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Old 9th February 2007, 11:39 PM   #1
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Default Subwoofer amp basics question

I tried to use search to get an answer to this but with no success.

Could anyone explain to me in a basic way how manufacturers take a sub amp and modify it to get a lower roll-off from their sub in its cabinet? For instance, I think the midbass sound my JBL 2020h creates is second to none, but it dies at 70hz. What if I could tweak an amp to get it down to 50hz? I don't know anything about amps; I'm just trying to get a basic understanding of how amps are modified to produce more power at certain frequencies.
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Old 10th February 2007, 03:59 AM   #2
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Maybe this could be your solution.
http://sound.westhost.com/project71.htm

or this

http://sound.westhost.com/project48.htm
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Old 10th February 2007, 07:20 AM   #3
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you have preamp circuitry with rolloff at 70 hz. you need to find any coupling capacitors in your preamp section and either increase the capacitance, or if they're not blocking DC, remove them and replace them with wire.
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Old 10th February 2007, 09:33 AM   #4
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"you have preamp circuitry with rolloff at 70 hz. "

He has a JBL 2020H, can you say: no bass, zip, nada?

This driver has Fs=60hz, low, low, low Qts=0.23, that spells no bass.

If you use the recommended venter box tuned to 40hz, it will be 92dB at 40hz, and over 105dB at 2Khz.

It has a coil overhang of 0.05", so don't bother trying to boost the bass.

This driver is intended for maximum midbass output on a large horn.
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Old 10th February 2007, 10:12 AM   #5
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Quote:
Originally posted by unclejed613
you have preamp circuitry with rolloff at 70 hz. you need to find any coupling capacitors in your preamp section and either increase the capacitance, or if they're not blocking DC, remove them and replace them with wire.
Sorry but who in their right mind is going to build a pre-amp that rolled off at 70Hz.

There is no need to change any caps. The issue is the driver.
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Old 10th February 2007, 01:42 PM   #6
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Well that particular driver is a side issue anyway; I was looking at the current 'low frequency' models by JBL as well. But the links are great. At least now I can get a handle on how its done.
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