Blog Forums DIY Speakers and Subwoofers ISO 100 Build – 20hz for under $100 Reply To: RE: ISO 100 Build – 20hz for under $100

Posted by: @ttan98
The subwoofer(vented) built by Paul is closer to 6l, you think is too small? Parts express recommends 0.26cu ft(equals to about 7.3 litres), you suggest closer to 10lit. to get closer to 35hz at -3dB?

Well, running the standard calcs as provided for by Thiele-Small, you get a box of 9.34 L (0.33 Cu.Ft.) with a Fb and Fp of 36.7 Hz and a F3 of 32.4 Hz. (Optimum)

Pump that to 10 L (0.355 Cu.Ft.) and you get a Fb and Fp of 35.6 Hz and a F3 of 31.1 Hz, albeit with a very minimal loss of 0.14 dB at Fb, basically unnoticeable.

And that’s just pure box, not taking into account what the driver takes up, or even the port. So even if it is a 10 L box, it is probably closer to 9 L or so once the driver is installed and even less with the port.

I can only surmise what Paul is thinking in his design choice, seeing as it’s a smaller driver and normally that size would be suited to a slightly higher Fb. (6 L = Fb 42, F3 40.5)
Parts express uses BassBox6, of which I am not acquainted in any way, but it seems they have a “High Quality” option that tends to shy away from absolute bottom end. (0.26 Cu.Ft. = Fb 39.3, F3 36.4) And did you ever notice they don’t specify anything for the port even though it is listed as “Ported”?

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