ScanSpeak Revelator 4R

Copyright 2015-2023 © Troels Gravesen

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Model discontinued and replaced by Revelator-51

Kit Instruction with full crossover schematics can be bought directly from me:

"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.
The speaker was designed for the Dayton 0.38 ft^3 (10.8 litres) cabinet. Not available any more. Cabinet has been slightly modified and allowing a larger crossover board suited for the Superior-Z caps.

As always: Stick to front panel dimensions, drivers' placement and volume

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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 20 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!

Useful links (Please read before writing!):

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.
Please read these files before e-maling: 


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



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.


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

The cabinet makes 11.3 litre gross volume, minus port, bracing, crossover, etc. I suggest 20 mm Baltic birch or 19 mm MDF. Keep outer dimensions and drivers' placement.
I strongly suggest attaching the rear panel with screws to allow easy access to the crossover. The crossover board for the level 1 version, Superior-Z caps, is also too big to be placed on rear panel through the midbass driver hole.


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.


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.


Kit Instruction with full crossover schematics can be bought directly from me:
Payment by PayPal or bank transfer.


Making a rather complicated crossover for such small cabinet is always a challenge. For the STANDARD-Z cap version there will be plenty of space available.
Start making the board and place on rear panel and mark the holes for the terminals, as these will protrude the board. Make sure the rear panel can fit in with the crossover board before drilling the holes for the terminals.

Crossover layout with binding posts protruding the board.
Connect only one of R1011 to C1021!
Highest value = lowest treble. Lowest value = high treble level.

Example of binding posts through the crossover board.

Speaker wiring