# How to EQ 2.1 without sub channel



## BloomBloom (Feb 15, 2013)

Hello there,
Im trying to figure out how to use REW to EQ my stereo setup.

It's a pair of B&W CM10 floor standers and a single REL S/3 sub.

I don't have a separate Sub channel and I'm sending all speakers a full range signal while using the cutoff and volume controls on the sub. 

my DAC is a Schiit Yggy and the speakers power amp is connected to it via the XLR outputs while the sub is connected to the RCA outfits (on the Yggy).

I'm applying the PEQ with Jriver.
The room is a rather reqtangualr 32sqm and 3m ceiling. 

I've been following these simple instructions to measure my speakers and generate EQ filters in REW:
https://mehlau.net/audio/room-correction-peq/

At first I ran this to both channels + sub at the same time and while it resulted in an improvement to the sound I got much better results from measuring each channel and generating (and applying individual filters). 

But I has a problem with the sub, so eventually I decided to measure each channel as one speaker and the sub operating on one channel (e.g. only the right input going in to the sub and the left disconnected). 

Now I have individual filters to each channel, which sound ok but I'm worried I may be EQing the sub twice - because its still a single driver and doesn't really have 'channels' as far as the audio output is concerned...

For example the left channel (Speaker and sub) has 3 filters bellow 70Hz:

36.4Hz -11.7dB 2.26Q
57.1Hz -8.5dB 5.33Q
67.8Hz -13.1dB 5.69Q
...and 2 other filters above

While the right channel (speaker + sub) has only one filter bellow 70Hz:

57.5Hz -18dB 2Q

the other is at 333Hz

Am I doing this right? Or do I double EQ the sub?

Please share your thoughts, 
Thank you!


----------



## tonyvdb (Sep 5, 2007)

Well, it is my understanding that applying EQ filters to both channels above 200hz should be done with care particularly if they are different for each channel. This can cause imaging cancelation between the left and right ch. 
Given that each channel is fed to the sub separately EQ should be applied to both however as bass is non directional the filters should be the same on both channels with one sub.


----------



## BloomBloom (Feb 15, 2013)

tonyvdb said:


> Well, it is my understanding that applying EQ filters to both channels above 200hz should be done with care particularly if they are different for each channel. This can cause imaging cancelation between the left and right ch.
> Given that each channel is fed to the sub separately EQ should be applied to both however as bass is non directional the filters should be the same on both channels with one sub.


Thank you, can you please clarify how I should proceed to EQ the sub?
I can't get the same filters to both channels if I'm EQing each speaker separately, as they are in slightly different acoustic surrounding...

Thanks, I'm learning, a bit slowly :flex:


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

BloomBloom said:


> Now I have individual filters to each channel, which sound ok but *I'm worried I may be EQing the sub twice* - because its still a single driver and doesn't really have 'channels' as far as the audio output is concerned...
> 
> For example the left channel (Speaker and sub) has 3 filters bellow 70Hz:
> 
> ...


With your set-up, unless you have the sub’s crossover set below 36 Hz, any low-end EQ you apply to the mains speakers will be applied to the sub as well. Not sure what you mean by “EQing the sub twice.” Unless you have dedicated EQ working on the DAC’s RCA outputs, then anything you apply to the sub will go to the mains as well.



> Or do I double EQ the sub?


Again, you can’t counter-equalize the sub with the equipment you have. The only way you will be able to apply EQ to the sub only will be to install an outboard unit between the DAC and the subwoofer. 

And even then, if you’re running the sub above 36 Hz, you won’t be able to fully counteract the filters you’ve employed. For instance, you have an 8 dB cut on the left speaker at 57 Hz and an 18 dB cut on the right speaker at 57 Hz. That means your sub has a 26 dB hole at 57 Hz (again, assuming you’re running it above 36 Hz). There’s no outboard EQ I know of that will allow for a 26 dB boost.

Your best bet is to run a measurement of your two main speakers with REW to determine their extension (i.e. what low frequency they start to roll out), and then only operate the sub below that point. Even at that you won’t be able to EQ the sub without an outboard unit.

