My BFD experience.

[Eddie Horton]

As the crossover is not a brick wall on the speaker side or the sub side, the sub will still be contributing to the FR above the crossover point, but with decreasing output depending on the slope of the crossover.

[bikeman]

If I am using an 80Hz crossover, what effect will the BFD have on freq's above that? It will be in the sub path, not the mains.

The BFD can be used at almost any freq. I found that there is no substitution for experimenting.

David

[Mag_Neato]

Thanks guys! I won't have a lot of "Tweak time", so I'm looking for the quick and simple. I realize I will have to experiment, but it never hurts to seek advice from those who have "been there, done that!"

Now, I should download the Snapbug instructions to get a grip on the setup process!

[BradJudy]

Ed,

The link posted by jimsfield here: http://forum.av123.com/showthread.php?s=&threadid=7719 is a set of 1/12 octave mp3s that can be burned to CD. They are 6 sec each IIRC and are slightly faded in and out to prevent clicking from sudden volume changes. I just made a list of the frequencies that I used in Excel and printed out a sheet for writing down the frequencies as it played. It goes pretty smoothly except for pausing when you need to switch the range on the SPL meter.

The BFD Excel file uses 1/6 octave measurement, so I just charted it in a new spreadsheet. To check the corrected values, I interpolated corrections for the additional data points. If there is interest, I could clean up my spreadsheet and post it.

[BradJudy]

BTW: Your crossover is likely 24db/octave (possibly 12db/octave) which means that if your sub is at 85db at 80Hz, it will still be putting out 61db at 160Hz. This is why the phase is so important, since the sub can destructively interfere with your main speakers for quite a while.

[Mag_Neato]

Brad...

My subs X-over max's out at 150Hz......that is where I have it set. My Outlaw 1050 is set at 80Hz X-over. Not sure of the slopes, I think the sub has either 18db/octave or 24. It is not a Linkwitz-Riley, so 18 may be right.

The guy selling me the BFD(Ajax) burned the test CD's for me(the Hsu and the Rives discs). I don't have a burner. I'll see if he can burn one from the link you posted.

I like snapbug's idea of measuring the sub without the mains running. I could see how high the frequencies are being reproduced above the cutoff.

I drew up my own chart in AutoCAD. I draw a Spline through the points, which automatically curves/smooths out the line.

I looked at the UFW-10 manual online to see how they setup the filter on it, and they are only using 1/3 octave measurements. The Rives test CD has a set of tones which are made specifically to correct the Radio Shack meter's readings without needing to manually interpolate them.

[BradJudy]

Ed,

While also measuring the sub without the mains is useful, you should definitely measure them with the mains to ensure you aren't getting destructive interference because of your phase setting. Ideally, you should measure with the mains using different phase settings to see which works best (see my measurement thread for my two phase graphs).

[Mag_Neato]

Oh lordy......

what am I getting myself into?!!!

[curtis]

Oh lordy......

what am I getting myself into?!!!

LOL!!

And do at least 1/6 octave!!

I think I am going to go the ETF route, and get as close to "right" as I can without pulling my hair out.

[Mag_Neato]

I went home at lunch and set up another measure session!

I had the HVAC off and closed the door behind the seating position. I sat behind the loveseat in a chair so I could read the meter. Meter was on a mini tripod, atop stacked couch pillows, angled at approx. 45 degrees up.

I set the 25Hz tone to read 80db on the meter(corrected).

Here go's;

20Hz = 80db(Surprised!!)

25Hz = 80db

31.5Hz = 85Hz

40Hz = 86db

50Hz = 80db

63Hz = 90db

80Hz = 80db

100Hz = 95db

125Hz = 71db(Huh?)

160Hz = 88db

200Hz = 87db

That's with phase at 0 degrees(0-180), playing in two channel mode. I listen to music mainly in stereo, so I left it in stereo for the test.

The biggest shock was having 20Hz the same as 25Hz. Must be the room. I wonder how far below 20 it will go? My sub's manual only rates it to 24Hz.
Actually, 20Hz was a tick stronger than 25Hz(maybe 1/4db).

Now what?!!