The “Blast Furnace”

Since building this subwoofer, my house has begun cracking up. I blame the clay soil and climate change, but secretly fear that the sub is slowly pulverising the sandstone piers. The price we pay for our passions....

 

  • Twin 10 inch Jaycar CS-2274 Drivers .
  • 350W (4ohm) Jaycar AMP
  • 130 Litre 4.6cu.ft enclosure - 68kg - 150lb
  • 1030H * 740W * 500D
  • Tuning Frequency 28 Hz
  • Twin 160mm external ports
  • WinISD Calculated Peak Output 113 dB
  • Measured Avg Output (Complex Sound) before distortion 107db
  • Estimated cost $900 Australian
  • This speaker is for sale $500 Aud. Contact me if interested
"Blast Furnace" (9kb)

For this creation I wanted something a little different. The “Blast Furnace” is so named because it is reminiscent of blast furnace at the steelworks I worked at a some years ago

Consisting of a "powerhead" , housing two drivers, and linked via a transfer port to a lower chamber which makes up the required volume, this speaker will give an extra 7db over the "Sidewinder"

Two external ports exit the "powerhead" at the sides and run through the lower chamber to exit at the front. These ports do not open into the lower chamber but are supported by it. The amplifier is mounted at the back of the lower chamber, with the controls and infra-red receiver at the front

Jaycar's 350W amplifier delivers 240W into 8ohms as presented by the two drivers in series

I had hoped to disable the 6db boost on this amp as it seemed similar to the Parts ExpressLink opens in external window models from the USA. When I opened the back of the amp and compared it to the photos from the net, it was too different!

 

Graph - SPL 6k

 

Two 160mm ports mean absolutely no port noise. Both ends of the ports were flared by 10mm using a rollover bit in the router.

Graph - Vent Velocity (4kb)

 

Flare-it screenshot shows that there is actually a bit of port headroom in this design

 

Because the amp has +6db boost at 35Hz, power is not as much in the excursion critical range of 25Hz and lower. No hi-Pass filter is required for this unit

Graph - Excursion (4kb)

 

Extra pages for this speaker

 

  • Don't forget to check out the Construction Gallery

  • Here is a comparison with some commercial subwoofers, along with some notes on THX certification

  • Wonder what those boxes with lower tuning frequencies are like? I did a quick experiment

 

Project file for WinISD Pro 0.50a7

 

The next speaker has the ports folded up inside it's box

Last update to this page 30th April 2008

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