The T3S Kit by Javad Shadzi

T3S speaker kit cabinets

Javad posted the Thompson 3-way project on FaceBook., which is a bigger more ambitious speaker system, but when I did the surrounds for that system I was shocked by how good they turned out, the response is truly ruler flat, distortion is low and they sound really good. It struck me that this is a remarkable and simple design for under $200 that virtually anyone can build, in many cases with scrap materials in your lumber collection.

These are about 5 liters, external dimensions are 11.5″ tall, 8″ wide and 6″ deep, with this size they come out to a Q of .9 as measured, and are flat to 70hz where they roll off below that at a typical sealed 2nd order 12dB/octave rate. This means they hit quite low bass notes even below 50hz with good audibility. Considering their size, this is a nice result and compromise. These can be made bigger, feel free to model, they can be made deeper up to 10-12 liters to extend bass even more, but be sure to keep the baffle dimensions the same.

The tweeter is centered on the baffle 2-3/4″ from the top, the woofer center is 8″ from the top, both drivers are centered on the baffle laterally. Hold these dimensions precisely from the top.

For the circle jig settings:

Tweeter – OD 4-1/8″, ID 2 7-8″ and .21″ deep
Woofer – OD 5-15/16″, ID 4-3/4″ and .19″ deep.
3/4″ material is more than fine for this design, I recommend a simple strut brace (can be a piece of 3/4″ by 1″ wide material) connecting the baffle between the drivers to the back panel, the rest of the panels are so small that they don’t have any resonance issues, but small struts going from that one to the sides could be added to further dampen those larger panels.
I used a smaller thumbnail round over but I’d recommend a 3/4″ round-over on the baffle sides.
Final Impedance is 4ohms with a few small dips to 3.8, any modern 4ohm rated amp will drive this speaker no problem, I ran it on a few with no trouble. These image well, are detailed and very balanced, I would say they are very true to the recording and sound much better than the price tag and effort would indicate, full range they are only limited by bass below 60hz, for acoustic music they will get quite loud safely.

Be sure to click 2 of each in the cart for a stereo pair.



ImageProduct TitlePriceQuantityAction
Peerless XT25TG30-04 Ring Radiator TweeterPeerless XT25TG30-04 $28.87
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Dayton Audio RS150-4 $38.00
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Solen, 7.5uf, 400V $5.00
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Solen, 5.6uf, 400V $3.77
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22uf, Non Polar ElectrolyticNPE, 22uf $1.27
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10W Ceramic Resistor6.8 Ohm, 10 Watt Resistor $0.79
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0.39mH 20ga. $4.00
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Layer-wound-18ga Air Core Inductor1.35mH 18 ga. $11.56
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Twisted Zisters 2 ohm $3.29
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The Bromo by SB Acoustics

A surprisingly good manufacturers kit by SB Acoustics.  Intrigued by this professional design – The Oscar Duo  Build your own version for a fraction of the price.

Be sure to click 2 of each in the cart for a stereo pair.



ImageProduct TitlePriceQuantityAction
SB26CDC-C000-4 Ceramic TweeterSB, SB26CDC-C0004 $58.25
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SB acoustics SB17CAC35-8 Aluminum Ceramic Mid WooferSB, SB17CAC35-4 $86.57
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6.8uf, 400V Audyn $3.92
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15uf, 400V Audyn $6.40
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5.6uf Audyn Q4 400V5.6uf, 400V Audyn $3.42
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3.3uf Audyn Q4 400V3.3uf, 400V Audyn Q4 $2.52
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10W Ceramic Resistor15 Ohm, 10 Watt Resistor $0.79
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10W Ceramic Resistor2.2 Ohm, 10 Watt Resistor $0.79
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10W Ceramic Resistor2.7 Ohm, 10 Watt Resistor $0.79
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0.15mH 20ga. $3.96
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0.10mH 20ga. $3.89
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0.36mH 16 ga. $8.05
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Placeholder1.00mH 16 ga. $12.91
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