Illuminator 4

Illuminator 4

This speaker actually came before the Illuminator-5, having done similar 4-way constructions from AudioTechnology, SEAS and ScanSpeak Discovery drivers. An ATS-4 set-up had to be tried with the best of ScanSpeak drivers. It may have been called Revelator-4, but I render the middriver the most important in these constructions, thus Illuminator.
I had this speaker running for 3 months before the idea of an Illuminator-5 appeared, and I really wasn’t thinking of the Illuminator-4 until a year later and setting it up again I found it to be too good to let go and here it is. Less elaborate than the Illuminator-5 and by having the 7100 tweeter with its good low-end response, it’s no problem taking the point of crossover between mid and tweeter down to around 1.7 kHz, delivering a presence close to the Ill-5.

 

DRIVERS

    

      

 

Speaker basics:
4-way speaker system or you could argue the 22W not having a high-pass filter makes it a 3½-way due to the use of two bass drivers having different low-pass transfers.
Bass reflex, closed box and aperiodic tuning is used for lower bass, upper bass and mid-driver respectively.
Points of crossover; 80, 200 and 1700 Hz, 2nd order LR, mid and tweeter time-aligned.
Impedance: 4 Ohms, minimum 3 Ohms.
Sensitivity: 88-89 dB/2.8 volts, 1 meter.
Amplifier requirement: Minimum 50 watts with decent current delivery.

CROSSOVER

Crossover components’ values come with the kit.

 
Above crossover simulation displaying working range of drivers and points of crossover. Lower graph display predicted impedance profile.


CABINET


Above the fairly simple way to making the Illuminator-4.
The side panels of the midrange cabinet are optional.
Midrange port: 50×100 mm. Stuff with acoustilux. Roll 10×20 cm acoustilux and insert in port.

If this is all to much, check this drawing:

It doesn’t have to be complicated as long as you stick to the few basics outlined on the drawing.
Make good non-resonant cabs and this will sound any bit as good as the more complicated constructions.

  
All things start with test set-up for fine-tuning cabinet design and make crossover work as easy as possible.
In particular tweeter and midrange front panels can make huge differences and jeopardize drivers’ frequency response.

Below the mid and tweeter cabs.

 
Starting with the mid front panel. I used 18 mm BB made from laminating 2 x 9 mm.
Matter of taste, 15 mm too thin and 20 mm too thick.

 
Front and side panels ready for further work. Checking out driver rebate.
Never route for drivers before you have them at hand and can measure exact diameter.

 
Gluing mahogany fillets to midrange front panel.

 
Mid front panels ready and routing side panel cut-outs.
The midrange front panel is cut 6 deg. at bottom and top to fit the tilt.

 
Right: Cutting side panels 6 deg. towards front.

 
Right: Chamfering cut-outs 45 deg. half way through.

 

 
Time for bracing, rear and top panels.

 
Bracing holes. Right: Add fillets to support top and rear panel.

 
I usually never use screws for assembling cabinets, but here I make an exception. Based on experience with pyramids, adding a few screws to keep the bottom panel i place helps enormously. They can be removed after the glued has dried.

 
Adding bitumen pads and starting mid cab assembly. Cut wedges to prevent clamps from sliding.

It’s the fourth time (Jenzen-ATS, ATS-4, Illuminator-5) I do tweeter cabs like these and from the beginning it’s been almost the same procedure. Making the rounded cut-out towards the rear is actually quite easy and I’ve tried to document better this time I think. Take a look at images below. The most tricky part is the mid cab side panel wedges not having a band saw, but I think I found a better way next time.

 
Left: Routing for 7100 tweeters.

 

  
Tweeter cabs ready for the top routing. Click right image to view large.

 
Making of the top routing. Add sides to the tweeter cabinet and keep in place by clamps. This prevent the BB from serious edge ripping. The support panels must be exact height of tweeter cab and cut 10 deg. to be flush with tweeter cab to allow the router to slide over the top.
Make support for the router – same height as tweeter cab. Click right image to view large.
I used a radius of 160 mm and made a groove to around 25 mm depth and used a 15 mm round nose bit.
The edge was rounded by using a rounding-over bit.

 
After finishing with the round nose bit, I used a straight bit for the rest and finished off by using the table saw. This allows some 0-7 deg. tilt of tweeter front panel.

 
Router bits used.

