So in a typical bass reflex enclosure, you'll often hear people say stuff like a larger port gives a peakier response or something like that.
All of this is assuming identical tuning and volume.
But for some reason on every program ive tried to graph this you get absolutely no change except for port velocity when changing port area. not even a 1/10th of a db across the band, no cone displacement change. NOTHING
Heres some photos in BBP comparing a 4" port and 8" port in a 4.5cf reflex using the same tuning.
Red is the 8" Purple is the 4". As you can see the red overlaps so perfectly you can't even see the 4" port anymore excluding port velocity.
All of this is assuming identical tuning and volume.
But for some reason on every program ive tried to graph this you get absolutely no change except for port velocity when changing port area. not even a 1/10th of a db across the band, no cone displacement change. NOTHING
Heres some photos in BBP comparing a 4" port and 8" port in a 4.5cf reflex using the same tuning.
Red is the 8" Purple is the 4". As you can see the red overlaps so perfectly you can't even see the 4" port anymore excluding port velocity.
Assuming this is true, a larger port is going to be longer and a longer port may have some resonances of its own in the upper bass. Shorter ones will too, but at higher frequencies the issue doesn't tend to show up.
https://www.diyaudio.com/forums/forum-problems/309064-attach-images-posts.html
Does port area actually affect frequency response? Hornresp can simulate it.
Assuming it does: box simulation software relies on assumptions and simplifications. If parameters are taken to the extreme, these may not hold and the prediction may be off.
Assuming it does: box simulation software relies on assumptions and simplifications. If parameters are taken to the extreme, these may not hold and the prediction may be off.
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It's my understanding from numerous posters over the decades that BBP isn't a very good program, at least by today's standards, especially for how much they [use to?] charge for it.
Hornresp and similar programs I've tried [LspCad, AkAbak and I forget the others] do it, but need to keep in mind that the driver's specs/cab alignment has a big impact on how much gain BW difference there is.
Historically, Av = Sd was the largest acceptable reflex vent area and even then it's restricted to Fb = Fs tuning, so if a program is going to factor this in, then you should see an obvious difference regardless of specs, assuming they're suited for reflex alignments.
GM
Hornresp and similar programs I've tried [LspCad, AkAbak and I forget the others] do it, but need to keep in mind that the driver's specs/cab alignment has a big impact on how much gain BW difference there is.
Historically, Av = Sd was the largest acceptable reflex vent area and even then it's restricted to Fb = Fs tuning, so if a program is going to factor this in, then you should see an obvious difference regardless of specs, assuming they're suited for reflex alignments.
GM