Box size help?

[SamClassA]

Hello, I've used a few box size calculators from the Net, but I keep getting different Volume sized from each calculator?? Can someone have a go and see what you come up with. My Bass driver is a Seas 10" CA25RE4X/DC. Vas=187.9, Qms=3.63, Qes=0.34, Qtc=.31, Free air resonance=25Hz,
This will be a vented box, Vent details??
Thanks for your help.

 

[ocaukrell]

this is straight from winisd pro

79.65ltr
tuned to 31hz
port - 10cm diameter 23.5 long

changing things like volume and port tuning alter the response.

Suggest you download a copy and play with it yourself.
Dont forget to add the 'room gain' which I think is about 6db/oct.
This will also depend of size of room etc.

 

[SamClassA]

0caukrell, thanks for your assistance. Are the figures you quoted for a box allignment "QB3 Quasi-Butterworth"?

 

[mashaffer]

BoxPlot gives 83 liters for maximally flat. Pretty close. It calls for 7.62cm dia port 10.59cm long FWIW.

mike

 

[Svante]

A design with a 98 litre box tuned to 24 Hz gives this response:

An externally hosted image should be here but it was not working when we last tested it.

The blue curve includes the baffle step for a 30x60 cm baffle, the red ignores it. The box is filled to 40% with ideal isothermailsing material (ie apparent box volume is 113 litres).

The reason that you get different box volumes from different softwares is that there isn't one "correct" way to do it. There are only more or less reasonable ways.

 

[ocaukrell]

0caukrell, thanks for your assistance. Are the figures you quoted for a box allignment "QB3 Quasi-Butterworth"?

Yup.

Why not download winisd (pro or not) and have a play ??
It is free.

 

[SamClassA]

Once again thanks for all your replys,
I downloaded WinISD 0.50a7, and got these figures: Box Vol 79.65, Tuning f 30.94Hz, Vent Dia 10.2cm, Vent length 24.6 cm,
slighty diff than your? Maybe3 because Diff Version of WinISD?
Another Quest? If I make the Box Vol larger, say, 100Litres, will this give me a better bass responce? or Lower Tuning frequency, or am I on the wrong track here?

 

[ocaukrell]

you got the exact same as me (no suprise) reason for the different port is I changed it from 10.2 to 10cm diam.

bigger is not always better.

if you are really serious about how it will work in a particular room, research 'room gain'.

 

[SamClassA]

just another thought? Now that we calculated the Box Volume using the various "calculators" do we deduct the driver and port volumes from thew calculated value to come up with the final Box Volume?

 

[ocaukrell]

The calculated volume will NOT include speaker and port volumes.
So if it says a 10ltr box, and the driver is 2ltr, port 3ltr, bracing 2ltr, then you need to design a box of 10+2+3+2 = 17ltrs.

 

[SamClassA]

thanks ocaukrell, you confermed my thoughts

 

[bremen nacht]

The calculated volume will NOT include speaker and port volumes.
So if it says a 10ltr box, and the driver is 2ltr, port 3ltr, bracing 2ltr, then you need to design a box of 10+2+3+2 = 17ltrs.

Anyone know a quick&dirty way of estimating speaker volume, given only its diameter and depth? That's usually all you get from a data sheet.

thanks

 

[ocaukrell]

Volume of a cylinder.

Pi * r^2 * h

Pi is the mathmatical constant approximately equal to 3.141592654
r is the radius of the base
h is the height of the cylinder.

Although I suspect with a little looking you should be able to find the Vd (volume of driver) without to much effort.

EDIT
Yup, quick google says Vd is 3 ltr (assuming your still talking about the Seas CA25)

 

[bremen nacht]

Volume of a cylinder.

Pi * r^2 * h

Pi is the mathmatical constant approximately equal to 3.141592654
r is the radius of the base
h is the height of the cylinder.

Although I suspect with a little looking you should be able to find the Vd (volume of driver) without to much effort.

EDIT
Yup, quick google says Vd is 3 ltr (assuming your still talking about the Seas CA25)

Cheers for the formula.

I wasn't talking about the Seas driver - apologies if this is a threadjack - it's actually an Eminence 15" driver I'm looking at.

Vd is indeed in the published TS, but I don't think it's the number I need; Vd is defined by Eminence as 'Peak Diaphragm Displacement Volume' and is half a litre for the Kappa Pro 15.

Guess I'll need to buy one and lower it into a bath and shout 'Eureka!'

cheers

Chris

 

[richie00boy]

You want the volume of a cone not a cylinder. The following is taken straight from a C program I wrote, but the maths should be obvious.

driver_vol=(pi*((cutout/2)*(cutout/2))*driver_depth)/3; /*driver volume as a cone*/
if(dual_flag==1) /*double volume if 2 drivers*/
driver_vol*=2;
driver_vol/=1000000; /*convert mm^3 to litres*/

 

[clem_o]

Do you normally include the volume of the magnet? For small drivers the magnet is negligible, but for the larger (i.e. 15 or 18") the magnet may be significant..

Just my thoughts...

Cheers

 

[richie00boy]

Yes I guess on a monster driver you could use the cylinder volume.

 

[SamClassA]

What about the Port Volume?? after all its only a hollow cylinder, do you calculate the the whole cylinder volume or do you calculate the volume that the walls of the port tale up and not the volume in the port, after all its only empty air in the port. I hope I made my self clear?

 

[ocaukrell]

The port acts as an "air spring" so you have use the entire volume of the port.
For the above, consider it a solid object.

 

[clem_o]

Hi all,

What normally I do - I calculate the volume of a loudspeaker driver by using 'volume of a cone', based on the dimensions of the driver cone. Then I add the volume of the magnet structure using 'volume of a cylinder' - this gives the approximate volume of the whole driver, though it skips whatever volume the frame might take up...

Cheers