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newb question about sound with trunk open

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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=46794
Printed Date: October 05, 2022 at 7:14 PM


Topic: newb question about sound with trunk open

Posted By: bigwise1
Subject: newb question about sound with trunk open
Date Posted: January 03, 2005 at 5:49 PM

I have two jl 10w6v2 in a sealed box facing the rear and when the trunk is open and volume is up they start making a weird sound (distortion?).  Talked to the shop that did the install and they said the trunk needs to be closed because when closed the trunk is sealed and  the air acts like a cushion for the woofers and pushes them back.  Does this sound right?  I've heard many systems blast with trunk open and none of them sounded like mine.



Replies:

Posted By: actionjackson
Date Posted: January 03, 2005 at 9:28 PM
it does make sense what your shop told you. Its designed  to be in a sealed trunk

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Jamie Jackson
*CRIMPING AINT EASY*




Posted By: oldskool92
Date Posted: January 03, 2005 at 9:36 PM
Absolutely, Your subs are going to sound differently when your trunk is open, because they are going from a very small room to an infinite room, and the air pressure on the cones changes.

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I'm gettin' 2 old for this sh*t!!




Posted By: overworked
Date Posted: January 04, 2005 at 6:41 AM
make those cones bounce baby oh yeah!!! gotta love that question, Distortion? yes it is most likely distortion as when you open the boot there is no contained pressure stopping the cone from overdriving and reaching it's P2P limit causing that "weird sound". Lower levels maybe alright, but do not run at high levels for any lengths of time....anyone smell tinsel leads burnig?

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Posted By: stevdart
Date Posted: January 04, 2005 at 5:01 PM

I don't buy it.  A speaker in a sealed enclosure means that the back of the cone is sealed, not the front.  Speakers don't need both sides in sealed enclosures.  If the front had to be that way too they would have specs on how much air space in the trunk there has to be!  C'mon guys, that's nuts.

My guess is amp gain set too high.  They likely sound like that all the time and you hear it differently in the vehicle.





Posted By: archemedes
Date Posted: January 04, 2005 at 6:17 PM
the interior of a car is also a sealed enclosure, to make sound air needs to compress it takes alot more power to do that outside since it won't actually compress just move. Look at outdoor concerts the speakers and enclosures are usually different from indoor ones




Posted By: supradude
Date Posted: January 04, 2005 at 10:03 PM
If you raise the trunk (or hatchback) of a vehicle, it will change the sound of the bass. I don't think "distortion". Usually the "deepness" of the bass will fade some.

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'85 Toy




Posted By: jstruckman
Date Posted: January 04, 2005 at 10:20 PM

My guess is your subs are distorting at the same volume with the trunk closed also, you just cant hear the distortion as well with the trunk closed. If an installer told me that you had to have the trunk closed or the subs would distort i would tell him he is full of sh!t!!!It will sound different opened and closed, but not cause distortion.

Jazzy



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Posted By: petergozinya
Date Posted: January 04, 2005 at 10:29 PM

scientist call it TRANSFER FUNCTION  you and someone else could talk about that all day. I't hurt my brain's,sound waves reflect, energy ,energy, energy...let's stick with this ..for now ..when WE run energy like we do we knock stuff off the wall's and bust windshields out...why ...anytime you make somethingmove it creates friction..guess what that make's./from start to finish we turn heat to bass wave's and back to heat=friction-------of course that big air pump has alot to do with your hatch being open or your trunk. But what ARCHEMEDES said earlyar =having that lid closed will keep the sub's impendence lower, becouse of the compression, depending on the resonant's of you're application(anything absorbed ) it was turned into heat! IN SOME ISTANCES (THIS IS TUFF) A bass wave at certin lenth will 'bounce'

this iz hard,i do know how to explaine it but it take's year's.. s.o.s     thad





Posted By: bigwise1
Date Posted: January 04, 2005 at 11:04 PM
So are my subs distorting when the trunk is closed? 




Posted By: stevdart
Date Posted: January 04, 2005 at 11:12 PM

When a speaker thrusts outward, hits as we say....it compresses the air directly in front of the cone.  That's what creates a sound wave.  Then when the cone fires backward, the air (at a specific volume) inside the enclosure is compressed...which results in maintaining control of the cone movement.  A sound wave is created at that point, too.  That back wave is 180 degrees off the front  wave and can have the effect of cancelling some of the front wave sound if the two waves reach your ears 180 degrees apart.  https://www.installer.com/tech/aiming.html

The space that the enclosure occupies, the barometric pressure and air temperature will have an effect on the sound waves and cone movement, too.  A little bit. 

But the air space in the trunk of a car is considered infinite baffle.  Think about this:  when you use an infinite baffle sub mounted so that the front fires into the cabin and the rear of the speaker goes into the trunk, you're using an infinite baffle arrangement.  That trunk would have to be barely bigger than the sub enclosure to give credibility to the notion that air compression is taking place within the trunk and controlling the cone movement.

You didn't say if the cone looked like it was out of control, or how the sound was from inside the car.  We can only infer that you don't hear the weird sound from inside the car.  And we're working on the assumption that the enclosure was built to proper specs and with proper amp setup.  So, with this much info, I would look into moving the sub enclosure around in the trunk until it sounds right both inside the car and outside with the trunk open.

edit:  just saw your last question..  You couldn't know unless you were willing to get in and allow a trusted friend (preferably your mother!) to close you in the trunk and play the system.  But I wouldn't go there....





Posted By: bigwise1
Date Posted: January 04, 2005 at 11:24 PM
stevdart wrote:

 

But the air space in the trunk of a car is considered infinite baffle.  Think about this:  when you use an infinite baffle sub mounted so that the front fires into the cabin and the rear of the speaker goes into the trunk, you're using an infinite baffle arrangement.  That trunk would have to be barely bigger than the sub enclosure to give credibility to the notion that air compression is taking place within the trunk and controlling the cone movement.


But my subs are firing towards the rear.





Posted By: stevdart
Date Posted: January 04, 2005 at 11:49 PM

I didn't make my point clear there.  I was describing an infinite baffle arrangement where the trunk space is considered infinite baffle:  to point out the fact that air space in a trunk is of large enough volume to be considered ineffective in controlling cone movement.  That's not particularly your case as you have a sealed sub setup. 

But the second sentence of that quote does apply to yours: 

"That trunk would have to be barely bigger than the sub enclosure to give credibility to the notion that air compression is taking place within the trunk and controlling the cone movement."





Posted By: bigwise1
Date Posted: January 04, 2005 at 11:57 PM
stevdart wrote:

I didn't make my point clear there.  I was describing an infinite baffle arrangement where the trunk space is considered infinite baffle:  to point out the fact that air space in a trunk is of large enough volume to be considered ineffective in controlling cone movement.  That's not particularly your case as you have a sealed sub setup. 

But the second sentence of that quote does apply to yours: 

"That trunk would have to be barely bigger than the sub enclosure to give credibility to the notion that air compression is taking place within the trunk and controlling the cone movement."


another forum suggested infinite baffle because of a leaking box. guess i'll check tomorrow.





Posted By: stevdart
Date Posted: January 05, 2005 at 12:20 AM

"another forum..."   posted_image





Posted By: bigwise1
Date Posted: January 05, 2005 at 12:36 AM
stevdart wrote:

"another forum..."   posted_image


just looking for other opinions.  what do you think about the theory of a leaking box?





Posted By: overworked
Date Posted: January 05, 2005 at 3:00 AM

Leaking Box? nah, mate ummm how can I explain this a little bit simpler......dunno but I'll try! lol

Sound doesn't just come from the front of the speaker, albeit.....the best quality sound does (although that can be argued in low hz as well) if you put a box around the front of the speaker then it compresses the front as well creating equal pressure on both sides ofd the conethis would create an incredible amount of sound, but.....as always there is a but....you wouldn't hear it properly would you?

SO, we dont create enclosure for the front of speakers (unless it is a bandpass box and that is a WHOLE other topic!) but if you were to put a speaker in a small area......your boot, then it is like an enclosure to a certain extent, it will compress the air around the cone creating a small amount of pressure making it harder for the cone to move....lowering the effiency of the woofer and raising it's wavelength (I still dont think I explained that right.....|) thus allowing you too push more power into the coil(s)so now lets talk numbers theoretical numbers mind you

each woofer is capable of 100 watts

and with the trunk closed your pushing in about 100-200(p) watts, so in all fairness everything is working fine........until............you open the boot

then all the pressure that was contained in the boot is gone, and the cones are able to freely forwards raising their effiency....forcing the volume up slightly and also now you pushing in 200 watts into the speaker and it's peaking like crazy maybe not distorting but it will be slammed forwards with subh momentum that it will almost make a popping noise or maybe a cracking noise......I think it was wise I your instaler to tell you this and you should pay heed to what he has said.......and under no circumstances are you too goto another forum!, hope this helps just ask if there is anymore questions



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Posted By: ~AFAccord~
Date Posted: January 05, 2005 at 11:16 AM

    For the most part I agree with every post here.  I think what  Bigwise is looking for is what everyone's already stated, but in a simpler form. 

    Bigwise, your assumption about your subs distorting was correct.  The noise you are hearing with the trunk open is in fact distortion.  The same thing is happening with the trunk closed, but it's not so drastic since the closed trunk area is providing a moderate amount of control for the woofers, and various other things like rattles and the physics of sound drown out any audible distortion from inside the car. 

    The installer at the shop was correct about being cautious when playing the subs with the trunk open.  It may sound cool for a while, but it really is doing your subs more harm than good.  As some people already stated, the lack of pressure with an open trunk allows the subs to be much more efficient and move much further.  That extra distortion can easily damage your subs.

    The last thing to remember is that all setups respond differently.  The subs, the enclosure, the vehicle, they all make a difference how the system plays, whether the trunk/hatch/door is open or closed, they will all sound different.  A setup in an SUV might be well adapted to sound nice in a free-air environment, while the subs in your trunk my handle much more power or sound better, they probably work best in a sealed, pressurized environment. 

    I hope this has helped answer your questions.  Just reply in this post if anything's still not clear.  Later man.



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Black Cherry
"Experience is something you never get until just after you need it."




Posted By: tuanmerica@juno
Date Posted: January 06, 2005 at 2:46 AM
Do you drive your car fast with an opened trunk?
If so that is the reason why you have your music becomes distorted. Just imagine your audio is a low frequency that travel slower than the win flow in your car. Scientifically, the audio of your voice or music is very slow when it moves from point A to point B. For example, if you are standing infront of a high speed fan, your voice will be distorted because the wind of the fan is flowing a little faster than your voice on the opposite direction that causes your voice to be delayed between the fan and your ears. Therefore, the audio sometimes travels at the same speed with the wind speed on the same direction that cause your ear to hear nothing at that movement.
Listen to the music with the trunk open while you park your vehicle will not make the sound distorts at all. I do not think that happens. If so, you may have a bad speakers.




Posted By: ~AFAccord~
Date Posted: January 06, 2005 at 3:11 AM
Hmmmm...  I belive tuanmerica is trying to describe the doppler effect.  Bigwise, I hope this isn't what you are asking about. lol  If you're riding down the road with your trunk open, then you have other problems to worry about...

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Black Cherry
"Experience is something you never get until just after you need it."




Posted By: overworked
Date Posted: January 06, 2005 at 3:26 AM
tuanmerica??!!??!!?? WTF?

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Posted By: bigwise1
Date Posted: January 06, 2005 at 8:33 AM

~AFAccord~ wrote:

Hmmmm...  I belive tuanmerica is trying to describe the doppler effect.  Bigwise, I hope this isn't what you are asking about. lol  If you're riding down the road with your trunk open, then you have other problems to worry about...

no, i was describing what happens when parked. 





Posted By: ~AFAccord~
Date Posted: January 06, 2005 at 8:41 AM

Bigwise, I didn't think you had any problems like what tuanmerica described lol.  Really I'm not sure what he was talking about...  After reading his post again, I withdraw my comment about the dopler effect... he doesn't know WHAT he's talking about.  The whole fan thing?? um.. NO.  That's just your voice reflecting off the fan blades back at you, and has no relevance to this post.  Sorry to throw that at you. 

Did my first post help any?  Lemme know and maybe we can carify it better.



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Black Cherry
"Experience is something you never get until just after you need it."




Posted By: bigwise1
Date Posted: January 06, 2005 at 8:41 AM
afaccord, you said it's probably distorting when the trunk is closed too. so do you think it's safe to play music at the same volume with trunk closed compared to when the subs start distorting with trunk open?




Posted By: ~AFAccord~
Date Posted: January 06, 2005 at 8:48 AM
Generally speaking, yes.  All speakers have some degree of distortion.  At the same volume, the subs will distort more with the trunk open since there's hardly any pressure outside the box controlling the sub.  This is when there's a much higher risk of blowing your woofers.   As long as it doesn't sound grossly distorted when you're inside the car with the trunk closed, you should be ok.  When listening inside the car under normal environments (trunk closed) most subs will seem to flatten out in volume, and become very sloppy when they're at their max.  Just get to know your subs and learn what they are capable of and you'll be alright.  And keepin the volume down when you do decide to open the trunk is a good idea. posted_image

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Black Cherry
"Experience is something you never get until just after you need it."




Posted By: stevdart
Date Posted: January 06, 2005 at 11:57 PM
Some of you guys are starting to convince me that the air in the trunk is controlling the sub to a degree....  But I still think if the sub enclosure were built properly for that sub, the volume inside the enclosure would control the cone without any help needed from the front.  His whole system should be gone over with a fine- toothed comb.




Posted By: bigwise1
Date Posted: January 07, 2005 at 12:36 AM

     Totally off topic and I have searched also but since you guys are here I would like your opinion with my particular setup and situation.  I'm already thinking about changing my enclosure.  I'm looking for something that hits a little harder.  I'm thinking about either keeping my 10w6v2's and going with a ported enclosure or spending more money and getting 12w6v2's in a sealed enclosure.  I would keep my amp setup the same (2 zapco 500/1's for each sub).  Is that enough power for the 12's?   Also, I have a friend who says to get a zapco preamp.  Would a preamp make a difference?  By the way, my deck is a Clarion  DXZ945MP.





Posted By: bigwise1
Date Posted: January 07, 2005 at 12:58 AM
4got to ask.   With the amount of power I'm running to the 10w6v2's, would going with a ported enclosure make them more susceptible to distortion since ported enclosures make them more efficient?




Posted By: stevdart
Date Posted: January 07, 2005 at 10:39 AM

I don't think this question was asked here:  do you know how your sub's voice coils are wired and how the two subs are wired together?  Two possible ways shown below.

posted_image

...or are they wired separately?  I'd want to know what impedance(s) we're talking about with this setup.

Manual is here https://www.jlaudio.com/subwoofers/pdfs/W6v2_MAN.pdf





Posted By: bigwise1
Date Posted: January 07, 2005 at 4:54 PM
stevdart wrote:

I don't think this question was asked here:  do you know how your sub's voice coils are wired and how the two subs are wired together?  Two possible ways shown below.

posted_image

...or are they wired separately?  I'd want to know what impedance(s) we're talking about with this setup.

Manual is here https://www.jlaudio.com/subwoofers/pdfs/W6v2_MAN.pdf


They are wired separately.  Each has it's own 500/1 amp at  2ohms.  I'm not sure what impedance, I'm a newbie.





Posted By: stevdart
Date Posted: January 07, 2005 at 7:57 PM

How there is any distortion at all with the equipment you're working with is beyond me!  The impedance load on each amp is an easy 2 ohms, the woofers are 400 WRMS, the amp outputs 500 watts into 2 ohms.....  is this your amp?  I wish I had this stuff to play with.  All the tools are within fingertip reach for designing and building  enclosures for  these subs.  The manual shows you a slotted box.  Why don't you build it and give it a go?  That size looks like it builds in a helluva bass boost at around 50 Hz, though.  Maybe that's what would work best for bassheads, but I think I'd give each sub 1.5 net cubic feet with the same slot port dimensions for a smooth response.  And install a pair of 30 Hz  f-mods to prevent below-tuning-frequency distortion.

If you want to learn how to design your own, get familiar with Win ISD Pro.  It's free and easy to work with once you get the hang of it.  That's what I was looking at.

A tip, too, on picking up more info:  use the forum 'search' button to learn more about specific topics and read opinions already posted.  (BTW, you can respond without a full quote each time...  :)





Posted By: bigwise1
Date Posted: January 08, 2005 at 1:27 AM
Yeah, that's my amp.  I have been searching but I was looking at opinions regarding my situation and equipment.  I looked at Win ISD and it's like trying to read a foriegn language.  I'm thinking about going with 2 12w6v2's in a sealed enclosure with the same amps.  A friend is telling me to go with these:https://www.woofersetc.com/product.asp?0=374&1=377&3=3073




Posted By: bigwise1
Date Posted: January 08, 2005 at 1:32 AM

I forgot to add another option I'm thinking about.  I also have a pair of 10w3v2's.  I was thinking about getting another a pair and running each pair off  a  zapco 500/1.  Hmm, I wonder how much space 4 10's would take up:)  What should I do?  It would be cheaper to go this route.





Posted By: overworked
Date Posted: January 08, 2005 at 10:37 PM
I cannot recommemd using mixed subs.....cause flat spots and peaks and various other things

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Posted By: bigwise1
Date Posted: January 09, 2005 at 12:02 AM

overworked wrote:

I cannot recommemd using mixed subs.....cause flat spots and peaks and various other things

no i'm not mixing subs. either 4 10w3v2's (each pair powered by zapco 500/1) or 2 12w6v2's (each powered by zapco 500/1)





Posted By: petergozinya
Date Posted: January 09, 2005 at 1:32 AM

lot's of good tech...input..one of them made my eye's go crossed  (lol)=0 . big wise...nice bass set up! sound's good in the car right? sound's bad with the trunk open. all of you can picture this( accept archmed..) take the windsheild out=( standing in front of the car now you're system sound's better than it dose inside.. why? think about what you just did accusticly. you gave it gain..by uttilizing the envirment it's in (a speaker in a tunnel or a speaker in a feild. in this application were are dealing with, all of us struggle to find the best of both world's. if you want you're sub's to sound good out side, give them reflection befor they enter the world other wise,they will go every where without control...

nice to get this out!

goood talking guy's    thad






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