EQ and Bass Management - AVS Forum
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post #1 of 6 Old 09-01-2013, 05:53 PM - Thread Starter
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I have a question that searching has not answered. Regarding manual EQing, let's say I choose +5db at 63hz for all 5 satellites in a 5.1 config and set all speakers to small with a 120hz x-over, does the receiver still boost the 63hz frequency by 5db, but send the boosted signal to the sub? Or is it ignored because that frequency is no longer output by the satellites? (I know it's not a brick wall)

Lastly, what happens when you raise or lower the speaker trim levels? If for example you raise or lower the center speaker by +/-10db (example only) does that effect the bass that the sub outputs below the center speaker x-over point?

Thanks in advance!cool.gif

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post #2 of 6 Old 09-02-2013, 04:45 AM
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Quote:
Originally Posted by D Bone View Post

I have a question that searching has not answered. Regarding manual EQing, let's say I choose +5db at 63hz for all 5 satellites in a 5.1 config and set all speakers to small with a 120hz x-over, does the receiver still boost the 63hz frequency by 5db, but send the boosted signal to the sub? Or is it ignored because that frequency is no longer output by the satellites? (I know it's not a brick wall)

The usual 12 dB octave high pass filters in your AVR's crossover are only about 12 dB down an octave below their corner frequency which is like 63 Hz wth a 120 Hz crossover.

If you boost overall response by 5 dB with a peaking you overcome almost half of this.

I'm thinking that you've discovered that if you boost 63 Hz to flatten the response of your system, your L & R speakers have audible distortion for peak levels.

The bottom line is that when you are out of dynamic range, you are out of dynamic range!

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Lastly, what happens when you raise or lower the speaker trim levels? If for example you raise or lower the center speaker by +/-10db (example only) does that effect the bass that the sub outputs below the center speaker x-over point?

Shouldn't. Speaker trims only affect the designated speaker.
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post #3 of 6 Old 09-02-2013, 05:03 AM
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Originally Posted by D Bone View Post

I have a question that searching has not answered. Regarding manual EQing, let's say I choose +5db at 63hz for all 5 satellites in a 5.1 config and set all speakers to small with a 120hz x-over, does the receiver still boost the 63hz frequency by 5db, but send the boosted signal to the sub? Or is it ignored because that frequency is no longer output by the satellites? (I know it's not a brick wall)

Lastly, what happens when you raise or lower the speaker trim levels? If for example you raise or lower the center speaker by +/-10db (example only) does that effect the bass that the sub outputs below the center speaker x-over point?

Thanks in advance!cool.gif

 

AIUI, no. Trim level settings only affect the speakers to which the trims are applied and this is independent of the setting of the crossover.

 

So in your example, you have boosted 63Hz by 5dB but you are telling the system to implement a crossover to the sub at 120Hz. So the 63Hz signal is never played by your satellite speaker but is sent to the sub instead. The trim level applied to the satellite has never had the chance to be implemented. 63Hz is now being played by your sub and the way to boost the level of the sub is via the sub trim setting. If you want to boost individual bass frequencies then you will need to add a parametric EQ between the preamp out and the subwoofer in (sub out/sub in) and use that to shape the response to your preference. I say PEQ rather than graphic EQ because the latter is just too crude to do much good - you really need the ability to affect not just the level but also the width of the correction.

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post #4 of 6 Old 09-02-2013, 06:30 AM
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Originally Posted by kbarnes701 View Post


So in your example, you have boosted 63Hz by 5dB but you are telling the system to implement a crossover to the sub at 120Hz. So the 63Hz signal is never played by your satellite speaker but is sent to the sub instead.

Not really.

Crossover filters in AVRs are never brick walls. The usual slopes are 12 dB/octave or in some cases 24 dB/octave. Using 12 dB/octave because its the most common, a 120 Hz 12 dB/octave high pass filter is only about 12 dB down at 63 Hz. Please see the blue line below:



(this drawing is for a 1250 Hz crossover, so you need to scale the frequencies by a factor of 10)

You might expect it to be as much as 15 dB down, but filter slopes are more gentle than nominal spec when they are close to the crossover frequency. If you add 5 dB via a peaking filter in the main signal path, it still affects response downstream of the crossover.
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post #5 of 6 Old 09-02-2013, 06:50 AM
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Quote:
Originally Posted by kbarnes701 View Post


So in your example, you have boosted 63Hz by 5dB but you are telling the system to implement a crossover to the sub at 120Hz. So the 63Hz signal is never played by your satellite speaker but is sent to the sub instead.

Not really.

Crossover filters in AVRs are never brick walls. The usual slopes are 12 dB/octave or in some cases 24 dB/octave. Using 12 dB/octave because its the most common, a 120 Hz 12 dB/octave high pass filter is only about 12 dB down at 63 Hz. Please see the blue line below:



(this drawing is for a 1250 Hz crossover, so you need to scale the frequencies by a factor of 10)

You might expect it to be as much as 15 dB down, but filter slopes are more gentle than nominal spec when they are close to the crossover frequency. If you add 5 dB via a peaking filter in the main signal path, it still affects response downstream of the crossover.

 

Agreed - I was ignoring the slope for simplicity's sake in my reply. The essence of my reply is, I believe, correct though.

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post #6 of 6 Old 09-02-2013, 10:49 AM - Thread Starter
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Thanks guys, the numbers I gave were all merely examples so we were all on the same page. I have wondered about this for a while and didn't have the knowledge on how to test it for myself.........Much appreciated!

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