First off a very big thank you to Yeo of diyparadise for lending me a pair of his Coral 8A-40s to audition in my Dallas III cabinets. I was initially surprosed at how small the light the Coral 8A-40 drivers were compared to the Fostex FE206E. I understand that full range driveres depend on massive acceleration of the cone to deliver the entire range of frequency, so I wondered how Coral 8A-40's smaller magnet would compare to the Fostex206E's massive magnet that is at least 3 times larger and heavier?...
I met Yeo one fine sunny weekend in January 2008, at his house. I took the opportunity to listen to his setup, the Coral Beta 6s in Hedlund cabinets. In terms of height the hedlunds are indeed an imposing pair of speaker, enough to give the "Tim the Toolman Taylor" in any of us the argh argh argh. But in real terms, both the Hedlunds and the Dallas III cabinets are similar in size, Hedlunds being a single fold horn and the Dallas III is a double fold horn. Once Yeo got his system up an running, we played some Led Zeppelin and cranked up the volume. Wow those speakers ROCK. They played loud and fast. That said, the first thing that hit me as odd was that the high frequencies were missing. Thus a lot of the "ambiance" in the music was lost. I would have loved to stay the entire afternoon and flip through different genre of music to see how the speakers would fare but I was in a rush. I listened to the speakers for less than 15 minutes in total. I know this is too short a time to form any real opinion. Here are the Fostex FE206E and the Coral 8A-40 front view. The Coral drivers a bit dirty as they are vintage stock....
Now to my Fostex FE206E in Dallas III cabinets, I had the speakers installed in the cabinets for over 4 months now and I have been listening to them almost daily. I play music through them every evening even if I don't intend to sit down for a listen, just to give everything a daily workout. The wire leads were still sticking out of the cabinets in an unsightly manner. Not only is this unsightly, Ron, the Dallas III designer has said to me that this would cause a loss in the horn efficiency which translates to its ability to play low and loud. Why? you ask... Well its because the wires will prevent an air tight seal between the drivers and the cabinets. But still I procrastinated, I left the speakers unfinished because it sounded so good to me.
After some urging from my other half, I decided it was high time I finished off the speaker and tested the Coral 8A-40s that Yeo was gracious enough to loan to me. So I installed a pair of binding posts to clean up the wire mess. And I installed rubber gaskets so that I could create an air tight seal for the drivers and the cabinet.
The first order of business was to test the Coral 8A-40s. Being new old stock, I was conscious of the fact that the drivers would not sound their best initially. And as I had already surmised they did not sound good at all initially. I left them playing off and on for about 2 weeks. I estimate that the drivers must have played about 50-60hours. I could tell that they were improving. Even my other half commented that the speakers sounded good. With this affirmation I thought it was time for me to sit down for a listen.
The Coral 8A-40s sounded very similar to the Coral Beta 6s. Guess there is a family resemblance. These drivers can rock, put in some classic rock and you are good to go. Put on some slower Jazz numbers and I discovered that the vocals were good too. Music was "fast" and "tight". However, the drivers exhibited the same high frequency roll off, just like its more sort after brethren, the Coral Beta 6. And like I said earlier, the music was missing some ambiance. I could not get used to this especially when I had an pair of ESLs that excelled in this department. I know that there are many who will not agree with my evaluation of the Coral 8A-40's high frequency roll off. But these are what my ears are telling me. To all Coral owners, you have a gem of a driver, and for the price there is no speaker thant can compare.
I met Yeo one fine sunny weekend in January 2008, at his house. I took the opportunity to listen to his setup, the Coral Beta 6s in Hedlund cabinets. In terms of height the hedlunds are indeed an imposing pair of speaker, enough to give the "Tim the Toolman Taylor" in any of us the argh argh argh. But in real terms, both the Hedlunds and the Dallas III cabinets are similar in size, Hedlunds being a single fold horn and the Dallas III is a double fold horn. Once Yeo got his system up an running, we played some Led Zeppelin and cranked up the volume. Wow those speakers ROCK. They played loud and fast. That said, the first thing that hit me as odd was that the high frequencies were missing. Thus a lot of the "ambiance" in the music was lost. I would have loved to stay the entire afternoon and flip through different genre of music to see how the speakers would fare but I was in a rush. I listened to the speakers for less than 15 minutes in total. I know this is too short a time to form any real opinion. Here are the Fostex FE206E and the Coral 8A-40 front view. The Coral drivers a bit dirty as they are vintage stock....Now to my Fostex FE206E in Dallas III cabinets, I had the speakers installed in the cabinets for over 4 months now and I have been listening to them almost daily. I play music through them every evening even if I don't intend to sit down for a listen, just to give everything a daily workout. The wire leads were still sticking out of the cabinets in an unsightly manner. Not only is this unsightly, Ron, the Dallas III designer has said to me that this would cause a loss in the horn efficiency which translates to its ability to play low and loud. Why? you ask... Well its because the wires will prevent an air tight seal between the drivers and the cabinets. But still I procrastinated, I left the speakers unfinished because it sounded so good to me. After some urging from my other half, I decided it was high time I finished off the speaker and tested the Coral 8A-40s that Yeo was gracious enough to loan to me. So I installed a pair of binding posts to clean up the wire mess. And I installed rubber gaskets so that I could create an air tight seal for the drivers and the cabinet.
