single vs. dual ports

[tajanes]

Are there any studies of the effects of using one vs. two ports -all else being equal- i.e targeting the correct tube volumes / lengths...(i.e. no issues with port noise due to too small a port, etc.)? If my math is correct; two 3.5 inch diameter ports of X length vs. one 4.95 inch diameter port of X length provide approx. the same ported volume for a given speaker box.

However, the internal surface area of the dual 3.5 inch ports is 1.4 times the surface area of the single 4.95 port. So does surface friction come into play and how does it affect the movement of air?

(and if my math is in error... still go with the underlying concept) - thanks

[isaeagle4031]

Yes your math is off just a bit. The dual ports you listed are only slightly larger than the single. In that respect as long as proper length is observed in relation to tuning, there probably won't be any audible difference. There will be an increase in believe in friction as there will be more surface area in diamter.

Surface area of a circle is Rsquared x pi. So 2 3.5" ports have surface area of 19.24 inches vs 19.24" for the 5.95". Circumfrence however will be 21.987" for the duals and 15.547 for the single. So I beleive there will be more surface tension/friction for the duals.

[tajanes]

..."So I beleive there will be more surface tension/friction for the duals"...

beyond necessary tuning via length adjustment(s), i.e. assuming both the dual and single tubes are adjusted for the same box tuning to account for the above, are you saying there should be no apparent affects to sound quality, etc?

thanks

[isaeagle4031]

No I don't think there will be. I've used dual ports, slot ports, etc in car audio and generally there was not a really noticable difference in the audio quality. There maybe some slight differences in overall SPL, but not nearly enough to notice by ear.

[Chris Roemer]

..."So I beleive there will be more surface tension/friction for the duals"...

beyond necessary tuning via length adjustment(s), i.e. assuming both the dual and single tubes are adjusted for the same box tuning to account for the above, are you saying there should be no apparent affects to sound quality, etc?

thanks

That's correct.

If you've got the same effective sq. area, the 2 (sets of) tubes will end up very close to the same length (if not exactly the same) to achieve the same tuning.

More importantly, a rear facing vent is just as good (for bass output) as a front facing vent, with the added advantage of not aiming any midrange "leakage" right at your ears. Chuffing is also somewhat masked with a rear vent.

AND, a good roundover (3/8" or more, or even JUST 1/4" - if that's all you can manage) will also deliver more output with less noise than a sharp ended vent exit.

Chris

[bkeane1259]

AND, a good roundover (3/8" or more, or even JUST 1/4" - if that's all you can manage) will also deliver more output with less noise than a sharp ended vent exit.

Chris


AND, an interior roundover + exit port roundover is even better for reducing turbulent ports. It's more work if you do it yourself, but studies have shown flaring both ends is beneficial.

Here's a very good research paper on ports:
http://www.aes.org/tmpFiles/elib/20120305/11094.pdf

[tajanes]

JBL & Infinity ...

[isaeagle4031]

yeah same companies. Even on a slot port I will use a flair if I think it will help. It doesn't always. But then I've been known to use some VERY big ports :)

[tajanes]

so given the option of using one very big port or two smaller (but equivalent with their much more surface area) you would choose .....

[isaeagle4031]

1 port if I can help it. Less chance of chuffing and less chance of error.