IIRC you asked this question a few weeks ago.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=41859
I guess I am not clear on what you call "distortion" and why you think making a bigger port would only change the frequency of distortion.
Post your T/S parameters and box design so people can model it and decide how realistic your expectations are. What is the power input that it starts occurring at?
Observations:
If your port is making that much noise, you probably would make more and cleaner SPL at that power input with a sealed box.
If you can't fit a larger diameter port, use a Passive Radiator.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=41859
I guess I am not clear on what you call "distortion" and why you think making a bigger port would only change the frequency of distortion.
Post your T/S parameters and box design so people can model it and decide how realistic your expectations are. What is the power input that it starts occurring at?
Observations:
If your port is making that much noise, you probably would make more and cleaner SPL at that power input with a sealed box.
If you can't fit a larger diameter port, use a Passive Radiator.
gentlemen!
forgive me for recurring post. it's just a new place for sub talk. and I decide asl society again.
well, dear m4dm4n, frared port done, I tried use it. without success. the same as egg glass port and several ports more.
my driver has: Fs 33hz
Pmax - 400W RMS
sensitivity- 88 db
Re - 4 ohm
effectiveness -0.36
Qts -0.39
Vas vent - 29-39L
I use box 27L inside, 35*35*35cm marble cube.
port 75mm, length - 250 mm
L=(2354*D^2/VF^2)-085D, so it's have be tuned to 40 hz.
it's ok for me, but noise!!!
forgive me for recurring post. it's just a new place for sub talk. and I decide asl society again.
well, dear m4dm4n, frared port done, I tried use it. without success. the same as egg glass port and several ports more.
my driver has: Fs 33hz
Pmax - 400W RMS
sensitivity- 88 db
Re - 4 ohm
effectiveness -0.36
Qts -0.39
Vas vent - 29-39L
I use box 27L inside, 35*35*35cm marble cube.
port 75mm, length - 250 mm
L=(2354*D^2/VF^2)-085D, so it's have be tuned to 40 hz.
it's ok for me, but noise!!!
ok. tomorrow I'll segregate my round port to section.
I mean lengthways pipe inside. will see.
I asked physicist theorists from Moscow University about flow turbulence problem. how can I get rid of this....
I hope they will offer me something. they always make it for spaceships and jet airplanes. let's help me now
I mean lengthways pipe inside. will see.
I asked physicist theorists from Moscow University about flow turbulence problem. how can I get rid of this....
I hope they will offer me something. they always make it for spaceships and jet airplanes. let's help me now
Yury said:
Hmm. Models like a boom box. Port velocity models at 40m/s with 40Volts input, although the real velocity will be lower. I bet the university physicists among us are snickering. You didn't answer what input level the noise becomes a problem, alhough my guess is about 25-30Volts.
Try this, fill up your lungs and blow through a fairly large (~8-10mm) straw as fast as you can, record how long it takes to empty your lungs. Catch your breath, then suck in through a straw as fast as you can, record how long it takes to fill your lungs. Which was faster
A better experiment would be to measure flowrates through an orifice with suction vs pressure at speeds comparable to what your port is generating......
Ever see: http://www.sunfire.com/
I figure they must not know enough physics, because they used a Passive Radiator.
BillFitzmaurice said:
Interesting that you never saw it in another Bose product that I recall. Bose has a marketing phrase "better sound through research". They seem to patent stuff just so they can present their product as technically superior. Was their port a good idea? Perhaps, but so is the Polk "Power Port" concept. Both have their limits in application.
that's right, Ron E.
this problem apear in the appointed output power only and appointed frequency.
ok. it's about 40hz 60w.
about voltage.
when I say power, I mean V amplitude/2*0.7 - mean-square value.
P=V^2/R, so V=square root(P*R)
this case is: 15-16V only.
Elso Kwak, explane me your idea please. I'm not understand exactly.
this problem apear in the appointed output power only and appointed frequency.
ok. it's about 40hz 60w.
about voltage.
when I say power, I mean V amplitude/2*0.7 - mean-square value.
P=V^2/R, so V=square root(P*R)
this case is: 15-16V only.
Elso Kwak, explane me your idea please. I'm not understand exactly.
gday all!
I've almost solve these problem. I made port by foam-rubber inside plastic port.
it seems like 2 layer of port. don't noisy, furthermore makes gain-frequency characteristic flat, couse port diam is 75mm, rubber diam - about 50mm. intereting effect. I like it.
I'll show my sub during hi-fi show in my city Nov 4-7.
I've almost solve these problem. I made port by foam-rubber inside plastic port.
it seems like 2 layer of port. don't noisy, furthermore makes gain-frequency characteristic flat, couse port diam is 75mm, rubber diam - about 50mm. intereting effect. I like it.
I'll show my sub during hi-fi show in my city Nov 4-7.
Noisy Ports
Yuri,
to get less turbulence from ports, they need to be bigger in diameter. Unfortunately this makes them much longer. I solved this by running them external. See what you think....
http://www.users.bigpond.com/bcolliso/sidewinder.htm
regards
Collo
Yuri,
to get less turbulence from ports, they need to be bigger in diameter. Unfortunately this makes them much longer. I solved this by running them external. See what you think....
http://www.users.bigpond.com/bcolliso/sidewinder.htm
regards
Collo
Jesus! I like it.
unfortunately I wont change design of my sub. I can't. pity.
your idea is very nice. and design of sub too, but not for me now.
like I wrote, I solve problem a little.
and I showed my subwoofer during hi-fi Kiev show last month
http://www.artmaydan.org.ua/exh.html
it was very interesting
but.... now we have revolution in our country
http://www.artmaydan.org.ua/revolution.html
so I can't working
I hope it's have to finish some day....
unfortunately I wont change design of my sub. I can't. pity.
your idea is very nice. and design of sub too, but not for me now.
like I wrote, I solve problem a little.
and I showed my subwoofer during hi-fi Kiev show last month
http://www.artmaydan.org.ua/exh.html
it was very interesting
but.... now we have revolution in our country
http://www.artmaydan.org.ua/revolution.html
so I can't working
I hope it's have to finish some day....
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