Question: Do you defeat your sub's crossover? - AVS Forum
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post #1 of 12 Old 08-02-2013, 04:19 AM - Thread Starter
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In my basic setup, my AVR lets me set a crossover frequency for the sub-out. So, theoretically, I should then defeat the crossover control on the sub, right?. But, I find I prefer the sound when I instead set the crossover on the sub to the same frequency as the AVR. Whiie I may be tone-deaf, somehow, it sounds as-if some higher-pitched signal still passes to the sub despite the AVR's setting. (AVR is Denon 3808ci fwiw).
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post #2 of 12 Old 08-02-2013, 05:09 AM
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Originally Posted by cjvnyc View Post

it sounds as-if some higher-pitched signal still passes to the sub despite the AVR's setting. (AVR is Denon 3808ci fwiw).
That's because it does. The AVR filter is not brickwall by any means, and as much as two octaves of above bandwidth content can be audible. Using the sub filter as well cascades the filter slopes and will remove far more above bandwidth content than either the AVR or sub low pass filter alone.
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post #3 of 12 Old 08-02-2013, 05:21 AM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

That's because it does. The AVR filter is not brickwall by any means, and as much as two octaves of above bandwidth content can be audible. Using the sub filter as well cascades the filter slopes and will remove far more above bandwidth content than either the AVR or sub low pass filter alone.

Thanks, Bill- I was worried I was imagining the effect.
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post #4 of 12 Old 08-02-2013, 05:42 AM
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Originally Posted by cjvnyc View Post

Thanks, Bill- I was worried I was imagining the effect.
This is one instance where you can trust your ears. wink.gif
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post #5 of 12 Old 08-02-2013, 07:44 PM
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I just recently discovered the same thing! My yamaha must have a very shallow roll off after the cross over because I found my subs sound much better when the sub cross is set the same as the avr. I actually got the idea from you Bill in another thread! Just want to say thanks for the tip!! I have learned alot from you in the last few months!!!
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post #6 of 12 Old 08-02-2013, 07:57 PM
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Just want to say thanks for the tip!! I have learned alot from you in the last few months!!!

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post #7 of 12 Old 08-02-2013, 10:14 PM
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Yup, Bill knows his stuff. Typical AVR roll-off is 12 dB/octave. That means for an 80 Hz crossover setting, 150 Hz is about half as loud. That is significant, and actually probably even sounds louder due to volume compression in the low frequencies. Putting the sub and AVR at the same point typically yields about 24 dB/octave and those higher frequencies (over the crossover) will be much better suppressed.

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post #8 of 12 Old 08-03-2013, 06:34 AM
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Originally Posted by DonH50 View Post

Typical AVR roll-off is 12 dB/octave. That means for an 80 Hz crossover setting, 150 Hz is about half as loud.
It can be just as 'loud'. Look at an Equal Loudness chart. 150Hz at 85dB is heard at the same volume as 80Hz at 95dB, so with only 12dB/octave filtering the sub can be easily located. AFAIK most newer AVRs use 18dB/octave filters, but that still leaves a lot of directional frequencies coming from the sub. But if the AVR filter is just 12dB and the sub amp filter is 12dB the total slope is 24dB/octave, and that's enough to do the job, even with a 100Hz crossover.

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post #9 of 12 Old 08-03-2013, 07:41 AM
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That's what I meant by volume compression. No argument.

I read 12 dB/oct in the subwoofer forum. I have several AVRs in the house and it looks like none of them list the crossover slope...

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post #10 of 12 Old 08-03-2013, 08:32 AM
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If it's a THX receiver or pre/pro, it's gonna have a 24 dB/octave slope.

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post #11 of 12 Old 08-03-2013, 01:24 PM
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I'm curious. Should the filter on the sub be set at 120hz since LPF of the LFE is recommended to be set at 120 on the receiver? I must say I am getting less localization of my sub by adjusting the filter on the sub. I have the receiver crossover set on 80.
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post #12 of 12 Old 08-03-2013, 01:33 PM
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No, leave the sub crossover at 80 Hz. Bass management should pass the higher LFE signals to the mains (except for Pioneer).

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