posted
I know its a theory but can anybody give me anything explaining quarter wave.
Posts: 1 | From: Vernon, Texas | Registered: Apr 2004
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posted
Its useless in realworld because it is based on aligning a cingular wave in a two dimensional plane so that when the wave hits the mic it is at a quarter of its peak (I'm a little rusty on how it exactly works).... but it does not work because there is more than one soundwave being produced from a speaker aswell as they are moving in all directions.. and when you add the third dimension in (height) you have cancellation to deal with....so in a perfect world..yes it works.. i the real world... no
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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posted
Yes teamobsession is right about the cancellation Normally on a Tline the 'port' and driver are a fair distance apart.You dont want this distance difference.
its not at a 1/4 of its peak necessarily.
The important issue here with a quarter wave pipe,is that it resonates at 1/4 wave long of the freq eg
40hz wave is always about 8m long if u have a pipe thats 2mlong, it will resonate at ~40hz
Note that a 30hz pipe requires an even longer pipe.
The effect is ,the pipe does the work,and the cone doesnt move much ,just like ported box near tuning
Like a ported box u can make it peak,or be flat.
Now knowing this,u have to know ur speaker t/s specs and put it into a MATHCAD sheet to get the response..
theres no magic involved,just another speaker box that took a little longer to model up in a program.
posted
if it does not have so much of a bearing then why is a crx box so loud in a hatch vehicle.
I believe it does work it's just not the only part of it.
build and box with the port near the sub then build I box with a port far from the sub.
put it this way find your peak frequency for your car then build the best box you can using this rule then play around with the box position in the car.
Also has anyone built a sloted flared port box. I am looking for a curve that can be used.
-------------------- atomic apoc 15 with spl mod and a atomic 1500.1 at .5 ohm
quote:Originally posted by dkmst23: if it does not have so much of a bearing then why is a crx box so loud in a hatch vehicle.
I believe it does work it's just not the only part of it.
build and box with the port near the sub then build I box with a port far from the sub.
put it this way find your peak frequency for your car then build the best box you can using this rule then play around with the box position in the car.
Also has anyone built a sloted flared port box. I am looking for a curve that can be used.
okay.... you still don't seem to get it that it is USELESS... A CRX box is just a very efficient design that works well in most applications... A friend of mine ha Also tested quarter wave theory in his car...didn't work worth a damn....see all this is theory...doesn't mean it will work... yes it works on paper and in TWO DIMENSIONS but not in 3D it's based on aligning one wave...when has any speaker , or in fact any sound producing device or thing ever producing a singular wave...or more specifically a wave that moves in one direction... quarter wave does not workplain and simple.... has nothing to do with crx's being loud. Yes you can put all the numbers into a program and have it tell you it will work... but the program does not take into account cancellation (like i said earlier), and it calculates all this in perfect world aswell... you can try it if you want, but its a waste of time....If you plan to compete i suggest just testing and tuning....and don't waste your time with any weird boxes either....and those snailshells too..... have good one
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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quote: and don't waste your time with any weird boxes either....and those snailshells too.....
so do they work or not?
i dont see how its physically possible.
you don't see how whats physically possible? the snailshells not working for SPL? As i can remember a while back thos P4S guys had a video of a 12" brahma and a ZR1000 that did a 142.2 or something and it was an sq box etc...thats apparently what made it so special anyway we build a 2.0 cube ported sq box in december for a neon and use a mid level crossfire single voice coil sub (P1 series 12") and 1000 watts from being hooked up at 4ohm on a crossfire 2000D and we are costantly hitting high 143's on termlab (143.6-143.7) with 1000 watts.. so i concluded that its not worth the time to build complicated boxes like that when we can just build a ported box that is pretty universal....and the box is tuned to 32hz.....aswell as a dude here built that horn and after some adjustments we figured it would have to be way to large to get the desired output than would be practical in a street application
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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posted
well then the next time you build put the port right against the sub.
You can not deny that the back wave is out of phase with the front wave that is why the crx works it moves the back wave the farthest distance inside the box without restricting the flow.
If tuning and test was the only thing that mattered then the only thing to look forward is adding more power.
I built a box that forced the spl out 140 old mic . Then i built a box to help the phasing and i gained spl 142(old mic). I built a better braced box and the spl increase 145( old mic). I built a better flowing box and the spl went up 147.
this was with the same 300 watt amp i am still using
But i am going from two audiobahn aw1200 to a 9512. I can't afford a thousand watt amp yet.
-------------------- atomic apoc 15 with spl mod and a atomic 1500.1 at .5 ohm
quote:Originally posted by dkmst23: well then the next time you build put the port right against the sub.
You can not deny that the back wave is out of phase with the front wave that is why the crx works it moves the back wave the farthest distance inside the box without restricting the flow.
If tuning and test was the only thing that mattered then the only thing to look forward is adding more power.
