Photograph 1: Fostex FE127E Cabinet Bracing

Used in the right location, wall loaded and in a smaller room, this speaker has very special sonics which can bring out spectacular mids. The enclosure design has a deliberate peak in the bass to add a bit more punch to the bass (F3 = 61 Hz) which is surprisingly good for the small size of the driver. There is no rule to say the response has to be flat and in this instance, sounded much better with the 1 dB peak.

The enclosure design has taken the golden ratio into consideration which helps with the final sonics. In addition to the cabinet bracing, small blocks of various sizes and shapes were glued to the inside panels (in random and non symmetrical locations) to further alter resonances and helped to use up the 1.07 L volume allowed for bracing.

Figure 1: 12.5 L Bass Reflex Enclosure Plan for Fostex FE127E

Fostex FX120 Transmission Line Speakers

Looking for more information about fullrange drivers, I found the Mathcad worksheets by M.J. King and decided to try a speaker design of my own. My first try was a speaker using the Fostex FE167E, but I never made proper cabinets for them because my wife said “No way, they are too big”. Searching a smaller driver the Fostex FX120, a 12 cm fullrange unit caught my eye. There is not much information available for this driver, but the feedback from people who have used was positive. On the Fostex data sheet they show a flat frequency response without great peaks and drops.

HiVi F5 / SD1.1A Center Channel Speaker

General Info:

* Four – HiVi F5 Kevlar MidBass Drivers
* Two – HiVi SD1.1A Dome Tweeters
* Fully Shielded
* 170 watts RMS @ 4ohms
* 2nd / 3rd Order crossover at 4kHz
* Frequency Response: 60Hz – 20kHz
* Overall Dimension: 43″x 7″x 14″

The enclosure design for the center channel is shown below.

Figure 1: HiVi Home Theatre Center Channel Speaker Enclosure Drawing

HiVi SP10 Subwoofer

General Info:

* 10″ HiVi SP10 4 ohm subwoofer
* O-Audio 500 Watt plate amplifier
* Freq Response: 25Hz up to chosen x-over point.
* Overall Dimension: 21″x 12.75″x 20″

The enclosure design and model frequency response are shown below.

Photograph 1: 6418 Sub-miniature Tube RIAA Phono Preamplifier Kit

The printed circuit board (PCB) is double sided, solder masked and silk screened. Almost the entire top layer of the PCB is grounded to provide shielding. To keep the kit price low, the passive components are very basic. A mix of metal film and carbon resistors, polyester, ceramic and electrolytic caps. Polyester caps are generally not used in audio circuits because some say they do not sound good. Of course one can choose to upgrade the passive parts. The contents of the phono RIAA preamp kit are shown below. A full parts list of the kit contents is included in the Oatley Electronics K282 Kit Instructions (PDF – 646kB).

Photograph 2: Oatley Electronics K282 Tube Based Stereo RIAA Preamplifier Kit Contents

The external power supply is a small 5V switch-mode power supply (SMPS) with a universal outlet adapter that can be used with American, European, Australasian and UK power outlets (100 – 240VAC). The circuit uses a MC34063A switched mode power supply integrated circuit (IC) to convert the 5V external supply to 30V. The switching frequency is set at around 100kHz. The phono preamp circuit is a two stage affair with each valve stage buffered by a 2SK170 Field Effect Transistor (FET). The new old stock (NOS) JAN 6418 tubes are used in pentode mode. The schematic of the tube phono preamp kit is shown in Figure 1. Please note that this circuit is © Oatley Electronics and permission to host the schematic on this site has been provided by Oatley Electronics. A high resolution image of the schematic is available in the kit instructions.

Figure 1: Oatley Electronics K282 Tube Stereo RIAA Preamp Kit Schematic

The kit is fairly complete, however the builder will need to supply input and output connectors (typically RCA) and most will likely want to build the kit into some sort of enclosure. A completed kit using only the supplied parts is shown below.

