Need Someone With Real Acoustic Knowledge. Waves

[IH8PunkRok]

yea james i think u messed up colder air is more dense than hot

*edit* comp is slow

lets assume a 40 hz frequency ok?

constant

the box type size shape and tuning are the variables. how do i determine how to create the best box for that one frequency?

Edited January 10, 2009 by IH8PunkRok

[wildbeast15]

cold air is way more dense so waves travel alot easier. the longer the wave the louder it can be because the shorter it has to travel just need to crank it..(in other words it has the capability of getting louder than a shorter wave does but it requires more energy to get to its peak compared to a 60hz

[IH8PunkRok]

cold air is way more dense so waves travel alot easier. the longer the wave the louder it can be because the shorter it has to travel just need to crank it..(in other words it has the capability of getting louder than a shorter wave does but it requires more energy to get to its peak compared to a 60hz

im gonna call false on this one. all frequencies can obtain the same decibel reading. im pretty sure there is no capp to any certain frequency. in any case that doesnt help me with the tuning aspect of the enclosures. good try tho

[banginAltima]

yea james i think u messed up colder air is more dense than hot

*edit* comp is slow

lets assume a 40 hz frequency ok?

constant

the box type size shape and tuning are the variables. how do i determine how to create the best box for that one frequency?

Box volume and box tuning.... Also knowing, for a lack of better words, how much freq. rise your vehicle likes. Ex. My box is tuned to 33 hz but i peak at 40Hz. 7 Hz rise, increase.... I can't think of the right words. but every vehicle peaks 5 to 10 hz higher then box tuning.

[IH8PunkRok]

ok and that peak rise has to do with the increase of volume from the box to the cabin correct?

*edit* shouldnt the new peak be a lower frequency if the air volume is larger?

Edited January 10, 2009 by IH8PunkRok

[banginAltima]

ok and that peak rise has to do with the increase of volume from the box to the cabin correct?

*edit* shouldnt the new peak be a lower frequency if the air volume is larger?

I believe in most cases the freq. of the vehicle depends on how much airspace is in the vehicle. Thats why most standard cab trucks are around 50 hz or so and a vehicle like my friends Excursion like the mid to upper 30's.

[IH8PunkRok]

I believe in most cases the freq. of the vehicle depends on how much airspace is in the vehicle. Thats why most standard cab trucks are around 50 hz or so and a vehicle like my friends Excursion like the mid to upper 30's.

so that itself is a totally different beast isnt it?

[banginAltima]

so that itself is a totally different beast isnt it?

I am having a brain fart, i don't understand what you mean?^^^^^

[IH8PunkRok]

cabin tuning

its a completely different aspect of the acoustics

[HHR Ed]

sorry I left for a bit.

Here are a few tidbits.

Colder air can be more dense but is not always more dense than hot air, humidity and altitude also come into play here.

Also, it isnt necessarily easier to get louder in more dense air.

30 deg F air to 80 deg F air will show very minimal differences in density, so any difference in SPL based soley on density is very minute. Also, the more dense the air is, the harder it will be to achieve the same SPL as with a lower density. This is because the air shows more resistance. Basically you have more air molecules to push so more energy is required.

Now, we know that sound travels faster through dense materials like solids than it does through lesser dense materials like air.

So basically the denser the air, the faster the wave can travel Changing the resonant frequency of the car and the enclosure.

Based on that theory we can say that SPL will be lower in more dense colder air, but the change in density is too small. Also, with a higher frequency you can create more energy per time. So lets says 60hz is 60 full waves a second compared to 30hz 30 full waves a second.

So it really effects frequency, and some systems are setup to play better at some frequencies than others, so if the temp drop changes your cars frequency, and you box doesnt matches it better than the hot air, then you score may go up. This can be predicted but it is extremely difficult.

Now lets talk about box tuning.

You can figure what size a box has to be for a given frequency based on the data of the sub. Cone mass, Motor strength, Moving force. Things like that can tell you how the woofer will move and react to a given power and air volume.

Now the car. Just think of the car and box together as a big bandpass. So you have 2 chambers. The Larger chamber is more related to the length of the wave, so larger vehicles usually play lower, smaller vehicles usually play higher.

If you tune a box to say 35hz, those formulas used to calculate that are based on infinite airspace around the box, and dont take into account a vehicle's internal volume. So when you shrink the infinite airspace down, you raise the tuning frequency of that enclosure.

It is true that in most cases it will raise 5-10hz above what the box is tuned at but is hard to calculate exactly because of the various shapes and sizes of different cars.

Sorry if I wasnt too clear, I have been drinking.