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Old 29th November 2009, 10:58 PM   #1
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Default Is my sub broke or is it the amp?

I have a JBL sub that has a preamp and its about 15 years old. I had a new speaker installed a year ago and it has never played as well since. It clearly will not play as loud as it did new. As a matter of fact I have it turned up all the way and before it would have shook the windows. I also have the output from the home amp feeding it at it max also. I'm thinking I need a new amp or could it be a poor speaker? Its a 12" sub...
Thanks in advance for any input.
Terry
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Old 30th November 2009, 12:23 AM   #2
gooki is offline gooki  New Zealand
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Was the replaced speaker the same as the original one?
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Old 30th November 2009, 07:11 AM   #3
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One of the first things you'll learn here is that you can't stick any driver in a pre-made box and expect it to sound it's best.

All speakers have things called Thiele-Small parameters. You don't need to worry about what they mean, but you must remember that they define what kind of box a woofer likes, how large the box will be, etc. The parameters differ for different woofers, therefore, a box that sounds good with one woofer will (90% of the time) sound rubbish with a different woofer, or, at least, sub-optimal.
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Old 30th November 2009, 09:58 PM   #4
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And to complete the conversation... much more detail is required to provide an answer for you. Just saying it was a 15 year old 12" JBL doesn't assist us in helping you. There are three ways to fix a loudspeaker (the whole unit, driver + cabinet). Either take the driver to have it reconed to the same original specs, select a new similar T/S parameter driver or design a new cabinet for use with a new driver. Just slapping some whatever replacement in your old cab will result in exactly what has happened to you.
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Old 4th December 2009, 08:29 PM   #5
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Well I did not realize its not as easy as tossing a speaker in a box and adding watts.
OK, well I think about and I had the speaker reconed. Will what I know and what I'm telling you, would it be safe to say the amp is fine and its more to do with the combination of box amp and speaker?
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Old 5th December 2009, 07:29 AM   #6
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There's a decent chance it's the speaker and box combination. If the box is ported, block the port and see if you get anything new. Sealed boxes will provide some kind of output, as long as it's of reasonable size. With ported boxes, there's no telling what it's doing...
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