The first order of business was to test the Coral 8A-40s. Being new old stock, I was conscious of the fact that the drivers would not sound their best initially. And as I had already surmised they did not sound good at all initially. I left them playing off and on for about 2 weeks. I estimate that the drivers must have played about 50-60hours. I could tell that they were improving. Even my other half commented that the speakers sounded good. With this affirmation I thought it was time for me to sit down for a listen.
The Coral 8A-40s sounded very similar to the Coral Beta 6s. Guess there is a family resemblance. These drivers can rock, put in some classic rock and you are good to go. Put on some slower Jazz numbers and I discovered that the vocals were good too. Music was "fast" and "tight". However, the drivers exhibited the same high frequency roll off, just like its more sort after brethren, the Coral Beta 6. And like I said earlier, the music was missing some ambiance. I could not get used to this especially when I had an pair of ESLs that excelled in this department. I know that there are many who will not agree with my evaluation of the Coral 8A-40's high frequency roll off. But these are what my ears are telling me. To all Coral owners, you have a gem of a driver, and for the price there is no speaker thant can compare.
So out came the Coral 8A-40s and back in went the Fostex FE206Es. If you have been observant, you would have realised that by this time I have been listening to the Corals 8A-40s in my bedroom exclusively for 2 weeks. Other than the High Frequency roll off, I had no other complaints about the Corals. At this point I could not compapare the Coral 8A-40s to my own Fostex FE206Es as I had trouble recalling what the Fostex FE206Es sounded like.
As soon as I had the Fostex FE206Es installed, and had music playing through them, I realised that they were a whole order more musical and also clearer compared to the Coral 8A-40s. It was like a veil was lifted. Just the clarity of the music was astounding. To make sure this was not a figment of my imagination, I swapped between the Corals 8A-40s and Fostex FE206Es a couple of times and even asked my other half to have a listen. And both of us preferred the Fostex FE206Es. However I noticed that the Coral 8A-40s had a slightly fuller mid bass, which made male voices and rock music sound forward. Both drivers played quite low, Corals 8A-40s till about 49hz and the Fostex FE206E till about 43Hz before dropping off. Here is another view of the Fostex and Coral Full Range Drivers. Not all 8" FR drivers are made equal... the massive magnets does make a difference....
As soon as I had the Fostex FE206Es installed, and had music playing through them, I realised that they were a whole order more musical and also clearer compared to the Coral 8A-40s. It was like a veil was lifted. Just the clarity of the music was astounding. To make sure this was not a figment of my imagination, I swapped between the Corals 8A-40s and Fostex FE206Es a couple of times and even asked my other half to have a listen. And both of us preferred the Fostex FE206Es. However I noticed that the Coral 8A-40s had a slightly fuller mid bass, which made male voices and rock music sound forward. Both drivers played quite low, Corals 8A-40s till about 49hz and the Fostex FE206E till about 43Hz before dropping off. Here is another view of the Fostex and Coral Full Range Drivers. Not all 8" FR drivers are made equal... the massive magnets does make a difference....
And u know what, I slapped on some Def Leppard, Queen, ACDC.... the Fostex FE206E in the Dallas III cabinets ROCKED too... as hard as the Beta 6s in Hedlund cabinets.Feel free to leave your commets. Or Return to Home.
and the Dallas III... much more attractive, but does the radiused corners affect the parameters and so the sound.... negatively?
Feel Free to leave your commets. Read on to my 
And I have also been waiting equally long to complete these BLH speakers. So why did I choose to build a horn speaker since I have already completed the ESLs... basically I wanted to experiment with the various speaker technology and designs. I have never been satisfied with the multi coned, multi way speakers. They have never sounded right to me, save for a few very well integrated 2 way speakers. That is why I am attracted to full range drivers and ESLs. The ESLs produce music from a single surface which makes the music "cohesive" for lack of a better word. The music is accurate, fast, with pin sharp imaging and well... they are musical. Instruments sound as they should, piano sounds like a piano, guitar is a guitar... it just jives. I love my ESLs to bits.
