# sub, with window down?



## makaveli (Oct 5, 2005)

real quick i was wondering if any1 had some ideas to why my sub seems to be louder with the windows down a crack. it doesnt seem as loud with them up, or down all the way. u have a 96 200sx (b14). any ideas?


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## sr20dem0n (Mar 19, 2003)

aren't vehicle acoustics fun?


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## captain_shrapnel (Sep 10, 2004)

The answer is pretty complex, but the quick and dirty version is because sound (especially bass) inside of a car does not behave like sound from a speaker playing into a room or outside. The car becomes an enclosure for the sub and creates a pressure field that can be adjusted by changing how "lossy" it is. Think of it like your car being a ported box, and your window being the port. When you get that window open just right, it resonates like any port and may increase the spl of a given frequency slightly.


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## makaveli (Oct 5, 2005)

captain_shrapnel said:


> The answer is pretty complex, but the quick and dirty version is because sound (especially bass) inside of a car does not behave like sound from a speaker playing into a room or outside. The car becomes an enclosure for the sub and creates a pressure field that can be adjusted by changing how "lossy" it is. Think of it like your car being a ported box, and your window being the port. When you get that window open just right, it resonates like any port and may increase the spl of a given frequency slightly.


lol cool thanks, i hate it though cause it sounds so much better with the windows cracked, that i end up driving with them cracked in the rain lol


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## 240sxstud (Sep 20, 2005)

makaveli said:


> lol cool thanks, i hate it though cause it sounds so much better with the windows cracked, that i end up driving with them cracked in the rain lol


I don't think I'd take it THAT far  

something to look into is getting your car "sealed"...I know my local shop does it for about 150 installed, and it keeps sound from "leaking" out. they install the material in your door panels, headliner and trunk.


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## wes (Apr 30, 2002)

240sxstud said:


> something to look into is getting your car "sealed"...I know my local shop does it for about 150 installed, and it keeps sound from "leaking" out. they install the material in your door panels, headliner and trunk.


This has nothing to do with how the car will sound with the windows down. That is a property of cabin gain in a sealed vs unsealed environment.


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## sr20dem0n (Mar 19, 2003)

It could also be due to cancellation

I get a significant boost in the lower octave (30-40hz) when I open my window or door, probably around 4-6dB. Most sedans will gain output with the window or door open, it's just a quality of sedans really. SUVs tend to be the opposite, when you open a door or window normally the output will drop.


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## makaveli (Oct 5, 2005)

sr20dem0n said:


> It could also be due to cancellation
> 
> I get a significant boost in the lower octave (30-40hz) when I open my window or door, probably around 4-6dB. Most sedans will gain output with the window or door open, it's just a quality of sedans really. SUVs tend to be the opposite, when you open a door or window normally the output will drop.


do you think that it will make a difference if i get another sub, or will it just be louder(same problem as be4, just louder)?


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## wes (Apr 30, 2002)

makaveli said:


> do you think that it will make a difference if i get another sub, or will it just be louder(same problem as be4, just louder)?


Has NOTHING to do with the audio system, it is the acoustics of the car. But yes, if you get another sub it will be louder, but still be louder with teh window down.


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## 240sxstud (Sep 20, 2005)

wes said:


> This has nothing to do with how the car will sound with the windows down. That is a property of cabin gain in a sealed vs unsealed environment.



I was saying that it would improve his sound of his system overall...


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## captain_shrapnel (Sep 10, 2004)

The only thing that may help is moving the sub around. The interior is a complex space, so sometimes just changing the direction your sub fires, or moving a couple of inches or feet can help. 

If you add another sub you might get the volume you enjoy, therby allowing you to close the window. That would be the only benefit.


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## JLTD (Oct 12, 2004)

You problem is a vehicle/enclosure/location mismatch. This is usually more common in pick up trucks, you don't usually hear about it in cars. 
Basically, the subwoofer system's peak is centered where there is a dip the the vehicle's sonic signature (which changes whent the window opens). Changing the design of the enclsoure will shift the peak somewhere else. When this occurs, it's usually due the the enclosure being too small for the vehicle and/ or tuned too high (if applicable). Because this is a car, you can also add in location and facing of the woofer as well. 
I had one of these cars back in 1995, I don't remember it being a problem.


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## makaveli (Oct 5, 2005)

JLTD said:


> You problem is a vehicle/enclosure/location mismatch. This is usually more common in pick up trucks, you don't usually hear about it in cars.
> Basically, the subwoofer system's peak is centered where there is a dip the the vehicle's sonic signature (which changes whent the window opens). Changing the design of the enclsoure will shift the peak somewhere else. When this occurs, it's usually due the the enclosure being too small for the vehicle and/ or tuned too high (if applicable). Because this is a car, you can also add in location and facing of the woofer as well.
> I had one of these cars back in 1995, I don't remember it being a problem.


well the sub is facing towards the trunk, which is covered in dynomat. ive tried to turn it around and you can barley hear the sub, and thats with the seat down. the box is tuned to 45Hz. it is a ported q logic. the size is a exact match with rockfords specs. i think i know the problem though.......
the box is made for 2 subs, and right now there is only 1 in there, the other side is stuffed with blankets, and the passage way that connects the two chambers is blocked off, could this be the problem?


