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I was wondering if the phase of the rear wave from a driver change around corners? If it does, does it do it say...around a 90degree corner it will reflect 180degrees out of phase(just an example, not sure if it does this or not.)
Just curious, not sure phase of the driver works really and how reflections work. Also, I'm going to be trying some different designs to see if I can come up with something good. Thanks for any input.
-------------------- ------------------------- ED 13av2 (Sealed 1ft3) ED Nine.1 ED Nine.2X ^_ _____ _ All stolen DLS UP6i Posts: 431 | From: Near one of the 10,000 Lakes | Registered: Jan 2003
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posted
The phase will not chage just because it reflects. Phase is a relative term. You have to compare two things to get a phase difference. With subwoofers, there are two types of phases that we often talk about. The first type is the back wave vs the front wave. They are 180 degrees out of phase at the origin. The other phase we talk about is phases from reflections. Since a subwoofer radiates in all directions, some of the wave will take longer to get to the drivers seat than others. For instance, lets say you've got a sub firing backwards from the backside of the rear seats, a direct wave that goes straight from the sub to your ear only travels a distance of say 15 feet, but a wave that gets reflected off the rear of the car will have to travel an extra 6 feet. The will cause (at least partial) cancelation at some frequencies and addition at other frequencies. In a car, there are so many reflective surfaces that it's pretty much impossible to get a perfect frequency response. Good luck with your experiments.
Posts: 112 | From: NB, Canada | Registered: Mar 2004
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posted
I was under the impression the back wave was 270 out of phase and travels more distance, thus the time that wave hits at a point the front wave will do the same=spl?
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Would anybody know a way or have an idea that would put the rear wave in phase with the front? Other than the standard ported enclosure. Maybe like a membrane or something of the sort.
-------------------- ------------------------- ED 13av2 (Sealed 1ft3) ED Nine.1 ED Nine.2X ^_ _____ _ All stolen DLS UP6i Posts: 431 | From: Near one of the 10,000 Lakes | Registered: Jan 2003
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quote:Originally posted by bassxtreme: Would anybody know a way or have an idea that would put the rear wave in phase with the front? Other than the standard ported enclosure. Maybe like a membrane or something of the sort.
I guess you are talking about the quarter wave theory.It does not really work in reality, only in theory.You won't gain any dbs if you tune the back wave with the front. You can look up for more about this theory on the search engine of caraudio and electronics magazine website
-------------------- Dbdragracing is not a sport... IT'S A CURSE! Posts: 249 | From: ATHENS GREECE | Registered: Oct 2003
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posted
Quarter wave theory is exactly what a transmission line is based on. It works well if you do it right. In theory it produces a comb-like frequency response. Every 1/2 octave the phase difference will become 180 degrees out (or back in, depending on which way you look at it).
Posts: 112 | From: NB, Canada | Registered: Mar 2004
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rear and front wave phase is also dependent on distance and freq.. so what is in phase at one freq, will be out for many other freq.. i have the same notion for ported box's being 270 deg out. not counting in rear wave, but looking at box pressure radiating out the port. some train of thought is that it is 90 deg out. true if it is a sine wave. because 90 or 270, it's the same result. but with music,.....270 is a big difference than 90. the reason i figure 270, is because obviously, the when the cone moves in, it is 180 out from the port pushing air out. but the time difference it takes for the compression and exit out of the port, shifts another 90 deg +/-. that's my theory anyway.
Posts: 540 | From: nor cal | Registered: Aug 2004
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