# BFD Accuracy



## BigPines (Jul 10, 2007)

Obviously the people here have a lot of experience and are very concerned with accuracy of equipment used. I would be interested in some comments about the accuracy of the BFD.

I have read several posts where it is not recommended to use the BFD for full-range EQ because it introduces an undesirable artifact or sounds "grainy". My question is how good is the BFD anyway? The specs are impressive and it seems like a thoroughly tested solution but what causes it to sound bad on main channels and why would we accept this in the sub channel? If it is good enough for the sub... Would all EQs no matter how clean cause this unwanted artifact?

I am still trying to learn so any information would be appreciated.

Mike


----------



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

Welcome to the Forum, Mike!

The artifacts some report when using the BFD full range most likely come from its less than stellar AD/DA converters. It’s not an issue with dedicated subwoofer use, because low frequencies are more forgiving of such things. 

For instance, it’s my opinion that the amps in subwoofers are not nearly as clean and transparent as the ones in your receiver. Just try to find a subwoofer with specs that include such things as signal-to-noise ratio, THD, etc. Obviously if a sonically pristine signal was an important factor for low frequencies, users would demand it and manufacturers would deliver.

So – that’s why the BFD works so well as a subwoofer equalizer, if not for the mains. For the former, it doesn’t _need_ to be sonically pristine.

As far as other equalizers being used on the mains, good ones aren’t going to add anything until you make an adjustment. Personally I prefer good-quality analog EQs for the mains, because I’d rather not have another AD/DA conversion in the signal chain. 

Hopefully someday we’ll get receivers with digital outputs for all channels that can directly feed to a digital equalizer. Until then, the digital EQs and tone controls most receivers have these days can do a decent job (if needed) without adding a lot of extra (and expensive) hardware to your system.

Regards,
Wayne


----------



## brucek (Apr 11, 2006)

Yeah, and certainly the noise floor that a BFD enjoys is readily amplified by a full range mains channel, but can't be heard through the subwoofer. Certainly, also the sub bandwidth represents a relatively small portion of the entire systems spectrum, and so we tolerate the digitizing of the subs signal to gain an equalized output that isn't as big a problem with the mains channels. We also don't need to worry about crosstalk from a device in the subwoofers mono channel. As Wayne says, things like THD aren't as big an issue in a subwoofer - they are already horrible in that department..

brucek


----------



## BigPines (Jul 10, 2007)

Thanks guys!

Makes sense to know when a compromise is acceptable and just go with it. I am amazed how cheap these BFDs really are and they seem great for what they are being used for. I guess live venues don't worry about the artifacts introduced by such a device since critical listening will not be done in that setting.

Wayne, you are right. I was actually surprised that I could find no mention of Signal-To-Noise ratio or THD on my M&K MX-350. I probably don't want to know... :yikes: ...ignorance is bliss. 

I know that room treatment should be the first place to look but if problems in the full range speakers can't be solved with room treatment alone, EQ is a useful tool. Wayne mentioned AudioControl EQs in your House Curve thread. I have always liked the AudioControl units. I have also been thinking about the Rane 44 or Rane 22. What units have people had good experience with? What is recommended if I really want to get into EQ in the mains? What is the best bang for the buck?

Mike


----------



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

The best bang for the buck is your receiver’s tone controls, especially if they’re the digital type with adjustable frequency settings. Adding full range equalization is an expensive proposition, by the time you get one per channel and any additional amplifiers you might need for any channels of your receiver that don’t have pre-out and main-in jacks. 

For instance, my three C-131s cost me $400 each, and that was with a substantial mail-order discount. Even if you find some relative cheap equalizers you’re happy with (not many of those I personally have confidence in, although some on this Forum do) – at say, a couple hundred for a stereo model – that’s $600 by the time you cover all five channels. Not to mention all the rack real estate that stuff requires (it does makes for an impressive looking rack, though!).

Both of those Rane units are out of production. Since you’d have to go with used ones anyway, I’d look for an AudioControl Bijou or Rialto. I’ve had bad experiences in the past with Rane’s equalizers having a tendency to introduce audible hum, by picking up EMI when they were mounted right above or below amplifiers, for instance. That was a long time ago, though, back in the early 90s. Maybe they fixed that problem with their more recent models.

Regards,
Wayne


----------



## BigPines (Jul 10, 2007)

Hey, as my wife often points out to me - this entire hobby is an expensive proposition. I would spend $600 on EQ but that is because I am sick like that. :coocoo: Of course, if I have to EQ a 7.1 system, I will need more than 3 units. :bigsmile:

Thanks for the tips on the other EQs. I have a feeling I will be getting some in the future.

Mike


----------

