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DRIVERS
CROSSOVER
CABINET
MEASUREMENTS
SPEAKER-KIT
CROSSOVER LAYOUT
SOUND
The first Ekta dates back to around 2005 and many times I wanted to
update this construction based on a client job and not taking into
account an optimal front panel design. The result was a 4th order filter
to the tweeter and even a notch filter to tame a 7 kHz peak creating
quite some sibilance if not attended. I believe I can do better today by
combining design and acoustics at the very beginning. And not only that,
I think I can make a more sensitive speaker, better bass, better power
handling, better midrange, a better sounding treble - and not least, at
lower price! The latter due to the use the the D2608/913000 tweeter,
which is kind of an overlooked tweeter, originally derived from the
Peerless HDS series. There's a lot of money to be saved from not using
the 7000 ring-radiator. The money saved can be used on better crossover
components. The 9130 tweeter simply delivers top-notch treble
performance with its double magnet, die-cast face plate, low-mass diaphragm, low Fs, etc., although I'm sure someone will think not. Not much I can do
about it. Should you be i doubt, read test here:
http://www.troelsgravesen.dk/6600-9130.htm
Some people believe expensive always means better. Or it's a
matter of show-off. You cannot use any other tweeter here than the 9130,
or you need a new crossover - and I can't help. And you cannot use 2 x
18WU/8741T00 either and make an Ekta Grande mkII from the same crossover. This
will require a complete re-tuning of the system. Have to say the single
18WU delivers a surprisingly potent, deep and articulate bass.
The cabinet front panel is going to be easy, only with the tweeter
off-set some 19-20 mm to bring it into acoustic alignment with the midrange
driver.
Better sensitivity is the easy objective using the 4 Ohms version of the
18WU Illuminator mid-bass. Not an issue for solid state amps, neither
for my 32 wpc
EAR
861 tube amp, but maybe not for an anemic 6 watt SET amp, but the
speaker wasn't designed for such amps.
The sandwich cone beats the Revelator in dynamic headroom - can be
pushed harder before compression sets in.
I've used the 12MU before in the Illuminator-5 construction and well, we
simply do not find a better 4" driver. It pays off in the
reproduction of female vocals, saxophones, oboe, clarinet, etc.
Due to excellent dispersion in the critical range of 1-3 kHz, listening position is less critical - even compared to my reference
ATS4-HE. What they also do is maintain focus and image stability at very
low levels. 6-7+4+1"s can simply be played louder than similar 6-7+1"s.
The 12MU has found its
way into seriously expensive high-end speakers over the last few years, from Wilson
Audio, B&O to Gryphon and others. See
Munich report. Interestingly we don't see any OEM versions of this
driver! I guess they could only be worse than the standard product.
Click images to view large
Basics:
Three-way floor-stander from 7+4+1 inch drivers.
You cannot use an overall flat front panel without
modifying the crossover and I can't help you here. And you cannot use
any other than the specified drivers - or you need a new crossover.
Sensitivity: 87 dB/2.8V/1 meter.
Impedance: 4 Ohms.
Points of crossover: 800 and 3200 Hz.
Cabinet dimensions: 22 x 34 x 100 cm (WxDxH) (without base support)
Power requirement: 20+ wpc.
Power handling: 150 watts, please also read this:
http://www.troelsgravesen.dk/power-handling.htm.
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
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-mailing:
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm
All technical questions to
troels.gravesen@hotmail.com
DRIVERS
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Click images to view large
Download spec here:
18WU/4741T00
12MU/8731T00
D2608/913000
Click images to view large
CROSSOVER
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Above the much simpler crossover compared to Ekta mkI. It features an
overall 2nd order LR topology with points of crossover around
800 and 3200 Hz. With a 19-20 mm off-set of the tweeter we can manage a
good phase integration of mid and tweeter. At 800 Hz wavelength
is of a size that doesn't call for any off-set of mid-driver with
reference to bass driver. We could pull out the bass by adding another
10-15 mm to the front panel, but it doesn't pay off in terms of overall
performance.
All technical questions to
troels.gravesen@hotmail.com
CABINET
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Click image to view large
The cabinet is designed to make it as easy as possible. The chamfering
of the side panels to the rear and front panel is optional. I only did it because I
think it looks nice and slims the overall look of the speaker. The net volume of the bass cab is ~30 litres,
making an F3 of 37 Hz. Quite good for a 7" driver.
You can place the port to the front or to the rear to your liking. And
obviously you can make a straight rectangular box as show above in the
right lower corner.
The drawing above is based on 20 mm Baltic birch. You can use
19 or 22 mm MDF. Keep front panel dimensions and drivers' placement! And
please read this before cutting wood:
http://www.troelsgravesen.dk/crossovers.htm
Chamfering of the side panels to the rear is optional. Chamfering of
front panel optional too. I used 20 deg to a depth of 16 mm. Also cut
the top of the bass-mid panel 20 deg. towards the tweeter.
The finished cabinets are rock solid and seriously heavy from the added
internal panels, bitumen pads and double front panels. What you get is
the sound coming from the drivers with no added cabinet colouration.
Please check this "tips" page before writing:
http://www.troelsgravesen.dk/tips.htm
Workshop images
First thing I did was gluing top panel and ensure 90 deg angle.
