# my first REW attempt



## Wull

Hi there. 

I have had a go with REW and would like to know what you think of my results. 

My room is 26'/14', the sub is positioned mid way between my speakers, behind my TV, and about a foot off a wall facing sideways.

I found moving the sub around had very little change in my results. 

Results are as follows:

1: sub anti mode on 
2: sub anti mode off 
3: main 
4: main sub 0 phase 
5: main sub 90 phase 
6: main sub 180 phase 

The reason I am adjusting the phase on the sub is my current set up does not allow speaker delay, so i found 180 phase to give the loudest amount of bass, is this correct way of balancing. 

My sub is an SVS PB13-ultra, I have this set to 15hz, also left the PEQ off.
My main speakers are Dynaudio audience 82's 

I look forward to you thoughts. Cheers. Will

Read more: Home Theater Forum and Systems - HomeTheaterShack.com - Post New Thread http://www.hometheatershack.com/forums/newthread.php?do=newthread&f=8#ixzz0lwyapTsY


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## Wayne A. Pflughaupt

> 1: sub anti mode on
> 2: sub anti mode off


Here we see the main reason why I don’t like the Anti Mode. It takes out the peaks in response and does nothing about the depressions. Depressions aren’t as annoying as peaks, but eliminating them usually makes an audible improvement in sound quality. You’d be able to boost them up if you had a more traditional parametric EQ like the BFD (except for the deep one at 55 Hz, which probably is a null).




> The reason I am adjusting the phase on the sub is my current set up does not allow speaker delay, so i found 180 phase to give the loudest amount of bass, is this correct way of balancing.


It’s an okay method if you’re going solely by ear, but if you have a sophisticated tool like REW you can see that it’s not always “correct.” The goal of phase adjustment is to get the best response through the crossover region. As you can see, you’re getting that best with the 90-degree setting. Note how response between 75-90 Hz is exaggerated with the 0 and 180-degree settings.

Regards,
Wayne


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## Wull

Cheers for your response Wayne.
I was thinking of getting an BFD, so I may keep my eye out for one now.
These results are from today, I had done other test which showed the response a lot flatter during the week, so I'm not overly convinced how accurate my Radio shack meter is.
To be honest I did get slightly better results with the sub sitting between my speakers next to my TV facing forward, but its in the line of sight then which the misses doesn't like the look of, so I don't want to push my luck.
I may try some more test over the weekend with 20hz setting, and have a go with the PEQ, but again to be honest I haven't had much luck with this.


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## Wull

Quick question.
BFD's, which one?? Behringer Feedback Destroyer DSP1124P???


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## Wayne A. Pflughaupt

Yup, that's the one. :T

Regards,
Wayne


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## glaufman

I agree with Wayne, 90 degrees is best. I don't like the idea of setting phase for "loudest" bass... for anyone playing along at home... if anything exaggerates the peaks/dips, your ear will tell you it's louder (even if the average is the same), when it's also not as smooth a response. We're going for smoothness, not how loud you can make one peak.


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## Wull

Thanks for your advice Wayne & Greg , I really appreciate it :T


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## Wull

*my secon attempt*

Good morning.

I've another go, I tried moving things around etc.

I started with the sub beside my TV but found the results worse this time, so it's back where it started, this time I removed the floor tiles I had it sat on as this wasn't helping either, so now it's back on my carpet which has a concrete floor beneath.
My ceiling it quite low for a long room so I think this has a lot to do with the overall result.

I found the phase set to around 110 and the PEQ set to 45hz FREQ with a max level gave best results.

Looking at my results would a BFD still improve things?

How do these work, do the main speakers go through the unit as well or is it just the sub. And could I still use my Anti-mode as well as the BFD or is there no really point?? 
:scratch:


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## Wayne A. Pflughaupt

> Looking at my results would a BFD still improve things?


I’d say it’s a toss up. Eliminating the depression between 30-40 Hz would probably make an audible difference, especially if you listen to a lot of music. If this is a primarily a home theater installation, I would call it a day.




> How do these work, do the main speakers go through the unit as well or is it just the sub. And could I still use my Anti-mode as well as the BFD or is there no really point??


The BFD connects between your receiver and subwoofer, just like your Anti-Mode does. Since you already have the Anti-Mode, there’s no reason you couldn’t continue to use it along with the BFD.

Regards,
Wayne


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## Wull

Thanks again Wayne for your advice. I think I shall probably sit on it for a while now and enjoy what I have got :T


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## Wull

magicj1 said:


> Thanks again Wayne for your advice. I think I shall probably sit on it for a while now and enjoy what I have got :T


Yeah right!

