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High Fidelity

Lewis

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A. Design
B. Listen
C. Specs
D. Crossover

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High Fidelity

Lewis Stand Mount Loudspeaker

Description of this page

The Lewis Standmount Loudspeaker is a compact two way bass reflex standmount loudspeaker,
built to consume a stock of spare parts, but producing reasonably good performance.



Finished Speaker


Speaker being Stained



A. Designing and Building the Speaker

This loudspeaker began life as a collection of spare bits left over from the disassembly of other speaker sets. The cabinets were already built for another unfinished project. The internal cabinet dimensions were 250mm high, 185mm wide and 215mm deep. Note wall thickness adds to the external dimensions. I tried the woofers in the cabinet and was pleased with the performance, so I decided to create a complete speaker system.

The cabinet is about 10 litres volume. No attempt was made to match the drivers Thiele/Small parameters to the case. The baffle is a piece of 18mm pine, with the speaker mounting holes cut using a router circle cutter. The baffle and the bare cabinet walls had no veneer applied and were rubbed down to be stained a convenient brown colour. The bass driver was sealed with speaker sealant (Jaycar CF-2762) to prevent leakage, while the tweeter was intimately mounted on the flat cutout produced by a circle cutting router, with the notches for the tweeter terminals cut by a jigsaw.

The bass driver is a no name 6.5" Chinese driver with a medium sized magnet and a cloth semicircular suspension. The cone was doped with Aquadhere PVA to improve the midrange performance. The tweeter is an inexpensive Jaycar CT-2005 25mm 20W Dome. The crossover network is a 12dB/octave Linkwitz-Riley at about 3500Hz, with driver voice coil impedence correction. The network was built on a Jaycar CX-2605 Crossover PCB with Jaycar PT-3006 speaker terminals.

The crossover network is placed on the back of the enclosure, mounted on two wooden rails, which spaces the underneath soldered joints away from the internal wall and adds rigidity to the enclosure. Note the solidity of the cabling between the crossover and drivers. The cabinet was then lined with insulwool and stained.

The speaker was finished with the application of a grille and grille cloth. The grille is a 1/4" fibre board sheet, cut out with circular holes for each driver and close mounted to the baffle on four speaker grille clips (Jaycar CF-2761). The grille cloth (Jaycar CF-2752) is acoustically transparent and glued plus stapled to the rear of the grille.



Drivers and Crossover wired up


The interior of the cabinet

B. Listening to the Speaker

Be under no illusion that these are clinically accurate monitors. They were designed to a price (low) and perform admirably at their price point. The speakers were set up in the lounge room for listening tests with the first thing being noted the early rollof in the deep bass, with a slight presence in the upper bass. There is also a reasonably defined midrange and clear treble. As a comparison, I would rate them with better accuracy than the mass produced Asian speakers attached to current multimedia systems, and more in line acoustically with the slight warmth of the American 'West Coast' sound.

They would be ideal for their intended use of filling a small lounge room in a flat with rock music. Without having a deep bass, they are capable speakers without the thumping performance that annoys neighbours. The speaker was given as a present to my nephew Lewis, along with a Sony 80w/chan 5.1 channel tuner amp and a CD player. I hope he looks after them and appreciates the work that went into building them.



Drivers mounted on the Front Baffle


Crossover mounted behind Insulwool

C. Specifications of the Speaker

Specifications : Two Way Acoustic Suspension Stand Mount
Bass Enclosure : Approx 10L Lined
Frequency Response : 105hz-20,000hz at -3dB
Efficiency : 88dB at 1W at 1 metre
Impedence : 7.5ohms typical, 6.0 ohms minimum
Power Handling : 20W rms
Crossover : 4,260hz 2nd Order Linkwitz Network
Impedence Correction : Woofer and Tweeter
Bass Driver : Chinese 'No Name' 165mm Bass/Mid Paper cone
Tweeter Driver : Response 25mm dome (Jaycar CT-2005)

D. The Crossover Network



Circuit for the Crossover Network