Ellam 98 mkII
Copyright 2014 © Troels Gravesen

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DRIVERS   CROSSOVER    CABINET    MEASUREMENTS    SPEAKER-KIT     CROSSOVER LAYOUT


This speaker has been on my to-do list for along time. The first Ellam 98 dates back to 2005 (can't believe it) and was designed around the common 2nd/3rd order filter as needed when drivers are placed on a flat baffle and the need to compensate for the lack of time-alignment. Placing the 15W driver some 20 mm in front of the 9800 tweeter allows a time- and phase-coherent system based on an LR2 filter improving mid-tweeter integration and overall sense of transparency.
The 9800 dome is not particularly cheap, but to my ears it's the best alu dome ever made and seriously rival the much more expensive beryllium domes.


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I've used the 15W/8530-K00 midbas driver in numerous constructions and no need to repeat its virtues again. Overall the best 5" ever made. You may find 5" drivers that excell in specific areas, but hardly one that does bass and midrange as well as this one and at the same time doesn't display some serious cone break-up that needs equalisation.

Complex cabinet constructions turn off many diy'ers and unfortunately only a few engage in the Ellam FLEX, thus a front panel design that everyone can make.

Overall this speaker presents an easy-to-listen-to soundstage with good balance of basic notes and overtones. If someone should think "metalic" sound from the 9800 tweeter, forget it! It's smooth and adds to the transparency of the soundstage. For the size of the bass driver it gives you a fair amount of bass information and again I was surprised to not only hear, but also feel some bass notes. This is only some 95 cm^2 and it doesn't get much better from such size driver.
The stepped baffle and the LR2 filter leaves no trace of transition between the drivers. Dispersion was another surprice. Horizontal dispersion may look good on paper but fail in reality. Here I can move over a wide horizontal line and maintain perspective and tonal balance. Enjoy!

DRIVERS
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Download drivers' specs: 15W/8530-K00    D2904/980000

 


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CROSSOVER
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Crossover values come with kit incl. layout as seen below.

The crossover is a straight forward 2nd order LR filter. Quite some effort has been done to linearise response in the critical midrange and to make sure the midbass follows a 2nd order roll-off as close as possible, hence R5+C2. These components ensures a perfect roll-off. R2041+L2041+C2041 ensures the 600-1000 Hz range. Without equalisation here we would have a huge bump due to the small baffle. The traditional aproach is to increase value of L2011, but this leaves a significant dip around 300-500 Hz taking the power out especially vocals.
Tweeter crossover features a simple two attenuation resistors, a cap and a coil. R2 controls the Q of L1. R7-C4+L3 is actually optional, but linearise the impedance bump and produce a smoother roll-off and increase power handling. Not unimportant for an LR2 filter @ 2.5 kHz.


Simulation of the above schematics looks like this. Here with an almost flat tuning.
Point of crossover around 2.4 kHz.

 

CABINET
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The black front panels are made from through-coloured MDF. This black MDF is really like HDF, high-density fiberboard, weighing some 0.84 g/cm^3 compared to 0.64 g/cm^3 for the common brown MDF, although it depends on MDF thickness. Thick MDF sheets often have a rather soft center as producers may cut production cost by reducing glue content. Black MDF has an almost ceramic feel to it and comes at approx. twice the cost of standard MDF. Alternatively you can use some exotic hardwood for the front panels. Might look good in oak or mahogany or whatever suits your taste. High-gloss lacquer might do well too.
The aim of this enclosure was to make it as simple as possible. Few people build the Ellam FLEX compared to Ellam XT despite better performance of the FLEX design. The two designs feature the same drivers but FLEX has a front panel taking a little more woodwork compared to XT. Thus, here's a front panel that can be made by anyone. If you cannot cut the bass outer panel 15 deg., cut it straight. No big deal.
Place port in middle of upper section.

Construction pics


Above the rough and un-assembled cabinets. I like doing small cabs! A couple of evenings and things start shaping up.


