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Old 07-06-2007, 11:51 AM   #1 (permalink)
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Subwoofer Box, should I vent it?

I just bought a 15" subwoofer and I decided to build the box myself... 12" deep x18"x18" I think it may be on the small side. The base sounds really good at low volumes but when I go over anything over half power it just sounds like it rattles and it doesn't get any louder.

So i'm wondering if I should vent the box, if that would help?

I'm not very educated when it comes to sound systems, so help is appreciated.
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Old 07-06-2007, 12:18 PM   #2 (permalink)
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Re: Subwoofer Box, should I vent it?

What sub are you using? How did you set the gains? (Not what position, but what procedure?) What is the rest of the system?

In general when porting a sub you will need a larger enclosure for it to work out right, unless the box is already too big.
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Old 07-06-2007, 01:15 PM   #3 (permalink)
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Re: Subwoofer Box, should I vent it?

The in dash unit is a panasonic CQ-C7301U has a separate subwoofer control feature. The sub is a Visonik V15S4(500w rms 800w max). I bought the amp used, its a sony xplod 480 watt. I was just using the settings that was already on it: LPF was set at 50hz low boost gain was set at +10db. I have tinkered with it for a while and The best sound I have found is with the setting stated and on the unit I set the LPF at 80hz and the HPF is off. What exactly is the low pass filter and the high pass filter for?
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Old 07-06-2007, 02:17 PM   #4 (permalink)
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Re: Subwoofer Box, should I vent it?

the cubic footage of your box should be tuned to your sub...

it's been awhile for me, but i'm sure the best sound is going to come from custom made boxes sized right for your speakers specs...
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Old 07-06-2007, 03:03 PM   #5 (permalink)
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Re: Subwoofer Box, should I vent it?

One other thing to try before venting it, is filling the box about half full with poly-fill (fake snow) available at any crafts store. It helps take some of the "slap" out of subs, especially larger ones.
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Old 07-06-2007, 03:15 PM   #6 (permalink)
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Re: Subwoofer Box, should I vent it?

Yeah I would try porting it. Probably put a ~14" piece of 1.5" ABS across the back the end cut cut at a slant (30 degrees). Don't just make a hole.
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Old 07-06-2007, 03:50 PM   #7 (permalink)
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Re: Subwoofer Box, should I vent it?

http://www.carstereo.com/help/Articles.cfm?id=5

you need to use the golden ratio when building your box. You should be able to find lots of information floating around on google about porting.
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Old 07-06-2007, 03:55 PM   #8 (permalink)
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Re: Subwoofer Box, should I vent it?

I will go out on a limb here and guess that your box is entirely too small for a 15" sub. That box is probably to small for a 12" sub.

As stated above you can stuff with Poly material. That fakes the sub into thinking it has a bigger box. Other wise you ll have to get a smaller sub woofer or learn to live with it.

Porting the box will only make your problem worse.
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Old 07-06-2007, 04:29 PM   #9 (permalink)
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Re: Subwoofer Box, should I vent it?

vent it. but ur box is too small. sorry dude what u could do is put a bigger amp in it. ur amp says 480 but that is its max and at its max it sounds like crap i would never suggest bridging amp it sounds bad and its horrible for ur amp. so i say buy a new box or make a new one that is much bigger. u could buy a vented box and it will rock ur world. i love vented boxes but i like my back seat [img]/ubbthreads/images/graemlins/grin.gif[/img]. ill try to send u some pics of my set up. but i have 2 cvr 12s in littl boxes and they hit pretty hard.
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Old 07-06-2007, 04:45 PM   #10 (permalink)
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Re: Subwoofer Box, should I vent it?

The manual for the sub called for a box between 1.5 cubic feet and 2.25 cubic feet, I'm pretty much right in the middle of that slot. I think I'm going to find an old pillow I don't care for and put that stuffing in there and see if it helps. Thanks all.
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Old 07-06-2007, 06:15 PM   #11 (permalink)
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Re: Subwoofer Box, should I vent it?

[ QUOTE ]
The base sounds really good at low volumes but when I go over anything over half power it just sounds like it rattles and it doesn't get any louder.

[/ QUOTE ]

You're either running into over-excursion or the amp is clipping. Porting/polyfill won't help this.
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Old 07-06-2007, 06:40 PM   #12 (permalink)
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Re: Subwoofer Box, should I vent it?

Whats "over-excursion" I actually made a few adjustments on the amp and it sounds much better, I think part of my problem it the box I built, It seems to vibrate too much.
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Old 07-06-2007, 07:16 PM   #13 (permalink)
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Re: Subwoofer Box, should I vent it?

[ QUOTE ]
Whats "over-excursion" I actually made a few adjustments on the amp and it sounds much better, I think part of my problem it the box I built, It seems to vibrate too much.

[/ QUOTE ]put lots of wood glue between the boards when u drill it that will take out some of the vib.
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Old 07-06-2007, 09:58 PM   #14 (permalink)
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Re: Subwoofer Box, should I vent it?

[ QUOTE ]
Whats "over-excursion"

[/ QUOTE ]

It's when the speaker's diaphragm (basically cone + voice coil) travel far enough that the coil moves out of the magnetic gap. In most cases, it means that the sound becomes distorted because the coil cannot control the cone until the speaker's suspension "snaps" it back into the magnetic gap.

In extreme cases, the diaphragm can travel so far that the voice coil bobbin hits the backplate of the magnet assembly. This usually sounds like a loud "crack" or pop, and is hard to miss.

[ QUOTE ]
I think part of my problem it the box I built, It seems to vibrate too much.

[/ QUOTE ]

what material did you use, and how thick?
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Old 07-06-2007, 10:35 PM   #15 (permalink)
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Re: Subwoofer Box, should I vent it?

[ QUOTE ]
[ QUOTE ]
Whats "over-excursion"

[/ QUOTE ]

It's when the speaker's diaphragm (basically cone + voice coil) travel far enough that the coil moves out of the magnetic gap. In most cases, it means that the sound becomes distorted because the coil cannot control the cone until the speaker's suspension "snaps" it back into the magnetic gap.

In extreme cases, the diaphragm can travel so far that the voice coil bobbin hits the backplate of the magnet assembly. This usually sounds like a loud "crack" or pop, and is hard to miss.

[ QUOTE ]
I think part of my problem it the box I built, It seems to vibrate too much.

[/ QUOTE ]

what material did you use, and how thick?

[/ QUOTE ]

Gotcha, as for the material... well... kill me now. I was too impatient to go to Home depot and buy MDF board so I used some 5/8 plywood I had laying around and braced it internally with 2x4s. I thought to myself even if this box doesn't work, I didn't waste any money, right? I knew it was temporary anyways, but I still wrapped it with this high grade carpet left over from our house, and it matched my interior. I have plenty of carpet to use on another box, and I think there will be another box in the future for me to build. [img]/ubbthreads/images/graemlins/crazy.gif[/img]
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