Photograph 3: Completed Oatley Electronics K282 Tube Based Stereo RIAA Preamplifier Kit

Valve (Tube) RIAA Phono Preamp Kit Construction

Following the instructions supplied with the kit, assembly is very straight forward, but you will require basic soldering skills. The inductor will need to be wound (14 turns) and full details for constructing the inductor are included in the instructions. The JAN 6418 valves are very microphonic. Two tight fitting rubber grommets (supplied with the kit) on each valve will help reduce microphonics significantly. Place the grommets on the tubes prior to soldering them to the PCB. There are no special tools that are required, but you will need the basics, such as a soldering iron, wire cutters and wire strippers. For my frist phono kit build, I used single strand fine copper wire (~26Ga) for the signal wiring. Usually with sensitive and high gain circuits one would use shielded wire as hook-up wire. If you used unshielded wire like I did, tightly twist the signal and signal ground wires (I used an electric drill) to keep unwanted noise out of the wiring. For the internal power connections I used multi-strand wire (~22Ga) which I twisted together. The on / off control is a single-pole, single-throw (SPST) swtich connected to the 5V supply with a faint blue LED to indicated power. The input and output connections are gold plated RCA jacks.

Photograph 4: 6418 Tube / FET Stereo RIAA Preamplifier Kit Construction

I decided to enclose the phono preamp kit into a medium size cast aluminum case. I always paint these cases and this time would be no exception. Usually I paint in a gloss black or red. The paint I use is epoxy enamel and though it takes a week to dry hard it forms a very tough coat. Prior to painting I thoroughly sand the exterior of the case and use an acid etching primer (rust primer). But for this build I wanted a totally different finish altogether. So I went with the Hammered Copper look (using an enamel rust paint). It turned out to be the “bad paint job” look but it is different. Maybe not that bad.

Photograph 5: Finished 6418 Tube RIAA Preamp Kit - Hammered Copper Finish

6418 Sub-miniature Pentode Tube (Valve) Matching

The small JAN 6418 sub-miniature pentode valves are shockingly unmatched relative to one another. The kit instructions include a simple method using a 9V battery, a current meter (a digital multimeter can be used) and a 820 ohm resistor (provided with the kit) which enables you to match the valves.

Figure 2: Sub-miniature 6418 Pentode Tube Matching Circuit Schematic

By noting the current flow through the valve, the 6418 valves can be measured for matching. You do not need four closely matched valves for the kit. What you do need is a close match of total valve current flow in both channels. The current in individual tubes can vary wildly between 50uA and 170uA. I had fourteen valves to work with and no two valves even came close to each other. But what I was able to do was pick four valves, in two combinations of two, which gave me close to equal gain in both channels. Less than about 10% difference between channels cannot be noticed so don’t worry too much about perfect balance here. I used the valves with the higher gain in the first stage and valves with the lower gain for the second stage. The kit comes with one extra valve to facilitate better matching.

Valve (Tube) Microphonics

These sub-mini valves will ring like a church bell on Sunday morning so be sure to use at least two grommets on each valve. The grommets should be placed on the valves prior to soldering them to the PCB (the valve pins can break). When soldering the valves to the PCB, try make the leads as short as possible to help keep the valves from swaying. Also before I screw the enclosure lid down I place a thin layer of Dacron (synthetic polyester fill) over the entire circuit which helps to hold the valves steady. This definitely helps as I have tried it with and without the poly fill. The polyester fill will also help reduce any resonance or audible echoing within the case further helping with microphonics. Don’t worry about the valves melting the poly fill as they hardly get warm. Use a good set of rubber feet to de-coupling the preamp from the surface it sits on. Other forms of damping and decoupling such as placing the preamp on a slab of marble or granite may further help reduce mechanical noise.

Special Edition MkII JAN 6418 Phono Preamp

Since completing and enjoying the phono preamp kit for many hours I decided to build another. This time I would use polypropylene capacitors and use a solid state DC power supply. Originally I wanted all the power supply components in the case but due to hum induced by the 24V AC wall wart I moved the rectifier portion to the back of the wall wart. This meant that only DC was entering the case. A double Pi filter network was used. That is small cap – small resistor – large cap – large resistor – small cap (C-R-C-R-C).