Alternately, you could install an outboard electronic crossover, and that could divide out the lows and highs to the appropriate speakers.

Regards,
Wayne


----------



## BloomBloom (Feb 15, 2013)

Thanks mate,
I understand that without an active crossover any EQ to the lower frequencies will be applied to the sub and speakers together. 

My sub is crossed around 80Hz (via the sub controls) and it pays along with the speakers which results in reinforced and fuller bass. 

What I'm concerned about is that by paying an EQ to one channel of the sub it still plays the 'non EQed' other channel and as it's a single speaker what happens?

It obviously generates peaks in the bass - hence the EQ filters. 

I'm trying to figure out the best way of applying EQ/room correction with this set up.

Any advice is appreciated - thank you


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

BloomBloom said:


> What I'm concerned about is that by paying an EQ to one channel of the sub it still plays the 'non EQed' other channel and as it's a single speaker what happens?


There will be a sort of “averaging” to the subwoofer. What happens is that any EQ applied to a single channel will show up in the sub as half of what you applied. For instance, if you applied a 10 dB cut at 40 Hz in the left channel only, it will show up as a 5 dB cut in the subwoofer, as the signal from the right channel that has no EQ at that frequency will negate some of the effect of the left-channel filter.

However, if you apply filters for both channels in the same frequency range, as you did at 57 Hz, the results will be “stacked” or cumulative.




> I'm trying to figure out the best way of applying EQ/room correction with this set up.


We typically recommend that people with multiple subs equalize them all as a single entity. The issue with trying to fine-tune each sub is that you’ll get a nice graph for each one individually, but when you play them all together you’ll find that response is a mess. Thus we recommend equalizing them all with a single set of filters, as if they were a single sub. Makes sense when you think about it: Bass frequencies are omnidirectional, so you don’t hear each sub individually, you just hear a single signal.

The same tact will work in your situation, too. Take a measurement from 15-200 Hz with both speakers and the sub running, and equalize based on that graph. You’ll have to apply matching filters to both channels.

Regards,
Wayne


----------



## BloomBloom (Feb 15, 2013)

Thanks!
I'll give it a try. though just to clarify I have one sub (that has two RCA inputs - left and right.

Part of my puzzlement is that I'm not sure my settings for the sub (cutoff and volume controls on the sub) are set up properly before I ask REW to generate an EQ. For example if I disable the EQ and listen to the music 'au naturale' the sub is way to loud - the EQ brings it back o decent sound levels - though perhaps there's a way of doing even less EQ with the right settings on the sub?


----------



## tonyvdb (Sep 5, 2007)

On the rear of the sub there should be a level control and a crossover. you want to set the crossover at 80Hz ideally. your EQ settings on the sub are likely parametric?


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

BloomBloom said:


> I'll give it a try. though just to clarify I have one sub (that has two RCA inputs - left and right.


Yes, I was aware of that.



> Part of my puzzlement is that I'm not sure my settings for the sub (cutoff and volume controls on the sub) are set up properly before I ask REW to generate an EQ. For example if I disable the EQ and listen to the music 'au naturale' the sub is way to loud - the EQ brings it back o decent sound levels - though perhaps there's a way of doing even less EQ with the right settings on the sub?


As Tony indicated, setting the sub’s crossover in the 80-90 Hz range is the norm, but that’s assuming there is a high-pass filter in the equation. In your situation, where the sub’s crossover _should_ be set it is anyone’s guess. You’ll have to make that call, since you’re using it more to give a bottom end boost rather than add extension, depending on if you want reinforcement for the lowest frequencies, the entire bass range, or somewhere in between, etc.

If the sub is too loud without EQ, then your EQ is probably doing double-duty as a level control. That’s poor form - not the way an equalizer should be used. I’d suggest bypassing the EQ, turn the sub down very low, play a pink noise signal through the mains and sub, and then raise the sub’s level to where you want it, to add the amount of reinforcement you’re looking for. After that, take new measurements and apply new filters as described in my previous post.