I haven't stopped messing around since that last reply.

So know I'm wandering what output balance I should have my receiver set to?
I had reduced the output to -8 so I could turn the sub's gain up to around 11 o clock, is this OK or should I set the output level on my MC-1 to 0 and adjust the sub accordingly, which is probably more like 9 o clock for a 75 db level :scratch:

I'm still thinking of getting a BFD just to have a play, I've read a bit about them but still are unsure how difficult they are to set up?


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## Wull

Like I said above I've been messing around, so I've got some more results to show.

I have just purchased a Behringer feedback destroyer DSP1124P which hopefully will come in the next few days. 

Looking at my results what Am I trying to achive, or should be able once a BFD is used?

Results in order:

1 Sub-Room comp large/main spk
2 Sub-Room comp off/main spk
3 Main spk only - small setting
4 main spk only - large setting
5 sub on it's own

I had set my MC-1 processor for these test's to 0 output level, and now the sub is set to around 8 o clock, this achieves 75db sound test tone sweep.

Is the goal to keep the line as flat as posible across 75 db?

Ant tip's on setting the BFD??


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## Wull

Oh, and another thing I don't quiet get.
When I set up REW for the sub, I use LEVELS (use sub woofer to check/set levels) set my MC-1 to 0db and adjust the PC's output volume to reach the required 75db.
If I use the same settings for the main speakers the output levels are greater than the sub's requiring me to turn the output down to reach 75db.
So what happens when I run Sub and mains, what the best way to achieve balanced output from the two?? :scratch:

Also, should I be using (use main speakers to check/set levels) for the main speakers, and do I need to change in the Analysis 'Target defaults' speaker 'subwoofer' to 'fullrange' :scratch: hmmmmmm??


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## Wayne A. Pflughaupt

> So know I'm wandering what output balance I should have my receiver set to?
> I had reduced the output to -8 so I could turn the sub's gain up to around 11 o clock, is this OK or should I set the output level on my MC-1 to 0 and adjust the sub accordingly, which is probably more like 9 o clock for a 75 db level


 At this point it doesn’t matter whether you use the receiver or sub to boost the sub’s output. 

However, it will matter once you get the BFD in the chain. You’ll set the receiver to get a good reading on the meters (about -10 dB is good), and then adjust the sub itself for the proper volume.

Regards,
Wayne


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## Wayne A. Pflughaupt

> 1 Sub-Room comp large/main spk
> 2 Sub-Room comp off/main spk
> 3 Main spk only - small setting
> 4 main spk only - large setting
> 5 sub on it's own


 Those graphs look way different from your earlier ones. What happened?

What in blue blazes are you running for your main speakers that get output down to 20 Hz??? The bass output is so great even in the “small” setting that it may well encroach on your subwoofer equalizing.




> Is the goal to keep the line as flat as posible across 75 db?


That’s a good practice for equalizing the subwoofer




> Ant tip's on setting the BFD??


Have you read through the BFD Guide?

Regards,
Wayne


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## Wull

Nice one Wayne, thats one more boxed ticked off. :T

I couldn't resist getting a BFD, I do listen to a lot of music, a lot more than I watch films so if I can improve on the sound from a bit of tweaking I shall give it ago, I've got nothing to loose except one angry misses! :gulp:


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## Wayne A. Pflughaupt

magicj1 said:


> Oh, and another thing I don't quiet get.
> When I set up REW for the sub, I use LEVELS (use sub woofer to check/set levels) set my MC-1 to 0db and adjust the PC's output volume to reach the required 75db.
> If I use the same settings for the main speakers the output levels are greater than the sub's requiring me to turn the output down to reach 75db.
> So what happens when I run Sub and mains, what the best way to achieve balanced output from the two?? :scratch:
> 
> Also, should I be using (use main speakers to check/set levels) for the main speakers, and do I need to change in the Analysis 'Target defaults' speaker 'subwoofer' to 'fullrange' :scratch: hmmmmmm??


Turn off the main channels when you’re running the REW program and setting the equalizer (and checking its settings). After the sub is equalized, turn on the main channels and adjust the mains/subs blend by whatever method you were using before.

Regards,
Wayne


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## Wull

I moved the sub Sunday evening, only a foot or so and things completely changed. It's now closer to my back wall which has really up'd the output, which I'm not saying is a good thing. Why do you think the results are worse now?

I have Dynaudio audience 82's, yeah they do go deep, but not very well controlled when you compare it to a SVS PB13. They do sound really good on some music, then others expose it's woolly bass.
I've been switching back and forth, sometimes preferring the dyn's, that why I'm chasing this REW so much.

