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Ekta 25
Copyright 2019 © Troels Gravesen

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DRIVERS   CROSSOVER    CABINET    MEASUREMENTS    SPEAKER-KIT     CROSSOVER LAYOUT

My STUDIO-101 mkII is a keeper! If it must be small and not cost a fortune, this speaker does it. With the updated 18W/8542-00 driver, now 18W/8542-10, we have the tools together with the 9130 tweeter to make extraordinary quality for a modest investment.
Finishing the Studio 101 mkII, a 2½-way was an obvious thing to do to get more of the same goodies. More bass, more power handling, more of everything.
Although the Ekta speakers were built around the sliced paper drivers, I decided to call this speaker Ekta-25 despite featuring drivers from the Classic and Discovery range. And as said many times before, the D2608/913000 tweeter deserves better placement than the Discovery series. It's a top notch tweeter and the 18W/8542-10 has become my "if you can't afford the Ellipticor 18WE" driver.

Setting up the Ekta-25 I experienced a vivid and dynamic presentation, yet delicate and smooth in upper-mid and treble. The two 18W drivers can throw quite some bass having a combined area similar to a ~9" driver. Giving the ~91 dB sensitivity also an easy load for my 32 watt tube amp. I'm more than pleased!

Basics:
2½-way, 3-driver speaker.
Dimensions: 22 x 32 x 100 cm, WxDxH (without feet).
System sensitivity: 91 dB/2.8V/1 meter.
Impedance: 4 Ohms
Point of crossover: 2500 Hz, LR2 crossover.
Power requirement: 20+ watts/channel.
Power handling: 160 watts. Please also read: http://www.troelsgravesen.dk/power-handling.htm, and remember any burned driver is a misused driver.

Useful links:
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
http://www.troelsgravesen.dk/chamfer.htm

FAQ:
You cannot change cabinet front panel dimensions and drivers' placement without needing a new crossover - and I cannot help.
You cannot use any other drivers with the crossover shown here.
Please read these files before e-maling:
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm


 


DRIVERS
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Click images to view large.

Download specs:   D2608/913000 (grey terminal = plus)      18W/8542-10   


CROSSOVER
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Like the Studio-101 mkII, this filter features an LR2 filter and the 18W driver coils need a by-pass resistor plus an RC circuit across the coils to perform a perfect 2nd order roll-off. The tweeter a little easier as a standard topology makes a perfect LR2 profile all the way from 800 to 20000 Hz.


CABINET
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Cabinets were made from 20 mm Baltic birch and front panels from 19 mm HDF. You can use 19 mm MDF throughout. And you can make the front panel like the Ekta mkII if you like the look of Baltic birch.

I suggest you add bitumen pads to your purchase (~5 pcs 4 mm 50 x 50 cm sheets). All internal panels are damped with 8 mm felt material acoustilux added according to recommendations below. I strongly suggest making the bottom panel detachable and place the crossover here far away from the driver magnets. 


Workshop images


There are many ways to construct a simple floor-stander like this and as I wanted to use the cabinets for more constructions, I had the rear panel rebated and attached by screws. Above to the left bitumen pads on internal panels.
Whenever I show images having rebated panels, I have the question if the panels are laminated. They are not. This is how it goes.


Rear panel with terminals and port. Ports usually leak midrange, so keep it to the rear.


All internal panels damped with 8 mm felt material. Towards the top, place four layers of 30 mm Acoustilux.
(disregard the fillets and rubber strips, I use these cabs for several constructions)

 
Left: Bottom of cabinet, place 8 layers of 30 mm Acoustilux. On rear panel behind bass drivers, place two layers of 30 mm Acoustilux.

 
Rear panel behind bass drivers seen from front. Wires from binding posts to crossover.


Routing the front panels. Right: Outer panel from back side.

 
Left: Inner panel from back side. Right: Final assemble from back side.
Read here on the importance of chamfering drivers holes. 


MEASUREMENTS
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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.


Final SPL at 1 meter, 2.8 volt, displaying some 90-91 dB sensitivity.


Final system impedance showing minimum 3.5 Ohms @ 200 Hz. Generally an easy load on your amplifier.
What also can be seen in the port-tuning of 40 Hz.


SPEAKER-KIT
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Above level 1 kit with Alumen-Z or tweeter.
Cut port to 70 mm total length.

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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Tweeter layout. Use half solder tag strip/crossover.
Connect + IN to either R1a or R1b depending on your preferred treble level.

 

 


Midbass crossover layout. Use half solder tag strip.

 


Crossover for tweeter.


Crossover for mid-bass drivers.

 

WIRING

 


Speaker wiring. Connect input wire to R1a or R1b depending on your preferred tweeter level.
R1a gives the highest level. My default is R1b, but some like it hot.