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DRIVERS
CROSSOVER
CABINET
MEASUREMENTS
SPEAKER-KIT
CROSSOVER-LAYOUT
The former SEAS CENTER-641 constructions have now been divided into
this SEAS-CENTER-PRESTIGE and
SEAS-CENTER-EXCEL, as the new SEAS nextel coated
range of drivers left too many options, thus now two files. Also the
CENTER-EXCEL has gotten a new tweeter, ScanSpeak
D2608/913000.
The SEAS-CENTER-PRESTIGE here is exactly the same as before, same
drivers, same crossover, same cabinet, with only a minor adjustment of
damping materials, mounting wire and screws for the drivers.
Many center speakers are made from the
popular 2-way d'Appolito - and I've made a few myself - but from a
center speaker we need a strong midrange projection and we need an even
horizontal dispersion, something 3-ways are good at. We need everybody
in a 4 seat sofa to get the same experience. Understanding speech and
vocals must be easy and in this
respect these center speakers are no different from the Classic 3-ways. The same goes for Ekta
mkII, Ekta
Grande and the classic 3-ways, all featuring 4-5 inch midrange drivers.
Basics
4-driver speaker.
Impedance: 4-8 Ohms.
Dimensions: 25 x 370 x 650 mm (HxDxW).
Useful links (Please read before writing!):
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
FAQ (Please read before writing!):
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.
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm
DRIVERS
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Download specs here:
27TFFC
MCA12RC
CA18RNX
CROSSOVER
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The basic topology is 2nd order between bass
and mid, and 4th order between mid and tweeter.
The vertical dispersion is in fact so good you could turn this speaker
upside down and use it as main speakers as well.
Crossover components' values only come from purchasing the kit from
Jantzen Audio and cannot be bough alone.
CABINET
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You can make the front panel upright if
placed high. Use 340 mm depth + front panel.
You can add mild faceting to front panel if
you like. This time I didn't, although it looks really nice.
Should your find routing into the tweeter
faceplate too troublesome, then try this.
Construction images
Building the cabs is pretty straight forward. Rectangular box, only the
front panel is slightly tilted (5 deg). Above fitting rear panel.
Front panel and initial driver routing.
Black MDF used for front panel.
Routing for the middriver takes special precaution as we route into the
tweeter face plate. This to get the mid and tweeter as close as
possible.
To the right what happens when it turns out tweeter magnet
hole was too small! Fix center again and enlarge hole.
1. First we need to fully mount the tweeter. Use jigsaw and make room
for tweeter terminals.
2. Mount the tweeter with a couple of screws. Unfortunately the
faceflate of the tweeter cannot be removed as the dome diaphragm is
glued to the faceplate.So, we have to do the routing with the tweeter in
place.
3. See below. Use two 3 mm spacers between router guide and front panel
not to slide over the dome.
4. Lower router 0.1-0.2 mm at a time and make the tweeter cut-out. Move
the router slowly and if you have a router with adjustable speed, lower
speed a little not to melt the tweeter faceplate. Generally I found this
operation easy.
Above the finished cut-out. Remove tweeter again and finish the other
driver routings.
DO NOT forget to chamfer driver holes, in particular the midrange. I
used a 25 mm front panel and the midrange needs to breathe!
Left: This is what the mid should look like from behind. Right: Prestige
drivers in place.
The blue dot on the middriver is PLUS. Guess SEAS ran out of red paint.
Cabinet parts ready for gluing.
Gluing the bracing/mid-tweeter cabinet.
Routing for the vent and finally gluing the cabinet. Port length is 120
mm total length.
CABINET DAMPING
The Kit comes with 0.75 m^2 8 mm felt and 0.5 m^2 Acoustilux.
FELT:
1. Cut two pcs 30 x 60 cm and place in bass cab like seen on photos
below. No felt on rear panel and panel towards mid.
2. Cut 1 pcs 35 x 14 cm for the mid cab. Ad felt to the side panels of
the mid cab as well.
3. Cut 2 pcs 20 x 50 cm acoustilux, fold and place at bass rear panels
to cover crossovers, bass crossover in one and mid/tweeter crossover in
the other.
4. Add 80 grams of wool to the midrange cabinet.
Right: Mid/tweeter chamber. Make sure to fill the wire hole with some
sealing once wires are in place.
Check tightness of mid-cab by stuffing the vent and pull one bass driver
while holding the other.
The middriver's cone SHOULD NOT move.
Use strips of glue to fasten the felt material.
Right: Gluing the front panel.
Instead of the acoustilux in the midrange cabinet, use 80 grams wool.
PRESTIGE ready for measuring data for simulation software.
Cabinet finished with water based paint and a roller.
MEASUREMENTS
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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 anything 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 way 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.
SEAS-CENTER-PRESTIGE MEASUREMENTS
Left: SPL from drivers driven from crossover and summed response
(green).
Right: Final system impedance.
Left: Vertical dispersion measured at 0.5 m distance, from below
midrange driver to over tweeter level.
Right: Horizontal dispersion at 0, 10 and 20 deg (red-green-yellow).
Quite and even dispersion ensuring an even sound from a 4 seat sofa at
3-4 meters.
SPEAKER-KIT
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Crossover components' values to come with the
kit and cannot be bought alone.
Kits can always be bought with/without
drivers, or some of the drivers.
All questions regarding purchase of kits, please
mail Jantzen Audio at
contact@jantzen-audio.com
All kit and component prices may be subject to
change and are always to be confirmed by Jantzen Audio Denmark.
Download
SEAS-CENTER-Prestige sales presentation:
All technical questions to
troels.gravesen@hotmail.com
CROSSOVER-LAYOUT
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Check this out before start making crossovers:
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
Bass section layout.
Mid-tweeter layout.
I suggest a 200 x 140 mm board as this can be
mounted through 18W hole.
The layout leaves space for Superior-Z, should you at a later point
decide to upgrade.
Make sure the mid-tweter section is tight!
Pull wires through hole and seal with silicone glue.
Speaker wiring
To the left the sections for mid-bass. Right: Tweeter-midrange section.
Crossovers mounted in cabinet.
SEAS-CENTER-PRESTIGE
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