ARKANSAS SPL

MORE THAN JUST CAR AUDIO!!!
 
HomePortalFAQSearchMemberlistUsergroupsRegisterLog in

Share | 
 

 periodic functions and phase shifts

View previous topic View next topic Go down 
AuthorMessage
craigjones806
Veteran
Veteran
avatar

Posts : 131
Join date : 2010-12-01
Location : Beebe

PostSubject: periodic functions and phase shifts   Sat May 28, 2011 11:12 pm

I'm looking for input from those of you that are more experienced with enclosure design here.

I was recently looking at sine functions [don't forget, I am an Algebra II teacher] and was thinking about discussions regarding 1/4 waves, 1/2 waves and how it might apply to port tuning using the Fs spec of a sub. It appears that most discussion for enclosure design centers on a 1/4 wave length. Is this because of a 45 degree phase shift would move amplitude to its highest on a sine wave? Just wondering if that is the case or if 1/4 waves are used because 1/2 waves would be extremely difficult in most cars/trucks for even the best "port folder".

For example, consider a sub has a manufacturer's spec, or even better, tested, Fs of 28 Hz. Using 1124 ft/s as the speed of sound (this was from memory of a physics class I had 20 years ago so let me know if I'm way off here since I was too lazy to look it up before I started typing), the full wave would be approx 40.14 ft, 1/2 wave at 20.07 ft, and 1/4 wave at 10.035 ft. In this case, the quarter wave length would be tricky, but if space were NOT an issue, would the 1/2 or full wave be louder all else being the same?

My apologies if it looks like I'm just being a math dork with this one.
Back to top Go down
View user profile
rob t
Pro
Pro
avatar

Posts : 832
Join date : 2009-07-28
Location : Searcy

PostSubject: Re: periodic functions and phase shifts   Sun May 29, 2011 10:59 am

The way I always understood it was that you do not want the wave to crash back into itself. If that happened then the two wave would be fighting each other instead of helping each other. The measurement of the vehicle allows us to know how long the wave is. Example if a car is ten feet long, with your calculations you determine that the first frequency that fits in the car is say 100 hz. Half that and the next frequency that fits in the car is 50, then your quarter wave would be 25. Those would be the three approximate frequency's that the car will "like", because they will be less likely to clash.
Back to top Go down
View user profile
craigjones806
Veteran
Veteran
avatar

Posts : 131
Join date : 2010-12-01
Location : Beebe

PostSubject: Re: periodic functions and phase shifts   Sun May 29, 2011 11:27 pm

I probably need to clarify some. I understand what Rob is saying about what the car likes, but I was looking at more of a hypothetical situation where there car size was not a factor.

So if the sub and port were coplanar and I wanted to use the rear wave to reinforce the front wave, would 1/4 wavelength or 1/2 wavelength be best?

In this hypothetical, the enclosure could be designed, tuned, and built and then [i]installed in the car at the proper distance from the "sweet spot".
Back to top Go down
View user profile
James Reed
Pro
Pro
avatar

Posts : 570
Join date : 2009-01-20

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 12:46 am

Do some reading on transmission line enclosure. This is the exact theory they are built on.
Back to top Go down
View user profile
AMI CUSTOMS
Moderator
Moderator
avatar

Posts : 1116
Join date : 2008-07-30
Age : 32
Location : Central AR

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 7:32 am

Full > 1/2 > 1/4 .......I bet you understand that lol.

_________________

www.ami-customs.com

2011 USACI Finals MOD 1001 - 2000 - 2nd (160.0 db)
2010 ARSPL Finals 501-750 - 1st (160.3 db)

Daily driver afro
2001 GMC Sierra- aka "The Black Nasty" - 160.4 db(termlab outlaw)

Weekend play toy cheers
2008 Mitsubishi Evolution X - I wanna go fast!!!!

