Fostex FX120 ML-TQWT Speaker Project

Martin from Germany has put together a great looking pair of tower loudspeakers. His speaker project uses the Fostex FX120 fullrange driver.


The speaker enclosure is a Mass Loaded - Tapered Quarter Wavelength Tube (ML-TQWT). As you can see, Martin has done a great job with the finish on the DIY speaker cabinet. He came up with the design on his own using the MathCAD worksheets available from Martin J. King at quarter-wave.com. His speaker project includes a design for a baffle step correction circuit which he found necessary to balance the sound.


Martin reports that the sound is relaxed with a detailed midrange and good highs. He also indicates that the ML-TQWT enclosure gets good low end extension from the small Fostex driver. Having recently used the FX120, I can confirm that this is one sweet sounding driver.

For additional information, pictures and the speaker cabinet design, see Martin's Fostex FX120 DIY ML-TQWT Speaker Project.

Related DIY Audio Projects:

• Fostex FX120 Bass Reflex Bookshelf Speaker Project
  
• Jordan JX92S Transmission Line Loudspeaker Project
  

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DIY OP Amp Based Preamplifier

INTRODUCTION
After building a OPA2134AP CMoy / Grado RA1 headphone amplifier in a timbre box, I wanted to try this high performance OP amp in a line stage / preamp. Rod Elliott's High Quality Audio Preamp (Mk II) which is a two stage preamp with balance control seemed like a good choice.

DIY PREAMP AND POWER SUPPLY
Two small pc proto boards (Radio Shack 276-159 / Dick Smith H5601) were used to accommodate all components. Metal film polypropylene capacitors were used in the signal path. It would have made the whole project easier by using physically smaller caps but for me the sound was a priority. For the power supply I used a 1.2A 18V regulated SMPS wall wart. I definitely do not need 1.2A, but I wanted a gutsy supply. Two 1k 0.5W resistors make up the "virtual ground" split supply. 220 uF low ESR capacitors and 0.1 uF decoupling capacitors are used for channel. This simple supply configuration works very well and is dead quiet.


PREAMP ENCLOSURE
The case only measures 115 X 90 X 55 mm (same size enclosure that I used for my Nanoo Gainclone) and placing all the components in this tiny space, including a dual gang volume control and balance control was going to be tough. Unless you enjoy working in ridiculously small spaces and/or you are masochistic, build this preamp in a bigger case. Even a slightly bigger enclosure would be better. For the finish I use an acid etch primer, allowed a few days drying and then the spray color over the top. This was the same technique used with the big red caps on the Synergy Roasting Pan Chip Amp / Gainclone.



RESULTS
I have used the preamp as a front end to my S-5 Electronics K-12 Tube Amplifier. The test setup comprised a NAD C542, modified bookshelf speakers and DIY Silver Interconnect Cables. The preamp added nothing and took away any CD player/ Valve power amp miss-match. For that reason I have named it Neutrino. The balance control has a very wide sweet spot and the volume control was non-twitchy, linear and easy to use. A very inexpensive project but it feels odd to build something that adds and removes NOTHING audibly in a cute box. Try it.

Mark Houston



Other DIY Audio Projects by Mark:

• DIY 12AX7 Tube Preamplifier Kit
• DIY Class A Mosfet Amplifier

Jordan JX92S Fullrange Drivers

Recently I aquired a pair of Jordan JX92S Fullrange Speakers as part of a group buy organized through diyAudio.com. Ted Jordan of E J Jordan Designs has been developing his drivers for some 50 years and his drivers are very well regarded. The Jordan drivers are different from most similar sized fullrange drivers in that they cover almost nine octaves! The Jordan JX92S speakers are well built and use a cast frame. The cone and dust cap are metalic. The pole piece is vented and the magnet is sheilded. I measured the T/S parameters using Woofer Tester 3. The measured parameters I came up with do not match very closley with those published by the manufacturer. See the Jordan JX92S Fullrange Speaker page for a detailed comparison of the T/S parameters. However, do note that the parameters measured by myself using WT3 are consistent with those measured by Zaph|Audio using SoundEasy and WT3.


Given that Qts was measured to be near 0.6, a relatively large vented enclosure will be required to get some bass depth from this driver. To try minimize the size of the enclosure (for WAF), an Aperiodic Speaker Cabinet Design can be considered. Seeing that I have a unused pair of 0.25 ft^3 curved Parts Express speaker cabinets, I may go this route. The JX92S drivers have been used successfully in a wide variety of enclosures. Francesco has reported very good results from his DIY Jordan JX92S Transmission Line Speaker.

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Fostex FE127E DIY Bass Reflex Speakers

Peter in Australia has put together a nice looking pair of DIY speakers. The speakers are a fullrange (single driver) design in a 12.5L bookshelf sized enclosure. The enclosure design is a simple bass reflex cabinet using the Fostex FE127E fullrange speaker drivers (shown below).


The DIY speaker cabinets are constructed using MDF and finished with a real wood veneer. The speakers can be run fullrnage or through a Baffle Step Compensation Circuit. Peter reports that these relatively small speakers work well in small to medium sized rooms and have very special sonics which can bring out spectacular mids.


For additional information, pictures and the speaker cabinet design, see Fostex FE127E DIY Bass Reflex Bookshelf Speakers.

Related Posts:

• Gio's Fostex FX120 DIY Bass Reflex Speaker Project
  
• Jesse's Aura NS3-194-8E DelSol - DIY Fullrange Speaker Project

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Fostex FX120 Bass Reflex Speakers

A few months back I posted some pictures and comments about the new great looking curved speaker cabinets from Parts Express. The cabinet I ordered are 0.38 ft³ and have a black piano gloss finish.


Having built a couple pairs of speakers using inexpensive fullrange Fostex drivers, I really wanted to hear what more expensive fullrange drivers sound like. So I ordered up a pair of Fostex FX120 fullrange drivers.


For the enclosure, I decided to try a simple bass reflex cabinet tuned to about 63 Hz. The dimensions and tuning is very similar to that recommended by Fostex. The results are pretty good (both looks and sound). The FX120 is a very smooth and detailed driver and I prefer over the Fostex FE127E driver (which is very good considering the low cost).


In a small sized room the speakers deliver decent bass extension and it also blends in well with a subwoofer. The FX120 has great sonics and a fantastic midrange. The relatively small bookshelf speaker also work great as near field monitors.

For more information about this DIY speaker project see the project page, Fostex FX120 Bass Reflex Bookshelf Speakers.

Related Posts:

• Peter's Fostex FE127E DIY Bass Reflex Speakers
• Jesse's Aura NS3-194-8E DelSol - DIY Fullrange Speaker Project

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