I shall have a look at the BFD Guide............


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## Wull

Well, what ever I do I can't seem to get the result to sit as flat to the 75dB as I got on Saturday.

Saying that there is less null now around 60hz, and the 30-40 hz is a lot smoother, .
It's mad how just moving the sub a few inches can alter the response so much.

Would the BFD bring a lot flatter response, ideally 75dB from 15hz to 80hz, or is it more to help smooth out say from 96dB-15hz, to 78dB-80hz? As my result is more of a slope...!

Also what about my main's, is there anything I can do to help that response. I have tried moving them, but there is not to much scope their..

(I know I keep going on, but I'm trying to get a full picture in my head as to what I'm after as a good result before my BFD arrive) :huh:


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## Wayne A. Pflughaupt

> It's now closer to my back wall which has really up'd the output, which I'm not saying is a good thing. Why do you think the results are worse now?


I didn’t say they looked worse, I said they looked different from your earlier graphs. Looks like that’s the result of your moving them?




> Would the BFD bring a lot flatter response, ideally 75dB from 15hz to 80hz, or is it more to help smooth out say from 96dB-15hz, to 78dB-80hz? As my result is more of a slope...!


The BFD would only equalize the subwoofer. We can’t tell for sure what all that would entail based on this graph, because it’s a combined subs / mains graph. You should do a new sub-only graph for your new location.




> Also what about my main's, is there anything I can do to help that response. I have tried moving them, but there is not to much scope their..


Helping the mains’ response, beyond what can be accomplished by moving them, would require them to have equalization as well.

Regards,
Wayne


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## Wull

Here we go, more test results Wayne:

No 1 Sub behind TV.
No 2 Sub beside TV.
No 3 Main spk Large.
No 4 Main 120hz.
No 5 Main 80hz.
No 5 Main 40hz.

The sub I'm all ears as to which results you think looks better, 1 or 2, any advice where the BFD should improve?


Now I moved my main spk's around and found the best result was where they started from.

Cheers. Will


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## Wayne A. Pflughaupt

I’d say the green trace looks best. It looks to me like you’d be getting really “bottom-heavy” sound with the sub, like maybe a car door closing sounding like a low-level distant explosion. If that’s the case, the BFD could tame the lowest frequencies. Also if you go with the green graph, some boost between 50-70 Hz would probably get audible results, especially with music.

I’d go for 120 Hz for the main speakers, but ONLY if you can set the sub for a lower frequency, like 80-90 Hz.

Regards,
Wayne


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## Wull

I’d go for 120 Hz for the main speakers, but ONLY if you can set the sub for a lower frequency, like 80-90 Hz.

My PC sound card has a variable crossover from 50hz to 250hz, so I could set this to 120hz, then use the SVS crossover set to 80-90hz.

I'll give the BFD a whirl and see how I get on, I've nothing to loose......:T


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## Wull

Hi again.
To add to confusion I have been carrying out test's using two different lap tops and a PC, the PC has a ASUS xonar 1.3 deluxe sound card.
The results on page one of this thread where taken using a Siemens L/T, the other results on page two using a Dell L/T. Now the results do vary slightly on these I guess this is down to the sound cards performance? 
However the results on my PC are way different, can any one advise me as to where I could be going wrong please, I have checked all the settings on all L/P and PC and they seem to be all the same...:scratch:

PC results below


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## Wull

I have just found that if I do not use a sound card calibrated file then the result is as below.
This again is a bit of a mystery as when calibrating the SC it is only out by 1dB at the most


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## laser188139

magicj1 said:


> ...
> This again is a bit of a mystery as when calibrating the SC it is only out by 1dB at the most


Your soundcard may have shown only 1dB over most of the range, but if you look in the two graphs in your penultimate message, you can see in dotted black line that is the soundcard curve that it falls off at the bottom, and is in fact -80dB down at your left margin below 20Hz. So removing it from the configuration will have a huge effect on the displayed measure at the low end. 

Now as to why your soundcard calibration starts falling off below 80Hz, I'm not sure. You mention that you have a variable crossover on the soundcard; perhaps you had it enabled when you generated the soundcard calibration file. 

Bill


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## Wull

Thanks Bill, I had my bass management. :rolleyesno:

I've managed to calibrate it now. But unfortunately my results have not improved that much, I guess my room sucks.

Below are some results from tonight, I have not run the Anti-mode as I wanted to see what the REW filters could achieve. The EQ result below only had two filters applied by REW.

I am going to have a go at using my DSP1124P this weekend to see if this will help, or at least to try ang get my head round it.

