DIY Loudspeakers: HOME  INDEX  UPDATES  RESPONSE  WHAT'S NEW 

ScanSpeak Discovery-3WC-10
Copyright 2023 © Troels Gravesen

   Go to on this page:

DRIVERS    CROSSOVER     CABINET    WORKSHOP PICS     MEASUREMENTS     SPEAKER-KIT    
CROSSOVER LAYOUT      Be-DOME VERSION

My classic 3-/4-way kits, primarily based on straight rectangular boxes, have become our best selling kits. Apparently these classics have the right combination of size, sensitivity, price, ease of construction and not least - sonic quality based on good drivers and premium crossover components. And coming to think about it, there really weren't that many kits like these on the market some 5 years ago. Mostly we find small "6+1"s or 2½-3way slim floorstanders, apparently targeting customers with WAF issues. But fortunately there was another audience out there, yearning for speakers that can replicate some of the dynamics of live music.
A lot of things have to come together to make a classic a commercial success. Size for one thing. The 10" bass driver is another good reason. It delivers decent bass, can play reasonably loud, the cabinets are easy to construct, they're not too big, not too small - it's the Goldilock of speakers.

This new 3-way classic builds on exactly the same principles, but here based on ScanSpeak Discovery drivers, delivering unparalleled performance from modest priced drivers.
Some may ask why I use a 6" midrange driver and not a 3-4". The answer is simple as a larger driver moves less, meaning less distortion. Also a larger midrange tends to be less critical on source material compared to a small 3-4" due to its wider dispersion. All things come at a cost. In addition to this I wanted a fairly low point of crossover to the bass. Actually the 18W/8424G00 is only 9 cm^2 larger than the 6RS140 midrange driver of the Faital-3WC-10. And by using a larger midrange driver we increase dynamic headroom. Not least, the Discovery 18W/8424G00 has a ruler flat response in all of the midrange with no rubber surround resonances. See measurements below. The reason for using the 18W/8424G00 and not the 18W/8434G0, as used in the Discovery-861, is the "-24"'s 1" voice coil, giving it extended frequency response - and here we have a high-pass filter and no need for the extra power handling of the "-34". I'd say the 18W/8424G00 is the "Vifa C17" of today, only with a much better frequency response and better bass extension.
The powerful 10" Discovery bass driver has been used before in my Discovery-4 construction, only here we use the 4 Ohm version to beef up the overall system sensitivity to around 90 dB. My 32 wpc tube power amp has no problem running this speaker to significant levels - and this from its 8 Ohm tabs. I've said it before, but what tab should be used on a tube amp must be tried. Just because a speaker has a nominal impedance of 4 Ohms doesn't mean it sounds the best from a tube amp's 4 Ohm tabs. Your ear is the final judge.
So, what's the difference between the Faital-3WC-10 and this Discovery-3WC-10? Please read my CHOICES file! Please read all of it carefully! I know some of you will try to get around this and ask which I like the best. Sorry, you won't get an answer. My job is not to tell you what is right, but to give you choices.

 

 

Quite a number of records were used for finetuning midrange and treble - as always. Some of the records above. The Barber record is - as almost always - a stellar recording, this time mastered by Bob Ludwig and cut by Bernie Grundman. Coming from the Ellipticor-A50 the 10" bass drivers did a really good job - and they go deep.
Danish String Quartet, Last Leaf, is a record I always use as these strings can be the litmus tests of any midrange driver. They came out really well without any aggressiveness.
So did the piano of Herbie Hancock. Well, too much material on this double LP to boil down to a few lines. If you like jazz and Joni, a must have album. The Discovery 3WC-10 was never short of delivering the goods.
It's been years since I've heard my Dali #1 CD! Hearing Hugh Masekela - Stimela (The Coal Train) again was a delight - with deep bass and powerful dynamics.

My first-to-hear friend: "Who said high-end cannot come from modest prices drivers?" I couldn't agree more. The exceptional linear response of the midrange driver plays a significant role in this. Bass and treble is pretty much a matter of speaker voicing.

 

Basics:
3-driver speaker.
Dimensions: 32 x 34 x 70 cm, WxDxH.
System sensitivity: 90 dB/2.8V/1 meter.
Impedance: 4-8 Ohms.
Power requirement: 30+ watts/channel.
Power handling: 100 watts.


Useful links (Please follow all links before e-mailing!):
http://www.troelsgravesen.dk/tips.htm
http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS
http://www.troelsgravesen.dk/crossovers.htm
http://www.troelsgravesen.dk/LCR-RC.htm
http://www.troelsgravesen.dk/Inverted-Polarity.htm
http://www.troelsgravesen.dk/choices.htm

http://www.troelsgravesen.dk/power-handling.htm


DRIVERS
BACK TO INDEX

  

 

 

Download specs here:  D2608/913000    18W/8424G00    26W/4534G00


CROSSOVER
BACK TO INDEX


CABINET
BACK TO INDEX

Cabinets were made from 20-21 mm Baltic birch and for front panel I decided to use 25 mm HDF, not that it matters, but just for the sake of change. And I kept outer dimension, too little to make any impact on bass performance.
Cover all internal walls with felt material except for the bottom panel, where the crossover will be placed. The midrange cabinet is further stuffed with 75 grams sheeps wool. The cavity behind the midrange cabinet is stuffed with a 25 x 50 cm piece of acoustilux. See further instruction of the use of acoustilux below.

The cabinets should be placed on stands having a height of placing the midrange driver at ear height.


Design to your liking :-)


Workshop pics
BACK TO INDEX


Cabinet materials piling up.
For rear panel, braces and midrange cabinet I used bits and pieces.
My front panels will be made from 25 mm HDF (Valchromat).


All drivers ready.


Braces and rear panel of midrange cabinet in place.


Testing driver rebates on front panel.


Cabinets ready for gluing.

Damping: Add felt to all internal panels except braces and bottom, where crossover is to be placed.
The bottom and rear panel of the midrange cabinet has felt on both sides.


With three straps and a handful of clamps, all glued in one operation.

Acoustilux:
4 pcs 25 x 50 cm
4 pcs 22 x 50 cm
4 pcs 20 x 50 cm
 


Left: Stuff cavity behind midrange cabinet with 1 pcs 25 x 50 cm.
Right: Add 1 pcs 22 x 50 cm to one side and rear of upper bass cabinet.
Remember to seal the wire hole with Superfix. Push the midrange cone to make sure the midrange cabinet is absolutely air-tight!


Left: Add 1 pcs 22 x 50 cm to other side of upper bass cabinet, so that the rear panel has two layers.
Fasten both sheets with staples/dots of Superfix towards front panel to secure position.
Right: Port in place.


Stuff midrange cabinet with 125 grams sheeps wool.


Cover side walls of lower bass cabinet and rear panel with 2 pcs 20 x 50 cm.
Right: Cover bottom with a folded piece of 25 x 50 cm to cover crossover.
(Crossover not mounted yet when this picture was taken)


Remember inverted polarity of midrange driver when you connect to crossover board.


All drivers mounted.


MEASUREMENTS
BACK TO INDEX

A few comments on MEASUREMENTS before you start interpreting 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, although dispersion characteristics play a vital role here. A two-way 7+1 and a three-way 7+4+1 may display similar horizontal dispersion, yet sound very different. 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 we 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 speaker, because speaker cones made from polypropylene, aluminum, Kevlar, paper, glass fiber, carbon fiber, magnesium, ceramics or even diamonds all have their way of adding spices to the stew. Nor do measurements tell what impact the quality of the crossover components add to the sound, from state of the art components to the cheapest of coils and caps, they all measure the same if values are correct, yet may sound very different.


The midrange 18W/8424G00 response on a 80 x 120 cm test baffle.
Ruler flat up to above 3 kHz and an extended response all the way to a little above 11 kHz.


Same driver on the actual cabinet. Green is minimum phase.
As can be seen it maintains the ruler flat response in all of the midrange and we see a minor decline at lower frequences due to baffle step loss.


Also the CSD looks impressive. Measurement from actual cabinet.
All in all I wanted to show the emphasis on midrange performance. This is where the majority of music information is.

 


Also the 10" bass driver performs very well, all the way to 2.5 kHz.
The rigid cone ensures pistonic movement in bass region.
Measurement merged with nearfield response at 200 Hz.


Final system frequency response measured at 1 meter distance and merged with bass nearfield reaponse @ 300 Hz.
System sensitivity around 89-90 dB.


Final system impedance. Minimum 3.1 Ohm at ~23 Hz.
My 32 wpc tube amp runs this speaker well to decent levels. For more bass impact use bi-amping or larger solid state.


SPEAKER-KIT
BACK TO INDEX

The items marked with colour are the positions replaced by cheaper components for level 2.
C1: Alumen-Z replaced by Superior-Z.
C2: C2 consists of 3 capacitors in parallel. Two of these are replaced by STANDARD-Z in level 2.
C3: Superior-Z replaced by STANDARD-Z in level 2.

For the Beryllium dome version, only level-1 is offered.

Remember bitumen pads are always optional due to weight.

Kits can always be bought with/without drivers, or some of the drivers.

 

All kit and component prices may be subject to change and are always to be confirmed by Jantzen Audio Denmark.

Download Complete Kit Sale Presentations:

All technical questions to troels.gravesen@hotmail.com

All questions regarding purchase of kits, please mail Jantzen Audio at contact@jantzen-audio.com


CROSSOVER-LAYOUT
BACK TO INDEX

Check this out before start making crossovers:

http://www.troelsgravesen.dk/tips.htm#CONSTRUCTION_OF_CROSSOVERS

 

Bass crossover layout.



 

 

Mid-tweeter crossover layout.

 


Mount first the bass crossover and connect to terminals.
Next the mid-tweeter section and connect to terminals.
Make sure you have wires in place for drivers.


Place first the acuostilux on lower side panels and fasten with staple.
Next cover the crossover with two layers as described above.

 

SPEAKER WIRING


Placement of crossover on bottom panel.
Fasten boards with screws!



Beryllium dome version

To find something in a suitable price range of the Discovery-3WC-10, I have chosen the magnificent SBAcoustics SB29BAC-C000-4 Be dome tweeter. I know of no other tweeter offering the performance of this tweeter - in this price range.

Download data sheet here.

The crossover schematics only vary by the value of three resistors in the tweeter section, thus layout and wiring is the same.