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Old 25th November 2001, 08:34 PM   #1
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OK, so in my car, the bass soundles all muffled unless the driver side and passenger side windows are down. In summer its fine, but in winter, since im in utah, that doesnt work so well. How could I help fix this problem without needing the windows down? I also fold down both rear seats to allow more space for the air.....
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Old 26th November 2001, 12:01 AM   #2
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Smart *** answer - turn it down.

Real answer that will get pounced upon by smarter people than me. In a car, especially for low frequency stuff, it is like you are inside the speaker box (actually, its the other end of a band pass box). Opening the windows means the speakers have a much bigger box to work with. It also means that your ears are hearing the pressure waves without the compression that occures in that small box of a cabin. Those compressions can create standing waves, the position and frequency of which will vary within the car. This causes the response curve to vary a whole bunch, but with lower frequencys boosted the most. For my car, my subs in "free" air like when tested in my house, only vary by about 6dB from 30 to 120 driven by my house low freq amp (a Hafler DH-500). In the car, these same two subs vary by more than 20dB from what I measured outside the car. I can now get 120dB down to 20Hz in the car - but it is unlistenable at that level since the car so interfers with the natural response to the sound.

How to cure - A damn good parametric EQ will help. This type of EQ allows you to select the exact freq. to cut and boost, plus set the shape of that boost and cut. If you are using a band pass box, stop. For sound quality, a simple sealed box is better since it will have a simplier response curve for you to work with. You don't really need the gain that even a ported box will give you, however, it may be better for you. If you have a ported box, try plugging it up with a sock to see if that helps.

Cars are really hard places to make sound good. Begin reading up on the subject and by your next project you might get better results. Without regard, it will require you to experiment. What works great for one car, won't work in another.

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Old 26th November 2001, 01:07 AM   #3
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Yes its in a ported box.
socks wouldnt be able to stay, its pushing to much air
I still need to dynamat it as well which apperantly will help a bit
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Old 26th November 2001, 02:49 AM   #4
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Where are the subs located? If they are in the cabin, and you have a trunk, you might want to try relocating them to the trunk temporarily, so pressure levels in the cabin aren't as high.
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Old 26th November 2001, 03:57 PM   #5
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Dynamat by the pound will help some. Chasing down rattles is just part of the deal... I have tore lots of skin off my hands looking for a rattle in my dash. Door panels, trunk lids, basically any large chunk of skin needs to be secured.

If you can't get access to a freq. generator, get a CD with tone sweeps and your handy SPL meter. That it measures exactly the right number is not important - that it is accurate from one freq. is important. Start looking for dips and rises... measure from different places in the car too. Move the boxes around if you can. Plug up the ports a little and then alot. Write it all down and then do some thinking. You may not cure your problem, but it can help. Like I said in the earlier message, my car has the same problem at the really low end if pushed, but its at a point that you ought not be listening to it anyway if you want to hear in ten years.
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Old 27th November 2001, 05:39 PM   #6
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The car is a (dont laugh too hard now) 93 Saturn SL1
I have 2 12' Alpine Type R competition subs in the back in a custom ported box. (I will try to get a picture sometime soon so you can see what im talking about) I cannot move the box except a few inches, otherwise the trunk wont open/close. Now if I would have been smarter, i would have just gotten one sub. I didnt think they would be as powerful as they are (idiot) I say that cause they are only getting 120watts each and they are already pushing dents in the trunk lid

As for rattles

OH DEAR GOD THE RATTLES
Is there anything for the underbody other than that foam spray stuff, and how well does that work anyways? As for SPL meter, I dont have the 40 dolla for one right now, but maybe Radio Shack will let me borrow it for a few minutes in thier parking lot (am i cheap enough for you?)
When I bought these, i didnt think I would need to spend so much more money on more and more things. (Sigh) Ive given givin an estimate of 150$ to dynamat the trunk area, this a reasonable price?
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Old 28th November 2001, 04:11 AM   #7
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Default Wavelengths

The wave for 30 Hz is around 36' so a quarter wave which is used for tuning pipes and transmission lines is around 9'. You need 9' or what the speaker thinks is 9' inside the speaker box for 30 Hz to be generated and just to be fair over 18' to get a 30 Hz wave before it is doubling back on itself twice. The answer is that with your windows closed you can not achieve 30 Hz. Even if your speaker will do 30 Hz, if your windows are up the inside of your car won't allow it. Another thing to consider is that liquids don't compress. Is it 90% of your body is water? You pump a sound wave that hard and that often through your body and the things that will compress will do it so often that you will be damaged goods. Have fun!
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Old 28th November 2001, 02:46 PM   #8
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Default Re: Wavelengths

Quote:
Originally posted by Thatch_Ear
Another thing to consider is that liquids don't compress. Is it 90% of your body is water? You pump a sound wave that hard and that often through your body and the things that will compress will do it so often that you will be damaged goods. Have fun! [/B]
lol thanks

as for pluging the ports, i did so, and it didnt make much of a difference, if anything what i noticed the most is that really low hz were no longer around
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