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rcf drivers on fire

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BrainlessTekno View Drop Down
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    Posted: 20 March 2024 at 12:07pm
hey, couple months ago i did a gig with 4x186 horns mounted with l18p300 and i did manage to burn 2 of them, i fed them like 800w each, HPF at 30hz.

Another gig is up in 2 weeks and im doing some changes to pass it without problems, i set HPF at 42hz hoping it would help drivers stay cool (cooler). Will this help ? I know part of the problem is the closed chamber and week diver like l18p300 can have problems to survive. 

Is there some tricks to relief the drivers temperature that you know ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2024 at 8:54pm

Main thing is to turn down the gain, as you are overheating the drivers with too high an average level.Evil Smile 
I think 42Hz is still plenty low with the 186 horn - Too high a high pass, can cause more overheating as it stops air movement.
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Andry View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Andry Quote  Post ReplyReply Direct Link To This Post Posted: 20 March 2024 at 9:00pm
Hi,
<first - I don't have a lot of knowledge on this, take it with a grain of salt>

I'd say the HPF was way lower that it was supposed to, as the design only goes to about 50Hz. (F3 is 51Hz for this box)
The drivers are going to run out of excursion (and thus thermal capacity) if the HPF is set like you originally had it.
If you're now using a LR 24dB/oct slope, you have been feeding the drivers full power as low as 43Hz, with less than -1.0dB attenuation  even at 36Hz .

What type and slope of HPF are you using?

You can try a Butterworth 24dB/oct @ 45Hz filter for a single 186.

Now for a stack of 4x186 - I'm not really sure on how low could you could go, considering that doubling the horn mouth area will give you probably 2-3Hz lower response; so say 5-6Hz lower for a group of 4 coupled ?
Probably 42Hz or a tad lower for the HPF in this case ?



I'm into BP6 designs and I from what I've been researching, the best way to avoid such issues is to properly set the HPF, regardless if you're going for lower than 100% of the drivers' power or a lot higher than that.
(I've also burned a speaker two weeks ago because of thermal runaway - the voice coil unwrapped as the glue melted, but the VC wire remained intact and thus still reading proper Re when measured; even played some faith sounds).


Edited by Andry - 21 March 2024 at 9:27am
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BrainlessTekno View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrainlessTekno Quote  Post ReplyReply Direct Link To This Post Posted: 21 March 2024 at 8:10am
Thanks for your answers guys,
xoc1, you are right, i should take a closer look at the gain, my logic was that 1000w driver shold survive 800w even in closed chamber witch was surely wrong train of toughts. Hey Andry, in fact im not sure witch HPF was set at last party, im gonna check that and look into the settings of the LPF.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 21 March 2024 at 12:05pm
Measure cabs, and try to model them on hornresp (amount of cabinets effects results). That way you get an estimate of cone excursion. Keep some excursion below F3 to help with cooling the VC down. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrainlessTekno Quote  Post ReplyReply Direct Link To This Post Posted: 21 March 2024 at 12:08pm
will im a mac user so there is no hornresp for me sadly Cry
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Andry View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andry Quote  Post ReplyReply Direct Link To This Post Posted: 21 March 2024 at 2:02pm
You should be able to get it running quite quickly using Winebottler - https://winebottler.kronenberg.org/
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 22 March 2024 at 12:09am
Originally posted by BrainlessTekno BrainlessTekno wrote:

hey, couple months ago i did a gig with 4x186 horns mounted with l18p300 and i did manage to burn 2 of them, i fed them like 800w each, HPF at 30hz.
Those drivers have a 1000w AES rating... that's not the same as rms. What amp was powering them and what processing was in use? Even with "only" 800w available if the signal was crammed into a limiter or otherwsie compressed so that there was no dynamics... or bass is just long droning sine waves, then the real long term power handling of these drivers is as low as 250w.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrainlessTekno Quote  Post ReplyReply Direct Link To This Post Posted: 22 March 2024 at 8:18am
Oh that are some bad news for me Shocked, well it was powered by fp10000q and processed by dbmark dp28, i still dont understand limiters on the thing (i sould look into these for sure) so there was no limiting settings and i just took care about the gain. Interesting part is that the drivers lasted the whole party (like 10 hours), i did find out they are fried later at home, they were still playing just fine but the cone movement wasnt smooth so they were not blasted in couple of minutes, it seemed to me it was long term overpowering by a little amout, im not arguing about your statement about 250w byt that seems real low 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2024 at 3:57am
Originally posted by BrainlessTekno BrainlessTekno wrote:

it was powered by fp10000q and processed by dbmark dp28,
Was that 1 box per channel or 2?

Originally posted by BrainlessTekno BrainlessTekno wrote:

i still dont understand limiters on the thing (i sould look into these for sure) so there was no limiting settings and i just took care about the gain.
And as you found out there is no protection in that technique. With that kind of amplifier power on tap you really need long term thermal limiting, it's a slow reacting scheme that manages how much heat is put into the drivers while allowing dynamics through. If your gear doesn't have than then you might get away with using peak limiters... just depends on the level of dynamics and the duty cycle of the program material. 

Originally posted by BrainlessTekno BrainlessTekno wrote:

Interesting part is that the drivers lasted the whole party (like 10 hours), i did find out they are fried later at home, they were still playing just fine but the cone movement wasnt smooth
Yeah you took them right to the edge of destruction, the glue on the voice coils melted which allowed the wire to shift out of place and the next time they were fired up the wire is crushed in the gap, shorted and it's all over. This means you very likely have 4 bad drivers, it's only production tolerances that kept the other two alive(for now) but they will likely fail very soon... maybe on the next event.

There are 2 ways to figure out where to set limiters.
1. Do the math. Lookup what input voltage is required to deliver full output from your amp, and what that corresponds to in output level from your speaker processor. Then figure how much you need to reduce that signal(in db) to protect the drivers and set the limiter at that.
2. Pay the piper. Hook up the system and run a signal through it to produce full output from the amp, then engage the limiter and start dialing it down until you see/hear it reducing the output of the amp. Try that setting on a gig, if the speakers survive it's good, if they die then the limiter needs to go even lower.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrainlessTekno Quote  Post ReplyReply Direct Link To This Post Posted: 16 April 2024 at 10:02am
this friday i did another gig, this time i set up peak limiters and changed xover settings to 51hz - 100hz. I expected some (not that noticable) positive results but the change from lost gig was masive, the 30hz-50hz was lacking but the SPL went up hard... i would say worth it, none of the drivers were fried and i even think they can take some more beating but lets not push it, still im gonna do some more gigs with this setup and then buy pd1850s and kick l18p300 out Smile

Conanski " Was that 1 box per channel or 2? "
it was 2 per channel -> 4ohms
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