Whats the best plan off attack for using this: 
Do I use the REW EQ suggested filters when I carry out the 'match response target', is there a limit to how many I should use, I guess fewer is better, but what if I used all twelve.
I've also read in the threads about not adding to much Gain above 3dB.....?

Any advice once again would be truly appreciated.

Man it's been one confusing last two weeks, It hasn't helped with my lap top's dying one by one!

Cheers.
Will


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## Wull

And out of interest.

Below are results:
1 anti mode off
2 anti mode on


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## JohnM

Will, your target level is much too low, possibly because you did not go through the SPL meter calibration step so your measurements are being plotted at SPL values much higher than they actually are (at least I hope so, 125dB+ would be quite a loud measurement )

After you have gone through the SPL meter calibration and made a measurement, open the Target Settings panel in the EQ window (click on the title bar) and make sure the crossover frequency ties up with what your sub is set to use. Then click on "Set Target Level" to get REW to adjust the level to tie up with the response. After doing that you can try "Match Response to Target" to see what filters REW suggests.

Your anti-mode plot is rather unusual though, it is normally very good at dealing with peaks so I suspect something did not go right in setting up the Anti-Mode.


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## Wull

Your right John, it was out.

It's hard to get an accurate figure when the SPL meter jumps around so much.
Is it best to take the highest level reading as the max, or average the middle, as it can jump around from 72dB to 75dB, even more so when the anti mode is off?
Green Anti mode on...


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## JohnM

magicj1 said:


> Is it best to take the highest level reading as the max, or average the middle, as it can jump around from 72dB to 75dB, even more so when the anti mode is off?


Take the average, the exact figure is not critical. Now that your levels are more sensible you can set the graph SPL axis to our preferred 45dB .. 105dB, having a consistent axis range makes it easier to visually interpret the graphs.

P.S. The anti mode plot is looking better now.


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## Wayne A. Pflughaupt

> Whats the best plan off attack for using this:
> Do I use the REW EQ suggested filters when I carry out the 'match response target', is there a limit to how many I should use, I guess fewer is better, but what if I used all twelve.


As John discussed, make sure your Target Curve is properly set before you start equalizing. If you do that, it’ll only take a few filters. You’re mainly wanting to eliminate the worst peaks and depressions; there’s little (if any) audible benefit to smoothing out every little ripple in response.



> I've also read in the threads about not adding to much Gain above 3dB.....?


Yeah, it’s one of those myths that just won’t go away, and it’s based on a number of flawed theories.

One misconception is based on the premise that boosted filters will require the input signal of the digital equalizer to be cut back, and that will decrease dynamic range and increase noise in the A/D converter. This is an old-school idea that dates back to the days of 16-bit digital converters. 

The high-input-levels-required theory confuses the unit’s overall dynamic range with the dynamic range of the A/D converter itself. The two are not the same. A 24-bit A/D converter has a theoretical dynamic range of 147 dB. However, other circuitry in the component also contributes to the component’s ultimate S/N and dynamic range spec – the power supply, balancing ICs, etc. The reason why no 24-bit digital processor is able to spec an actual 147 dB dynamic range is because the analog circuitry in the device can’t deliver that kind of performance. 

If a 24 bit A/D converter has a theoretical dynamic range of 147 dB, is reducing the input level 10 or 15 dB going to have an appreciable affect on its dynamic range? Of course not – not when the equalizer itself only has a dynamic range of 105 dB or less. Bottom line, modern 24-bit processors function just like analog processors, and input levels are a moot issue – hence the reason they don’t have the handy front-panel level controls they used to.

Another myth says that you shouldn’t boost dips or nulls in response because it doesn’t accomplish anything. We’re told that nulls are caused by phase cancellations, where the sound reaching the measurement point is a combination of the original direct soundwave and a reflected soundwave that is 180˚ out of phase (one half wavelength). When you add a gain filter at the depressed frequency, not only does the direct sound increase by the number of dB of the filter, but unfortunately the 180˚ out-of-phase signal also applies an equal and opposite signal to counteract. The result is that your dip is still there and you have wasted the gain you've thrown at it.

This theory is technically correct, but it’s based on the silly expectation that bass emanates from a subwoofer like a laser, with the primary “sound beam” reflecting off a perfectly-perpendicular wall and meeting the original “sound beam” half-way in between, 180˚ out of phase, causing cancellation.

