Slot port calculation help

[tomkail]

I have a 7 cubic ft. box that has a width of 21" (inside) and I need to tune it to 35hz. via a slot port. how tall and deep does the slot port have to be.
Thanks

[Dirk]

> I have a 7 cubic ft. box that has a width of
> 21" (inside) and I need to tune it to
> 35hz. via a slot port. how tall and deep
> does the slot port have to be.
> Thanks

I honestly couldn't tell ya (no tools handy), BUT slot ports can be calculated like round ports. Just use the same cross-sectional area. So if you wanted to try calculating for a 1" high slot, you'd find a round port that was about 21in^2. Let's see...
pi*r^2. 21 / 3.141 = 6.69. Square root of 6.69 is 2.59. Ports are measured in diameter, so let's multiply by two and we get 5.18". So in Unibox or whatever, try calculating the length of a 5.18" dia port. Wash, rinse & repeat until you get the port height & length you like.

I usually work from the opposite direction, assuming a length & width (since these two variables are tied to the shape of the box). Then I try and work backwards to find a port height that meets the required length and won't result in chuffing.

[lgraves]

Provided Link: http://www.carstereo.com/help/Articles.cfm?id=31


this calc. page might help

[unknownuser]

Provided Link: RPGINC (http://www.rpginc.com)


21x1x2.8
21x2x7.8
21x3x13.2
21x4x18.75
21x5x24.4

all yield 35hz tuning in 7cuft




(Originally posted by: KevinP)

[romanbednarek]

> I honestly couldn't tell ya (no tools
> handy), BUT slot ports can be calculated
> like round ports. Just use the same
> cross-sectional area. So if you wanted to
> try calculating for a 1" high slot,
> you'd find a round port that was about
> 21in^2. Let's see...
> pi*r^2. 21 / 3.141 = 6.69. Square root of
> 6.69 is 2.59. Ports are measured in
> diameter, so let's multiply by two and we
> get 5.18". So in Unibox or whatever,
> try calculating the length of a 5.18"
> dia port. Wash, rinse & repeat until you
> get the port height & length you like.

> I usually work from the opposite direction,
> assuming a length & width (since these
> two variables are tied to the shape of the
> box). Then I try and work backwards to find
> a port height that meets the required length
> and won't result in chuffing.

I've found that if the slot port is located along one of the walls of the cabinet then this method usually ends up with the actual slot port tuning being lower than the equivalent round port due to the effects of the added length of the one wall. I really haven't figured out how much to compensate and in my earlier projects often ended up with the port tuning a bit low.

[jasonb]

I have tried that page before and have never been able to get the slot port calculator to work

Jason

> this calc. page might help

[jasonb]

Are you simply converting the slot area to a round port of the same area and calculating the length that way, or is there some other method I am missing out on.

Thanks,

Jason

> 21x1x2.8
> 21x2x7.8
> 21x3x13.2
> 21x4x18.75
> 21x5x24.4

> all yield 35hz tuning in 7cuft

[unknownuser]

Provided Link: RPGINC (http://www.rpginc.com)


Just using winisd from <A HREF="http://www.linearteam.dk/">http://www.linearteam.dk/</A>



(Originally posted by: KevinP)

[tomkail]

Thanks for the info.