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DRIVERS
CROSSOVER
CABINET
MEASUREMENTS
SPEAKER-KIT
CROSSOVER LAYOUT
Model discontinued and replaced by
Revelator-51
Kit Instruction with full crossover
schematics can be bought directly from me:
troels.gravesen@hotmail.com
"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.
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 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!):
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.
Please read these files before e-maling:
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/choices.htm
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 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.
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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Kit
Instruction with full crossover schematics can be bought directly
from me:
troels.gravesen@hotmail.com
Payment by PayPal or bank transfer.
CROSSOVER-LAYOUT
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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
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