Ported Ecnlosures & You

[Nikuk 1]

Kent asked for this a while ago... I dug up some links.

Enjoy.

http://audioforum.termpro.com/cgi-bin/ubb/...ic;f=8;t=021625

http://forum.soundillusions.net/showthread.php?t=45647

http://hyperphysics.phy-astr.gsu.edu/hbase/pfric.html

Good reading, good points, easy read.

-Nick

[mrray13 30]

thanks man!!!

so it's about air slowing down at the edges and the actual tuning freq that it produces...in a nutshell...

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[Nikuk 1]

In a nutshell, yup.

Port linearity = good

Turbulent wind = bad

LoL

No prob.

[ANeonRider 3]

Good read.

[Aaron Clinton 2,372]

I wanted to get a discusison on standing waves, hence the reason I at least 45 out all my internal corners

[Nikuk 1]

standing wave or cancellation..?

two similar animals with very different resolutions. in theory at least

-Nick

[Aaron Clinton 2,372]

standing wave or cancellation..?

two similar animals with very different resolutions. in theory at least

-Nick

standing waves, usually caused by air flow having to bend around corners and those corners not being smooth, so some air flow gets trapped in a counter rotational motion in the corners, makeing the final execution of the enclosure not as efficent

well atleast thats how I understand it

[req 0]

so what if we applied some sort of 'smoother' surface to the inside of the port? like a layer of fiberglass resin wetsanded to shinyness?

would this make the turbluance go down noticeably?

[Nikuk 1]

standing waves, usually caused by air flow having to bend around corners and those corners not being smooth, so some air flow gets trapped in a counter rotational motion in the corners, makeing the final execution of the enclosure not as efficent

well atleast thats how I understand it 

<{POST_SNAPBACK}>

What You're describing isnt standing wave, but I cant recall wht the ef it is... Vortex...? chit. Anyhow, You are right on with the problem though. More bends OR surface area are bad. But when you're talking about a vortex (?), this is where the famous 45* corner boards come into play.

Standing wave is when the internal wall layout causes waves to cancel eachother out in direct fashion. -or- the perfectly cubic box (12x12x12)... a single wave will reflect and destroy itself. iirc.

You absolutly struck the nail on the head though....

making the final execution of the enclosure not as efficent

The key is to try to get the box as efficient as possible. Though... I'm still newbish.

[Nikuk 1]

fiberglass, turtle wax, duct tape, 45* boards, cust & glassed cardboard tubes... these have all made differences for me in the past. Some more then others, but as always - it varied by box & car.

[ANeonRider 3]

Isn't a perfectly round enclosure ideal for eliminating standing waves and turbulence like vortexes.

[Aaron Clinton 2,372]

Nick your right, the vortex effect is the swirlling air caught in the corners

[Nikuk 1]

Isn't a perfectly round enclosure ideal for eliminating standing waves and turbulence like vortexes.

<{POST_SNAPBACK}>

Yes it is... in theory. I've never seen anyone try it realistically. I'd love to If I could think of a decent way to implement it...

But that would bring on all new issues of linearity, tuning, backwave control & cone control...

[Aaron Clinton 2,372]

I thought that is what RF did with their Xterra install a few years ago, with the huge bongo like suspended enclosures

[traksta15 0]

i saw an add for a perfectly round enclosure in a car audio & performance mag...some company i can't remember it, i'll try and dig it up....

[Jmac 24]

[More bends OR surface area are bad.

More surface area implies more port area ...

[Nikuk 1]

[More bends OR surface area are bad.

More surface area implies more port area ...

<{POST_SNAPBACK}>

implies in the conventional term, but thats not accounting port wall surface.

[LB audio 0]

Round edges or 45 deg helps eliminate standing waves and it is good for SQ but SPL is other thing. If SPL box is made correct then you should make standing waves inside box and all 45 deg or smooth corners destroy them. All boxes from 1st, 2nd...places I saw arround the European 3x competitions were made in this maner. When you create standing wave in box at right freq. than you gain your SPL quite a bit.

It also help if you make your box and port inside as smooth as you can!!!! difference can be up to 0.5 dB.

Be wery careful when you do bracing!!! braces MUST have smooth edges!!! But at first try without it!!!!

[Nikuk 1]

generally, You wont have standing waves with subbass frequencies... the wavelength is just too long.