Regards,
Wayne


----------



## BloomBloom (Feb 15, 2013)

Thanks Wayne, 
I suspect my room is causing the weird SUB/lower bass behaviour. 

I might post some measurements once I figure out how to do it... Sadly life/work interfere with Audiophila...


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

BloomBloom said:


> Thanks Wayne,
> I suspect my room is causing the weird SUB/lower bass behaviour.


Of course it's the room. Nothing unusual there, just about all residential rooms have bass issues. Proper placement and EQ can effectively deal with most of it.

Regards,
Wayne A. Pflughaupt


----------



## BloomBloom (Feb 15, 2013)

Hello again,
Here is a measurement using Pink noise PN

For some reason the SPL level isn't calibrated - I'm using a Umik-1 mic - so REW says it's already SPL liberated...

The reason the sub is set high s the dip at around 80z, if I lower the usb that dip will become a real 'cavity' - so I set up the sub high and then EQ it.
I also tried applying a house curve...

Any advice is welcome. Thank you.


----------



## BloomBloom (Feb 15, 2013)

I think a big part of my problem is that my room is slightly not quite rectangle...

I attach a proper survey model of the listening room. I try to divide the room in 5 (or 4) equal parts and place the speakers at the intersections along the top 1/5 of the room.
Because of the angled back wall one speaker has more space than the other and so sound a bit weaker... even though they are around more than 1 meter away form the back wall...

My listing position (sofa, really) is along the lower 1/5 of the room in the horizontal middle. 

Also, I'm not sure how to model this shape into REW room simulation because its not a symmetrical square. 

I'd love to hear your thoughts. 

Thanks,


----------



## Wayne A. Pflughaupt (Apr 13, 2006)

Actually, the more _non_-symmetrical a room is, the better.

Have you tried EQing the speakers and sub as I recommended in Posts #6 & #8? If not I really don’t have anything to add, except that it would be helpful to add your speaker and sub located to your diagram so we can know where they’re located in the room.

Regards, 
Wayne


----------



## BloomBloom (Feb 15, 2013)

Thanks,
I did follow your advice - of EQing the sub and speakers together.

I think I should sort out the speaker locations first and then progress. 

One of my problems wit this room is that it's not symetrical, so when trying to follow the rule of thirds (or the 0.29 variation) I'm not sure which wall to measure...

I'll try to add the current speaker locations - I don't have an image editing software on this computer.

Thanks!


----------



## Lumen (May 17, 2014)

I agree with Wayne and would like to see where you intend to put the speakers/subs. You need to start somewhere; so first try general positioning, then measure and fine-tune. The "rule of thirds" applies to rectangular rooms, not your asymmetrical one. You can still benefit from it by locating each speaker a different distance from the side and front walls. For example: if distance from tweeter to side wall is 3 feet, then make distance to front wall 2 feet or 4 feet. Avoid even multiples like 3 feet to side and 6 feet to front.


----------



## BloomBloom (Feb 15, 2013)

Thanks,
Here is my bad sketch of the room and positions. the think black line on the right side of the room represent the real boundary - taters a big library there - it doesn't show in the room plan.

I tried to place the sub in the top right corner (as per REL's recommendation) but think it sound better in the middle between the speakers. 

I'd be grateful for any recommendations regarding the speaker placement. Do to various factors I can't place them anywhere other than along the top wall. I think they should be further away form the back wall because I don't really get a 3D soundstage - not much sense of depth. 

I tried to follow the rule of thirds by dividing the room into 5th and placing the speakers along those intersections - I know understand that I probably placed them in less then ideal position as the distance form the side wall to the back wall was very similar (around 1.06m). Once I find a good place for the speakers I'll deal with the sub.

EDIT: 
The speakers (B&W CM10s) and sub are floated on Townshend seismic isolation bars. The room has a wooden floor and the ceiling is quite reflective. 

Thank you!


----------

