# BFD vs ANTIMODE



## marty1 (Jun 29, 2010)

I thought I'd move my question onto a different thread as I did not want to hijack Veger69's thread any longer.

After eqing my new dual 18 sealed subs, my aim is to achieve the PB13U depth but still have the sealed subs upper bass punch, something that the PB13U was not capable of.

I've managed to achieve a good measurement on REW with the BFD by applying 2 36db cuts, 1 at 30hz and another at 55hz. I wanted to avoid any boosting as I found it made the sound very unnatural. So to bring the lower end (below 20hz) up to match the PB13U I lowered the upper bass.

The problem is, as Wayne pointed out, as the cuts are so big I have to have the receivers subwoofer trim and my pro amps volume dials all at max 

The sound is pretty good and you can tell the low end is there, however it seems that the upper bass punch has gone, also watching certain movie scenes I know well, the bass doesn't sound quite so smooth.

The antimode is a different story. It sounds great, the sound is much more dynamic, the upper bass chest thumping punch is better and overall it sounds much smoother.

The downside to the antimode's results are that the 30hz region is a bit high which results in certain bass moments being a bit too heavy, not muddy or boomy but just a bit overbearing, resulting in me having to quickly turn the master volume down for a moment not to upset the neighbours. Also the measurement shows that below 20hz the sound drops off, which is what I didn't want to happen.

Unfortunately the antimode has done it's job and cannot improve on the low end or lower the 30hz region anymore so I feel that the BFD is the only I'm gonna achieve the results I am after.

So how do I get the BFD to sound as good as the antimode but with the lower end impact of the PB13U and the 30hz region more balanced?

I think my BFD is faulty because when it clips, the output to the subs is cutting out and apparently this is not meant to happen. I've switched the studio setting on so it shouldn't clip anymore but I'm concerned that the uneven sound may have something to do with the device being faulty but for now let's assume it's fine and it is more than likely my filters that need fine tuning to achieve the best results.

Here are my results without smoothing, of both the bfd and antimode measurements, I've also attached the subs alone result without eq or crossover applied so you can see where I was working from and to.

I would really appreciate your help as I seem to be one of the only people to prefer the antimode to the BFD in the results department.

Regards
Marty


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

> I wanted to avoid any boosting as I found it made the sound very unnatural.


Unfortunately, you didn’t really “avoid” boosting. By sucking out pretty much the rest of the bass frequency range with those two 36 dB filters, you’ve left a huge “smiley-face” curve that has factually boosted the extreme low end. The red BFD trace in your graph, compared to the unequalized graph, proves it. Call up your REW graph and look at the electronic response of the equalizer filters and see for yourself.



> The antimode is a different story. It sounds great, the sound is much more dynamic, the upper bass chest thumping punch is better...


The Antimode slightly sagging response a bit between 30-50 Hz, with the area between 50-60 Hz boosted a bit, accounts for the “chest thumping” you’re hearing.

Why not use the BFD in conjunction with the Antimode? You could set a broad 1.5-octave filter at 20 Hz and boost it to increase extension at least down to 15 Hz (which should be plenty low enough). Other BFD filters could counteract the boost you’d get above 20 Hz. Basically, you’d be using the BFD to lower extension below 20 Hz, but leave the Antimode’s curve intact above that point.

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Thanks Wayne :T

I did try boosting at 20hz with bfd after antimode and found that the 30hz peak just went up drastically but I never really thought about applying a cut after that boost.

So what you suggest is basically the antimode will be the first point of eq then use the bfd to apply 2 filters.

1. Boost 20hz to bring it up to the antimodes level (how many dbs would you suggest?)

2. Apply a cut around 30hz to bring the potential peak that will appear.

Is that right?

Regards
Marty


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

marty1 said:


> 1. Boost 20hz to bring it up to the antimodes level (how many dbs would you suggest?)
> 
> 2. Apply a cut around 30hz to bring the potential peak that will appear.
> 
> Is that right?


That’s basically it. :T However, it might take more than a single filter to tame the BFD's response above 20 Hz back down. As far as how much boost for the 20 Hz filter, that depends on just how much you want to “shore up” the <20 h Hz range. Looking at your graph with the red/blue traces, it looks like you’ll need something on the order of 10 dB to get anything close to your red trace.

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Okay Thanks Wayne.

Maybe before I do this I should change the graphs limits to 20db-130db and apply 1/6 smoothing as I believe you suggest in our minimal filters thread. This may prevent me from applying too larger filters right?

Regards
Marty


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

The techniques discussed in the Minimal EQ article aren’t applicable for what you’re doing here. 

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

What is the difference and what should i set the graphs and smoothing to?


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

Just use the normal "no smoothing" - it's fine for what you're needing.

Regards,
Wayne


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## marty1 (Jun 29, 2010)

And 45db-105db for graph?