The backside.... pretty uneventful here... 
A view of the business end of the horn. The wires are hanging out coz I have not installed the binding posts yet. Standing next to the Dallas III are my old faithful... TDL's RTL2 transmission line speakers. They just sound dull and wooly compared to the Dallas IIIs. 
The Dallas III twins, sitting pretty in my room, with the tube amp that in then middle. 
Internally, the Dallas III back loaded horn is a folded horn... 3 folds to be precise. Here is a picture that shows the folding. How did I make the bends? Trade secret! 
And here is a side profile showing the beautiful curves...
Also presenting the Little Dot III, this little 2 watter is a beauty, just ignore the cheesy blue leds. Comes with an external power supply. (The Little Dot III amp that drives the Dallas III... coincidence... I think not!!)
And finally a closer look at the Fostex 206E, the cone is made from banana pulp. 
The music is achieved thru massive acceleration of the cone using this massive magnet. The magnet measures almost as large as the speaker basket.... 
More of the driver unit... 
Feel free to leave your comments. Read on to my 
The cabinet is constructed out of 2 main modules. In this picture you will see a box with 4 aluminium legs. This box measures h320xw600xd250mm. This will serve as a base for the ESL panels. It will also house the EHT and transformers. Behind the base and leaning against the wall, you will see the removable panel. This panel forms the rear of the base. The large round hole will house the speaker binding posts and the small rectangle will hold the power cables connections.
In the next picture you will see a large rectangular frame that will house ESL panels. The frame measures h1300xw600xd160mm. I did a mockup, and I was surprised as it seemed a lot larger than I expected. Its going to dwarf everything else in my listening room. It stands at about 1.6m. The frame holding the panels will screw onto the base as shown in the mockup. I originally wanted to make the base and the top using one piece of wood, but we did not have a piece large enough. Well, can't always get what you want...
And here are the braces that will go into the top module. These braces serve 2 basic purposes. 1. To 'brace' the top module so that it is more rigid and resists sideways motion. 2. To serve as a backing to support the panels. The braces are also radiused so as to reduce reflection.
Before I can install the panels, my first task was to install the channels where the panel will sit in. This was a simple affair, just nailing the appropriate length of square cross section wooden rod into the top module.
Here is another picture of the channels being nailed into place.
With the channels installed, I test fit the panels. Perfect fit! I love the look of the ESLs, really majestic. I am wondering if I need some kind of cover or should I leave them naked. Opinions...
Rear view of the panels during the test fitting.
A closer view of the Panels sitting snugly in their channels.
I also test fit the braces. While the fit is good, but the support points are too narrow don't quite line up with the edges of the panels that it is supposed to support. I will have to fashion a new support that will extend to support the all the panels properly.
Satisfied that everything fits, I remove the panel to clean them and the cabinets up. Here is a picture of the completed cabinets without the panels.
Here is another view of the empty cabinets. Notice that the channels at the bottom are different from the other channels. They are screwed on to aid easy installation and removal of the panels. They were an afterthought and so the wood is not finished in the same colour as the rest of the cabinet. Notice that I have already predrilled holes in between the channel brackets so that the wires can be passed through to the base that will house the EHT supply and transformer. This will make things look neater.
I clean the cabinets up thoroughly and give the room a good vacuum. I then start installing the panels into the cabinets. I make sure that all screws are tight. Here is a rear view of the final install.
I place the EHT and the audio transformer into the base. I connect all the wiring. The ESLs are now in position. They are right next to the side wall and about 2 feet from the rear.
After making the final connections, I turn on the ESLs, put in some Nat King Cole, Marsalis, Hall and Oates, Eagles..... I am left speechless. The ESLs were used without the cabinets for a good 2-3 months and they were just wonderful. But now in a proper enclosure.... they just got better. The sound emanating from the ESLs has just been elevated one level better. It sounded fuller, mid bass has much more presence and goes the panels go down another half an octave. I'll whip out the sound analyser for tests later. For now I just want to go enjoy the ESLs.
I flip the switch... and no sparks. So I go ahead and adjust the bias voltage for the panels. I let the panel charge up for about an hour before I do anything further with them. Here is a picture of the voltage regulator used to adjust the bias. 