"Hit em til it Hertz"
Back to top Go down
View user profile http://www.ami-customs.com
bruce leroy
Pro
Pro
avatar

Posts : 314
Join date : 2010-06-06
Age : 43
Location : conway

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 9:06 am

my head hurts. time for a beer
Back to top Go down
View user profile
fritosaregood
Pro
Pro
avatar

Posts : 591
Join date : 2008-09-20
Age : 28
Location : Bryant, AR

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 6:10 pm

AMI CUSTOMS wrote:
Full > 1/2 > 1/4 .......I bet you understand that lol.

this. and right now my car is actually peaking at the 1/8 wave of the freq length from my sub face to kick panel. but gain again at my 1/4 wave length but isnt as strong because of my low tuning, once i tune in the 50s my 1/4 wave will jump ahead.
Back to top Go down
View user profile
craigjones806
Veteran
Veteran
avatar

Posts : 131
Join date : 2010-12-01
Location : Beebe

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 8:54 pm

Does a peak on a 1/8 wave make follow theory or experiment? I know that physics theories don't always work out in real-world applications so I was wondering if this is a case where theory says the 1/8 wave should work or a situation where experimenting shows that it just does.

Again, just looking at a sine wave, it looks like the 1/8 wave would not be a big enough phase shift (only 22.5 degrees, if I'm looking at the graph correctly)to really reinforce as well as a 1/4 wave.

In regard to t-lines, what if the "enclosure" used a 1/2 wave and the baffle was placed a 1/4 wave from the metering point? Should there be cancelation issues or would there be reinforcement?
Back to top Go down
View user profile
demented
Veteran
Veteran
avatar

Posts : 101
Join date : 2009-12-18

PostSubject: Re: periodic functions and phase shifts   Mon May 30, 2011 11:21 pm

theory is simple look at a sine or cosine wave it has peaks around a center line one minimum and one maximum. you will want your wave peaks to match as close as possible. the combination of your waves will create a standing wave. which is what happens when your front waves clash after hitting the window in your car. the theory im stating is just my overview of it. so for basics try your best to get your wave lengths from your backwave to be a full wave length for full combination but if you get to 1/2 your lose alot of sound. so i suggest on the enclosure stay cclose to the 1/4 wave length or over your 3/4 wave length.
Back to top Go down
View user profile
fritosaregood
Pro
Pro
avatar

Posts : 591
Join date : 2008-09-20
Age : 28
Location : Bryant, AR

PostSubject: Re: periodic functions and phase shifts   Tue May 31, 2011 1:04 pm

craigjones806 wrote:
Does a peak on a 1/8 wave make follow theory or experiment? I know that physics theories don't always work out in real-world applications so I was wondering if this is a case where theory says the 1/8 wave should work or a situation where experimenting shows that it just does.

Again, just looking at a sine wave, it looks like the 1/8 wave would not be a big enough phase shift (only 22.5 degrees, if I'm looking at the graph correctly)to really reinforce as well as a 1/4 wave.

In regard to t-lines, what if the "enclosure" used a 1/2 wave and the baffle was placed a 1/4 wave from the metering point? Should there be cancelation issues or would there be reinforcement?


its there, but your right, its not as strong as the 1/4 wave
Back to top Go down
View user profile
rob t
Pro
Pro
avatar

Posts : 832
Join date : 2009-07-28
Location : Searcy

PostSubject: Re: periodic functions and phase shifts   Sun Jun 05, 2011 9:41 am

I skipped that math class haha.
Back to top Go down
View user profile
MadMaxx
Veteran
Veteran
avatar

Posts : 128
Join date : 2011-01-17

PostSubject: Re: periodic functions and phase shifts   Sun Jun 05, 2011 11:49 pm

wow I had to sober up a bit before I even had a chance of understanding that first post.....
Back to top Go down
View user profile
craigjones806
Veteran
Veteran
avatar

Posts : 131
Join date : 2010-12-01
Location : Beebe

PostSubject: Re: periodic functions and phase shifts   Mon Jun 06, 2011 8:14 am

There are a couple of things in this thread that helped out yesterday. I know a 144 is not super loud, but for a single$ 70 sub, Lanzar power and completely stock electrical, I was pleased.

Now if I could get that race quad and enclosed trailer sold, things would change.
Back to top Go down
View user profile
Sponsored content




PostSubject: Re: periodic functions and phase shifts   

Back to top Go down
 
periodic functions and phase shifts
View previous topic View next topic Back to top 
Page 1 of 1
 Similar topics
-
» Help, car shifts from 4th to 3rd gear
» 2011 Boys PHASE 1 Academy " 4 more spots available!"
» 1973 Chevelle Phase 3 Baldwin Motion
» Citizen Eco Drive Moon Phase watch BU0011-63ZB Review
» New wireless headphone setup from phase technical

Permissions in this forum:You cannot reply to topics in this forum
ARKANSAS SPL :: General Discussion-
Jump to: