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Windows Up VS Windows Down


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First off, I'm nowhere near loud enough for this to affect me, but it's something I'd love to learn about. I'll just throw out a list of questions, feel free to answer any you can or expand on different topics as well.

  • Why are some vehicles louder with the windows down/door open (scientific explanation would be awesome!)?
  • Approximately what spl level does this start to make a difference?
  • Does the type of box make a difference? Are some better with up vs some with down?
  • What type of vehicles are better up/down?
  • Which competitions/formats require windows up/down?

Feel free to expand upon anything, I'm mostly interested in the theory of why windows down can sometimes be louder and what factors make this happen.

2008 Subaru WRX STI

K&N Typhoon Intake

Invidia Polished Stainless 3" turbo back with cat

Cobb Accessport

Dyno tune from Kaizen Tuning

320awhp 330ft-lb awtq

MTX 421D Sub amp

American Bass SQ900 Highs/Mids amp

Sundown Audio SD-2 10 D4

JL Audio XR653-CS 3-way Components

3sixty.2

Second Skin Damplifier Pro

Custom fiberglass wheel well enclosure

Transmission Line quasi-floor enclosure

http://www.stevemeadedesigns.com/board/forum/13-member-rides-builds-show-off-your-whip-show-off-your-system/

Bill Fitzmaurice TLAH line-array hifi towers

9 Goldwood 4" mids (each)

12 Goldwood 1/2" tweeters (each)

NAD 1020 Preamp

MiniDSP 2x4 Balanced processor

Thorens TD166mkII Turntable

Hafler DH-200 Amplifier

http://www.stevemeadedesigns.com/board/topic/192638-line-array-hifi-tower-build/

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Acoustics. That's the simple answer.

There's so many variables, but consider the one main factor: Opening the windows changes the acoustic properties of the cabin, which in turn affect the way the enclosure reacts to the change of air pressure at the listening (or metering) position. A good example is the difference between metering with the doors and windows shut and the meter on the dash, or the driver side door open with the meter in the kick. Same vehicle, same cabin, same equipment but the acoustics have changed dramatically. For the most part, there can be increase in SPL with the door open in the kick because there is a difference in cabin pressure from one side of the vehicle to the other. Again, not all results are the same due to the vast changes in cabin acoustics from vehicle to vehicle.

As far as the enclosure goes, you can design it to specifically work with the windows down, up, doors open or closed , no doors, no roof, whatever. It will perform in that particular environment well, but as soon and you change the environment, so will the output change. Of course, it may not be a noticeable change, but if you're talking about 0.5 db then it does matter.

That's just scratching the surface, but to go into more detail would mean I need a degree in acoustic engineering.

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we really only have nespl up here so we do burps sealed on the glass, we also have music runs that allow a window or door to be opened

2002 Honda CR-V
Alpine 9887

My Build

Rebuilding...

Second Skin Damp
4 DC XL 15's
2 DC 5ks
Singer 320 amp
6 cap banks
Sky High wire
2 VM-1's
OM-1

all under window line

Team DC Audio

Obama has a law he's trying to pass right now, trying to ban Leo for being a threat to children everywhere.



EDIT: Not in a JP kind of way.

I thought I was going to die from all the jizz filling my ears.

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Acoustics. That's the simple answer.

There's so many variables, but consider the one main factor: Opening the windows changes the acoustic properties of the cabin, which in turn affect the way the enclosure reacts to the change of air pressure at the listening (or metering) position. A good example is the difference between metering with the doors and windows shut and the meter on the dash, or the driver side door open with the meter in the kick. Same vehicle, same cabin, same equipment but the acoustics have changed dramatically. For the most part, there can be increase in SPL with the door open in the kick because there is a difference in cabin pressure from one side of the vehicle to the other. Again, not all results are the same due to the vast changes in cabin acoustics from vehicle to vehicle.

As far as the enclosure goes, you can design it to specifically work with the windows down, up, doors open or closed , no doors, no roof, whatever. It will perform in that particular environment well, but as soon and you change the environment, so will the output change. Of course, it may not be a noticeable change, but if you're talking about 0.5 db then it does matter.

That's just scratching the surface, but to go into more detail would mean I need a degree in acoustic engineering.

Thanks for the reply, any acoustic engineers in the house???