Figure 4: Special Edition MkII JAN 6418 Phono Preamp Power Supply Schematic

The Special Edition MkII JAN 6418 Phono Preamp is shown below. I also used a piece of copper clad board for additional shielding.

Photograph 6: Special Edition MkII JAN 6418 Phono Preamp PCB

Photograph 7: Special Edition MkII JAN 6418 Phono Preamplifier Kit

Listening Impressions – Oatley K282 RIAA Phono Preamp Kit

This is an unusual RIAA phono preamp kit that uses a strange mix of parts and ideas, but one not scared to deliver exceptionally good music at a cheap price ($47AU). For the novice DIYer wanting to get into analogue music or those who just likes kits in general, this phono kit will tick many boxes: Valves, ICs, SMPS, FETs, RIAA.

Listening Impressions - Oatley K282 RIAA Phono Preamp Kit This is an unusual RIAA phono preamp kit that uses a strange mix of parts and ideas, but one not scared to deliver exceptionally good music at a cheap price ($47AU). For the novice DIYer wanting to get into analogue music or those who just likes kits in general, this phono kit will tick many boxes: Valves, ICs, SMPS, FETs, RIAA.

I have managed to get in a few hours of listening with the SE MkII version. I’m not convinced it is better than the basic kit version. Sonically, both builds appear to be equal. There will be those who just can’t stand the thought of polyester capacitors, carbon resistors and the two SMPS. I would say whichever way you go on to build the kit, you will not be disappointed. In a blind listening test the basic kit outperformed two Cambridge phono preamps and a Hafler phono preamp in front of six very critical listeners of the Melbourne Audio Club, across three different turntables and cartridges. Impressive!

Photograph 5: Jordan JX92S Tower Loudspeakers at Local Audio Event

Enclosure Design – Jordan JX92S Vented Loudspeaker

The goal was to get a good amount of low end response from this tower loudspeaker. Figure 1 shows the calculated frequency response for the JX92S in a 1.3 ft3 for a bass reflex cabinet (no damping material) and tuned to ~ 35 Hz. The frequency response was calculated using WinISD. The calculated -3dB point is about 30 Hz.

Figure 1: Calculated Frequency Response - Jordan JX92S Tower Speaker

See the Jordan JX92S fullrange driver page for the measured and factory Thiele-Small Parameters. As can be seen in the model of the frequency response, the T/S differences do not make much of difference in the frequency response. The enclosure design for this loudspeaker project is shown below in Figure 2. See the construction photographs and notes for more details.

Klipsch WB-14 Icon W Series Furniture-Grade

Advanced Design for Phenomenal Sonic Performance

Klipsch engineers managed to generate excellent output and dispersion from these small speakers by employing an all-new proprietary technology called the XT Tractrix Horn. Horns have been the driving force behind Klipsch speakers since 1946. The XT engineering takes this time-proven philosophy to new heights by altering the surface geometry of the horn with four “bumps” that are shaped like flower petals. It’s a technology that creates a wider dispersion pattern and provides more latitude in placement.

The WB-14 4.5-inch woofer design allows for a small, attractive cabinet yet provides excellent low-frequency response and power-handling. The lightweight, triple-woven Fiberglass woofer provides robust low frequencies with great detail. Heavy-duty ceramic motor structures power these high-tech wonders and accommodate even the most aggressive power handling requirements.

The ported enclosure design, with both internal and external port flares, provides improved output and lower distortion–with better air-flow and extremely low port turbulence. Finally, the crossover networks consist of premium components manufactured to precise tolerances for a consistent sound from speaker to speaker and system to system.

