# [SVS PC13-Ultra] Help with major dip and rise



## Flipmode (Jun 26, 2012)

This graph is just the sub alone

I am new to this so if there is something I am doing wrong let me know.

Not that this makes much differnce but these are the low pass settings I used to see if they made a difference.

Blue 80Hz
Yellow 63 Hz
Green 50 Hz

If those colors don't look right it could be my little laptops screen 

I have a major dip at 65 Hz of 25 db to 30 db

And a major peak at 83 of about 20 db

Currently I have the sub in the corner of my room.

Would this be caused by my location?

What would I look for in a balanced system +/- 3 db?


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## fusseli (May 1, 2007)

Ya, a response like that indicates a significant problem. Clearly, changing the LPF on your sub has no effect. Do your main speakers have an HPF on them?


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## hjones4841 (Jan 21, 2009)

These look like room resonances, or "modes." Please post your room dimensions. Also, move your microphone around and take more measurements. If these are room modes, moving the mic will change the measured response quite a bit.


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## Flipmode (Jun 26, 2012)

Ok here we are

Red Sub in Corner
Blue Sub in Middle of Room
Mic Listening position on couch
No Smoothing
Sub set to 16 Hz

When I move the mic around the room I definatley get different dips 

What smoothing should I use for sub?

Any suggestions/tips on the FR?

*Update*This graph does have all mains and sub running


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## fusseli (May 1, 2007)

I'd say the red curve looks better, single subs often do best in corners anyways. That's much much better than the first problematic curve you posted. You might try the room treatments forum for more help.


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## planetc (Jun 21, 2012)

Your results look a lot like my first tests. I tried various locations before settling on one of 3 corners. I think I can still improve on mine, but I have found its easier to deal with humps than dips. 
The progress I have made with time and patience testing different locations, crossover and phase settings is quite astonishing to the ear so it is worth the time investment. 
I notice that your sub rolls off very quickly at the bottom end, much like mine. I wonder if this is a limitation of the sub or the mic?


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## marty1 (Jun 29, 2010)

It's a phase issue, it looks like you have the crossover on your amp set around 60hz.

I will cover all setups so you can check they are all correctly set.

On your amp you must set the Low pass filter of your lfe channel has high as possible, fully open, usually 120hz.

Your speakers should be set to small and crossover set to 80hz.

On your SVS make sure that your peq on the backs db level is at minimum just in case you have a filter in place. The crossover setting should be a max, fully open.

As you measure your subs response alone start the phase dial at 0, measure, then move the phase dial 1 notch up, measure, another notch, measure and keep going until you have measured all steps of the entire phase dial. You will find that one of the settings will reduce or remove that dip.

Then you can add your speakers into the measurement, you will find that once the speakers and sub work together the dip should disappear as the speakers pick up where the sub starts to dip.

Marty


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## Flipmode (Jun 26, 2012)

Thanks for the relies!

*fusseli*

Unfortunately my wife won't let me alter the room in any way, I will have to make the best with what I have. When I moved the sub from the corner her first words was "That is NOT going to stay there"

*Planetc*

Yes I think right now playing with crossover point will help, I was playing around with it last night with some improvements which leads to marty1's post

*marty1*

Current setup on the amp is
Low pass 80 Hz
Main Speakers 80 Hz

Current setup on Sub everything is disabled at the moment, so crossover will be full open, no PEQ set.
My bad for not explaining in the 4th post that graph I do have all speakers running not just the sub.

I will work on the phase and crossover tonight if I get time.

Thanks!


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## marty1 (Jun 29, 2010)

Again i wouldn't worry about the speakers crossover yet, keep it at 80hz. If you can get your lpf higher say 120hz it would be better as lfe signals can sometimes go upto that level.

Try your phase dial measurements then once you have found the phase position that minimises the dip the most the next thing to toy with is your subwoofer distance settings on your amp, try increasing and decreasing the distance regardless of how far away your sub actually is from your listening position, measuring each step you will find that at a certain distance the speakers and sub should work in harmony to again smooth out the cancellation of that frequency.

Marty


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## PuckDaddy (Apr 21, 2012)

marty1 said:


> Again i wouldn't worry about the speakers crossover yet, keep it at 80hz. If you can get your lpf higher say 120hz it would be better as lfe signals can sometimes go upto that level.
> 
> Try your phase dial measurements then once you have found the phase position that minimises the dip the most the next thing to toy with is your subwoofer distance settings on your amp, try increasing and decreasing the distance regardless of how far away your sub actually is from your listening position, measuring each step you will find that at a certain distance the speakers and sub should work in harmony to again smooth out the cancellation of that frequency.
> 
> Marty


Chiming in here with a question. Given that trying different phase settings and different distance settings will require multiple measurements, would it be possible to use REW's Real Time Analyzer to see the effect of the changes in real time? For example, by repeatedly playing a pink PN tone? Just looking for a way to make the process more efficient. Thanks!