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

Yes. :T

Regards,
Wayne


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## marty1 (Jun 29, 2010)

Okay Thanks again Wayne, i will get tweaking at the weekend.

Just out of curiousity what is the minimal eq guidelines for?

Regards
Martin


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

It’s for manually equalizing, or when using REW to recommend filters. We’ve seen lots of people seemingly obsessed with getting flat-line response using a whole slew of filters, many of which would be only 1-2 dB in gain and/or ultra-narrow – i.e., filters that would make no audible difference. In other words, over-equalizing. And REW tended to recommend some of those “useless” filters as well.

Obviously, if you have an auto-EQ system like the Antimode, none of this applies because you must use the equalization it generates “as is.”

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Okay Thanks Wayne.

You were right, the big cuts did destroy the volume. I have now run antimode and applied 2 filters.

1. 20hz >>> +5db >>> 0.25Q
2. 29.9hz >>> -5db >>> 0.25Q

Apart from a new eq device that can boost frequencies at 10hz I cant seem to get the response down to 10hz any higher, I tried more db boosting and all different Q widths but it just kept affecting above 20hz so I think the pb13u results are not achievable with these subs with the bfd. Unless you have any other suggestions?

There is a dip around 76hz, should I try boosting that aswell or leave it as is, I found I had to boost it by +15db to get the dip up to the rest of the line but when I ran the sweep tone it sounded strange, for a brief second it went really loud then back down again, looked even but didnt sound even, any ideas?

This is my result without smoothing.

Do you think it needs more work or is that as good as it gets?

Regards
Marty


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

marty1 said:


> I have now run antimode and applied 2 filters.
> 
> 1. 20hz >>> +5db >>> 0.25Q
> 2. 29.9hz >>> -5db >>> 0.25Q


You aren’t really going to get anywhere applying two wide, sweeping filters that are so close to each other. The 29 Hz filters is effectively wiping out anything the 20 Hz filter accomplished. Your above-20 Hz filters (yes, “filters”) are going to have to be much narrower than that.




> Apart from a new eq device that can boost frequencies at 10hz I cant seem to get the response down to 10hz any higher, I tried more db boosting and all different Q widths but it just kept affecting above 20hz so I think the pb13u results are not achievable with these subs with the bfd. Unless you have any other suggestions?


 Your best bet would be to get an EQ that can be set below 20 Hz, like the Rane PE-17 or Symetrix 551. :T




> There is a dip around 76hz, should I try boosting that aswell or leave it as is, I found I had to boost it by +15db to get the dip up to the rest of the line but when I ran the sweep tone it sounded strange, for a brief second it went really loud then back down again, looked even but didnt sound even, any ideas?


I wouldn’t worry about it, for a number of reasons. 

For one, it’s probably really close to your crossover frequency, so you may well have the main speakers overlapping it and (a) either overwhelming the equalization, or (b) “filling in” that space and therefore eliminating the need for equalizing entirely. REW measurements with the mains going beyond the sub range could give you that information.

Second, it’s at best only 1/6-octave wide, and probably not even audible, especially once the mains are added in.

Third, any ~8 dB dip that requires 15 dB of correction is probably not a mere depression, but a null, and should be left alone.

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

The reason why I applied the 29hz filter was that as I applied the 5db boost at 20hz, anything wider than 0.25 was causing a massive peak to build up around 30hz and it got to the point where the 15hz region wasn't moving up anymore, so at 0.25Q that is the widest I could apply the 5db boost to bring up the low end. I then had to target the 30hz region with a narrow filter but again to smooth it out to reach the 20hz db levels it ended up reaching 0.25Q.

I thought the response looks pretty good. It does sound the best I've heard it so far.

I'm not sure how else to do this, what would you suggest?

I would like to avoid another eq device at this time, it is something I will look at later on down the line.

Regards
Marty


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## marty1 (Jun 29, 2010)

Just to let u know those measurements are with mains.
So that dip is there no matter what.
At what point do i start applying the smaller filters to bring the massive 30hz peak that goes up as i boost the 20hz region, how wide should the smaller filters be and how many should i apply.

Regards
Marty


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

Hey Marty,

Unfortunately there’s no way for me to predict the point where the filters should be applied, or what their bandwidth settings need to be. You want to drag the BFD’s effect above 20 Hz low enough so that the Antimode overwhelms it - i.e., above 20 Hz, output from the Antimode is greater than that of the BFD. Apply as many filters as you need to accomplish that. Basically, you’re using a bunch of filters to simulate a low pass filter.

I guess you know this is a pitifully poor method to accomplish the < 20 Hz boost you want. This post should help explain what all those superfluous filters might get you. You might well end up with things sounding worse than if you’d just left it alone, even if the graph “looks” better, which is why I recommend simply getting a different equalizer that can do the job with a single filter.

That said, experimenting never hurts...