Of course, the theory falls apart with the realization that bass frequencies are _omnidirectional,_ not directional. They discharge from the subwoofer in all directions and in like manner bounce around the room in all directions. This quote from this article explains things nicely:

_These nulls are related not only to the distance from the rear wall, but also from the other walls, the floor, and the ceiling. So in order to create a deep null a precise balance is needed, and that balance is easily disrupted by the many other reflections bouncing around the room._

In other words, since bass is omnidirectional, sound is reflecting at every angle from every boundary in the room. So while there may well be a point and/or frequency that exhibits wholesale cancellation due to a reflection being 180˚ out of phase with the original signal, there is no shortage of other, non-canceled reflections present for an equalizer to work with. Plus, the EQ introduces phase changes itself. This is why you’ll seldom see a case where a depression won’t respond to EQ.

The other problem with the “never boost nulls” theory is that it presumes all depressions, dips, troughs etc. in response are nulls. The explanation above should be sufficient to show that true nulls are pretty rare. They’re usually the result of a poor subwoofer location. 

It’s pretty easy to identify nulls: Typically they are deep and narrow and won't respond to equalization, as we see with these graphs:















​

Here’s the second graph, but with EQ. As you can see, the nulls didn’t budge.







​

By contrast, here’s a graph of a sub with a rather severe depression that boosted just fine with equalization. Obviously it wasn’t a null.















​

Another “no boosting” myth says that boosting enacts a headroom penalty, because it places increased demands on the amp and driver. In reality, virtually any equalization always enacts a headroom penalty, even if cut-only filters are used.

The common situation is that there are one or two peaks in the room. Those hot frequencies are what’s determining the volume setting you’re using for the sub before equalization. Eliminate (cut) those peaks and you’ll now perceive that your sub is too quiet. So, you have to turn it up to compensate. Well guess what? Now you’re driving your sub harder than you were before. 

This is exactly what happened to the little 8” M&K sub I used to have for my computer audio system. It required some substantial EQ cuts to smooth it out – no boosts, only cuts. Sounds much better, of course, but the 10-11 dB of SPL lost to the cuts required that I had to increase its gain. Well - now it doesn’t take much for it to bottom out.

Also, consider what happens when you make a series of cuts. It shouldn’t take much to figure out that _you now have peaks in between them! _

For instance, consider the graph below, which depicts the equalizer’s _electronic response_ after equalizing. In other words, the equalization changes the electrical signal that was originally flat (i.e. the flat blue line, which also includes the slope of the crossover). So, did we make three cuts here...










...or did we make three boosts, one being a power-robbing shelving filter?










See what I mean?

Bottom line, there’s no free lunch. In most cases, equalization requires that you have ample headroom going it, because you’re going to end up with less than what you started with. If you don't have ample headroom, you shouldn’t equalize.

It also should be mentioned - for those with ported subs, it’s not good to boost below the tuning frequency of the port. It will run out of headroom much sooner than a sealed sub with low frequency boost will.

Regards,
Wayne


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## Wull

Thanks for your help chaps :T

'I'm getting fed up of moving my sub around, it's got to come to an end soon!'


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## Wull

Right, I've added my REL storm in to the mix to see if this would improve things. After trying all different settings etc I found that the REL out of phase by 180 degree's with the SVS gave best results.
However, when I added my main speakers to the mix I found I had to have them running at the same phase, also leaving my mains at 80hz cut off so far worked best.

My question is before I spend all day tomorrow messing around trying to get this set up should I leave the REL out, or is it a case if it works leave it in ?? :scratch:


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## Wull

Don't think you need to answer. I've just listened to some music and it sounded awful, really boomey.
It did sound a lot better when I reversed the phase on the REL......

But think I will try and set up my system without it, it will make things alot easier.


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## Wull

Sorry, was meant to say:

First pic:
SVS-phase 0, REL-phase 180, Main spk's set to 80hz 

Second pic:
I ran and EQ on it to see what it predicted.

Third pic:
I ran EQ on SVS-phase 0, REL-phase 180 only.

Could a BFD be used for both sub's if used before the Anti-mode?


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## JohnM

When the mains are active you need to change the target curve to "full range", the subwoofer target is for use when only the sub was active during the measurement. Also click on "Set Target Level" to get REW to adjust the level to better track the response, the target level is too low in the plots you posted.


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## Wull

Well I've been testing all day and I am not moving that sub no more. I found the sub sitting in line with my main speakrs gave the best result, the Misses will just have to put up with looking at it!

The results are 'hope I've done them correctly this time'

1 sub-anti-mode and BFD used
2 sub EQ ' 10 filters used'
3 Main spk's 120hz, sub 80hz Anti BFD used
4 Main spk's 80hz, sub 80hz Anti BFD used.

So far what I have listened to sound really good. The BFD has tightened the Bass up nicely.


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