Scanspeak 4 Way Active DSP Build with Illuminator/Revelator Drivers

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mikes875

Member
Joined 2017
#1
Having finished a modified curved wall version of the Zaph Audio ZRT 2.5 towers a year ago I have caught the bug and have been planning my next build. I want to build from scratch without a kit. Designing a passive crossover seemed a bit too daunting so I decided to go with an active crossover and make use of a miniDSP 10x4 HD.

Below is a picture of my Curved ZRT’s. I am really happy with the sound that these things produce, they have replaced Dynaudio Contour 1.4LE’s (and Contour 1.8 v2 before that) and are a major step up from either.

Curved Zaph Audio Based ZRT 2.5 - Google Photos

With the ZRT I laminated the sides with seven layers if 3mm MDF to get the curve. This time I need to build multiple chambers, so thought I would try building it up as a series of 25mm horizontal sandwich slices. I am using dowel spines around the outside in order to provide support, and to help line everything up. Not the most economic method as there is a lot of waste, and there is a lot of routing involved, however it does give me a great deal of freedom in the design.

Sketchup design
Google Photos


For this build I have chosen the following drivers installed in this configuration
Upper Bass - ScanSpeak 22W/8851T-00 8"Revelator Woofer
Midrange - ScanSpeak 12MU/8731T-00, 4" Illuminator Midrange
Tweeter - ScanSpeak D2908/7140 Beryllium Dome Revelator Tweeter
Midrange – Another 12MU/8731T-00 wired in Parallel with the one above (MTM)
Lower Bass - ScanSpeak 32W/4878T Revelator 13" Subwoofer

A few pictures of the build so far
Hugh stack of around 100 slices of 25mm MDF ready to start assembling, will cut out the centres as I build it up..

Google Photos

Starting to come together this is the main chamber for the Scan-Speak 32W/4878T Revelator 13" Subwoofer. The port can be seen coming up from the bottom of the chamber, it will be a L slot that comes out the front below the chamber.
Google Photos

By cutting as a series of slices, bracing is pretty easy to include in any shape I want, this one is designed to go around the back of the 32W
Google Photos

The small cylindrical chamber is for a Scanspeak Illuminator 12MU/8731T-00, 4" Midrange. There will be two of these, another above the tweeter in a MTM D'Appolito arrangement. I made it this shape as from what I have read it produces less internal reflections.

https://photos.app.goo.gl/7JkJfan0lMyqGMwp1

https://photos.app.goo.gl/V4Lbr9SwO5uEBpas1

Trying to decide where to next, either build the base/port assembly or the tweeter section. It is going to be mounted sloped backwards, with the tweeter section vertical and the upper section sloped forward. The next stages therefore involve creating a wedge structure for each end.
 
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#4
You should go for Raal instead. I would not spend $520 on a dome tweeter when you can get a Raal for a little bit more. The voice coil weighs too much for a tweeter and causes distortion. It is possible the dome tweeter is better at upper midrange, like 2000-3000 Hz, but above 4000Hz nothing I have heard beats a Raal. I cross mine in a horn from 2000Hz, but that a is a bit low. Will make another version eventually.
 
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#5
studiophone said:
Nice. I’ll be following your progress on this.im curious to see how the 12mu and tweeter work. I’m thinking of using those same drivers but only one 4”. I like the design.
Click to expand...

Thanks, I will keep up with updates. Unfortunately spare time is scarce or progress may take a while...

I have received the 12MU's they are impressive little units to look at/hold, can't wait to hear them in action
 
#6
Rewind said:
You should go for Raal instead.
Click to expand...
I agonised over that decision for ages, and decided to play it safe and stick with Scanspeaks.

They have been ordered now, and are on there way around the world from Europe, so decision made.

From what I have read on the D2904 Be dome it is an excellent tweeter, so can't imagine I will be disappointed, but then there is always that feeling of 'what if...' . That is part of what keeps you coming back for more I guess...
 