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Hi Wayne,

I will have a look at the link tonight after work, thanks :T

I'm just not quite understanding what the difference is between what I've done and what you suggested about smaller filters.

I've started by boosting the low end up with a narrow filter but I just get a 20hz peak, so I apply a wider filter which to reach the 10hz region also reached the 25hz region. I already have a slight peak at 30hz (after antimode), this now creates an upward slope from the 20hz region to the 30hz region peak. So I then had to cut the 30hz region. I applied the cut and slowly applied wider filter, 1 step at a time measuring each step. The 30hz region went right down but still left a big peak at around 25hz, so I just kept on measuring each q value until the line smoothed out. So doesn't that mean that I have balance the 2 filters to work in harmony?

Applying smaller filters around this area would essentially still be doing the same thing right?

Regards
Marty


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

You need to attenuate the BFD's response above 20 Hz - the red line - so that it's significantly below that of the blue line. Again, there's no way I can tell you how many filters that will take, or what their parameters should be. Sorry...










Regards,
Wayne


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## marty1 (Jun 29, 2010)

Hi Wayne,

No need to appologize i appreciate your help. I'm not trying to find out how many or how wide now really im just trying to understand the difference between applying 2 wide filters, 1 cut and 1 boost that appear to smooth out the 20hz-30hz region whilst still keeping the below 20hz up to a fairly good level and 1 wide filter boost at 20hz with several smaller ones to cut around the same areas?

Regards
Marty


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

Hey Marty,

No difference, really. It appears that I misled you in Post #14 when I said:


Wayne A. Pflughaupt said:


> marty1 said:
> 
> 
> > I have now run antimode and applied 2 filters.
> ...


It doesn’t seem to me that two broad filters located so close to each other, one boosted and one cut by the same amount, would work. But if you were able to get the results you’re after with those two filters, then go for it! :T

Regards, 
Wayne


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## marty1 (Jun 29, 2010)

Thanks Wayne, that's a relief to know :T

I know they are close together but like I said I measured every time I adjusted the q value by 1 step so I could see that peak at 30hz slowly get ironed out and I stopped just before it started affecting the boost I had applied, so I'm pretty sure they only just overlap.

I think you are right though a new eq device is definately on the cards. Out of the ones you suggested which would you go for and if money was no object is there something even better?

Regards
Marty


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

I think the Rane and Symetrix are about equal in the quality department; however, the Symetrix is the only one I’ve personally used. These are the only two parametric EQs I know of that facilitate filter settings below 20 Hz (not that there aren’t others; I just don’t know). Both are vintage discontinued analog models that can be found on ebay for $150 or less.

Regards,
Wayne


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## marty1 (Jun 29, 2010)

Thanks Wayne,

Of coarse there is the audyssey pro eq adjust kit which is about £2000 and the svs aseq1 which is pretty much impossible to find.

Regards
Marty


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## marty1 (Jun 29, 2010)

Me and Dan (Moonfly were trying to figure out why the antimode and BFD were not working in harmony and I finally figured it out, now here is the response below.

Almost there just gotta figure out how to remove the cancellation dips at 76hz and 105hz......any suggestions?


I've tried moving mains in every feasible position and the dips still there at 105hz and i've tried adjusting subs distance to see if that 76hz dip irons out but no chance. Boosting with the bfd doesn't help.


As for the below 20hz to reach 10hz Adam suggested 1 really wide cut from 20-50hz to bring it down to 10hz level, I may try that at a later date but I feel that it will rob the system of upper punch. I found just by cutting the 2 big peaks at 30hz and 54hz down to 10hz db level wiped the bass energy out as the cuts were far too big, I mean were taslking over 20db cuts.


When I first got the subs Dan suggested to do filters with bfd then run antimode to smooth things off. I found that the bfd got the response almost ruler flat but when I ran antimode suddenly the response went all over the place, dips everywhere 


I couldn't figure out what went wrong so I reversed it and done antimode first then bfd. The results were better but still never quite right. I took the antimode out of the equasion and just used the bfd. Again the results looked good on REW but were still not sounding right, a bit lifeless and harsh. 


Again Dan insisted on using the bfd first then antimode and Adam suggested it to, these guys know their stuff so I thought Id give it another try. As I was reconnecting it I had a eureka moment! Initially I had my avreceiver connected to the bfd, then bfd to antimode, then antimode to subs. Made sense as I was eqing with bfd first it should be first in the chain......WRONG! I forgot that when the antimode does it's measuring tones it doesn't take into account the signal being received, it outputs it's own tones and calibrates based on them, the fact the bfd was in before the antimode means the antimode did not account for the filters I applied, so when it finished they were clashing.


So remember if you are trying something similar remember to connect antimode first, then the bfd so when it outputs it's tones they are sent through the bfd taking into account the filters and therefor giving a pretty good end product.


Marty


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