Revelator 4R
Copyright 2015 © Troels Gravesen

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"4" for 4 Ohms, "R" for ring-radiator. Just to get the name in place. 15W/4531G00 is the more lively sibling in the Revelator 15W family of drivers. "30" means coated, "31" is un-coated. "45" means 4 Ohms version, hence the increased sensitivity compared to the "8530" driver used in Ellam FLEX and Ellam 98 mkII.
Un-coated means its cone has a different sonic impact on the overall presentation. A little more lively, more lush, if you will. To balance this I picked the classic ring-radiator, providing a balanced and very neutral sounding treble.
The "4531" may sound more dynamic compared to the "8530" due to its low-resistance voice coil, drawing more current from your amplifier and just simply plays louder for the same volume setting. At the end of the day a matter of taste.
This speaker should possibly be compared to the classic Ellam XT. Unfortunately I don't have the XT for comparison, so I can't tell the difference.
The crossover provides an extremely flat frequency response from its 2nd/3rd order topology, similar to what is used in the Ellam XT. Not having the stepped baffle like Ellam 98 mkII and Ellam FLEX, necessitates a steeper crossover to provide proper phase integration of the two drivers. It's a trade-off, but a loudspeakers are always full of compromises.
For those with limited woodworking skills, this speaker is designed for the Dayton 0.38 ft^3 (10.8 litres) cabinet. Still, you do have to be able to use a router to make drivers' rebate. Obviously you can make your own cabinets as long as you stick to front panel dimensions, drivers' layout and volume. The two first are imperative to make the crossover work as intended.
The cabinets come with a ready made front grille and I think it's the first time ever I've launched a speaker with a front grille. As you will see below, the front grille has quite some impact on frequency response and for any serious listening, I suggest you leave it off. Use it when your neighbor's kids pay a visit and want to check out drivers' compliance. They usually do.


Click image to view large

Basics:
2-way mini from ScanSpeak 15W/4531G00 Revelator midbass and ScanSpeak R3004/832000 ring-radiator.
System sensitivity: 87 dB/2.8V. 1 meter
Impedance: 4 Ohms.
Point of crossover: 2.7 kHz.
Bass extension: - 3dB @ 47 Hz.
Amplifier requirement: Minimum 10 watts.
Power handling: 60 watts (ScanSpeak specifications). Please read here about power handling, it's not that simple, and please remember that any burned driver is a misused driver!


DRIVERS
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Download specs: 15W/4531-G00      R2604/832000


CROSSOVER
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Simulated horizontal (left) and vertical (right) dispersion.
Optimal listening height is between bass and tweeter.
Place the speakers on 60 cm stands and tilt 3-4 deg depending on your listening postion.
As always distances to floor, rear wall and side walls plays a major role in overall sound.
In my listening room I have 100 cm to rear wall (from front) and 180 cm to side walls.


CABINET
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For 10.8 litre we see F3 = 47 Hz. Port tuning (Fb) 45 Hz.


The Dayton cabinet makes 10.8 litre. You can realise this from standard 22 mm MDF by making a rectagular cabinet of
203x264x355 mm (WxDxH). Add a vertical brace like the Dayton to make room for the crossover.


Use tape to prevent the router from damaging pre-painted front penels.
DO NOT for get to chamfer the bass driver hole to allow free air ventilation.


Checking out driver routings.


Make sure to hit the right depth for the 15W driver, 5.5 mm to allow room for the gasket and make a smooth flush mount.


Left: Cut a 80 x 900 mm piece of 8 mm felt and place in front part of cabinet.
Right: Cut two pieces of 100 x 320 mm 8 mm felt and place on sides of rear chamber. Ad felt to top and bottom as well.

 
Left: Crossover mounted on rear panel. Place 15x10 cm piece of acoustilux above port.
Right: Fold a piece of 30 mm acoustilux, 20 x 20 cm, and place above crossover on rear panel.


MEASUREMENTS
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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 drivers, because cones made from polyprop, alu, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of colouring the sound. 

 
Left: The important midrange! Here we see the impact of RCL2031. Right: Flat midrange and smooth roll-off.


Response of driver driven from crossover. Point of crossover = 2.7 kHz.
Right: Inverting tweeter polarity creates a deep suck-out around point of crossover.


Left: Final response of left and right speaker.
Right: Impact of front grille (green). As expected front grille frame doesn't better the nice and smooth response. Leave it off for serious listening.


SPEAKER-KIT
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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 Kit Sales Presentations here. pdf file.

 
All technical questions to troels.gravesen@hotmail.com




CROSSOVER-LAYOUT
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This is a pretty tight layout. Make sure not to short any wires.
You may stack the additional tweeter attenuation resistors on top of R1011 (but only connect one as seen below).


I glued R1011 alternative resistors on top of C1021.