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Old 11th September 2012, 11:29 PM   #11
DrDyna is offline DrDyna  United States
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Quote:
Originally Posted by dareo View Post
I have a JBL GTO 14001 car amp and a power supply to run it.
What kind of power supply? You'd have to have something seriously beefy to supply enough current to satisfy that amplifier.

Car batteries with hundreds of amps of current capability are very hard to duplicate in a power supply.
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Old 12th September 2012, 12:17 AM   #12
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Originally Posted by dude2010 View Post
Err.. what??
Yep, much stiffer than mdf and stiffer than baltic birch too. Should be internally damped with a coating though.
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Old 12th September 2012, 12:18 AM   #13
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...but what liter size- and type enclosure, to reach under 20 hz straight?
Am I better off with an Earthquake unit instead? In fact how are they compared?
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Old 12th September 2012, 02:12 AM   #14
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Here's a pic of what i actually built.

It ended up being 2 layers of .75" MDF for the front, and 2 sheets for the top/bottom with bracing for the rest. The box took nearly 2 full 4x8 sheets and a It is slightly more than 12 cubes, port was a bit more than 8" tuned between 21hz and 22hz.

Power supply puts out 35 amps at 15 volts or about 525 continuous watts. The amp is not getting all the current it wants but it still can produce 120 decibels at 3' distance without distortion. I could beef up the DC current but this gets it more than done.

Click the image to open in full size.
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Old 12th September 2012, 05:48 AM   #15
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Quote:
Originally Posted by dude2010 View Post
...but what liter size- and type enclosure, to reach under 20 hz straight?
Am I better off with an Earthquake unit instead? In fact how are they compared?
At least 567 L vented to a 16 Hz F3, so will need some room gain to get it 'flat'.

Not familiar with Earthquake subs.

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Old 12th September 2012, 01:52 PM   #16
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Quote:
Originally Posted by dareo View Post
Here's a pic of what i actually built.

It ended up being 2 layers of .75" MDF for the front, and 2 sheets for the top/bottom with bracing for the rest. The box took nearly 2 full 4x8 sheets and a It is slightly more than 12 cubes, port was a bit more than 8" tuned between 21hz and 22hz.

Power supply puts out 35 amps at 15 volts or about 525 continuous watts. The amp is not getting all the current it wants but it still can produce 120 decibels at 3' distance without distortion. I could beef up the DC current but this gets it more than done.

Click the image to open in full size.
When using a power supply like this, does it make sense to put a large cap or SLA battery in parallel? I'm also looking to run a car amp off a power supply.

That thing must be heavy.
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Old 12th September 2012, 02:48 PM   #17
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The box alone took two people and a dolly to get up the stairs. I could add a capacitor but like i said, for home theater use, its plenty. I don't usually turn it up high enough to dim the lights on the amp. It plays lower than i can hear, shakes all different parts of the house, and probably can be heard from the adjacent houses as is. A cap, battery, or even second supply could be installed parallel for more current. I probably would have built it smaller if i did it again today, but this huge box is amazingly efficient. I bought the subs from a guy who had TWO in 4.2 cubic feet sharing a port. He thought they sucked, but it was his box! I also designed this so that i could convert it to a dual sealed box by enlarging the port. However i think i'l use the second GTI in my car or something as i'm happy with what this can do.
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Old 12th September 2012, 03:20 PM   #18
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Quote:
Originally Posted by dareo View Post
The box alone took two people and a dolly to get up the stairs. I could add a capacitor but like i said, for home theater use, its plenty. I don't usually turn it up high enough to dim the lights on the amp. It plays lower than i can hear, shakes all different parts of the house, and probably can be heard from the adjacent houses as is. A cap, battery, or even second supply could be installed parallel for more current. I probably would have built it smaller if i did it again today, but this huge box is amazingly efficient. I bought the subs from a guy who had TWO in 4.2 cubic feet sharing a port. He thought they sucked, but it was his box! I also designed this so that i could convert it to a dual sealed box by enlarging the port. However i think i'l use the second GTI in my car or something as i'm happy with what this can do.
I'm sure it's pretty awesome. I have a long throw 15" in about 4 cubes for my truck, and it's actually pretty flat response wise that size enclosure, but not tuned nearly as low. Based on the datasheet, looks like the jbl needs a bigger box and low tune to have a flat response.

I would throw in a cap just for peace of mind. I'm not sure what a lack of current during transients would do, maybe a voltage droop that could push the amp into clipping? I'd look into it.

Last edited by turbodawg; 12th September 2012 at 03:23 PM.
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Old 16th September 2012, 11:55 PM   #19
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Does anyone know the difference between 15W GTI MK II with:
Silver "JBL" dustcap
and
Black, White, Orange "JBL 5000WATTS" dustcap?
JBL - W15GTi MkII - 15" Subwoofer with Kevlar®-impregnated-paper woofer cone and Dual 6-ohm voice coils
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Old 18th September 2012, 02:50 PM   #20
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Default Power supply

I used a car amp for my subs (a car crossover too) and kept blowing power supplies.
I was using Pyramid 0-14V, 35 amp power supply (MCM-$125) for a 300 watt amp, that lasted 6 months and smoked.
It was a class D amp and should have had no problems with a 35 Amp power supply. Also, the speaker impedance was limiting it to closer to 200 watts.
After the second power supply smoked, I bought a 1 Farad cap and put that in parallel with the power supply.
What a difference, it sounded tighter, way better and the power supply lasted 10 years until a crappy wiring job shorted it and it smoked.
.
WARNING SECTION:
I finally just brought an old car battery inside so I could have music.
With nothing hooked up to the battery, no amp, no charger....BOOM.
I was not home when it happened and have no idea why it happened.
It blew acid in a line all the way up one wall, across the ceiling and down the other wall.
It left a puddle that dissolved my industrial tile and was just a disaster.
Don't ever try it, even just for that one afternoon when you need something to power your amp.

A word to the wise is sufficient,
Dave
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