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Adding a board under a sub on carpet


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4 replies to this topic

#1 of 5 OFFLINE   Chase

Chase

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  • Join Date: Jun 09 2002

Posted September 28 2004 - 07:26 AM

I have the JBL PB-12. A 12 inch downward fireing 250 watt driven sub. However I have noticed it can't repouduce frequinces in the 85-150hz range as strong as most subs do. If I put a wood board under it over the carpet for it to sit on would this help out any?
My system
----------------------
Onkyo TX-SR800 AV
Polk RT600i -front
Polk CS400i -centerPolk RT28i -surroundJBL PB 12 250watt -Sub36" Panasonic Panablack CRT

#2 of 5 OFFLINE   Lee Carbray

Lee Carbray

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Posted September 28 2004 - 08:13 AM

It is hit or miss at best. There is no telling what if any diff it would make or in what region. Have you plotted the responce of you sub? Where is your crossover? Possibly you have a phase issue. In the 85-150HZ if you have a typical 80Hz crossover your mains are having as much impact on the sound as you sub. The subs you have heard with better impact in this range, did you hear them in your system or with other speakers?
"You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer." Frank Zappa

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#3 of 5 OFFLINE   Chase

Chase

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Posted September 28 2004 - 08:52 AM

My speakers are the same ones I have used on some of my other subs. I have some smallmed size kenwood speakers at the momoent. I have the reciver set to small speakers cause they can't do much in that area. The sub's crossover is set around 120hz
My system
----------------------
Onkyo TX-SR800 AV
Polk RT600i -front
Polk CS400i -centerPolk RT28i -surroundJBL PB 12 250watt -Sub36" Panasonic Panablack CRT

#4 of 5 OFFLINE   paul clipsel

paul clipsel

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Posted September 29 2004 - 06:08 AM

I have a downfiring subwoofer and I could not measure any difference with a big mat under it or direct on the wood floor. If you have it in the best position you should measure the rooms freq response at the main chair and see whats happening. PC

#5 of 5 OFFLINE   Lee Carbray

Lee Carbray

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  • 308 posts
  • Join Date: Oct 23 2002

Posted September 29 2004 - 06:11 AM

With a crossover at 120hz phase could be the problem. Have you tried adjusting the phase on the JBL? The only way to really see if it is lacking in the region you are describing is to plot the output with test tones and an spl meter. But if you have some scrap wood give it a go. You may also want to try a patio stone. I have read people having good results with that. Not specifically for your problem but it may help
"You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer." Frank Zappa

Dealer listing for Toronto & Area

My Shiva




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