Topic: Tuning frequency and peeking frequency questions.
Sayar Kuchenski
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The resonate frequency of my vehicle is 47 Hz. I also play loudest at 47 Hz. I entered my current box design into three box building programs and into the "tuning frequency" formula. All four sources told me that my box is tuned around 37 - 40 Hz. According to WinISD it is tuned to 40 Hz. @ 80 degrees. I looked at the transfer function magnitude graph on WinISD and it showed that I peek out at about 43 Hz. However I have tried adding and subtracting five inches to my port in resolutions of one inch. As I did so I measured the SPL produced using the Term-Lab SPL meter. I found it is loudest with the current port length. However WinISD shows that the port does not peek out at 47 Hz., but instead 43 Hz. Additionally, I was told that boxes peek out about 3-4 Hz. higher then they are tuned to, and WinISD verifies that. But, all these programs are saying my box is tuned to about 40 Hz. Well my SPL meter does not lie and it shows it is loudest with the port tuned (according to various programs) to about 40 Hz. But, if I raise the tuning frequency so the peek of the waveform on WinISD is at 47 Hz., I loose SPL. So are all these programs wrong or what?
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with a wall your resonant frequency is 47hz... LMFAO
no one in spl uses programs... ask any world finals competitor what their enclosure is tuned to. in most(99%) of cases they will not know, but they will tell you what their note is.
note does not equal resonant frequency.
ps. you would be better off reading old things from the forum discussing these issues before you post... if not, you discredit that MIT under yourname.
-------------------- US Battery Ohio Generator Loudest superstreet 1-2 car west of Missouri EVER!!!!!!!
quote:Originally posted by shizzzon: you can import automotive situations, i think its in bassboxpro 6, but if you know all that, u dont need the program anyways....
lol exactly
one problem with bbpro6 is the default auto environemtn is generic as well. Those numbers are 'approximated' to simulate the car-like interior. There is a feature to boost it 12db also *shrug*
All that feature does is alter the gain/loss at specific frequencies...which can be manually adjusted and saved as what ever car you choose (perdy cool). That would take some serious testing to get it accurate though.
But like you mentioned...if you do all that stuff I doubt you'd rely on a program like that to build a ported box
--------------------
quote:it would all be for nothing without my favorite cawk-smoker NAvi
quote:Originally posted by jarfunkz: with a wall your resonant frequency is 47hz... LMFAO
no one in spl uses programs... ask any world finals competitor what their enclosure is tuned to. in most(99%) of cases they will not know, but they will tell you what their note is.
note does not equal resonant frequency.
ps. you would be better off reading old things from the forum discussing these issues before you post... if not, you discredit that MIT under yourname.
I couldn't agree more.
-------------------- Get loud daily... not burping. From Finals 2005:
quote: It's World Finals. A certified event. A 4x scoring event. It's the "pinnacle" of the "sport".
If I showed up to Game 7 of the World Series and was found to have a Corked Bat in pre game warm-ups, what would happen to me? Even if I said that I 'didnt see it in the rulebook, my bad'.
From Finals 2004:
quote:Originally posted by dBSteve: Everybody in the top 8 in every class bent the rules.
1. The box program only takes into account the spring element on the rear of the cone, or the enclosure's acoustic springiness. In open situations, this works, but in a car you have the acoustic springiness of the cab to take into acount as well. Being you have a large box and a wall, it is probably nontrivial. As you probably know, in a spring-mass system, resonance raises with increased stiffness.
2. At higher SPL levels, air becomes nonlinear. The stiffness of the spring is a function of pressure, and it becomes higher at higher pressures, forcing the "effective resonance" of the spring-mass system higher.
3. With very large ports, the acoustic mass model may not be a good approximation. With smaller ports, neglecting the acoustic compliance of the air inside the port and the acoustic mass of the air inside the box works, but with larger ports these become nontrivial.
Quite simply, box programs are usually designed under assumptions that just aren't valid for a setup like yours.
Posts: 3954 | From: Bloomington, IN | Registered: Sep 2000
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