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SEAS CENTER PRESTIGE
Copyright 2022 © Troels Gravesen

   
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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.

Kit can be ordered plus/minus 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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