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SB12+ REW curves and positions

1pudding1

Established Member
Hi. I took delivery of my new SB12+ sub last Friday, and have just been playing with various positions and REW now Ive a day off. This is my 1st sub and time doing anything like this so would like any advice.

Ive tried 6 positions for the sub and have generated response curves for each. In each position I re-ran the input calibrate and input volume setups in REW. These are the 6 graphs Ive got. Which is the best? All controls on the back are off. Only the gain has been changed so far on the sub and left in a fixed position for all graphs.

Position 1 = in between front right speaker and TV stand facing forward


Position 2 = Along right wall ~50cm forward of front right speaker facing diagonal into room


Position 3 = Along right wall ~50cm from rear right speaker facing into room


Position 4 = Along rear wall begind sofa next to center rear speaker


Position 5 = Under staircase in middle of left side of room facing across into the room


Position 6 = Under staircase in front left corner of room facing diagonal into room


I dont think the overall gain level in all positions is quite correct, but i suppose its the shape which is more important at the moment; I can change the level after the response shape is better. Comments and recommendations welcome. :thumbsup:
 

AngelEyes

Distinguished Member
I would try moving it very slightly around position one to try and lose / reduce the dip at 37hz. Even a few inches can make a difference.

If your speakers aren't currently switched off / disconnected try position 1 again and see what difference that makes. Once you have the curve as good as you can get it add the speakers and adjust crossovers and phase to try and integrate with the mains.

Adam
 

1pudding1

Established Member
Ive currently got the output from my PC connected directly to the input on the sub. I'll try to tweak position 1 then connect the input to my amp and see how it looks with the main speakers too. Ta.
 

AngelEyes

Distinguished Member
You really need to go via the Receiver or your volumes will be off. You are EQing for your favourite volume or reference volume, so you need to have the volume on your amp set to that all the time.

Also this will be the only way to adjust the levels of all the speakers, sub included to the correct volume for a smooth curve.

Adam
 

1pudding1

Established Member
Well Ive been running up and down the stairs like a madman fine tweaking the settings, bloody knackered now! Hard work this subwoofer malarky. Ive connected the REW output into my amp, and have all speakers playing so have the complete response output. Here's the best Ive got so far:



I have all speakers set to small and the amp's crossover at 80Hz. I found that the response was slightly better if I also enabled the sub's crossover and set that to the maximum of 120Hz, and filled in a few dips.

I also used the P-Eq on the sub to remove the hump at about 50Hz. Took a while to get the frequency knob for that spot on, and at first I didnt think I could get rid of it, but was worth persevering. There's a large dip around 65Hz, but I cant seem to do anything about this :mad: Does this look a fairly respectable freq. response now?
 

AngelEyes

Distinguished Member
Don't use the crossover on the sub, just the one on the amp. You can get in a right pickle if you try and use both.

If your speakers go much lower than 80hz you could try lowering the crossover to let the speakers fill in some of the lower troughs. Also experiment with the phase in this respect as it may affect the crossover area.

The graph is ok but not ideal. A house curve is preferable which means your entire graph gradually slopes up until the sub drops off at the lower frequencies. At the moment your speakers are quite high compared to the most common mid-bass your sysetm should produce.

Adam
 

AngelEyes

Distinguished Member
Hopefully someone will chip in with some more advice, I am not really an expert but have spent more than a few hours messing about :D
 

1pudding1

Established Member
Ok crossover on the sub is off. The crossover freq is currently at the lowest it can go on the amp at 80Hz. I hadnt thought of playing with the phase so will give that a go.

Not exactly sure what you mean with the house curve? The response is with both sub and mains, so i was trying to obtain a flat response until the sub response slopes off at the lower freq's?
At the moment your speakers are quite high compared to the most common mid-bass your sysetm should produce.
Lost me here :confused:

Thanks for all the help :thumbsup:

Oh, and all the measurements were made with the automatic measurement from 20-500Hz, hope that ok?
 

AngelEyes

Distinguished Member
Not exactly sure what you mean with the house curve? The response is with both sub and mains, so i was trying to obtain a flat response until the sub response slopes off at the lower freq's? Lost me here :confused:

Thanks for all the help :thumbsup:

Oh, and all the measurements were made with the automatic measurement from 20-500Hz, hope that ok?

A house curve is basically not a flat line but one that emphasises the bass in your system. So instead of aiming for a flat response have the main speakers lower than the peak of your sub output. A gentle sloping curve going up as the frequency goes down is great fro movies as you get slightly more volume at the lower bass which is where the fun is.

I will try and find a picture somewhere...

Adam
 

AngelEyes

Distinguished Member
See how this graph gradually goes up...

This is a typical house curve. The pink curve is the improved EQed curve in this case. This is a manual plot so is smoother than the more accurate REW graphs.
 

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1pudding1

Established Member
Yeah i see. Dont know I can do that though, Ive only got the limited controls on the back of the sub :( Guess it just a case of raising the gain to get an average higher volume from the sub that the mains here?
 

AngelEyes

Distinguished Member
Yeah i see. Dont know I can do that though, Ive only got the limited controls on the back of the sub :( Guess it just a case of raising the gain to get an average higher volume from the sub that the mains here?
...or lowering the level of your speakers :)

The graph was just what I meant by a house curve, I wouldn't expect you to be able to EQ it flat with the sub controls. The general shape is what you should aim for. You can cut a peak with the sub EQ controls but not fill a trough so do what you can to avoid the troughs with placement / phase etc. and use the eq to trim the worst peak.

I know the SB has some other 'room' settings so it may be best to try each of those before the EQ controls to find what best suits your room as well.

Adam
 

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