Bracings and we're ready for gluing.


DO NOT forget to chamfer bass driver hole.


Cabs sandet, front panels ready for sanding and small fillets added to cabs for making threads for mounting screws.


Bitumen pads added to sides, bottom and top.
The tweeter crossover is going to sit next the tweeter on the side panel and do no bitumen pad added on this side.
If you have the speaker where the tweeter is off-set to the left, add bituman pad to the left side.
Crossover is placed on the right side of this tweeter. This way we have room for it all. Drawing below.
I used 8 pcs 240 x 150 mm and 2 pcs 80 x 240 mm pads for two speakers.

Do not make the crossover boards before your have bitumen pads in place and yoy can can exactly measure how much space you have left. I used 4 mm bitumen pads and reduced the size of of the bass crossover board by 5 mm on both height and width.
Next, the crossover boards can only be placed in the cabinets before you add front panels, so in case you want to glue your front panels, make sure all connections are correct. Alternatively the rear panel can be attached by screws. Making small speakers is a challenge in terms of space and making sure the crossover will fit in. 

 

First I added bitumen pads, then bass crossover board was placed on rear panel and connected to terminals. Finally the felt material was cut to size and fixed by a few drops of glue. Last two layers of 30 mm acoustilux was placed on top of the crossover.
I used 2 pcs 180 x 450 mm 8 mm felt sheets for the bass sections and 2 pcs 180 x 230 mm for the tweeter sections.

I used some felt strips to seal the front panel as can been seen from upper right picture. Check here for options on gaskets.

Finally front panels can be mounted and drivers installed.

 

MEASUREMENTS
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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 anything 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 way 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.

Cardboard comes handy when doing the first steps in design, like placing the tweeter to make the best frequency response. Distances to edges, shape and distance of outer bass panel. All things that influence performance and ease crossover design when done optimally. Above to the left the response from the tweeter from a flat panel (red) and stepped baffle (green). As can be seen the stepped baffle has minimum impact on tweeter response and nothing that impacts crossover design noticeable aiming at a point of crossover around 2.0-2.5 kHz.

 

Above the cumulative spectral decay from the 9800 tweeter. I think this is one of the best alu domes ever made. To the left the response above 20 kHz. As can be seen the usual break-up node at 20-25 kHz is absent, maybe due to the small phase plate in front of the dome.

Above left: The graph here to display the need for equalisation of the 15W on a small baffle. Without the LCR curcuit we have a huge bump at 600-1000 Hz and it's very noticeable if not reduced. The RC curcuit across L2011 smooth the upper roll-off profile. The final result to the right, a close to perfect LR2 profile.

 

Upper left: Significance of tweeter LCR curcuit flattening impedance peak and shaping the roll-off towards lower frequences. It furthermore increase ower handling. To the right the final spaker response from my preferred tweeter attenuation. As can be seen below tweeter level can be adjusted to personal taste.

 

Upper left: Impedance of final system. Green = electrical phase. Upper right: Inverting tweeter polarity display a huge dip around point of crossover, ~2300 Hz.


 

SPEAKER-KIT
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Crossover components' values to come with the kit.
You can buy the kit with or without the drivers - or some of the drivers if you already have some.
Please ask Jantzen Audio for options.

Download Complete Kit Sale Presentations:

 

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

All technical questions to troels.gravesen@hotmail.com

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


Kit Instruction following the kit

 

CROSSOVER-LAYOUT
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The bass crossover board is placed on the rear panel behind bass driver. Make holes for terminals as seen on drawing. The tweeter section is placed on side panel next to tweeter.
Depending on the use of bitumen pads you may have to reduce bass section further. Ised 4 mm bitumen pads and reduced bass crossover board to 150 x 150 mm.
All this is based on removeable front panel as the bass section cannot pass driver hole. Placing crossovers in small speakers is always a challenge.

Make sure coils are as far away from driver magnets as possible.

 

Speaker Wiring


Crossover components for two speakers

 


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