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Astro Power 15th February 2006 11:52 AM

i got 2 new subwoofers. need help for desing a box - t\s per' inside
i want to build a the Highest spl box that tuning to get the maximum in 55HZ

i have all the tools to build the best box. is for my car...

the maximum volume of the box is 180Liter\6.357 Cu.ft.

the information of the woofers:

2 X 13' square woofers.

3' dual voice coil 4 ohm + 4 ohm - 700W
Qts 0.7
Qms 5.81
Qes 0.9
Fs 26Hz
Spl 90dB
Vas (Cu.Ft) 4.146


richie00boy 15th February 2006 12:15 PM

1. Put the parameters into WinISD Pro
2. Set box tuning to 55Hz
3. Start off with a small box size, like 30 litres. Look at the power handling graph. You should find that the design is thermally limited, i.e. by the voice coil power handling not by excursion (at your chosen 55Hz anyway).
4. Increase box size and you should hit a point when the design is excursion limited.

This is your optimum box size. It will give you best efficiency against your chosen 55Hz. It will sound like dirt though. And you will deafen yourself.

sreten 15th February 2006 12:20 PM


as Qts is 0.7 you simply put them in a sealed box.

as Vas is 4cuft per driver use the biggest box you can.

You need 2cuft (Q=1) to 3cuft (Q=0.9) per driver.


richie00boy 15th February 2006 01:29 PM

I would otherwise agree with you completely, but I think you have misunderstood his application. He wants to make a boom box for car SPL competitions, with no concern to the sound quality.

Astro Power 15th February 2006 02:36 PM

2 Attachment(s)
the box in isd : it is on 600WRMS amplifier.

the vent much is ok ?!



Astro Power 15th February 2006 02:37 PM

2 Attachment(s)
more one.

richie00boy 15th February 2006 03:02 PM

No you need to tune to 55Hz as I said. That will give you maximum power capability at that frequency.

Astro Power 15th February 2006 05:20 PM


and what about the "vent much"....?


simon5 15th February 2006 10:14 PM

richie00boy, according to the graph, I think he's better to tune at 45 Hz like he did, he get that nice "free" efficiency peak.

Do you know the Xmax of your drivers Astro Power?

Vent mach need to be under 0.1 at full power, so 0.03 is perfect.

owdi 15th February 2006 10:18 PM


Originally posted by Astro Power

and what about the "vent much"....?


Plain WinISD sucks at predicting air velocity in the vent, since it doesn't show you how velocity changes with frequency. As a _very_ general guideline, for high spl applications calculate the speaker cone area and make your vent 1/4 of this area.

Your dual 13" square woofers sweep about 240 sq. inches, so you need about 80 sq. inches of vent area.


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