1. ## sub cone area 18

is the surround counted when finding cone area of sub?what is the equation to figure it out?whats cone area of 18.not solox..just regular 18
Last edited by marleyskater420; 09-20-2003 at 04:03 AM.

2. ## Re: sub cone area

Sd - 'The area of a loudspeaker cone'

Example:

Kicker CompVR15
Sd, SqM.0881

Kicker Solo-Baric L715
Sd, SqM 0.1056

- Steve

3. ## Re: sub cone area

Originally Posted by Jmac
Typically it's ...

Diameter of speaker - 2*width of surround = Effective Diameter

Then you punch it into the formula for calculating the area of a circle ...

Pi*R^2

So say you have a 18" speaker with a 1" surround, so you get 16" for effective diameter and 8" (20.32 cm) for effective radius.

Pi*(20.32)^2 = 1297.17 cm^2
k thanks.i get the piR^2 part.and the subtracting the surround..how do i get it into ^2 inches?cuz i need to figure out if its under 260 ^2inches(i think)or not

4. ## Re: sub cone area

1/3 of the surround is usually taken into consideration when you're doing your own SD figures.

5. ## Re: sub cone area

Originally Posted by Electrodynamic
1/3 of the surround is usually taken into consideration when you're doing your own SD figures.
so then if the cone area is 16 1/2 i do 3.14x68=213 is that how many square inches there are?

6. ## Re: sub cone area

math math math!! I HATE MATH!

7. ## Re: sub cone area

Originally Posted by Jmac
Typically it's ...

Diameter of speaker - 2*width of surround = Effective Diameter

Then you punch it into the formula for calculating the area of a circle ...

Pi*R^2

So say you have a 18" speaker with a 1" surround, so you get 16" for effective diameter and 8" (20.32 cm) for effective radius.

Pi*(20.32)^2 = 1297.17 cm^2
It's not really that simple. You typically end up overestimating the cone area of the driver when you do it that way.

We'll use the RE XXX 18 as an example. Now it is an 18" diameter driver, with a 1.5" wide surround.

So using what you outlined above, we have a 15" effective diameter, and a 7.5" radius.

Now that would of course lead us to believe that we have an Sd of about 177 in.^2 (1135cm^2).

Now that figure is actually incorrect. When you actually measure, using the far more precise 1/3 surround method, which eliminates any ambiguity on where the surround actually starts.

The actual measured Sd of the XXX 18 is 1095cm^2. Not a dramatic difference in this case (about 4%), but as I'll show next, it does make a difference.

The next example is the Eclipse Ti 15. It has a 2" wide surround. So we have 11" to work with, radius of 5.5".

We get an Sd of 95in.^2. This translates to about 613cm^2. The actual measured Sd is 650cm^2. That's about a 6% difference.

Let's look at the Adire Audio Tempest. It has a 3/4" wide surround. So we have 13.5". Radius of 6.75".

So we get an Sd of 143in.^2. This translates to 922cm^2. Pretty impressive.

Now when we actually measure Sd, we get 780cm^2. Wow. That's about a 16.5% difference in Sd. That's fairly significant.

Now why didn't the method work? Because the Tempest has the surround spaced away from the gasket, so it actually results in a much lower Sd than merely subtracting the surround width from the driver diameter would suggest.

The method is reasonable, but I just want to make it clear that in many instances, it's not very accurate, because you aren't really being as specific as you should be, and the equation doesn't really account for things like that which I specified above.

Hope that helped someone.

8. ## Re: sub cone area

Originally Posted by Warbleed
It's not really that simple. You typically end up overestimating the cone area of the driver when you do it that way.

We'll use the RE XXX 18 as an example. Now it is an 18" diameter driver, with a 1.5" wide surround.

So using what you outlined above, we have a 15" effective diameter, and a 7.5" radius.

Now that would of course lead us to believe that we have an Sd of about 177 in.^2 (1135cm^2).

Now that figure is actually incorrect. When you actually measure, using the far more precise 1/3 surround method, which eliminates any ambiguity on where the surround actually starts.

The actual measured Sd of the XXX 18 is 1095cm^2. Not a dramatic difference in this case (about 4%), but as I'll show next, it does make a difference.

The next example is the Eclipse Ti 15. It has a 2" wide surround. So we have 11" to work with, radius of 5.5".

We get an Sd of 95in.^2. This translates to about 613cm^2. The actual measured Sd is 650cm^2. That's about a 6% difference.

Let's look at the Adire Audio Tempest. It has a 3/4" wide surround. So we have 13.5". Radius of 6.75".

So we get an Sd of 143in.^2. This translates to 922cm^2. Pretty impressive.

Now when we actually measure Sd, we get 780cm^2. Wow. That's about a 16.5% difference in Sd. That's fairly significant.

Now why didn't the method work? Because the Tempest has the surround spaced away from the gasket, so it actually results in a much lower Sd than merely subtracting the surround width from the driver diameter would suggest.

The method is reasonable, but I just want to make it clear that in many instances, it's not very accurate, because you aren't really being as specific as you should be, and the equation doesn't really account for things like that which I specified above.

Hope that helped someone.
thanks.that helped.

9. ## Re: sub cone area

No problem, glad to be of assitance.

10. ## Re: sub cone area

Originally Posted by Jmac
Any more accurate way of calculating it without being able to physically measure the speaker in person ?
Honestly, just try and take a look at the driver, so you can get an idea if it's a situation like the Tempest.

Otherwise just make sure to consider it a liberal estimate.

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