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

PuckDaddy said:


> Chiming in here with a question. Given that trying different phase settings and different distance settings will require multiple measurements, would it be possible to use REW's Real Time Analyzer to see the effect of the changes in real time?


 Yes! :T

Regards,
Wayne


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## marty1 (Jun 29, 2010)

I would have recommended that but ive never used it so i couldn't......but that would be a lot easier.

Marty


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## Flipmode (Jun 26, 2012)

Well I tried marty1 suggestions and nothing worked, I may have reduce the dip at 55hz by about 3 db.

Still in the end I could not reduce the dip very much at 55 and really nothing at 80Hz.

I believe it comes down the to room geometry, and I would have to use fusseli's suggestion if I were to improve the bottom end. Definitely room modes I cannot get rid of.

I didn't bother to post any graphs because it wasn't with while.

Unless I add another sub or build a Home Theatre Room I am going to have to live with it.

Thanks for the help.


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## marty1 (Jun 29, 2010)

Did you try the distance adjustments?

What frequency are your speakers good to, what you can do is try lowering the crossover down to 70hz or 60hz to see if they can compensate for your subs dip. I also found with my speakers that there was u dip that I couldn't shake off, it was around 50hz, I had limited placement options so I was trying other methods, what got rid of it was I had ports on my mains, I plugged them and the dip disappeared. This means that they must have been outputting a frequency that was clashing with a subs frequency causing a cancellation.

Don't give up hope mate, try and eliminate every option, it's probably something quite simple that can rectify it 

Marty


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## Flipmode (Jun 26, 2012)

marty1 said:


> Did you try the distance adjustments?
> 
> What frequency are your speakers good to, what you can do is try lowering the crossover down to 70hz or 60hz to see if they can compensate for your subs dip. I also found with my speakers that there was u dip that I couldn't shake off, it was around 50hz, I had limited placement options so I was trying other methods, what got rid of it was I had ports on my mains, I plugged them and the dip disappeared. This means that they must have been outputting a frequency that was clashing with a subs frequency causing a cancellation.
> 
> ...


Yes I did try the distance and that did not help either, I though for sure your ideas were going to work! 

I took the crossover down to 40Hz on the mains which did help a bit but really only about +3 db.

My speakers are good to 48hz in *This Post*

I noticed they have a presence adjustment? Kind of an odd name but I will pop the grilles off and check them out.


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## marty1 (Jun 29, 2010)

Flipmode said:


> Yes I did try the distance and that did not help either, I though for sure your ideas were going to work!
> 
> I took the crossover down to 40Hz on the mains which did help a bit but really only about +3 db.
> 
> ...


It's probably a silly question but when you were measuring the adjustments of phase and distance you did have your mains on and set to stereo on your amp?

Also does your amp have eq on?


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## Flipmode (Jun 26, 2012)

Yes the Amp was in stereo, it does have an EQ.

I think it can only adjust about 10 to 12 frequencies. 

It starts at 63 Hz then 125 Hz then 250 Hz etc. 

I did play with that a bit too but didn't make much of
A difference. 

I will play some more this weekend.


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## marty1 (Jun 29, 2010)

Flipmode said:


> Yes the Amp was in stereo, it does have an EQ.
> 
> I think it can only adjust about 10 to 12 frequencies.
> 
> ...


Have you tried measuring with eq off? Or any bass management like standing wave adjustments, try measuring with it all off if you haven't already and do the phase and distance adjustments again, if you haven't already that is.

It may be as you already said that you are sitting in a null zone but if your listening position isn't flexible you have to try everything possible to smooth out your response. If you can move your sub to different postions even rotate the sub where it is, different orientation can bring different results.

It is a long process, I've had so many problems getting mine right and even now it isn't perfect but probably as best as it's gonna be.

What I did was to start off with sub measurements only, all eq on sub and amp off, crossover on amp at 80hz. 

listening position 1, sub position 1. Measured all 9 phase dial (on sub) postions
listening position 2, sub position 1. Measured all 9 phase dial (on sub) positions
Listening position 3, sub position 1. Measured -"-

Listening position 1, sub position 2. Measured -"-
Listening position 2, sub position 2. Measured -"-

On and on you get the picture.

This way I gathered all possibilities and I built up a picture of where I will get the flattest response.

Then you can fine tune it with eq and distance setting. You may find you have that null no matter what but at least you know you've done all you can :T

Marty


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