Understanding port length and flare radius...

[Bradley]

I must be having a major brain fart today since I feel like I missing something regarding port length with and without flares. I've read the WinISD help and Collo's website already. If you are supposed to add 1/2 of the flare radius to the straight tube length to get the effective port length, then why does the port length in WinISD go down when you switch from no flares (two free ends) to flared (flanged) at both ends? This makes me think that the port value displayed in WinISD (and Collo's Boxnotes) only refers to the straight tube section and does not include the length of the flares. For example, in Boxnotes if you go from zero to 2 flares the tuning frequency goes down, which suggests that the effective port length has increased.

Can someone PLEASE explain and clarify this for me?

Also, flare radius has to play a role but it seems like all of the software applications and discussions I've seen treat all flares the same, regardless of actual radius.

Thanks.

Bradley

[WillyD]

The reason you're confused is because the free/flanged end business in WinISD doesn't refer to flared.

The default setting in WinISD is one flanged end, which would mean one end of the port is flush with a baffle. This is the norm. Has nothing to do with whether the port is flared or not.

[Bradley]

Really?! Oh, for the love of... That actually makes a lot of sense now. I thought it was a language/translation thing, so I equated flanged with flared. But looking at the WinISD help file and the illustrations, I can see "flanged" means inserted into a baffle.

Thanks, Will.

[WillyD]

No problemo.