Next gluing rear panel. Bit tricky as we can't use the front edge for
the clamps. I know I don't make life easier with the choices I make.
Next I glued all braces in place held in position by the remaining side
panel.
Final side panel and front is glues last - and at once. This is
necessary when panels are cut 45 deg. Not easy!
Bitumen pads in place. I used 0.8 sqm. 4 mm bitumen in total.
Bitumen pads are optional due to weight. Order special if you want
bitumen pads.
Add felt as seen on image. No felt on front panel. I used 0.9 sqm. in
total. 1 sqm. supplied.
The bitumen pads are optional and
must be added to your order.
BTW: I use a scalpel for cutting felt. 2-3 blades are needed for a small
speaker like this. They go blunt very quickly.
Add acoustilux as seen on photo:
Roll one piece 25 x 50 cm for the bottom.
One piece 16 x 50 cm behind 18WU driver.
One piece 15 x 25 behind midrange driver.
2 pcs. 16 x 50 cm in upper compartment.
In total I used 0.8 sqm. 1 sqm. supplied.
Routing and chamfering inner front panel. Make holes as wide as bracing
allows and chamfer as much as possible. Holes are Ø 170 and 130 mm.
This time I added lacquer twice to the front panels before routing for
drivers. This to avoid edge ripping. Quite a problem with laminated
panels.
Left:
This time no edge ripping from routing for the drivers due to the
lacquer.
Right:
Chamfering driver holes for 18WU and 12MU.
Make sure sealing the wire hole for mid and tweeter! There must be no
leakage here.
Middle: Measuring drivers' response for crossover simulation. Right:
Crossover fine-tuning in living room.
MEASUREMENTS
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Everything that can be counted does not
necessarily count; everything that counts cannot necessarily be counted".
Albert Einstein.
A few comments on MEASUREMENTS before you start
interpreting all 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. 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 us 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. .
Response of midrange and tweeter with no crossover. Nice frequency
response making crossover work easy.
Final system impedance. This is a 4 Ohm speaker with a minimum
impedance of 3 Ohms.
Response of drivers driven from crossover and summed response
measured at tweeter height, 1 meter, 2.8 volts.
Points of crossover = 800 and 3200 Hz. Overall system sensitivity
87-88 dB/2.8V.
SPEAKER-KIT
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The kit includes screws for drivers as the
12MU requires screws with smaller heads than those needed for tweeter
and bass.
The bitumen pads are optional
and must be added to your order.
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.
Bitumen pads are optional due to weight.
All kit and component prices may be subject to
change and are always to be confirmed by Jantzen Audio Denmark.
Download Kit
Sale Presentations:
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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Bass section.
MT section.
L3 was later replaced by air-core coil and board extended to 13 x 25 cm,
allowing C4 to be Superior-Z if you cannot live with the STANDARD-Z
here. It's inaudible, but some believe not.
Use a piece of wire connecting C4 to the output of L4. See image below.
WIRING
Mid-tweeter section
Bass section. Premium ELKO has been replaced
by CrossCap PP.
Mounting the crossover. Fortunately we have lots of space for this.
SOUND
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What you get here is something rarely seen in
commercial speakers, a 7+4+1. The vital 4" midrange driver bridging the
gap between bass and tweeter. That's not to say the 6+1 or 7+1 cannot be
made very well, it surely can, but it doesn't compare to the real thing
of paying attention to the troublesome upper-mid/lower-treble. The
transition from a 6-7" midbass to the 25-28 mm tweeter is a
compromise.
The rationale for few commercial speakers using this design is cost. And
fair enough, adding a 4" midrange driver adds considerably to overall
production cost. For the DIY guy, not so much, although I admit the
12MUs are not exactly cheap. A speaker like this from a commercial
company would probably reach some 5-10 kEUR depending on
overall fit'n finish. Production cost must be around 10-20% of
final retail price to make a commercially viable business. This rarely
leaves room for the quality crossover components used in this
construction.
The midrange is clean, neutral and effortless in
character and the 4" midrange driver allows us running the speaker
louder than a similar sized 6-7+1. It obviously doesn't match a bigger
speaker with 10-12" bass drivers, but the 18WU can be driven quite hard
here, thanks to the 4" middriver handling the delicate upper mid. The
9130 tweeter delivers a crystal clear treble very well integrated with
the midrange. Fortunately we have soft-domes these days that rival the
best hard-domes and choice is down to a matter of taste - and belief.
Vocals have delicate presence and clarity with no edginess - unless poorly recorded
or poorly mixed, the latter not an unusual thing.
The Ekta mkII throws a wide and deep soundstage
and my 32 wpc EAR-861 has no trouble driving the speaker to significant
levels, this from the 8 Ohm taps! Solid state amps may produce a
slightly more
solid and firm bass, but maybe not the delicate midrange of the modded EAR-861.
Same goes for my GlowMaster KT88 power amp. In fact, the EAR 868(P)L +
EAR 861 + the Ektas mkII make one hell of a system.
Playing my OPUS3 Test Record #4 presents a soundstage with performers
precisely located similar to my reference ATS4-HE speakers, only lacking
the impact of the lowest octave although I'm pretty impressed by the
bass performance of this single 18WU. Phenomenal driver!
Adding my
26W subwoofers, makes these speakers almost similar to my reference,
although it cannot cope with the 10" upper bass of the ATS4-HE. Size
matters as always.
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