#7
studiophone said:
I’m curious to see how the 12mu and tweeter work. I’m thinking of using those same drivers but only one 4”. I like the design.
Click to expand...
Wood Envy
You might get ideas from: Taipuu Speakers in Finland builds a ScanSpeak 4-way design which showcases solid wood. Both a DSP and a passive crossover version are available. Unusual upper-lower placement of side-side 30 cm Scan-Speak woofers. Measurements at:

Taipuu Speakers

Taipuu_4-way
Specifications:
Enclosure type: Closed
Dimensions: 300 x 1170 x 500 mm (W x H x D)
Weight: 50 kg (Birch), 80 kg (HI-MACS + MDF)
Sensitivity: 89 dB/2.83V/1m (86 dB/W/1m)
Nominal impedance: 4 Ohms, minimum 3.5 Ohms at 71-92 Hz
Recommended amplifier power: 50 - 500 W into 8 Ohms, unclipped

Drive units
Subwoofers: 2x 30 cm, Scan-Speak Discovery, coated aluminum cone
Woofer: 18 cm, Scan-Speak Illuminator, paper cone
Mid: 12 cm, Scan-Speak Illuminator, paper cone
Tweeter: 26 mm, Scan-Speak Illuminator, beryllium dome

Crossover frequencies
140 Hz, 800 Hz, 3.6 kHz (passive)
150 Hz, 760 Hz, 4 kHz (active)

Frequency range:
31 Hz - 24 kHz (-10 dB, passive)
21 Hz - 24 kHz (-10 dB, active)
 

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#8
mikes875 said:
I agonised over that decision for ages, and decided to play it safe and stick with Scanspeaks.

They have been ordered now, and are on there way around the world from Europe, so decision made.

From what I have read on the D2904 Be dome it is an excellent tweeter, so can't imagine I will be disappointed, but then there is always that feeling of 'what if...' . That is part of what keeps you coming back for more I guess...
Click to expand...

Yeah, as I said a dome tweeter might have more meat to it in upper midrange. Just don't use one as a midrange down to 1600 Hz, like in the Arendahl 1723 THX, that a friend bought.. It pairs a large dome tweeter with two 8" with strong midbass and the midrange is either strained or scooped and the top end has a bit of distortion.
Nothing is preventing you from getting a smaller Raal as a super tweeter later on.
 
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#10
Hi Mike,

Love the build mate. Glad to see another 4 way active being constructed.

I have just finished a 4 way active myself here. http://www.diyaudio.com/forums/multi-way/307752-4-using-active-crossovers-11.html#post5305316

I used the same SS midrange and bass drivers as you. I followed John Dunlavy's design principles as I wanted to recreate the Sovereigns. I am absolutely thrilled with my result.

What were you planning on using for the active crossover? Something like you are building deserves a decent Active front end.

I will watch your build with great interest.
 
#19
mickiboi007 said:
Hi Mike,

Love the build mate. Glad to see another 4 way active being constructed.

I have just finished a 4 way active myself here. http://www.diyaudio.com/forums/multi-way/307752-4-using-active-crossovers-11.html#post5305316

I used the same SS midrange and bass drivers as you.
Click to expand...

Thanks for the comments. Speakers look great, certainly a talking point in that shape. Would love to hear them.

Assume you mean you used the the same 12MU and 22W? What crossover point did you use for these? It looks like the 22W can only go up to around 700-800 Hz before breaking up, so might be pushing the 12MU a bit to get that low?
 
#20
studiophone said:
with active how are you handling the impedance spikes and up swings of the drivers?
Click to expand...
I was planning on connecting directly to the amp apart from a protection capacitor on the tweeter (for DC and low freq). Was hoping the miniDSP and amp would take care of the rest.

Haven't purchased the amp yet. Do have a 6 channel power amp and a couple of NC400 NCore mono blocks for test purposes.

Looking at Nord Accoustics NCore multi channels
Nord Hypex NCore, B&O ICE Power 1200AS NC500 NC400 Amps For Sale

They allow you to mix and match modules, thought perhaps
NC500 X 2 for the 32W
NC250 x 4 for the 22W and 12MU (each NC250 will drive 2 12MU in parallel)
and NC100 x 2 Tweeter modules
 
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