Axiom Home Page Forums General Discussion Home Theater BFD?

Allright. Enough of looking at bigger amps and more expensive receivers. I want to make a purchase that is going to make a significant sonic difference in my system. So I figure that if I can buy something that will flatten out the nulls and peaks in my frequency graph I would be making a wise purchase.

So here's the question. Is the BFD that is frequently mentioned around here really going to help me? It would appear that it is for two channels, so what about multi-channel for music and movies? I read the info at the Behringer site but I am still confused.

How many of you out their have made this purchase and did it make a significant difference. It would seem that if it could flatten out the frequency response that it would be one of the best additions to any system that you could get.

Any help is much appreciated as always.

Ask MarkSJohnson. He's had his BFD for about 6 months now and should be an expert on it!


Seriously, I believe Tharkun has one, but it was Peter and Ken who set it up. Maybe they can chime in. I've had my eye on that BFD for some time, but have avoided it because it looks like a headache to deal with.

Good one, Sean.

AFAIK the two channel limit isn't a big deal because you most commonly use it to level out your subwoofer response... and two subs is all that most of us are likely to have...

... or, at least, that anyone is likely to use on a single system at the same time

I'd first measure your sub's room response to see the extent to which you are dealing with room nulls and peaks. Although you didn't say so in your post, I assume you are interested in addressing your sub, rather than the peformance of your mains. The BFD is not suited to EQ frequencies much above those handled by subwoofers.

If you haven't already check out Sonnie's BFD Guide and Forums:

http://bfdguide.ws/

Be aware that adding a BFD into your system may introduce a ground loop. Safely addressing that issue may involve the purchase of a ~$100 transformer.

In reply to:

---

... and two subs is all that most of us are likely to have...

---

And then....................................there is Craigsub! I believe he's the exception that proves the rule.

What does BFD mean?

Big Freakin' ...

Seriously, Behringer Feedback Destroyer. I haven't used one myself, but I understand it includes a pretty good parametric equalizer which a number of people use to improve their low frequency response.

>>I'd first measure your sub's room response to see the extent to which you are dealing with room nulls and peaks.

Ahh, you obviously haven't read the Mother Of All Posts. Suggest you do a search on "mother of all posts" then take a quick (ha !!) read through Mark's excellent production. Graphs, photographs, objectives, alternatives, everything. You will be impressed.

EDIT - my mistake... there is another thread where Mark is wondering about how effective a BFD would be. This, however, is not that thread. Ignore the above... unless you haven't read the MOAP in which case I do recommend it anyways (even though it describes someone else's room ).

>>And then....................................there is Craigsub!

Yes... I had to add that second line to the post to cover Craig. While he may have owned every sub under the sun, I believe he rarely uses more than two at a time in the same room... on the same system... playing the same disk... (what other qualifiers can I think of ?).

In reply to:

---

I believe he rarely uses more than two at a time in the same room... on the same system...

---

I'm sure he doesn't. The only instance of that I can remember was when he had 4 UFW-10s up and running at the same time, in the same room, on the same system.

The best response curve I was able to get was with a 60hz crossover setting with the sub located in the front left corner of the room about 3 feet out from the side wall and 1 foot out from the front wall.

16hz 74db
20hz 71db
25hz 67db
31.5 68 db
40hz 67
50hz 68
63hz 71
80hz 73
100hz 73
125hz 75
150 71
200 71
250 72

This is using 1/3 octave warble tones and an analog radioshack meter(adjusted measurements) positioned at the listening position at a 45 degree angle. The head unit is set in stereo mode and my Hsu sub was tuned for maximum extension.

Note: These numbers look fairly good but I noticed that when I ran the 1 hz increment test tones there was some ugly differences from one hz to the next. Some of the measurements taken with the 1/3 octave warble tones had to be estimated in the middle because the dial was traveling back and forth a significant amount on one warble tone.

I'd kill for that response!

No. Really.

Kill.

The more I look at my numbers the more I think that I could turn my sub up about 3db. Who cares if I have a peak at 16hz from 60 to 20 hz my numbers would match more of what the 60's are doing. It might actually be a flatter response that way with just that one peak.

Hmm. . .more bass. . . .hmmmm

kill.

Was away for 3 day weekend along the Oregon/California coast and just returned home late last night, so slow in a reply.

I do have the BFD set up for the twin 600s, but at the time I'm working on re-locating the subs and re-adjusting the BFD. Ken was not here for the BFD set up, and Peter was doing the programing the BFD. The person that was suppose to be the bay area sub person made most of the decisions on setting up the BFD.

There are several issues with the sub/BFD set up I have not been happy with, basically the sub gain levels were turend very low, and the set up for the subs in the C2 processor was set at -15db. So after many months of wondering why I was lacking in base, I decdided to start over and do it again.

