1850 and 186 horns - rcf drivers on fire

Is there some tricks to relief the drivers temperature that you know ?

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.

Hi,

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).

Thanks for your answers guys,

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.

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.

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.

Conanski " Was that 1 box per channel or 2? "

it was 2 per channel -> 4ohms