# To BFD or not to BFD



## gperkins_1973 (Aug 25, 2008)

Been thinking about EQing tonight and looking at various options.

FEEDBACK DESTROYER PRO DSP1124P - £70 approx

FEEDBACK DESTROYER PRO FBQ2496 - £120 approx

ULTRADRIVE PRO DCX2496 £220

ANTI MODE 8033 - £240

The first one seems to quite popular but am worried about the frequency response only starting at 20hz. What about frequencies below this as I am sure mine will hit a bit below that. How does that get measured. The second one has an auto facility on it from what I have read which would be handle with the option of manually tuning it. The third has a frequency response starting at 10hz and the Anti mode is 16hz. Does all this really make much difference.

Opinions would be appreciated please.

cheers
Graham


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

Hi Graham,

The BFD operates well below 20 Hz. It's just the lowest frequency that you can set a filter for.

The Ultradrive is primarily a speaker controlling processor that has equalization along with crossovers and other features. For the most part it's way overkill for subwoofers

Unless you need to kill a peak below 20 Hz, the BFD is your best bet.

Regards,
Wayne


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## UreiCollector (Oct 29, 2009)

I'm using the UltraDrive and it is top notch...very flexible...and on top of doing EQ duty, you can also use it for crossover, dynamic eq, etc etc....it's worth the extra money!

Frederick


gperkins_1973 said:


> Been thinking about EQing tonight and looking at various options.
> 
> FEEDBACK DESTROYER PRO DSP1124P - £70 approx
> 
> ...


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## Drizt (Aug 21, 2006)

Is there anything that the BFD does for EQ'ing subs better than the DCX ?

Im looking at EQ'ing my new subs for both HT and HIFI use and im currently researching my options. If the DCX can do everything the BFD does, then Ill most likely just get one of those.


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## brucek (Apr 11, 2006)

> Is there anything that the BFD does for EQ'ing subs better than the DCX ?


Not that I'm aware of. It doesn't come close to the features on a DCX, but it does EQ subs at an inexpensive price.

brucek


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## Drizt (Aug 21, 2006)

cheers.

I figure if the DCX does what the BFD can do, then i might be worth the extra dollars as it could be later used for a more complex task if the need arises. Whereas the BFD is really only for one thing from what I can tell.


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## gperkins_1973 (Aug 25, 2008)

Thanks guys for your replies. Gives me food for thought.

cheers

Graham


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## recruit (May 9, 2009)

It might be useful Graham considering an EQ device which also works in the time domain as decay times or what some call ringing can still be bad even when a response looks flat, I believe the Anitmode also works in the time domain and seems to do a very good job or else you have the more expensive option which is the SVS EQ1...


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## brucek (Apr 11, 2006)

All the Behringer equalizers use IIR filters that counter room modes in the time domain.

brucek


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## gperkins_1973 (Aug 25, 2008)

Hi chaps,

Complete novice. Can you explain what time domain is please.

cheers

Graham


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## recruit (May 9, 2009)

brucek said:


> All the Behringer equalizers use IIR filters that counter room modes in the time domain.
> 
> brucek


Thanks Bruce, I'll get my coat then :doh:


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## brucek (Apr 11, 2006)

> Can you explain what time domain is please.


In addition to the frequency domain (that is plotted using a frequency response graph), there is a time component to the signal that you measure in a room. The signal has an amplitude (which can be graphed as mentioned), but it also has a decay time. You can observe this decay time by graphing in both the frequency and time domain using a waterfall plot. 

You can insert a BFD in a loopback configuration of a soundcard and examine what a filter looks like in the time domain using a waterfall plot. 

brucek


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## gperkins_1973 (Aug 25, 2008)

Bruce,

Thanks for explaining that. I am having a nightmare finding a soundcard that supports vista 64 bit.

cheers

Graham


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## recruit (May 9, 2009)

When you think about it the BFD is one of the most cost effective EQ devices on the market then and with REW it makes it even better, when I used the BFD there was no REW and all I had was correction values for the SPL readings and to plot graphs which was a knightmare and then use the filters to EQ...:sweat:

graham - yes Vista 64bit is one of those systems where you can run into problems to find compatible software, but they must have caught up by now?


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## Nick (Oct 28, 2009)

Wayne, I can see that the BFD is a great choice for adding a sub and setting the crossover point between it and the mains. Is it also appropriate for EQing my full range speakers without a sub?

I am also interested in biamping my mains as they have wire posts that separate the woofers from the M/H freq, and likely adding a pair of subs after that. If I have to take the crossovers out of my speakers, then I would not bother biamping -- but I am wondering if there is a product that will address each of the issues above, or do I need two different products?

Thank you,
Nick

So, I am curious if I need one something like the BFD for integrating a sub (or


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## brucek (Apr 11, 2006)

> Is it also appropriate for EQing my full range speakers without a sub?


No, not really. You would want a higher quality device for your mains.

brucek


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## Nick (Oct 28, 2009)

Would something like the ULTRADRIVE PRO DCX2496 be appropriate, or can you point me to products that good for mains?

nick


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

recruit said:


> It might be useful Graham considering an EQ device which also works in the time domain as decay times or what some call ringing can still be bad even when a response looks flat, I believe the Anitmode also works in the time domain and seems to do a very good job or else you have the more expensive option which is the SVS EQ1...


