BFD Question (1 Viewer)

[Jonathan_D]

This may be covered in earlier posts, if so I apologize. When building filters, is it best to start low and work up or start high and work down?

Thanks!

 

[Allen Ross]

i take it you mean frequencies?

i honestly don't think it makes a difference.


but if you are talking about gain and loss, i have always believed that its better to take out the peaks then to raise the shallow parts

 

[Jonathan_D]

I meant frequencies but then started thinking that hitting the peaks first was the way to go anyway. Of course, that raises the question low frequency peaks to high or vice versa? Guess you're probably right that it doesn't matter. I was just curious what others might have experienced. My BFD is being delivered today (though only God knows when I'll get a chance to set it up).

 

[GeorgeS]

I've worked out all the filters in software and set it up 'in one shot', as well as incrementally (look at the current response graph for the largest single correction required, apply the filter, remeasure).

The latter gave superior results and has the added benefit that you get to both begin enjoying the results immediately (one broad filter can make quite a difference) and take as long as you want to work through the entire process.

Take good notes on what you were trying to accomplish, the parameters selected, and check your results. Don't worry about getting it "perfect". You'll most likely get usable results the first time and if you decide to redo it it will go much faster the second time.

 

[Anthony_Gomez]

not sure if this is best or not, but I like to start with a flat (disable XO) nearfield adjustments and then I move to room adjustments. For the room, I don't work high to low, but from large bandwidth to small bandwidth adjustments.

 

[Rick Guynn]

The advice I have seen in the past is to start low and work your way up.. this is because adjustment to the lower frequencies can affect the harmonics further up the scale.

RG

 

[Ronnie Ferrell]

I still don't know the "best" way to set up the BFD. I think a lot of trial and error is needed, along with Tony's Excel worksheet and 1/12 octave test tones.

I spent about 4 hours the first time and set it up on preset #4. I just added some more room treatment and spent about 6 hours setting it up on preset #5 so that I could compare the two. #5 is flatter, but I prefer the sound of my original setup. Go figure...

Anyway, I am just curious how many filters you guys actually wound up using? Also did you set it up with your mains on or off.

This is what I did. I went low frequency filters to high. I used both cuts and boosts. My mains produce a bad cuffing noise when "trying" to playing a continues low frequency tone. This cuffing is pretty loud and interferes with my measured SPL. So I measure from 10Hz to 42.2Hz with the mains off. I then turn my mains amp on and continue the measurements. I know this is probably not the "best" way, but it sounds pretty darn good after setting it up this way! My preset #4 uses 9 filters and my #5 preset uses 8 filters.

Also, once you get the hang of setting the BFD settings, and using Tony's spreadsheet to calculate the fine tuning of the frequency, its a piece a cake to use!

Ronnie

 

[Chuck Bogie]

So, is this the dsp1124? I'm thinking of getting one...

 

[Allen Ross]

thats the newest model, btw check my link for some great pics

 

[Wayne A. Pflughaupt]

Ronnie,

My mains produce a bad cuffing noise when "trying" to playing a continues low frequency tone. This cuffing is pretty loud and interferes with my measured SPL. So I measure from 10Hz to 42.2Hz with the mains off. I then turn my mains amp on and continue the measurements. I know this is probably not the "best" way, but it sounds pretty darn good after setting it up this way!

Actually, the way you did it is just fine. The main reason to play the mains and subs together is to get readings that include the crossover and phase-induced response irregularities. Phase irregularities can generally get corrected with equalization, so you want the readings to reflect them. Phase problems typically show up most predominantly an octave or so above and below the crossover point, so at 42Hz and below you were probably far enough “downstream” from the crossover point and phase effects.

Irrespective of that, it sounds like the mains are struggling to deliver frequencies below their range, which is peculiar. If the mains are set to “small,” as they should be for best sub performance, the signal to the mains should be down at least 24dB at 42Hz, and off the map by 10Hz. Either your speakers are set to large, or the crossover is not performing as it should, or you were playing your test tones at extremely high levels – a definite no-no.

