ken12

Well-l-l, since you asked.
AMO speed ratings are oriented around an arrow for a 60 pound bow with a draw length of 30 inches. The rating arrow would weigh 540 grains.
Pretty heavy arrow, but these standards have been in existence for a long time and have served us all very well over the years.
But the problem with this standard and any standard that uses only one weight bow and one weight arrow is that bows set at different draw lengths and or weights vary greatly. Some bows are faster (proportionally) than others at short draw lengths. Some are more efficient at the longer draw lengths.
Simply, the standard has evolved to a use of the minimum weight arrow for a particular bow peak weight. Most manufacturers use 70 pounds of bow weight and a thirty inch draw.
However this is really an incomplete comparison.
If a manufacturer wants to provide real world comparisons, I would suggest they use a chart that shows 25 or 26 thru 31 or 32 inches in draw length. Some start shorter on different models and go longer on some models.
If they really want to show good info they should also use several peak weight bows such as 50,60 and 70.
Now that would give a buyer some really good information.

While we are at it a bow speed with a bow with a peak weight of 120 or 150 pounds or a not real accurate draw weight is NOT good information. It does not matter if the arrow weight is at 5 grains per pound or not. With all due repect to the folks that shoot those kind of bow weights, not many of us do.

Finally, accurate draw lengths. If there would be an IBO standard it would be the same as AMO. Measure to the throat of the grip and add 1.75 inches.
It would not be to the throat of the grip. It would not be to the back of the shelf. It would be as I suggested.
I know that is more information than you wanted or needed but this is a sort of pet peeve of mine.
Hope this helps.
ken12