how many 5 inch basses have same surface area as 2 ten inch basses

[homertooties]

Hi all
i wish to put some five inch basses in a box with a tweeter in the middle.
i was wondering how many i would need to get same area as 2 ten inch basses


cheers

[DIY_newbie]

You'll need 8. By defenition 4 5" circles have exactly the same area as 1 10" circle

Area of a circle = PI*R^2, if you double R you quadruple area. However what you really want to know is the pistonic area of the driver, you'll need to compare the drivers Sd to know the real answer



--Chris

[homertooties]

many thanks for reply..

[Jezz-the-Fezz]

Although I'm not much of a tekki, & spend much of my time tinkering with speakers that you can't get spec's for, I'd be inclined to agree with DIY_Newbie; use the old Pr^2 malarkey, not forgetting to take the dustcaps into account where necessary (not all dust caps form part of the "piston" where others obviously do).
Depending on the function that you have in mind for your array, there are a few tricks you can employ in order to give the drivers an effectively lower Fs; hence the question - what do you want to get out of them?

[eddog]

when it is not presented on a spec sheet.

[454Casull]

Estimate the diameter of the cone minus the surround, plus 1/3rd of the surround on both sides. Divide that value by 2, and plug it into sd = pi*r^2.

[noah katz]

If you want to equal the output capability of a 10" you have to consider xmax as well; the average 10" will have much huigher xmax than the average 5".

[DeonC]

If you take Vifa as an example of a normal drive-unit manufacturer, and look at their drivers you will see what I mean. Their 5" drivers have an Sd of between 80cm2 and 86cm2, and their 10" drivers have an Sd of between 333 cm2 and 337 cm2. Furthermore, the 5" drivers have an Xmax of between 2mm to 4mm, and the 10" drivers have an Xmax of around 11mm. Considering this, it will take many more than eight 5" drivers move the same amount of air as a SINGLE 10" driver.

Let's take for example the 10" driver that has an Sd of 337cm2 and a Xmax of 11.6mm, and take the 5" driver that has an Sd of 86cm2 and a Xmax of 4mm. Now use the following calculation to calculate the volume of air that can be moved by each driver, so that we can compare apples with apples:
For the 10": 337cm2 * 11.6mm = 3909.2
For the 5": 86cm2 * 4mm = 344
Now: 3909.2 / 344 = 11.4
So out of the above we can see that it will take more than 11 of those 5" drivers to move the same volume of air as the single 10" driver. Unfortunate but true.

Enjoy,
Deon