2008 Subaru WRX STI

K&N Typhoon Intake

Invidia Polished Stainless 3" turbo back with cat

Cobb Accessport

Dyno tune from Kaizen Tuning

320awhp 330ft-lb awtq

MTX 421D Sub amp

American Bass SQ900 Highs/Mids amp

Sundown Audio SD-2 10 D4

JL Audio XR653-CS 3-way Components

3sixty.2

Second Skin Damplifier Pro

Custom fiberglass wheel well enclosure

Transmission Line quasi-floor enclosure

http://www.stevemeadedesigns.com/board/forum/13-member-rides-builds-show-off-your-whip-show-off-your-system/

Bill Fitzmaurice TLAH line-array hifi towers

9 Goldwood 4" mids (each)

12 Goldwood 1/2" tweeters (each)

NAD 1020 Preamp

MiniDSP 2x4 Balanced processor

Thorens TD166mkII Turntable

Hafler DH-200 Amplifier

http://www.stevemeadedesigns.com/board/topic/192638-line-array-hifi-tower-build/

https://www.facebook.com/HolyMountainGlass

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we really only have nespl up here so we do burps sealed on the glass, we also have music runs that allow a window or door to be opened

We need to meet up soon. I've gotta hear your system now that it's finally running (it's still running right?).

2008 Subaru WRX STI

K&N Typhoon Intake

Invidia Polished Stainless 3" turbo back with cat

Cobb Accessport

Dyno tune from Kaizen Tuning

320awhp 330ft-lb awtq

MTX 421D Sub amp

American Bass SQ900 Highs/Mids amp

Sundown Audio SD-2 10 D4

JL Audio XR653-CS 3-way Components

3sixty.2

Second Skin Damplifier Pro

Custom fiberglass wheel well enclosure

Transmission Line quasi-floor enclosure

http://www.stevemeadedesigns.com/board/forum/13-member-rides-builds-show-off-your-whip-show-off-your-system/

Bill Fitzmaurice TLAH line-array hifi towers

9 Goldwood 4" mids (each)

12 Goldwood 1/2" tweeters (each)

NAD 1020 Preamp

MiniDSP 2x4 Balanced processor

Thorens TD166mkII Turntable

Hafler DH-200 Amplifier

http://www.stevemeadedesigns.com/board/topic/192638-line-array-hifi-tower-build/

https://www.facebook.com/HolyMountainGlass

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we really only have nespl up here so we do burps sealed on the glass, we also have music runs that allow a window or door to be opened

We need to meet up soon. I've gotta hear your system now that it's finally running (it's still running right?).

yup still running lol, gna be out of comission for a week or two while i redo some stuff though

2002 Honda CR-V
Alpine 9887

My Build

Rebuilding...

Second Skin Damp
4 DC XL 15's
2 DC 5ks
Singer 320 amp
6 cap banks
Sky High wire
2 VM-1's
OM-1

all under window line

Team DC Audio

Obama has a law he's trying to pass right now, trying to ban Leo for being a threat to children everywhere.



EDIT: Not in a JP kind of way.

I thought I was going to die from all the jizz filling my ears.

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Tron explained so well, nice reading ;)

I´m the SPL Gains topic creator!! wanna get louder?? check this: SPL Gains. Panamenian 2009 & 2010 & 2014 Bass Race 149.9 Champion!

2 15" subs and a 2K wired at 1 ohm, http://www.stevemeadedesigns.com/board/topic/167788-fecupe2001-2-15s-on-a-2k-video-on-page-3/

8 Massive 15" subs and small power, http://www.stevemeadedesigns.com/board/topic/179296-fecupe2001s-8-15s-4th-order-bandpass-wall/

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it all depends on how you design/test your system, my explorer dropped 1.2 dbs when i opened the door or window lol

I´m the SPL Gains topic creator!! wanna get louder?? check this: SPL Gains. Panamenian 2009 & 2010 & 2014 Bass Race 149.9 Champion!

2 15" subs and a 2K wired at 1 ohm, http://www.stevemeadedesigns.com/board/topic/167788-fecupe2001-2-15s-on-a-2k-video-on-page-3/

8 Massive 15" subs and small power, http://www.stevemeadedesigns.com/board/topic/179296-fecupe2001s-8-15s-4th-order-bandpass-wall/

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