What is the possible bleed of Bl(x) and Kms(x) values between each other with Klippel testing?
Looking at B&C Speakers 18DS115 with long coil and 14mm Xmax, things apparently look different than they are. The voice coil doesn't leave the gap till past 13mm travel one way, yet Bl falls rapidly in the graphs.
Also, at Xvar of 14mm, this beast is run past 20mm in their 2hr test, making it more IPAL-ish than conventional? What could we take from that? Could I use it safely past Xmax for short/peak use?
Looking at B&C Speakers 18DS115 with long coil and 14mm Xmax, things apparently look different than they are. The voice coil doesn't leave the gap till past 13mm travel one way, yet Bl falls rapidly in the graphs.
Also, at Xvar of 14mm, this beast is run past 20mm in their 2hr test, making it more IPAL-ish than conventional? What could we take from that? Could I use it safely past Xmax for short/peak use?
The 20mm Xmax 18IPAL voice coil doesn't leave the gap till past 16mm travel one way, but is rated for the same power as the 18DS115 and has a lighter cone.
Considering the 18DS115 can do 60mm peak to peak (30mm Xlim) without damage, 20mm should be mechanically safe for short/peak use, but beyond it's Xvar of 14mm the loudspeaker force factor (Bl), or the total suspension compliance (Cms), or both, has dropped to less than 50% of their small signal value.
The heat from pushing it to 20mm in a cabinet would probably be more of a concern, as it would have 3mm less coil in the gap at 20mm than the 18IPAL, around 19% "less cool".
Considering the 18DS115 can do 60mm peak to peak (30mm Xlim) without damage, 20mm should be mechanically safe for short/peak use, but beyond it's Xvar of 14mm the loudspeaker force factor (Bl), or the total suspension compliance (Cms), or both, has dropped to less than 50% of their small signal value.
The heat from pushing it to 20mm in a cabinet would probably be more of a concern, as it would have 3mm less coil in the gap at 20mm than the 18IPAL, around 19% "less cool".
I haven't seen Klippel tests on either driver.
Mms of both 18IPAL and 18DS115 is (curiously enough) the same. I was not putting 18DS115 on the same level with 18IPAL. Just noticing the same unusual Xmax to Xvar ratio, pointing out that in a way, a speaker is possible to use beyond Xvar, giving the example of 18IPAL. THOUGH it needs additional processing. Indeed the free-air test and in-enclosure usage are two very different scenarios.
Although I noted particular drivers, the question was more general.
With 18DS115, simply put, the Bl value of 18DS115 falls too steeply with cone position outside zero. So steep it evokes the idea that the measurement is not very clean.
Although I noted particular drivers, the question was more general.
With 18DS115, simply put, the Bl value of 18DS115 falls too steeply with cone position outside zero. So steep it evokes the idea that the measurement is not very clean.
I found it curious that the shorter voice coil 18DS115 Mms of 348G was more than the 18IPAL's 330g.
Anyway, I wouldn't want to count on excursion much past Xvar, whatever it is.
This is what results in the Qts (x, Tv) graph on a klippel report. Xvar is just B&C's interpretation of this at 50% from rest position, which does not correlate to any sort of THD threshold.
The 8Ohm version of 18DS115 is same 330g.
The IPAL coil is split winding, the 18DS115 isn't.
Thi IPAL "obviously" works past Xvar. Not much doubt about that.
@hurrication Highly nonlinear suspension to not correspond with THD figures? Hard to believe. With IPAL this is easy - the system corrects for that. Not so for 18DS115.
I see. Indeed. But they somewhat have this specced in their Klippel measurements. Though, as much as they try, there are still some discrepancies. They say the Xvar value is reached if suspension compliance or Bl drops to 50%. For 18DS115 it is 14mm. Yet in their Klippel data, it shows that the suspension is that compliant at 12.5mm or so. So it does not add up, apart from 18DS115 being really stiff, making it unsuitable for high excursion designs.