BFD plot, after 2 weekends I'm finally getting somewhere.

[kexodusc]

Ringing is when the signal stops and the speaker still plays a harmonic for a few ms. It's easy to hear, play a test tone un filtered and listen to the tonal characteristic, then add a narrow Q filter with about 10db of boost, then listen to that tone again, it will not sound like a solid tone. You should notice that it will have some sustain and harmonics that make the tone sound like…..Ringing. In addition, make sure you are using very high resolution in you test tone measurements, I play tones with 1Hz spacing, you could do it every 2 Hz, but I wouldn’t recommend any less rez then this if you really want to know what’s going on in the room.

Thanks for the description. Am I correct in assuming then that the ringing would occur at harmonics only above (and in multiples) of the fundamental? And, narrow Q cuts won't result in any ringing? Or would they also apply cut effects and possibly diminish at harmonics?

I play sine waves test-tones in intervals of 1Hz. Takes forever, but you're right, it's the only way to know what's going on. I'm also at the mercy of my 3 SPL meters accuracy. Correction values for the standard Rat Shack meters are available only at 1/6 octave increments. My Galaxy Audio meter is highly praised, we use it at our shows when setting up, but I'm not sure of its accuracy below 50 Hz or so.

[kingdaddykeith]

Thanks for the description. Am I correct in assuming then that the ringing would occur at harmonics only above (and in multiples) of the fundamental? And, narrow Q cuts won't result in any ringing? Or would they also apply cut effects and possibly diminish at harmonics?.

They are harmonics but I'm not sure about the details, I only know there is nothing you can do to avoid this side effect, I have a narrow 12db dip at 53 Hz and could get it moved out of the pass-band with a lot of EQ, but it sounded worse then leaving the dip there because of the ringing. Cutting frequencies don’t have this side effect, only boosting. The only way to properly fix a dip is broad-band absorption, IOW, Room Treatment.

I play sine waves test-tones in intervals of 1Hz. Takes forever, but you're right, it's the only way to know what's going on. I'm also at the mercy of my 3 SPL meters accuracy. Correction values for the standard Rat Shack meters are available only at 1/6 octave increments. My Galaxy Audio meter is highly praised, we use it at our shows when setting up, but I'm not sure of its accuracy below 50 Hz or so.

Eric Wallin has posted a method of modifying the RS SPL meter that makes it very accurate from 20-20K, I did it and it works great.

http://mysite.verizon.net/tammie_eri...5/33-2055.html

[Andrew Pratt]

I thought I'd let you know that Sonnie has set up a forum to help us BFD owners. Its located here http://www.nextlevelav.com/forum/forum.asp?FORUM_ID=39

Andrew