# some intresting woofer ratios in 5.1 speakers

Discussion in 'Speakers' started by lakshmant, Mar 23, 2006.

1. ### lakshmant Agent

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Feb 25, 2004
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i was just going through the MK and other THX speaker manufacturers pages

this is what i found out you can use this for buying speaker with optimum woofer output.

for this i calculated the total woofer area of each channel ,

i:e if front have 2*5.25 inch woofers =10.5 inches.

but for a single channel as reference

so with that in mind i did some math(i am weak at it though)

for the THX select 750 system from MK the ratios of the woofer size of the sub vs a single stage channel and of the sub against surroudn and stage are as follows assuming LCR is same .

surround to stage speaker is 1:2

surround to sub woofer size ratio is 1:2.28

single stage channel to sub woofer ratio is 1:1.14

so to get a balanced coverage of bass as per THX yu will need the front LCR to have a woofer area of 1.2 times the surround channel and the sub 2.4 times the surround channel.

ex yu have a 5.25 inch woofer cone for surround then for THE total of each woofer area of each LCR speaker must optimally be 2 times the surround speaker cone size is 2*5.25 =10.5 inch

then the sub cone size when related to LCR is 1:1.14 times so the sub woofer size should be 1.14*10.5=app 12 inches.(11.97 precisely)

surround to subwoofer cone is 5.25*2.28= is again 11.97.

this would help as the THX speaker perform bass output in theory properly at 2000 cubic feet

i will just check about THX ultra2 and also post the ratios

2. ### derekBannatyne Agent

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instead of doing 2 * 5.25" = 10.5", shouldn't you multiply 5.25" by 3.14(r^2), and then multiply it by the number of drivers?

3. ### Jacob C Second Unit

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Mar 19, 2005
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Basically, the diameter of the driver is not linearly proportional to its area (which should be obvious by looking at the equation). What you actually have to is get the radius and then plug it into Pi*(r^2).
Pi=3.14 etc.. r=radius d=diameter a=area r=d/2

Or, you could say: a=Pi*((d/2)^2)

Then, there's the travel of the cone but I wont get into that. It is just as important as the diameter if you are comparing speakers. Try running the calculations again I would like to see them. Hope this makes sense. I just worked an overnight shift and am about to go to bed. I write weird stuff when I'm tired.

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