Actually, any equalizer with IIR filters has an effect on time domain. The Antimode merely generates filters to perfectly match the “size and shape” of room modes.

There are a few problems with this technique, IMO. For starters, the measuring and processing platform tends to treat every peak in response as a room mode, whether it is or not, and “over equalize” – i.e., use more filters than is necessary to make things sound good. Not every high point in response is a room mode.

Second, depressions in response are ignored, which of course will result in the sub not sounding good.

Third, the “optimal time domain” equalizing is only valid in the location where the measurement was taken.

And finally, while the measurement platform is stable enough (REW for example), the transducers involved – the speakers and elements in the microphones – are not. Their physical (and consequently electrical) properties are altered with changes in temperature, humidity etc. Consequently, when you take a second REW reading in six months and you’ll find it doesn’t look exactly like your original one, and REW will recommend different filters. A waterfall generated today with last year’s filters isn’t going to look as good as it did back on the day you fine-tuned the filters for minimal ringing.

I first observed this phenomenon nearly fifteen years ago when I got my AudioControl real time analyzer/pink noise generator. I would painstakingly set my 1/3-octave equalizers based on the RTA display, only to check it again a few months later and find, to my great dismay, that my response was no longer perfect, but off a little here and there. At least that’s what the visual display was showing. There was no detectable (read audible) difference.

In the end, the best an equalizer can do is reduce the ringing from a room mode and bring it back in line with the rest of the frequency spectrum's decay times (fortunately enough, that's all that's needed to improve the sound quality). It isn’t going to reduce the mode’s decay time to something faster than the rest of the frequency spectrum.

Regards,
Wayne


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

Nick said:


> I am also interested in biamping my mains as they have wire posts that separate the woofers from the M/H freq, and likely adding a pair of subs after that. If I have to take the crossovers out of my speakers, then I would not bother biamping -- but I am wondering if there is a product that will address each of the issues above, or do I need two different products?


I’m not sure which issues you’re referring to..

Regards,
Wayne


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

Nick said:


> Would something like the ULTRADRIVE PRO DCX2496 be appropriate, or can you point me to products that good for mains?


I really haven’t seen anything yea or nay on the DCX. You might post a query in our DIY Speakers Forum, where someone might be using it for management of an active system. Our BFD Alternatives thread has a few options that have been confirmed as suitable for full range. The link for the Rane EQs contains some tips to help determine if the equalizer you’re considering is good or not.


Regards,
Wayne


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## Nick (Oct 28, 2009)

Wayne, I just got started with measuring my room. I have seen some nice results from moving the speakers around. Now I would like to experiment with a few things and I can't tell from the forums which product(s) might be best.

1) Brucek has indicated that BFD is not suitable for running with my full range speakers, so I am wondering what product might be suitable for that purpose? If it has to be something like the neptune, I would rather buy subs. 

2) I wanted to try biamping my speakers and I believe I need an external crossover to do that properly. I'm unclear on whether any of the EQ products in the forum can do both what I am looking for above and provide what I need to biamp?

It may be that my next step should be to add a sub and the FBQ rather than trying to EQ my 'full range' speakers as I can't get anything like a 'house curve' with my speakers.

Thanks,
Nick


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

Nick said:


> 2) I wanted to try biamping my speakers and I believe I need an external crossover to do that properly.


 Well, you’ve already indicated that you don’t intend to remove the speaker’s passive crossovers. In that case, biamping using the speaker's dual terminals is merely using a separate amp for each set of binding posts. The speaker’s internal crossovers will do the filtering, so none is needed from an external processor.

Many consider passive bi-amping like this to be a lot of hooey, but one advantage would be the ability to add an equalizer for the low driver. Typically any negative artifacts attributed to equalization (if any) are most audible in the upper frequencies. Typically it’s the speaker’s lower frequencies are more in need of equalizing than the upper frequencies (although that’s just a generalization and is not always the case)

Regards,
Wayne


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## Nick (Oct 28, 2009)

Thanks Wayne, I think I am starting to get it. I just want to try to EQ the low frequencies on the speakers before I buy a sub, so it sounds like the FBQ ought to be fine for that. I'll bi-amp only in the sense of running the woofers only with the EQ. I actually need some boost, so I think I'll ultimately need the sub anyway. 

BTW. I appreciated your great review of the SB-12. 

Thank you very much,
Nick


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

Nick said:


> BTW. I appreciated your great review of the SB-12.


Thanks for the kind words, Nick. :T

Regards,
Wayne


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## recruit (May 9, 2009)

Wayne A. Pflughaupt said:


> Actually, any equalizer with IIR filters has an effect on time domain. The Antimode merely generates filters to perfectly match the “size and shape” of room modes.
> 
> There are a few problems with this technique, IMO. For starters, the measuring and processing tends to treat every peak in response as a room mode, whether it is or not, and “over equalize” – i.e., use more filters than is necessary to make things sound good. Not every high point in response is a room mode.
> 
> ...


Thank you Wayne


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