# REW and Sub EQ



## hifikid80 (May 30, 2016)

Hi,

I would like to know when EQ sub which option should i select in Speaker type in EQ window ? Should i select subwoofer or none?. I am trying to EQ my LFE output from the AVR, crossover is set at 80hz in AVR.

and what is the slope range (LF Rise, HF fall) i can experiment with?

Thanks


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## JohnM (Apr 11, 2006)

Select subwoofer and set the crossover filter settings to match those in the AVR. LF rise is the adjustment to alter to apply a form of 'house curve' to the target at low frequencies.


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## hifikid80 (May 30, 2016)

Hi,

Thanks for the reply. If i select sub woofer, the predicted response in not flatter then speaker type set to none. Is this normal?. screen shot attached.

and which crossover should i select 24db/octave or 12db/octave ?


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## JohnM (Apr 11, 2006)

Changing the speaker type is altering the target response. The target response of a sub output that has a crossover filter applied to it is not flat, it has the shape of the crossover filter.

It isn't really possible to say what the slope should be from the images you posted since the original response isn't shown. A sub crossover filter would normally be 24 dB/octave though. 

Make sure the test signal is actually passing through the crossover filter though, i.e. it is having the AVR's bass management applied to it (for example, signal is going into Left input, Left speaker is set to small, Left speaker itself is not connected so only the subwoofer is generating sound). If you apply the signal on an LFE input then different filtering is applied in the AVR, which may be a low pass at 80Hz, 120Hz, 150Hz or some other frequency depending on the AVR.


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## hifikid80 (May 30, 2016)

Hi John,

I have attached a new screenshot with settings, I am bit more confused now. should i EQ the output from a LFE signal (i.e HDMI Channel 4) or output from a L/R with the crossover from an AVR?. which is the right way to do?.

1. if i EQ the L/R output then i use Cutoff (HZ) value of 80 right? 
2. if i EQ the LFE output then i use Cutoff (HZ) value of 120 ( in AVR LFE set at 120) right? 
3. if you see my plot there are two big dip at 25 and 90 Hz , is there a way to fix them?. sub is already in the best position and cant be moved.

please help me to understand and EQ. thanks


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## JohnM (Apr 11, 2006)

hifikid80 said:


> 1. if i EQ the L/R output then i use Cutoff (HZ) value of 80 right?


Yes, if by "L/R output" you mean feeding a signal to the L/R channel, but only if you have turned off or disconnected the L/R speaker. If the speaker is playing you would be aiming for a full range overall target, since sub+speaker should be full range in combination. Your measurement does not look like a sub playing on its own.


> 2. if i EQ the LFE output then i use Cutoff (HZ) value of 120 ( in AVR LFE set at 120) right?


Yes


> 3. if you see my plot there are two big dip at 25 and 90 Hz , is there a way to fix them?. sub is already in the best position and cant be moved.


To have an impact on sharp dips within the sub range you would typically need to move the sub, or move the listening position, or add another sub elsewhere. Sharp dips often don't have as big an impact on the sound of the system as one might think from the graph, though, if you don't have flexibility in positioning just ignore them. Sharp dips near the crossover frequency with sub and main speaker playing together may indicate a problem with the sub phase setting, inverting the sub phase might correct that.


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