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## wes (Apr 30, 2002)

makaveli said:


> well the sub is facing towards the trunk, which is covered in dynomat. ive tried to turn it around and you can barley hear the sub, and thats with the seat down. the box is tuned to 45Hz. it is a ported q logic. the size is a exact match with rockfords specs. i think i know the problem though.......
> the box is made for 2 subs, and right now there is only 1 in there, the other side is stuffed with blankets, and the passage way that connects the two chambers is blocked off, could this be the problem?


Is it completely sealed off wood? Are both sides ported? Are both sides exactly the same in terms of air space and port volume? 

This has NOTHING to do with why the sub gets louder when the window is down. NOTHING.


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## Sentrixx (Apr 30, 2002)

wes said:


> Is it completely sealed off wood? Are both sides ported? Are both sides exactly the same in terms of air space and port volume?
> 
> This has NOTHING to do with why the sub gets louder when the window is down. NOTHING.



From my understanding, its the pressure in a car that causes this. And when opening/cracking a window or sunroof. That helps release the pressure causeing the excursion of the cone to move more rapidly. You can also notice that when you leave the windows up you will get a lot more rattle from the body panels. 

edit::: The pressure has a lot to do with loss and gain of db's also.


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## makaveli (Oct 5, 2005)

wes said:


> Is it completely sealed off wood? Are both sides ported? Are both sides exactly the same in terms of air space and port volume?
> 
> This has NOTHING to do with why the sub gets louder when the window is down. NOTHING.


well no there is just towels in the passage way. both sides are not ported they combine into one port. and yes the chambers are exactly the same. from above a cross section would look like this... sorry i was never good in art


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## sr20dem0n (Mar 19, 2003)

oooooo, not cool

you've got some kind of quasi transmission line hybrid thing going on there

to pull off what you're trying to do you need to block off half of that front port, boxes like that are NOT meant to be used with only one sub.


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## makaveli (Oct 5, 2005)

sr20dem0n said:


> oooooo, not cool
> 
> you've got some kind of quasi transmission line hybrid thing going on there


:wtf:


sr20dem0n said:


> to pull off what you're trying to do you need to block off *half of that front port,* boxes like that are NOT meant to be used with only one sub.


what do you mean front port they connect into one port..... but its sealed on the side w/o sub.... i was actually thinking of getting a new box and more powerful sub due to weight problems... mabye im gonna go take a pic of it.... just for you :thumbup:


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## makaveli (Oct 5, 2005)

here they are....

































my pics are showing up right...?


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## wes (Apr 30, 2002)

It is NOT sealed! The towels do not seal it properly if at all. As a result the sub is seeing that as an additional port. You really should get another sub or another box!


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## captain_shrapnel (Sep 10, 2004)

^^ This is true. Also, the center port has been sized to work with the output of 2 subs. Look at your drawing, one outlet port for 2 subs down the middle, your port has too much airspace to work correctly with just one. Also, simply dividing it in half may not be a workable solution because the geometry of the port may need less or more than a perfect division of 2. You would be better off dropping a matched sub in the other side and running the amp at a lower impedence (if it can handle it!).


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## sr20dem0n (Mar 19, 2003)

captain_shrapnel said:


> ^^ This is true. Also, the center port has been sized to work with the output of 2 subs. Look at your drawing, one outlet port for 2 subs down the middle, your port has too much airspace to work correctly with just one. Also, simply dividing it in half may not be a workable solution because the geometry of the port may need less or more than a perfect division of 2. You would be better off dropping a matched sub in the other side and running the amp at a lower impedence (if it can handle it!).


That's what I was getting at. Even if those towels did perfectly seal it off, your port doubles in area half way through (hence the quasi transmission line comment). If you were able to block off half of that front port it would work though (port area is additive, it would work how it's supposd to), you would have to block off the other half with something strong and rigid, however, a towel wouldn't work. It would probably just be best to use another identical sub in the other hole or buy a new box.


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## makaveli (Oct 5, 2005)

sr20dem0n said:


> That's what I was getting at. Even if those towels did perfectly seal it off, your port doubles in area half way through (hence the quasi transmission line comment). If you were able to block off half of that front port it would work though (port area is additive, it would work how it's supposd to), you would have to block off the other half with something strong and rigid, however, a towel wouldn't work. It would probably just be best to use another identical sub in the other hole or buy a new box.


thats the problem i cant find anpther fosgate RFP4410 anywhere. its the same as the p2(200wmin 400wmax/4 ohms) but it has little differences, like magnet size, q factors, moving mass, freq responce etc. would this cause problem?
*Current Sub(rfp4410)*








*other sub(p210s4)*


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## sr20dem0n (Mar 19, 2003)

it would matter, to use a box like that they would need to be the exact same


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## makaveli (Oct 5, 2005)

sr20dem0n said:


> it would matter, to use a box like that they would need to be the exact same


fuck i guess im shit outta luck then....


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