Stunning High-End Cabinetry Looks Fantastic in Any Room

While the WB-14 employs modern advancements on the inside, it reflects a classic approach on the outside, featuring a timeless wood veneer cabinet finished in Cabernet or Espresso. Unlike most speaker manufacturers who opt for domestic veneers (cherry, oak or maple), Klipsch selected an exotic, non-endangered Berlinia veneer from West Africa. Berlinia is a sister veneer to Zebrawood, which is often featured on other luxury goods.

The WB-14 cabinets are carefully sanded, sealed and stained. Much like in high-end furniture manufacturing, the stain is then top coated with a polyurethane finish. This spray application involves 10 coats, with sanding between each coat to achieve the proper thickness. The cabinet is also inspected at every sanding level to ensure clarity over the stained veneer. As beautiful as the cabinets is, it is also internally braced to reduce cabinet resonance and transmission of internal vibrations outside of the cabinet box, which makes the bass tighter and midrange clearer.

The Klipsch WB-14 and the entire ICON Wood series is timelessly designed high-end furniture which happens to be loaded with numerous cutting-edge Klipsch speaker technologies and details, all delivering the signature Klipsch high-impact, low-distortion sound. No matter what material you play on them or what room you place them in, the WB-14s will always exceed expectations and look as good as they sound.

The advanced XT Tractrix Horn design creates a wider dispersion pattern

What’s in the Box
One pair of Klipsch WB-14 bookshelf speakers, adhesive shelf bumpers, magnetic grills, and an owner’s manual

Klipsch WB-14 Icon W Series Furniture-Grade details:

• Exclusive XT Horn-tweeter design produces smooth & lifelike sound with legendary low-distortion Klipsch sound.
• Premium titanium tweeter for precise highs & Fiberglass woofer for amazing lows
• Slender, elegant enclosures with Magnetic grille (no visible fasteners)
• Exotic furniture-grade wood veneer finish
• Threaded insert for easy wall mounting (brackets optional)

Klipsch Reference Series RB-61

The RB-61’s front-firing port eliminates turbulence noise and makes installation into custom cabinetry a breeze. Increased baffle ribbing around the horn mouth dramatically improves acoustics across the sonic range. For signal purity and perfect driver integration, the crossover on the RB-61 features the finest components and Klipsch custom internal wiring.

Klipsch Reference Series RB-61 details:

Klipsch Reference Series RF-52

The RF-52’s rigid cabinet offers improved internal cross-bracing to minimize panel vibrations that can color sound and a rear-firing port to eliminate turbulence noise. Increased baffle ribbing in the lower panel and around the horn mouth dramatically improve acoustics across the sonic range. For signal purity and perfect driver integration, the crossover on the RF-52 features the finest components and Klipsch custom internal wiring.

Klipsch Reference Series RF-52 details

• FREQUENCY RESPONSE: 34Hz-23kHz +/-3dB
• POWER HANDLING: 100W RMS / 400W Peak
• SENSITIVITY: 96dB @ 2.83V / 1m
• NOMINAL IMPEDANCE: 8 ohms compatible
• Single Speaker – Sold Individually

Klipsch RB51 Black (Pr)

The RB-51 employs a 5.25-inch woofer for a solid bass foundation. This Cerametallic(TM) woofer with inverted copper dust cap exhibits a very high stiffness-to-mass ratio and superb damping characteristics. Increased baffle ribbing around the horn mouth dramatically improves acoustics across the sonic range. For signal purity and perfect driver integration, the crossover on the RB-51 features the finest components and Klipsch custom internal wiring. Available in a black woodgrain vinyl finish, the RB-51 comes with a low-diffraction, magnetically attached grille to further accentuate the elegance of this speaker.

Klipsch RB51 Black (Pr) details:

• Nominal Impedance – 8 Ohms Compatible
• High Frequency Drivers – 1 (2.54cm) Titanium Diaphragm Compression Driver Mated To 90×60 Square Tractrix Horn
• High Frequency Crossover – 2000hz
• Low Frequency Drivers – 5.25 (13.3cm) Cerametallic Cone Woofer
• Enclosure Type – Bass-Reflex Via Rear-Firing Port