Regards,
Wayne A. Pflughaupt

 

[Jonathan_D]

So, has anyone done the method described at http://www27.brinkster.com/jmag999/? (You won't be able to pull it up very often as it seems to recently run into bandwidth problems.) But it describes the use of the EFT software rather than a spreadsheet. If you have a computer near your setup, this appears to give realtime analysis.

Since I have a computer as part of my whole HT setup (or vice versa?) I'm going to give this way a try.

 

[Ronnie Ferrell]

Irrespective of that, it sounds like the mains are struggling to deliver frequencies below their range, which is peculiar. If the mains are set to “small,” as they should be for best sub performance, the signal to the mains should be down at least 24dB at 42Hz, and off the map by 10Hz. Either your speakers are set to large, or the crossover is not performing as it should, or you were playing your test tones at extremely high levels – a definite no-no.

I set up my BFD in stereo mode using a red book audio CD. My receiver does not have a lot of bass management in pure audio stereo mode. With DD and DTS I have a lot more options (Large, Small, 40, 60, 80, 100 x-over points, sub=LFE, sub=LFE+L/R, etc.) My options in stereo mode are no sub, or sub x-over at 40 or 60 and that is it. I cannot adjust the main speaker size when the receiver is set to pure music stereo mode. My mains play full range in pure music stereo mode too. The cuffing is only present when playing a continuous tone at a given frequency way below the natural roll-off point of my mains. It is not audible at all with normal listening levels of actual music. And for HT use the x-over on the mains will have kicked in by then. I wish I had a DVD with DD 5.1 encoded 1/12 octave test tones on it from 10Hz to 100Hz.

Thanks for all the good info and the conformation on my steps used in setting up the BFD. I was winging it and those steps seemed the most logical. I have read your old post on the house curve, and you are correct, my original preset looked more like a house curve than flat.

Take care,

Ronnie

 

[PaulDF]

I am no expert by any means, but I'll throw in my two cents..

So far, I have seven presets. Only five are for real (not experimental). I'll try and list what they are, in order... The first four are for my movie "sweet spot", and a few are reserved for my music "sweet spot".

Movies:

#1 very flat
#2 house curve (no RS correction)
#3 High house curve (exagerated house curve)
#4 my first attempt at flat, with no help from Excel

Music:

#5 flat (very boring)
#6 experimental

For movies I like the flat the best. Has more impact for me. For music, I have lately just been disabling the BFD. Pretty good gain in my sweet spot there. Havent found a suitable curve to suit my music.

I tend to start setting with the lower freq's, and move upward. Doesn't really matter I don't think. I try hard not to boost much, especially below 50 hz. My BFD has a buzz to it, most always there, and if a preset has any boost in it, the buzz is louder. Is that normal?

Has anyone ever had their BDF shut itself off? I went to use my system the other night, and noticed the BDF was not lit up. (I usually leave it on 24/7 due to the thump factor). Thought the wife musta shut it off, (imagined her jumping out of her skin... THUMP!!) So I pushed the on/off button. It came OUT and of course no power up. ? So I pushed it again and it came to life. Kinda weird thats all.

I will say Anthony's Excel program is VERY cool, its hard to believe such a minute change can make such a BIG difference. Makes me wonder how long it would take to set up a preset by ear....

Maybe I shoulda bought a second Tempest....

 

[Jonathan_D]

My BFD has a buzz to it, most always there, and if a preset has any boost in it, the buzz is louder. Is that normal?

From what I've read in the various FAQs, the buzz is caused by a ground loop due to the BFD's grounded plug. This sometimes happens because something in the house (e.g. phone, cable) is grounded somewhere *other than* the power ground.

I used the EFT software to measure the sub and help set up my filters. My sub is not in an optimal place in the room, but I have no other choice. I had to boost a huge dip at 20 hz, and flatten out peaks at approx. 32, 60 and 70 hz. I left frequencies higher than 100 alone for now as my crossover is set at 60hz. Took 7 filters, but with my 122L Tempest I'm 3db down at 20 and flat (+- under 1db) to about 95hz after EQ.