor ring and cabinet. Removing the decor ring by rotating until it slips the magnets and lift with another small neo magnet. The tweeter decor ring pops up by itself. The D84 doesn't.
When routing for the D24 and D84, make the rebate diameter +0.5 mm.

The screws for the tweeter need to be well countersunk. I found some good torx 20, 4 x 20 mm screws at the local Bauhaus and for the tweeter I did some grinding to reduce the head size and to make sure the decor ring doesn't ride the edge of any screws and cause buzzing. This is important.

Left: Decor rings in place.
Right: BTW: The D84 is a nice driver for gently soldering the wires to the terminals as the shape of the rear chamber lets it rest nicely in the driver hole. Nice feature - because the D84 is seriously heavy!

MEASUREMENTS

A few comments on MEASUREMENTS before you start interpreting the readings.
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.

Impedance of 21WE/D84/D24 section (both speakers). Tube amps just love it!

Frequency response merged with nearfield responses of 21WE and 38WE drivers at 225 and 80 Hz. In this way we can have a reasonable idea of bass extension. Port is not included here, which will further extend the lower bass area.
The intrinsic increase in on-axis response the D2404 tweeter in the 10-20 kHz range was left as is. For those who can hear the upper octave, this may add just a little more airiness to the soundstage.

Horizontal dispersion at 0, 10, 20, 30 and 40 deg. off-axis.

For those interested, near-field response of 21WE and 38WE drivers, driven from crossover and Hypex module.
As predicted the 21WE, not having a high-pass filter, does roll off smoothly below ~80 Hz due to the small closed cabinet.