Delay line length vs stuffing



				Table 3

.............................................................

			Delay msec	Distance in.	% length increase


Empty box		1.5		20.5		-
Wool			1.54 (1.8)	21.06		2.7 (22)
Hollofil		1.6  (2.0)	21.88		6.7 (35)
Foam			1.76		24.07		17.4
((Wool+Hollofil))      ((2.2))		((30))		((35))



Normal times were measured using 8 oz. of stuffing in the 1280 cu in line,
This is a higher density than what is usually considered. The () times
were measured with 1.3 lb cu ft. The (()) were measured using a very
cramped 2.6 lb cu ft!

This represents my measurments which contradict normal transmission
line stuffing delay theory. Normal theory says the delays can be achieved
with alot less stuffing, and, delay varies with frequency. I can not
agree with that theory according to my own testing. To say the least,
this stuff is hard to measure. There are some who would agree with my findings,
and some would disagree. Take it as you will. 

More about the test. I made the test at various time periods and with
different methods. The first was delay time using a pulse method. The
second time around I used tone burst. Delay times MUST be made using at least
two identical microphones. The initial wave must not be triggered with the
electrical pulse. It must be derived from the driver output because
of mechanical delay characteristics. My box is much smaller than what
would usually be used, however I believe it was a valid for delay measurment.
There may be other factors to consider when using long lines.

				End