My BFD results are in! (1 Viewer)

[MikeHalder]

After a few hours of tweaking with the BFD I finally a graph that looks pretty good...I think. Take a look and see if this is as good as I am going to get. Any feedback is always appreciated.
TIA
Mike
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[Sonnie Parker]

Mike,
That looks super smooth.
Why don't you overlay the 2 lines on one graph and have one link to view? It would be interesting to see the 2 lines together. You could post the graph here on the forum I believe.
That BFD is sweet isn't it?

 

[MikeHalder]

Sonnie,

Since the two sets of data were taken at slightly different volume levels(wife and daughter wanted to watch a movie after the first set), I will take a before and after sampling tomorrow morning at the same volume setting and post it. I ended up boosting @22HZ+5dB, getting that nasty dip at 50HZ boosted and smoothing out the >50HZ region using 11 filters.

Mike

 

[Nick P]

Mike,

I'm far from an expert but from what I've been reading and what I've found out from my own BFD experiments is you might have been better off bringing the peaks down to your 22hz level rather than boosting 22hz. That way you don't cut into your amp headroom. Reduce all the peaks and then recalibrate your overall sub level with VE or AVIA back to your prefered SPL level in relation to your mains. With all the peaks gone you should actually have more, not less, headroom to play with.

 

[Thomas_Berg]

i ordered my BFD around Wednesday of last week, and it was scheduled for delivery this past Tuesday. it is still not here. apparantly it has gone out on the truck for delivery twice, but FedEx hasn't delivered it here yet. needless to say, i am VERY unimpressed with FedEx. i know for a fact that they deliver to our campus, and someone in the mail room signs for all packages that need it. i'm really anxious to get my hands on this thing!

 

[MikeHalder]

Here is the composite graph of befor and after BFD.
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I ran some good base scenes(Titan AE-Ice Fields $ Toy Story 2 openning scene) a much higher than normal listening volumes(105dB) and had no problems with the sub clipping, so I think I am safe with these settings. I agree with others who have posted that there doesn't seem to be as much bass when listening to music, but it sounds cleaner.
Mike

 

[Sonnie Parker]

Mike, now that I see the 2 together, I agree with Nick. I would cut the peaks and and not boost anything in your case.

You could bring everything down to 83 db and be in the drivers seat, with no boost at all.

I believe you would get more of the bottom end (20-22hz) back into the picture too.

Why don't you try using another preset and play around with it. Once you get it set, switch back and forth and see which one you like. While you are at it, set up another with a house curve and switch between the 3.

I prefer the house curve myself. At least for now I do. I have some more experimenting to do myself.

 

[Nick P]

Mike,
If you do try what Sonnie and I are suggesting don't forget to recalibrate your overall sub level back to even with your mains, 3db over mains or whatever you normally calibrate to. Overwise your volume level will be really low.
Sonnie,
I'd like to take this opportunity to thank you for your work in putting together the BFD user's guide. I understood your directions and explanations perfectly. Great job!

 

[MikeHalder]

I followed your advice and recalibrated cutting the freq instead of boosting....how does this one look?
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Thanks again for all your help!
Mike

 

[Wayne A. Pflughaupt]

Frankly Mike, I think you've been given some bad advise. Sure, you brought down the peaks (if you can call a 2/3-octave plateau a “peak”), but now your overall level has been reduced by at least 6dB – which means you will now have to increase the sub’s volume.
So, where’s the increased headroom?
I think you had it right the first time.
I do agree with Sonnie about the house curve, though. Your response is vitrually ruler-flat, and would probably sound better with a gradual rise from 100 to 32Hz.
For more info, check out this thread:
http://www.hometheaterforum.com/htfo...threadid=51646
Regards,
Wayne A. Pflughaupt

 

[MikeHalder]

Wayne,
I changed the filter array to use the plateau as the base line. Is this more of what you had in mind?
Mike
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[Nick P]

Wayne,
I'm probably getting in over my head here because as I stated above I'm not an expert. It is my understanding that when you have peaks in your curve and you calibrate with Avia or VE which uses a mix of frequencies in their subwoofer tones you end up setting the 75db or 85db or whatever db to the highest frequency peak. So if you have an 8db peak at 45hz then your 20hz freq., which is 8db lower, doesn't play as loud as 45hz. The amp and/or driver will run out of steam at 45hz quicker than the 20hz. If you lower the 45hz down 8db you now have more headroom at 20hz because it now has the opportunity to play as loud as the 45hz tone. And of course I think it's generally agreed that boosting frequencies does cut down on overall amp headroom. That's why I said he will have more headroom. The amp level should stay the same. The amp input level will have to be increased to compensate for the 8db lowering of volume. This, I think, is how it was explained by Vince Maskeeper in another thread. Wayne, I know you and Vince don't see eye to eye on the house curve either and I'm not sure how I feel about it yet myself since I haven't tried it yet. Please be gentle with me if I'm way off base here.

 

[Brian Corr]

What exactly is a house curve?

 

[Sonnie Parker]

Thanks Nick, for the comp on the BFD page.

Wayne, does this mean that if he cuts the frequencies and then turns the volume up to compensate for the cuts he just made the amp will use more headroom? Because he's boosting a wider range?

