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Anyone using partial or full B&C IPAL solution?

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airbell View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote airbell Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2022 at 1:09pm
Once I had a broken cone on one of my B&C 21DS115-4 drivers,
so i cut the diaphragma out, the voice coil was still ok and I connected it in free air with a laboratory power supply and measured the temperature with infrared and also attatched a temperature sensor to the coil.
Mabye temperature measurements were not 100% exact, but here are some results anyway:

Voice coil heated up from 25°C to 180°C within 120seconts @23V*10A=230Watt.
With reduced power at 18,5V*5A=100W the temperature remained constantly at 180°C.
With more power from that point the temperature went up and the coil turned already a bit dark.
At 250-300°C the coil stared to smoke a lot @35V*7,5A=262,5Watt power and the temperature sill went up. So the resistance went up from 2,3Ohm to 4,66Ohm!
This would reduce the BL²/re so actual motor force in a working speaker quite a bit! LOL

I know this experiment is a little bit extreme because you have no cone movement at all but maybe you can imagine what happens with your driver when you feet it 500W real power constantly at tuning frequency..

I mean, comon, a voice coil only weights some gramm and the surface isn't that large, then you have double layer or even 4 layer as for the 21DS115.What do you expect?

Imagine a soldering iron, it only needs 25W average to get 400°C or more.




Edited by airbell - 29 April 2022 at 1:37pm
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airbell View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote airbell Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2022 at 1:30pm
Hello Heini,
I think I know you from facebook and some forums, I guess you are the one with the 12x double 18NTLW5000 reflex right? :D  I am Fritz from Fritz Audio Berlin.
Anyway, send me your Email adress as a pm and maybe I can help.

But I already can tell you that you won't be very happy with the results
using the IPAL Mod with the 18NTLW5000.(-4?).
The Ipal mod needs very strong drivers or better with a very high bl²/re to mms ratio.

This is not only theory, I tested the Ipal mod with 18SW115-8 and also "G03229" Lacoustics KS28 driver and there was no major improvement in impulse response or dynamic but just a bit less nice sound compared to using Lab PLM14000. 
Even with the 18DS115-4 the improvement using Ipal Mod instead lab g was not as great as with the 18IPAL drivers. 
My initial plan was to use the 21DS115-4 with Ipal mod and DPC, yes, it is a bit more tight but it's not a magical thing that makes a 21inch sound like a 12" in a sealed box.
With the 18IPAL in a 105L 35hz tuned reflex enclosure which is already "tight"sounding using Lab PLM14000, with the IPAL and DPC it sounds just better and kind of "processed", very clean and tidy, just the very deep notes at tuning, the typical "bassreflex full deep bass sound", suffers a bit from it.

But the important thing when using the 18IPAL is also the advanced limiting of the IPAL mod.
You really need it! You could use Lab G or the china clones or other amps, but you need a lot of voltage to bring the heavy punch out of the 18IPAL in a reflex, but with the same voltage
@ tuning frequency, for example 160Vpeak, you would feed the driver 6,4kW which is much too much.
Powersoft X or T series would work also btw.

Can I ask why you consider to use the 18NTLW5000 with the IPAL mod? Just for testing?

Btw PK Sound Gravity 218 uses 18IPAL and IPAL mod solution,
but I really don't understand how it could sound any good except at very low bass notes, because the encolsure is way too large, from my guess 180L per driver, for the 18IPAL and even with the IPAL mod it can't compensate such a large volume with the DPC.
But maybe I miss something here because I can't imagine a company like this would produce something in large format without testing it extensively.


Edited by airbell - 29 April 2022 at 1:49pm
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infrasound View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 29 April 2022 at 4:24pm
Yes, if you stop the cooling system, it can't take much power Shocked. Perhaps 2000w fan heaters also can't take the full power if you block their inlets?

Although in all seriousness you raise a good point - the only cases that drivers can take their full power is when the cone is moving the full amount (in the flux region of course). This is not always the case with music signals, given there is a good proportion of power away from the lowest frequencies. Raising the HPF can exacerbate this problem, while lowering the HPF can cause other issues. Tricky.
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