At this stage put some music on and turn up the volume. Well, I hear music coming out through the panels. If only you could hear them. All the superlatives that you have ever heard reviewers and owners sprout about ESLs apply here. These speakers were made for music. It’s an all new listening experience with all my CDs. Instruments sound so real... one thing that struck me was the snare drum from some acoustic pieces. None of my cone speakers, my Fostexs full ranger included can reproduce the sound of a snare drum as accurately as the ESLs. If you have taken notice of the sound of a snare drum you'd know what I mean. From rock to techno, to vocals, to classical... the music is just great. Even my better half who is quite critical of audio equipment (but not fussy) said that they were very "nice". 
Somemore thoughts about bass thru ESLs. I think the ability of the ESL to do bass is really dependent on a host of factors and the most important one is step up transformer. For reasons that I have yet to understand, the number of octaves that a transformer can handle has a practical limit. I read the limit to be 6-7 octaves. One solution is to use a high freq transformer for a treble panel and a low freq transformer for the bass panel. The problem here is working out the crossover and integrating the panels. However I have it on good faith that the ESL's that I have DIYed has a freq response of +or- 6db from 35Hz to 200Hz. However, I do believe the cabinet and placement plays a very important role in achieving this, particularly the use of walls for reinforcement. 
A quick and thorough wipe with the swab followed by a wipe with some dry tissue did the trick. The swabbed, cleaned and dried diaphragms are now ready for the application of the conductive coating. See how clear and reflective they are...
All panels swabbed and dried.
Here is a picture of the bottle of conductive coating and the utensils for the job, a small plastic cup, a foam applicator and a syringe to measure the amount of fluid to be used.
Specific amounts are used to coat each panel. This helps ensures the correct coating density for each panel. No guesswork here.
Using the foam applicator, I carefully apply the conductive coating onto the diaphragm. I apply until all the liquid measured for the diaphragm is completely used up. This takes a little practice to get right.
Here is a view of the coated treble diaphragm once it has dried. At this stage I started getting the feeling that the coating was a bit thick, more on this later.
Here is a view of one of the Full Range Panels. Although it has dried, it would take from a couple of days to a few weeks for the conductive coating to cure. Again looking at the panels, I had a sneaky feeling that the coating was too thick.
Next, I put the front and rear halves of the one complete panel together. The front half of the panel is made up of the support structure, the stator and a tensioned conductive diaphragm. The rear half of the panel is made up of the support structure, the stator and a strip of copper foil that will pass high voltage polarising charge to the diaphragm. This foil will come into contact with the conductive side of the diaphragm when they are sandwiched together. I place the 2 completed halves, front and rear together. I do a final check to ensure everything is in order before I marry the halves together. Notice the foil and the diaphragm will come into contact when they are sandwiched together.
Carefully, the 2 halves are placed together. I ensure that they are correctly oriented. Then I bring out the plastic channels that will be used to clamp the halves together. A channel is required for each side of the panel. So its 4 channels per panel.
Here's a partially clamped panel.
Remember that I had this niggling feeling that the conductive coating applied earlier was a little too thick and did not go on as consistently as I would have expected. A quick check revealed that it was indeed too thick. Rob from ER Audio, said that this will lead to a degradation of the Bass. As such I must reapply the conductive coating again. The conductive coating must be diluted with distilled water. It’s my own fault really for not reading the instructions more thoroughly. But before I can apply the correctly diluted coating, I will have to strip the old conductive coating off. I was worried that I may damage the diaphragm and then have to start from scratch. But as it turned out the process of stripping is really very easy. The conductive coating is a water based acrylic, as such I needed an acrylic solvent to strip it off. Acetone was the best choice. All the local hardware stores do not carry Acetone. But I got lucky and found a can at Ace Hardware. 
I wet some tissue generously with acetone and begin wiping the conductive coating off the diaphragm. The stripping is actually very easy... just be generous with the acetone and tissue. Here is a diaphragm that I have completely stripped. I also clean the diaphragm with the medical grade alcohol swab. Incidentally, after the acetone and isopropyl cleaning, the diaphragm did not look any worse for wear. See for youself...
I then mix up a batch of conductive coating, diluted to the correct coating density. Here is a picture of the correctly coated diaphragm.
When viewed directly from above, the diaphragm is clear, but when viewed at an angle it has a bluish haze. This is exactly the outcome that I was expecting from my conversations with the designer.
The entire process of stripping and re-applying the coating probably took about 2 hours. I am getting really good at this. Well the panel build is finished. I am finally able to clamp all the halves together.
Here is a picture of the 6 panels, all finished.
And another closer look at the 3 panels that make up one side of the speaker.
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