I was on the same thinking as Nick.

Now I'm thinking that if Mike had several peaks (1/6 or 1/12 wide or so), then it would make sense to cut the peaks but since he has a fairly smooth plateau (not really a peak), the first recommendation Nick and I made would not come into consideration. But Nicks last post makes sense too.....I need more tutoring here.

If it is appropriate for him to start his house curve sloping off somewhere between 31.5hz and 40hz then he could prevent boosting the 56hz as much. Then he could tame the 63hz peak to continue his house curve slope. Would this be logical?

Brian, follow the link Wayne posted and you will learn more about a house curve.

 

[Wayne A. Pflughaupt]

Nick,

Wayne, does this mean that if he cuts the frequencies and then turns the volume up to compensate for the cuts he just made the amp will use more headroom? Because he's boosting a wider range?

In this case I believe so. Look at Mike’s baseline curve: Except for a 7-8dB, 1/3-octave dip centered at 50Hz, his response it is essentially flat from 25Hz to 63Hz, a wide, 1 1/3-octave span.
In this situation Mike could have flattened the entire span with a single filter. After EQing his sub probably would not have required any gain adjustments (which is very unusual). So, his sub amp would have only been required to work a little harder at and around 50Hz.
But what happens if you try to bring down everything else to the level of the 50Hz dip? You’ve reduced gain virtually across the board. Of course, now the sub is operating at a much lower level than it was before EQ, so you have to increase the amp’s gain – which only puts you right back were you started. So yes, all the “headroom” you created by cutting that broad area is lost by the need to increase the sub’s volume to restore the output you had before.
Please keep in mind that Mike’s situation is unusual. More typically there are one or two narrow, offending response peaks. Even though you really don’t want them, you get the loud peaks for “free” from the room – not at the amplifier’s expense (as described above). Since the level is so high at a couple of places you compensate by turning down the sub’s volume, and by doing so you have a lot of unused headroom. So, you reduce the peaks with an equalizer and now you have to turn up the sub. Yes, you are now demanding more amplifier power, but it was already there – you just weren’t using it.
Also consider: It is not easy to bring down a broad, flat area and keep it flat. It is the nature of equalizers to introduce humps and valleys – that’s why they are good at addressing those types of response problem – and as such equalizers don’t do so well addressing a flat area. So, it would have taken something like 3-4 filters to reduce Mike’s plateau, which was nearly 1-octave wide, and keep it flat. In addition, another filter would have been needed to address the peak at about 59Hz. Thus it would have taken 4-5 filters set to cut to accomplish what one could have by boosting. While I’m a big fan of equalizers, I’m never in favor if using more when less will do.
In any event, this may all be moot, since it looks like Mike simply shifted the EQ’d line down for clarification, not actually lost 6dB of gain across the board.
I had some other thoughts about what I think are overblown myths relating to equalizers and headroom, but I’m sure I’ve already over-extended everyone’s patience.
Regards,
Wayne A. Pflughaupt

 

[brucek]

Really good post Wayne - thanks.

I feel another addition to the reasons not to wholesale drop an area like Mike was doing, is that you also can easily mess up your dB/octave drop after your crossover point.

In his original and last graph he appears to have a nice 24dB/octave 4th order drop happening after 60Hz, but in the graph where he wholesale brought down the entire area, it seems to be quite different from that scenario. This can significantly affect the sub/mains integration.

Do you agree or disagree with this thought..

brucek

 

[Sonnie Parker]

Thanks Wayne, I understand it better for sure now. Don't worry, my patience won't thin up any. It's all about learning. Hey, brucek knows I will listen, huh Ken? lol

 

[MikeHalder]

Thanks for all your resposes! I have the following respose curve based on these filter settings:
22HZ +4dB
40HZ -1
45HZ -1
50HZ +9
56HZ -1
63HZ -1
71HZ +2
80HZ -2
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The volume(gain) on the subs are only turned up to the second position (2 out of 10 ~ 20%) and the sub is about 5dB over the mains volume. I am very happy that my room was kind in allowing such an easy task of flattening out the response. Any suggestions as to any changes I might consider in my filter selection?
TIA
Mike

 

[jeff lam]

After playing with my new BFD this past week I tend to agree with what Wayne is saying. I keep hearing "you loose amp headroom if you boost". But when you cut everything, you have to turn up the amp level to get it back to calibration so I don't understand this. It seems to me that if you are running well above normal listening and the amp still doesn't clip you can boost as much as you want. Am I wrong in thinking this? I set a movie preset(4) and a music preset(5) on my BFD, my music preset has a 10dB boost @30Hz with a large bandwidth, which is the way I like to listen to music. Before the boost, you could barely tell the sub was even playing. I can't think on one reason not to have the boost if my amp isn't clipping, it sounds better this way, and the sub plays louder this way then with the response for movies.

What is all this talk about loosing amp headroom when boosting? If it actually plays louder when you boost, how is that loosing headroom, does this make it clip at a lower level?

 

[Harold Leroy]

"I do agree with Sonnie about the house curve, though. Your response is vitrually ruler-flat, and would probably sound better with a gradual rise from 100 to 32Hz."

Wayne, how much of a gradual rise do you suggest?