Monday, January 14, 2008

DIY Back Loaded Horn Speakers / BLH - Fostex FE206E in a Dallas III Cabinet

Horny, I'm home. Funny? I have been waiting a longtime to say that... 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 "not so good" of the ESLs are that they are a pain to drive, needing serious wattage and current from a amp that puts out heat like an oven... I kid you not. A monster amp with 200watts with ample current and able to deal with the quirky impedance of the ESLs are what they need to perform their best.


Now on the other end of the scale are these eccentric full range drivers. My first memorable experience with them were in an Audio Note showroom. I forget what amp was on show, but I am quite sure it is one of the famed amps from Kondo's stable. There were also some funny looking speakers singing in the back room. I asked the sales attendant and found out that they were.... Lowthers was the name. They resided in some cabinets huge cabinets that I mistook for a chest of drawers!! They sounded lucious and "complete"!! What do you do when you don't have a couple of hundred thousand to plonk onto one of Kondo's famed amps with a matching lowther driver and those very fine cabinets... DIY of course...

Fast forward 10 years or so, I finally decided that it was high time I got my tube amp plus a pair of horns setup to recapture the magic. So I shopped around for an amp and speakers. I thought I was going to DIY a tube amp, but I came across a deal for a Made in China tube amp that I could not let go. So I bought myself a Little Dot III tube amp with switchable modes between Triode and Pentode. This amp sounds beautiful and only produces 2 - 3 watts, but what beatiful watts they are. All parts of the amps including the tubes are made in china save for the volume control which is from alps and power connectors from amphenol. I may yet DIY a tube amp in the future.... you never know. Now for the star of the show, the speakers.


After scouring the internet I considered, various forms of full range drivers... in bass reflex, open baffle, and various flavours of horns (spiral was really interesting). I settled on one of the best bang for the buck Fostex FE206E full range drivers that work best in a back loaded horn configuration. People tell me that Corals are better, they probably are better but I could not find much information about them. The pair of Fostex 206E drivers cost me less than RM600 shipped from Japan. The only drawback with these full range drivers that I garnered from all that reading was the inherent "shout" that had to be dealt with or tolerated..... As for the BLH design, I can't design any speaker to save my live. So I scoured many sources and forums for something that I could build. I came across several designs and of course there is the recommended design for the 206E from Fostex. I then happened across http://www.fullrangedriver.com/ . This site contained much information about horns and full range drivers, horn calculators, designs and a collection of people passionate about them. After much reading I was taken up by a BLH design made specifically for the Fostex FE206E called the Dallas II. The completed cabinets looked like the usual box type folded BLH. The designer goes by the name of Ron in the fullrangedriver forum. While I have never listened to these speakers, something about this guy just struck a cord in me. In addition several DIYers had built the Dallas II and were very happy with the result. I must admit that the rectagular/boxy Dallas II did not appeal to me aesthetically.


Then from out of nowhere the Dallas III surfaced. Now I am not sure if the Dallas III was actually designed by Ron himself or drawn by a fellow enthusiast. But the Dallas III was a much more aesthetically pleasing speaker. The externally the Dallas III had discarded the boxy look for a curved and flowing design. The internal folds are smooth as well, containing no sharp angles. For all intents and purposes the dimensions of the Dallas II and III were identical. So I thought I'd try to build this. The fact that it looked nice, gave me an oppurtunity to blend my music into my surroundings. After showing the desings to the Home Minister, we desided it would be nice to have them in our bedroom, as a sort of functional Art Deco piece.


These sepakers sound as beautiful as they look, they are really enjoyable and can go really LOUD. Who new what 2 watts could do? As luck would have it I have a large bedroom which suited these speakers fine both visually and sonically. Bass while not prodigious is fast and accurate. It goes down low to about 35Hz. The inherent shout is only evident when you are listening on axis, with the speakers suitably toed in/out, its hardly noticeable. It plays all music with equal aplomb. Bach's Dorian sounded great, Dire Straits' Money for Nothing was really rocking, Janet Seidel's Agua De Beber was pure liquid.... I am listening to CCR as I am writing this post, very nice!!


Presenting the Dallas III and Fostex FE206E.
Front view of the speakers, I placed a 6 inch ruler so you can get appreciate the scale of these behemoths, while not as big as my ESL, they are still more than a handfull. They stand about 1.2m tall 45cm deep and 30cm wide. 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 update 01 or return to Home.
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1 comment:

Heng said...

Wow! When's the audition?