I built a box that forced the spl out 140 old mic . Then i built a box to help the phasing and i gained spl 142(old mic). I built a better braced box and the spl increase 145( old mic). I built a better flowing box and the spl went up 147.
this was with the same 300 watt amp i am still using
But i am going from two audiobahn aw1200 to a 9512. I can't afford a thousand watt amp yet.
yes technically it is out of phase... but the only thing that matters in real life and in competition is testing.
that is NOT how a crx works....if the box worked like that it would work in every vehice (if i read that right)its not the car...its the box..that box works well in most every car and applicattion weve tried it in and firing every which way.. And also in every test we've done with every vehicle... it is loudest with the subs farthest away from the port (on the inside of the box if the port is bend...lets see some numbers from your car on the new meter..the old one isn't quite as accurate and does not self calibrate... Bracing doesn't always help (actually decrease from internal bracing in street from what we've tested) but the point isn't that its about quarter wave...which does not work...you can test and tune until you think quarter wave is working...but i'll stick to a normal box and do some testing for now thanks
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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posted
This might be way off base but if I remember correctly, this is how a 1/4 wave "box" works. The woofer is effectively at one end of a "tunnel" and the other end of the "tunnel" is right beside the woofer. The front wave of the woofer plays unrestricted into the car and the back wave must travel through a tunnel and exit beside the woofer. The length of this tunnel depends on what frequency you want to be in phase. This is an easy calculation, it's 1/4 of the wavelength for the frequency you desire. This "box" will work perfectly for the frequency you desire and every octave above and below this frequency (until of course the wavelength of the frequency starts to get too close to the diameter of the "tunnel" at which point you will start to get modes). The problem with this design is that at every half octave above and below, the wave comming out of the tube and the woofer's front wave will be completely out of phase. Another problem is that the diameter (or cross-sectional area) of the "tunnel" must be large enough not to restrict air flow because a restricted air flow means an indrease in the spped of the wave (thus the tube would have to be longer to make the woofers front wave still be in phase with the back wave).
These theories are proven to work perfectly in the wave-guide field for radars.
Posts: 112 | From: NB, Canada | Registered: Mar 2004
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posted
I don't see how it can't work. Forget waves as literally being that, think of them as a time vs. pressure graph. What you're trying to do do is align the front and back waves so that their pressure peaks occur at the same time. Good luck with that though.
Justin
-------------------- Hooked on sonics worked for me! Posts: 766 | From: Tucked65's Trunk | Registered: Mar 2003
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quote:Originally posted by Thedrumming2ba: I don't see how it can't work. Forget waves as literally being that, think of them as a time vs. pressure graph. What you're trying to do do is align the front and back waves so that their pressure peaks occur at the same time. Good luck with that though.
Justin
YES that works in 2 DIMENSIONS it does not work for three because it does not take into account height.....and sound waves move in all directions.....for every constructive wave you have a deconstructive wave.....get it now????
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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quote:Originally posted by Rrrrolla: These theories are proven to work perfectly in the wave-guide field for radars.
totally different application though am i right? however not proven to work in a car......
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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posted
commonly known as transmission line inclosures, they have worked very well in home audio use for a long time(labrinth or folded labrinth is space is an issue) in theory they are the closest you can get to a perfect inclosure with the efficiency(if not more)of a ported box but with less phasing issues. also the 'tube' should be tapered to prevent reflections from one wall to another. they can be made to work but can be very time consuming to get right as its all trial and error and in the end you would probably be just as sucsessful with a normal ported box
that didn't stop me using quartertheory in my extreme car! and all the tuning i did with a tapemeasure has been spot on when it came time to do the tuning on the meter, i mean so much to an extent i even shocked my self so it works in my car
-------------------- _ _____________ _ *on 2004 rules - *australian extreme 1 record holder!* *Owner and builder of australia's loudest extreme spl car* 1 Digital Designs 9915 + 4 concept d2400a's -"160.9" on new termpro meter Posts: 37 | From: western australia, | Registered: Jul 2002
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quote:Originally posted by tuneman: commonly known as transmission line inclosures, they have worked very well in home audio use for a long time(labrinth or folded labrinth is space is an issue) in theory they are the closest you can get to a perfect inclosure with the efficiency(if not more)of a ported box but with less phasing issues. also the 'tube' should be tapered to prevent reflections from one wall to another. they can be made to work but can be very time consuming to get right as its all trial and error and in the end you would probably be just as sucsessful with a normal ported box
that didn't stop me using quartertheory in my extreme car! and all the tuning i did with a tapemeasure has been spot on when it came time to do the tuning on the meter, i mean so much to an extent i even shocked my self so it works in my car
what kind of numbers are you seeing and with what?
-------------------- Canadian Street Max 1-2 record holder 152.5 db's PROUD MEMBER OF TEAM GATES Posts: 433 | From: Fort Saskatchewan | Registered: Dec 2002
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posted
in extreme 1, 160.9db which was the cars first and only run to date on the new meter as they only started using them this year for the first time in australia!. the car is console tuned and unfortunately still has a stock windscreen i know its not as impressive as you guys in the US but its getting there...slowly
-------------------- _ _____________ _ *on 2004 rules - *australian extreme 1 record holder!* *Owner and builder of australia's loudest extreme spl car* 1 Digital Designs 9915 + 4 concept d2400a's -"160.9" on new termpro meter Posts: 37 | From: western australia, | Registered: Jul 2002
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