Mid cabs side panels

 
Preparing for the side reinforcement bars. This is not an easy task unless you have a band-saw, which I don’t, hence use my table saw and cut from both sides and hopefully follow the cutting line exactly. The side bars add to the rigidity of the mid cab and well, look nice too. Making it all from MDF and doing spray paint is quite a lot easier.

 
Gluing the side bars. No dimensions given here, really up to you how you make them, or if you want them at all.

 
Right: Gluing side bars.

 
Side bars ready for gluing to cabs. The side bars were cut 38 deg. with reference to outer side.
What height front and rear you want is up to you.

 
Right: Next is some hours of tedious sanding, a little filler here and there and they are ready for lacquer.
I use grade 120 and 180 before lacquer. Lacquer is applied with a roller. First coating is dried 48 hours before sanding with grade 180 and second coating applied. I use semi-gloss synthetic lacquer. See tips file.

Next time I have to make side panels for a mid cabinet, I’ll do like above: Make a 50 mm plank of solid wood and cut it in sections 0 or 10 deg. and glue it together. Assuming 3 mm at bottom we have with a 50 mm thickness a top width of 11.82 mm. Next you cut vertical to make 11.82 mm at top, etc. I haven’t tried it, but I will.

Tilt of mid and tweeter cabs

I’ve made two wedges for the tweeter and mid-cab, 10 mm high and I use some sorbotane pads to reduce vibration from the bass cabinet. The max height of the wedges obviously depends on you listening distance, but try out various positions to make the best integration of sound from the various cabinets. Normally the tweeter takes some tilt to make the best integration of sound.

MEASUREMENTS

Everything that can be counted does not necessarily count; everything that counts cannot necessarily be counted”Albert Einstein.

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 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.
Here are a few measurements:

I’ve chosen a measurement here of the midrange-tweeter section @ 0, 10, 20 and 30 deg, off-axis (red/green/orange/blue). This shows a very even power response in all of the midrange and treble range up to 15 kHz. There’s not hot seat here.
Overall sensitivity is around 88 dB/2.8V/1 meter.
I won’t show the full-range profile as this has to be composed from merging near-field response of upper bass, lower bass and ports – and in any case is highly manipulated and can look like anything depending on how it is done. Looking at the simulation above gives a better idea of bass extension. Feel sure this speaker goes deep!

Above the final system impedance displaying an unusual smooth result with no sharp phase angles – and easy load on any amplifier – although not suitable for tube amps with a minimum impedance of 3 Ohms. As said elsewhere, my workshop Jungson 80 wpc solid state as well as my living room GlowMaster/Hypex combo both loves this speaker and runs it to thunderous levels without problems.
Port tuning can be read to a little below 30 Hz. The mid-tweeter section is an easy load on any tube amp.

Finally the response of mid and tweeter driven from the crossover. The point of crossover may seem a little higher than specified, but the middle of the suck-out when I reverse tweeter polarity is around 1.7 kHz. Note smooth roll-off of both tweeter and midrange.

SPEAKER-KIT


In level 2, 8 Superior-Z caps, C5, are replaced by STANDARD-Z and six Alumen-Z caps are replaced by two Superior-Z caps.

CROSSOVER-LAYOUT

Mid-tweeter layout and wiring

For level 2 replace four of C5 with STANDARD-Z caps and the three Alumen-Z caps with one Superior-Z cap.


Please not the 18WU driver must be connected with inverted polarity. Plus from the crossover goes to minus terminal on driver.

Bass section layout and wiring


Bass crossover here shown with the new Premium Elko caps. Wiring the same as seen below.


Bass section crossover. Same as for Illuminator-5.

 
Crossover from four angles. Make the board in one. I have this bank of large caps for midrange used for prototypes, hence two boards.

 


Click image to view large.

SOUND

There’s no point in trying to describe the sound. Some like Brussels sprouts, some don’t. Same thing with speakers. What flavour is to taste, appearance is to speakers. This speaker does it all, from deep bass to shimmering highs. The overall voicing is very similar to the Illuminator-5. The Illuminator-5 may have a little extra in dynamic headroom due to the small 4″ handling upper mid, but having the 7100 tweeter doing it all down to 1.7 kHz makes a truly coherent overtone structure. In its range, it’s one of the top three speakers I’ve ever made and I can only say ENJOY! I do.

 

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