Beating a dead horse
OK, as you know I have a pair of Depths to go with my Prodigy. And I absolutely love them.
I have since had a very nice email discussion with Peter Soderberg, MartinLogan International Sales Mgr.
The speaker level/high level input makes a better match in my system than line level. Peter mentioned that ML's experience is that using the speaker level input tends to cause the internal amps to take on the characteristics of the "Main" amp, and therefore a better blending. Thus the current choice of high level input only, on the current top two models, for their internal amps.
Now to the dead horse;
As you also know I asked for an unpublished spec. (xmax). ML's position is that, that spec could be very misleading given the way other manufacturer use it.
As an example, the following website publishes the spec I was looking for, however it is for the older Descent.
http://www.listening.co.nz/index.asp?PageID=2145839495
“Each of Descent's 10-inch aluminum-cone drivers weighs 8 pounds and has a maximum peak-to-peak excursion of 1.2 inches. That works out to a total displacement of 30 cubic inches - typical for most high-quality subwoofers. Descent has three of these drivers, however, yielding the equivalent acoustic power of a 24-pound driver with a maximum peak-to-peak excursion of 3.6 inches and a total displacement of 90 cubic inches. Moreover, each of these drivers is individually servo controlled for absolute minimum distortion. The single-driver alternative would be an extraordinarily robust 18-inch unit, which by virtue of its size and very long excursion would inevitably generate considerably higher distortion. Descent enjoys all the advantages of the smaller, more refined drivers while achieving the output capability of a huge 18-inch driver.”
Using the above numbers this would make an effective radiating diameter of 9.77” from this 10” driver.
http://www.sunfire.com/TrueSubwooferEQPR.htm
Sunfire published specs for their number two sub (true subwoofer eq) which according to them has an 8” “bore” and a 2.35” stroke and moves 235 cu. inches of air!
{I am using these examples because Daniel referred me to this wonderful website that tested the Sunfire EQ and the Depth
http://www.avtalk.co.uk/forum/index.php?t=msg&th=18352&start=0&rid=14&SQ=1147288566 )
My calculations put the active driver at about 118 cu. inch. so they must be getting another 117 from the passive radiator (assuming the same stroke) – at the frequencies at which they are in phase with each other.
So here comes the logic. According to Sunfire the True Subwoofer EQ moves 2.6 times more air, at max than the old Descent as listed on the website from New Zealand.
OK the Depth is in a 30% smaller cabinet than a Descent. Next the three 8” drivers have approximately 33% less driving area then the 3 – 10” drivers in the Depth. Therefore the Depth, given the same maximum “stroke” should move about 30% less air than the Descent or about 60 cu. inches.
That would mean that the Sunfire moves almost (3.91) four times the air as the Depth.
If one opens two browser windows and compares the graphs of the Sunfire to the Depth one will see that the Depth is equal to or out performs the Sunfire in almost ever test.
http://www.avtalk.co.uk/forum/index.php?t=msg&th=18352&start=0&rid=14&SQ=1147288566
http://www.avtalk.co.uk/forum/index.php?t=msg&th=22062&start=0&rid=14&SQ=1178745521
I guess that is why it is an unpublished spec for Martin Logan. It is one of those “All things being equal…..” and they never are.
Bruce
