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J

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Discussion Starter #1
Hey guys, it's me agian with another question, I just instaled my stereo suystem but it seems that it doesn't sound as is supposed to sound, I have 3 Alpine SWR-1221D 12" 2ohm subs with 3 amps, 1 amp for each sub, the port on the box is right through the rear deck but there is only 2 4" tubes coming in from the box, you think that the box needs to breath a little more? should I cut a bigger hole in the box and the rear deck? by the way the box is like a bandpass where the subs are inside the box and covered with a plexiglass, please comment on this one before I start cutting my rear deck, thanks

Here are some pics of the install

 
D

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Discussion Starter #2
Are the amps bridged or running each sub in stereo?

Also, if the amps are 4 ohms and the speakers power output is rated at 2 ohms, you wont realize the potential of the speakers since they will only receive loads of 4 ohms. Even if you run the amps bridged, they most likely bridge to 4 ohms. I think you may only be getting half the rated power of your amps at 4 ohms.

I wouldn't start cutting anything yet! You need to verify the power rating, output rating, and actually load the subs are being driven with.
 
J

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Discussion Starter #3
The amps are mono amps 500watt RMS at 2 ohms, and the subs are 300watt RMS 1000 watt peak 2ohm+2ohm dual voice coils, the sub and the amps should be an OK combo,
 
J

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Discussion Starter #4
Also ports are for tuning the frequencies of the box and not for letting the box breathe so cutting the rear deck would be bad. Is this a custom box made by somebody or a store bought box that is supposed to handle those speakers?
 
J

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Discussion Starter #5
I biult the box to fit the car my self, what I'm trying to say here is that the box only has 2 air outlets that are 4" diameter,
 
J

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OK, so you have a bandpass ported box. How did you know what size to make the ports? Did you use a computer or jsut kind of guess. Sorry just trying to figure out what ya did and help. If you just used those ports for the heck of it I would start to experiment with different port lenghts. Try a port that goes in the box a ways ans not flush with the outside and goign to up to the rear deck. Sounds like you tuned the box to a high frequency (like 90Hz) instead od a good 20-30HZ. I would make a two tubes that touch the box floor and reach up to the rear deck. Insert the tubes in the box (outside of car or pulled up to front of trunk). Start pulling the tubes up till the desired sound is found (a test cd would be great for this). Now the tubes will be to long. Push the tube bakc in the box about 1 inch (general rule) and then cut the top of the tubes to be even with the rear deck. You might even want to make 2-3inch tubes with a filler (since hole is 4") and try the same thing. My email is [email protected] if you want to talk about this offline.
 
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Discussion Starter #7
are your subs wired at 4 ohms or at 1 ohm? you just said your amps do 500wrms @ 2ohms but if your running dual 2 ohm subs, they can't be wired at 2 ohms. you would need dual 4 ohm, or dual 1 ohm subs. www.linearteam.dk and download winisd, its a speaker box design program. punch in your subs and your box size, and then your front size. then select bandbass, make sure u get the right order of bandpass box. then see if your mach port speed is in the green or red. it should be in the green, more the better. sounds like you didn't tune your box right, your subs are prolly getting 250 wrms so they should move alright. fill us in brotha
 
J

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Discussion Starter #8
I'm in the process of remaking the ports on the box, I will let you know how it turns out later, by the way the link that you just posted does not work, can you please post it again
 
C

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Discussion Starter #10
i just fixed it. i wasn't thinking when i posted it. what are the interior demisions of your box for the front and back. i'll run the numbers and see what i can come up with just to help.
 
J

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Discussion Starter #11
Camel, I will email you direct with the dimentions of the box off topic, later and thanks everyone for all your help
 
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Discussion Starter #13
Just for your info, I have pulled the tube ports out of the box and the sound is 5 times beter, I will try someting new and I'll let you guys know.
 
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Discussion Starter #14
Jose

You need to call Alpine & get the specs for the ports on the woofers, every Mfg is different & even some models are different from the same Mfg.

Port length is also very important. Not just por diameter.

Also your speakers are not wired right for you amps, it is eihter loaded to low of an ohm @ 1 ohm running in parallel (sp) (run hot & shut down) or not loaded enough @ 4 ohm in series (not get enough power from amp).

Also running multiple amps to mulitple speakers in a combined air space box can have some problems, not every amp puts out the same power at a certain level on the gains.

You might take it to a shop & have all the amps checked with a meter to make sure they are all working the same.
 
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Discussion Starter #15
I know what the problem might be. Well besides the box if that's not built right. It's not sounding as good because of restrictions getting into the cabin. I used to have 2 12's in the rear deck and the sound was awesome. Now i added 3 new 12's and put them back in the trunk. Let's just say i'm pretty dissapointed right now with that sound. I have pics for you to see. The first album is my new system and the second book(labeled older pics) has the 12's in the rear deck. If you are going to rebuild the box and have the skill to fiberglass and cut away some metal then put the subs in the rear deck. One of the first systems I had in the SS was 2 12's facing rearward. They were not that loud to I had a 12 by 6" inch hole cut in the rear deck. I had a grille with gray spreaker fabric put over it. If you're not going to put them right in the cabin than this might work for you. Sorry i don't have any pics of that old layout scanned. If you have any questions e-mail me. My e-mail is [email protected]. I have had many different layouts in the Impala and will definately share some secrets of how to get more pressure in the cabin. http://community.webshots.com/user/sean96ss

Sean Keane
96 BBB LISST
 
J

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Discussion Starter #16
How is it coming? I had already mentioned that port length was the problem and how to correct it. Alpine will not be able to tell him the port length without running a program cus his box is custom. They could give a rough estimate and the program mentioned above should do this as well. If you make a port the max. length and then pull it out of the box to the desired tuned frequency works. You are tuning by ear and what you like. Play some music you listen to or a buy a test cd. If the ports should not extend from the box however you can add tubes to the port to direct the air/sound into the cabin via the rear deck. Man it is so much easier showing then saying. If I get time this weekend I will make a AutoCAD sketch and post it.
 
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Discussion Starter #17
twig, i talked to a friend about how to tune a box by ear. he says that you can't tune by just pulling the port out of the box, because you still have the same port area. the only thing that changes is that the box displacement gets a little bit bigger each time. if your going to do it like that jose, you have to cut a little bit off the ports each time you pull the port out of the box. i'm going the rear deck route as soon as i save enough money to do so. sean if you have those specs for your old box in the rear deck i would love to see them, or even the demensions. i'l just curious what your final height was on the hump by the backseat. jose when i get your wisth of your box i'll run it in the program and see what happens.
 
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Discussion Starter #18
Hey Camel,

Sorry I had to destroy the old box to get it out of the car. It was actually 2 pieces. The one box went on the hump and rested there with two rectangles cut in it. The other box sttached to the box that was on the hump. I swear the people at GM don't build cars for us to put stereo's in. Well if you look at my old photo album you will see a pic of the box that rested on the hump. The other pics will show you the back part of the box. Sorry no dimensions on hand for the box. After the two were screwed together. Some liquid nail did an awesomejob of sealing the rest of the area. Only down fall the box wasn't coming out of the car together. Oh well if you have any other question e-mail me. See ya
 
J

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Discussion Starter #19
Guess I forgot to mention that part
. You cut the port about 1 inch from the top of the box so you can grab onto it. Sorry about that. Usually you do it in 1/2" to 1" intervals. It does not take long to do, maybe an hour. Unless you are slow at sawing :D
 
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