While in the biquad subject, max to pd translating, I learned that the order and values of coefficients in both don't match... I checked mmb's patches and I see they match pd's native biquad~, but both don't agree to max...

Max does suggest a different order of the coefficients in its help file, but what we see in practice is yet some other order, and also some reversal in signs (positive/negative) in a couple of terms.

Just wondering, why the hell is that? Anybody?

Can't deal with formulas really well, but I see they're supposed to be the same... and I take that from mmb's patches, whose formulas are exactly as depicted in max (although the help from native pd's biquad~ is somewhat different, but seemingly equivalent mathematically)

cheers

ps. by the way, here's a patch that converts the order of coefficients from "max to pd"

#N canvas 150 47 214 262 10; #X obj 32 7 unpack f f f f f; #X obj 125 31 * -1; #X obj 101 55 * -1; #X obj 41 80 pack f f f f f; #X msg 41 115 $4 $5 $3 $2 $1; #X obj 32 -23 inlet; #X obj 41 143 outlet; #X text 69 -24 max; #X text 87 143 pd; #X connect 0 0 3 0; #X connect 0 1 3 1; #X connect 0 2 3 2; #X connect 0 3 2 0; #X connect 0 4 1 0; #X connect 1 0 3 4; #X connect 2 0 3 3; #X connect 3 0 4 0; #X connect 4 0 6 0; #X connect 5 0 0 0;