posted
I wonder if my theory is right.. about the round shape.
Round port help to keep very efficient and narrow peak freq because the pressure is better distributed in the diameter. Other shape such as square or rectangle have problem about pressure not homegene.. ex: in the corners..
Aeroport style respect round shape about the tube and the flare.
I wonder if the aeroport monted out is also a principle that proof this theory..
The pressure at end of that port exit as a sphere shape.. soit's like the wave refract on the cabin coming from one point and going to all surface and refract to the front of the car (street and SS car) and have better chance to stay in phase then other port type..
My conclusion is:
Aeroport style are the best way to get higher SPL cause of the phase and the narrow peak achieved. .. Narrow = more efficient..
Euro guys had understod that and the result proof that.
Sinewave is in relation with circle.. a basic shape.. a pure shape... The tone we use need to be narrow... and narrow peak = less harmonic... = more energy for the fundamental.. .. = SPL...
SO ROUND PORT GIVE NARROW TUNING FREQ
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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posted
I do concur that corner effects on moving air include friction and thus the stimulation of energy at non principle frequencies.
However, as to the united wave front caused by a more spherical radiation, I think the boundary reflection scenario is too complex to suggest such a simplistic answer. Symmetry is a lovely idea, but the port isn't in the middle of the car typically anyway, and if it was, a round port would need to be big to get the port area most SPL setups require.
Thoughts? ShadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect. Posts: 2578 | From: Somewhere In the Northeast | Registered: May 1999
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quote: Symmetry is a lovely idea, but the port isn't in the middle of the car typically anyway,
Mic too is'nt in the middle of the car.. so that's why i suggested that the port end can be placed at the rear uf the cabin.. to be symetrical to the mic placed in front of the cabin...
Shadowstar, i'm french Canadian .. and i have difficult to explain the exact idea i'm thinking.. .. I know your knowledge is good, and mine is too, I would like to explain better my idea, but in my case it's language problem.. My advenced knowledge in SPL , acoustical or physics is good, but i have difficult to translate and explain it the best as i can..
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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quote: Symmetry is a lovely idea, but the port isn't in the middle of the car typically anyway,
Mic too is'nt in the middle of the car.. so that's why i suggested that the port end can be placed at the rear uf the cabin.. to be symetrical to the mic placed in front of the cabin...
Shadowstar, i'm french Canadian .. and i have difficult to explain the exact idea i'm thinking.. .. I know your knowledge is good, and mine is too, I would like to explain better my idea, but in my case it's language problem.. My advenced knowledge in SPL , acoustical or physics is good, but i have difficult to translate and explain it the best as i can..
hey You need to read some fluid dynamics - thats what id do if I was investigating this,also check aes.org search function see if you can find anything about it.
Hi Guys, Has anyone read the Audio Engineering Society preprint 4855 'Maximising Performance from Loudspeaker Ports'? The AES don't provide abstracts, so I want to know what I'm getting before I shell out my $10 (OK, I'm a tightwad, I know). I'm looking for info on how port shape affects the response of the cabinet (particularly flared ports & 'Karlson' slots). Any references or info appreciated.
quote:Posted by John Sheerin ( A ) on November 04, 2004 at 11:30:43 In Reply to: port area?? shape?? location?? posted by mike tame on November 03, 2004 at 23:58:07:
Shape is important. Round flaired tubes (flaired throughout the entire length) have been shown to perform much better (20dB more output for the same subjective sound quality in one paper) than straight tubes even when the straight tubes have a large radius at both ends. Look for a recent JAES article by Alex Salvatti and some of the other JBL guys. It desribes the shape they found to be optimal as well as how to calculate the tuning frequency.
posted
Humm.. flared port seems to become more important!.. I like that... I have the entire JBL acoustic book.. and in PDF also...ah haaa.. I will search for info about that. thanks!
I always belived that port shape and end are criticaly important for SPL.. I'M happy to know that people in this comunity become more concern!
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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quote:Originally posted by Doctorbass: Humm.. flared port seems to become more important!.. I like that... I have the entire JBL acoustic book.. and in PDF also...ah haaa.. I will search for info about that. thanks!
I always belived that port shape and end are criticaly important for SPL.. I'M happy to know that people in this comunity become more concern!
The sound system design PDF is good.
Well yes flares are important. Having a port with the same area as teh driver is a good start. JBL has some patented port flaring thing,cant find any info though.I think the entire port is flared.
If you go horn,then you dont get problems with this!(decware WO too)
Im sure many are interested in this in SPL.It is mostly empirical though.
Im wondering about using FEA($$$$)to model subs/horns in vehicles BEFORE doing it physically.
posted
I thought about doing a slot flared port but what curve would a optimal i thought about taking the suggested port area as the average for tuning it then using the cone area for the mouth of the port then building a exp port flare.
-------------------- atomic apoc 15 with spl mod and a atomic 1500.1 at .5 ohm
quote:Originally posted by dkmst23: I thought about doing a slot flared port but what curve would a optimal i thought about taking the suggested port area as the average for tuning it then using the cone area for the mouth of the port then building a exp port flare.
Id be thinking along those lines. Thats why I was interested in JBLs paper. Search AES,there should be something.
You could do it empirically,by just trying and measuring what it is tuned to.
posted
i thought i would do an ss 1-2 nw with an 18" round port for 06.i found a pattern for the tube, but i'll have to make the flare(s). i also want to try a few tricks i found in the rex, last season, to see if it will work on this one, too
had great results from the 4" flared ones i used last season. haven't done any testing there, yet, because of starting from scratch on a different ride.
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
2005-2006 Street A Champion in Quebec province!
CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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posted
Deaf Tones, I too did the same thing and came across the same info. Fallon, Eric and I did a ton of research prior to building the van. We looked at several theories and incorporated a little of both principles.
posted
Yes, you have to munipulate the waveform. This is done in a few ways. That is what brings us back to the question at hand. Does round shape help SPL. We know that it does. Now we just have to figure out were and how to use it. To much can be a bad thing here.
Jason West
-------------------- **In Loving Memory of Greg Welch**
II Grad, June '02 Posts: 858 | From: Asheville, NC | Registered: Jan 2004
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posted
I agree Jason. We have done a few designs were too much rounding was bad. You must also constrict and control the waveform through the process. I have yet to really decide if too much rounding was bad because it either opened up too much volume, or displaced too much volume depending on how it was used.
posted
That is the same reason that a T-Line box is very hard to construct. If it is a little to big or a little to small in the wrong place, then the entire box design and the entire overall performance will suffer.
Jason West
-------------------- **In Loving Memory of Greg Welch**
II Grad, June '02 Posts: 858 | From: Asheville, NC | Registered: Jan 2004
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