# Questions about parametric eq boost.

Discussion in 'Archived Threads 2001-2004' started by Jones_Rush, Apr 4, 2001.

1. ### Jones_Rush Stunt Coordinator

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Let's say I'm using a parametric eq like the BFD to boost 53hz by 4db and use a very small bandwidth for the boost.
By doing this I actually reduced the dynamic range of my system: BFD/AMP/SUB by 4db, the first one to "suffer" from this is usually the amp, if the amp is stronger than the sub then the sub will be the first to clip, and if both the amp/sub are stronger than the BFD, then the BFD will be the first to clip. My question is, after the first boost of +4db at 53hz, If I choose to boost any OTHER frequency at +4db (and make sure the bandwidth is small enough to not affect 53hz), will it further decrease the dynamic range of my system ?, according to common sense, any other boosting by 4db (at OTHER feq's than 53hz) shouldn't reduce the dynamic range any further than the first boost has already reduced it, am I right ?.
Another question, If I use a 250W amp and boost a frequency at 4db, does it mean that I'll now have the headroom of an approx 100W amp ?. If my calculations are correct, it means that those who use a 250W plate amp with the notorious +6db at 30hz boost, actually get headroom of a 65W amp. How can you watch a movie with a headroom of 65W sub amp ??? at enjoyable listening SPL's any "boom" will end with a clip...

2. ### Greg Monfort Supporting Actor

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Dynamic range is frequency dependent, so you haven't limited it over a wide BW. What you have limited is max wide BW continuous SPL assuming a ~flat FR.
250W = 10*log(250) = ~24dB. 4dB boost = 2^[(dB2-dB1)/3.01] = 2^(24-4/3.01) = ~100W (~20dB). 6dB boost = ~63W (~18dB) headroom at the EQ'd frequencies. The rest of the BW has ~24dB.
Whether this is sufficient is dependent on how efficient the speakers are, how far away you sit, program material, etc..
GM
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Loud is beautiful, if it's clean

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