Since I will be up at Axiom this Friday I hope to have some input from Ian on my 600s and the area they live in. The BFD can be a bit complex, but with some reading and playing, its not impossible to set up for a novice like me. lol

those response #s do look quite good, you certainly wouldn't expect as profound an effect from the BFD. Speaking from my personal experience, i did have 20db swings in response (on 1/3 octave testing). After the BFD i was able to get those swings down to less than a couple of db. That was the extent of my "scientific" testing and i did not do a lot of pre-post tests. I suppose it would be quite easy to flip the bypass on and off and test out a few specific pieces but i haven't gotten around to doing that yet. What i will say is that the overall performance of the sub has increased. To me it has been very noticeable - bass appears considerably less "sloppy", better punch, and overall output has increased. Again, i haven't performed any blind testing or anything, so take this for what it is worth, but i have noticed a marked diffference.

Those are pretty nice numbers. Your response looks like most people's "after" curves. No wonder Mark hates you.

I would agree with turning the sub up 3-4 dB.

In reply to:

---

I would agree with turning the sub up 3-4 dB.

---

Thanks for the responses guys. Sorry Mark!! Sorry for ever posting this! I guess I should just be happy with what I have. Rats there I go saving money again. The need is clearly more present to invest in my car audio anyway due to these wonderful axioms.

Thankun, Did you say your system was lacking in bass??

How on this green earth could YOUR system be lacking in bass?

Long story, but to solve one issue that should have been solved another way, the expert adjusted the gain(volume) control on the 600s to about a four oclock position, then more adjustement through the C2processor to the -15(adjustment is -15 to +15)....which basicaly disabled the 600s mostly. So there was lots of base, but not any where near the base that should be "felt" from the 600s.

You might also want to check out this product, sounds like it does the same thing as the BFD.

The Velodyne SMS-1 is actually a better unit as in its software driven, has a video output so you can see whats being done, uses a mic to aid in the set up. It can be found for $500-600, and may be my next choice if I'm not happy with the set up this time around. I believe Craigsub has one so perhaps he will give us his opinion.

SS, the numbers that you show are very satisfactory from the standpoint of smoothness. At those levels 25HZ and below is below the level of audibility for those extremely low frequencies.

I have the SMS-1 with my new EP500. Although a little pricey for a sub eq, it is very impressive. I think the on-screen graphics showing real time results is worth the price of admission. I also like that I can set different curves (up to 5) that can be toggled through with the remote. I am planning on creating a movie curve and a music curve for two different seats. I am not sure what I will do with the 5th preset though. I was thinking maybe a less severe bass bump curve for movies, for when I listen at louder volume than my normal listening levels.

In reply to:

---

for two different seats

---

Hmm. That begs an interesting question: Is there a way to take multiple readings throughout a room and "average" them? As an example, my sweet spot requires that I sit dead in the middle of the loveseat. On the nights when I'm too lazy to sit upright, I'm crashed horizontally and the sound is noticably different. And of course if I'm in the chair to the left of the loveseat it's different again. So my question is, is it possible with the SMS-1 to take three different readings in three different spots and come up with a workable average for any of the listening positions? Forgive my ignorance; I'm probably asking if the sky is blue, but I really know absolutely nothing about how all of this stuff works.

No, it's a very good question. Hopefully someone knows the answer 'cause I don't

I don't think it can as of yet, but I did hear Velodyne was working on a 5 microphone setup and hub that would allow this. It is supposed to be out in the next month or two for an additional $100.

In reply to:

---

16hz 74db
20hz 71db
25hz 67db
31.5 68 db
40hz 67
50hz 68
63hz 71
80hz 73
100hz 73
125hz 75
150 71
200 71
250 72

This is using 1/3 octave warble tones and an analog radioshack meter(adjusted measurements) positioned at the listening position at a 45 degree angle. The head unit is set in stereo mode and my Hsu sub was tuned for maximum extension.

Note: These numbers look fairly good but I noticed that when I ran the 1 hz increment test tones there was some ugly differences from one hz to the next. Some of the measurements taken with the 1/3 octave warble tones had to be estimated in the middle because the dial was traveling back and forth a significant amount on one warble tone.

---

I have to wonder that while these numbers look good on paper, the human ear hears different frequencies with a different sensitivities. For example, the human ear is least sensitive to low frequencies. It is also less sensitive to high frequencies; all relative to the approximate middle frequency of 4000 Hz (supposedly where human hearing is most sensitive and, likely not coincidentally, about where most speech occurs). The human ear sensitivity response curve is something like a distorted bell curve. (Trying to remember years back to my vibrations and acoustics course).

Combine this with a room's imperfect acoustic properties and a decent sounding system can have a very strange response curve.

These sort of numbers in Mark's room may actually "sound worse" to him than his current setup.

Have people who own the BFD or the Velodyne SMS-1 found anything in the documentation that talks about "setting up an ideal response curve for your room"? I can not imagine that a flat response would sound best.