ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3  All   Go Down

Author Topic: fusing horn drivers.  (Read 9299 times)

John Sabine

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 255
Re: fusing horn drivers.
« Reply #10 on: May 07, 2014, 04:32:26 PM »

And so my question goes back to what it was in the beginning what size fuses should I use? The horn drivers continuous power handling is 100 W and The load is 8 ohms. according to the lovely calculator on the crown website 100 watch at 8 ohms should be about 3 1/2 Amps. does that sound right to the guys who have experience and knowledge in this area?


Sent from my iPhone using Tapatalk
Logged
"I think it needs more barn"

John Sabine

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 255
Re: fusing horn drivers.
« Reply #11 on: May 07, 2014, 04:33:56 PM »

all I really want to do with this fuses protect the speaker in the event of DC.


Sent from my iPhone using Tapatalk
Logged
"I think it needs more barn"

John Sabine

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 255
Re: fusing horn drivers.
« Reply #12 on: May 07, 2014, 04:50:13 PM »

I just looked at my original post and I was not completely clear that I was requesting some of the gurus to help me figure which values of fuses to use in this application.


Sent from my iPhone using Tapatalk
Logged
"I think it needs more barn"

Tim Perry

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1251
  • Utica-Rome NY
Re: fusing horn drivers.
« Reply #13 on: May 07, 2014, 11:51:28 PM »

I just looked at my original post and I was not completely clear that I was requesting some of the gurus to help me figure which values of fuses to use in this application.


Sent from my iPhone using Tapatalk

Here you go: 16 ohms at 50 watts.  use the formula I= sq rt P/R to get  1.77 amps.   Use the nearest standard fuse value depending on your personal philosophy 1.5 or 2 amps.   

Personally I do not recommend doing this: in general fuses and breaker are to prevent fires, not protect loads.

You said the amp went DC. Likely the coil will fry before the fuse blows. Even a fast blow.

If the fuse  (or breaker) is followed by a "crowbar circuit" you will stand more of a chance of achieving your goal.  In this case a Triac or SCR acts very fast. Often the crowbar give is life in the protection of the load.  Search crowbar circuit for examples.

This would be one fuse and circuit per speaker.

Note to engineers: basic calculations were used for simplicity. Certain assumptions were made in the interest of not playing 20 questions with this. 

edit: addendum:  The DC resistance of voice coils is always less then the nominal impedance however 16 ohms was used to get a ballpark answer.  In most cases the voice coil IS in effect the fuse.
« Last Edit: May 08, 2014, 12:04:29 AM by Tim Perry »
Logged

John Sabine

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 255
Re: fusing horn drivers.
« Reply #14 on: May 08, 2014, 08:43:22 AM »

Thank you for your answer Mr. Perry :) I had actually gotten a few free minutes to think about it yesterday and decided to use a 4 amp fuse in series with the drivers but in parallel with the capacitor as suggested by Jens Droessler. I had decided on a 4a fuse since the drivers are in parallel in the cabs (2 16ohm 50w drivers in parallel = 8 ohms, 100w). I also remembered that I have a couple of diaphragms laying around from when some suffered glue failure so today I'm going to use my 15a DC power supply to try to confirm that a 4A fuse will do the trick by connecting the diaphragms in parallel just like in the cabinet, connect them to the power supply and insert fuses in series with the circuit until I find the point where the drivers smoke before the fuse blows then back down one size.
Here you go: 16 ohms at 50 watts.  use the formula I= sq rt P/R to get  1.77 amps.   Use the nearest standard fuse value depending on your personal philosophy 1.5 or 2 amps.   

Personally I do not recommend doing this: in general fuses and breaker are to prevent fires, not protect loads.

You said the amp went DC. Likely the coil will fry before the fuse blows. Even a fast blow.

If the fuse  (or breaker) is followed by a "crowbar circuit" you will stand more of a chance of achieving your goal.  In this case a Triac or SCR acts very fast. Often the crowbar give is life in the protection of the load.  Search crowbar circuit for examples.

This would be one fuse and circuit per speaker.

Note to engineers: basic calculations were used for simplicity. Certain assumptions were made in the interest of not playing 20 questions with this. 

edit: addendum:  The DC resistance of voice coils is always less then the nominal impedance however 16 ohms was used to get a ballpark answer.  In most cases the voice coil IS in effect the fuse.
Logged
"I think it needs more barn"

Tim Perry

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1251
  • Utica-Rome NY
Re: fusing horn drivers.
« Reply #15 on: May 08, 2014, 10:22:18 AM »

Thank you for your answer Mr. Perry :) I had actually gotten a few free minutes to think about it yesterday and decided to use a 4 amp fuse in series with the drivers but in parallel with the capacitor as suggested by Jens Droessler. I had decided on a 4a fuse since the drivers are in parallel in the cabs (2 16ohm 50w drivers in parallel = 8 ohms, 100w). I also remembered that I have a couple of diaphragms laying around from when some suffered glue failure so today I'm going to use my 15a DC power supply to try to confirm that a 4A fuse will do the trick by connecting the diaphragms in parallel just like in the cabinet, connect them to the power supply and insert fuses in series with the circuit until I find the point where the drivers smoke before the fuse blows then back down one size.

Every bit of this sounds like an exercise in futility.

Discard the amplifier that "goes DC". Replace with modern amp. Bring enough rig for the gig. Forget about fuses.
Logged

Tim McCulloch

  • SR Forums
  • Hero Member
  • *
  • Offline Offline
  • Posts: 23736
  • Wichita, Kansas USA
Re: fusing horn drivers.
« Reply #16 on: May 08, 2014, 10:34:41 AM »

Every bit of this sounds like an exercise in futility.

Discard the amplifier that "goes DC". Replace with modern amp. Bring enough rig for the gig. Forget about fuses.

This.  Right.  Here.
Logged
"If you're passing on your way, from Palm Springs to L.A., Give a wave to good ol' Dave, Say hello to progress and goodbye to the Moonlight Motor Inn." - Steve Spurgin, Moonlight Motor Inn

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2201
  • Santa Fe, New Mexico
Re: fusing horn drivers.
« Reply #17 on: May 08, 2014, 11:18:18 AM »

Every bit of this sounds like an exercise in futility.

Discard the amplifier that "goes DC". Replace with modern amp. Bring enough rig for the gig. Forget about fuses.
Absolutely. Back in the days of "Flame Linear" amps, fuses (or capacitors) were always used. The fast blow fuses would blow regularly on peaks, and would be replaced with progressively larger fuses that eventually would make it through a show without failure. Then, when the Phase Linear amp would blow an output transistor then would dump it's full PSU DC on the output, the drivers would smoke.

Capacitors were sure "fire" prevention, but muck up phase and frequency response even when chosen to be nominally an octave or more below the crossover point.

An amp using output relay or crowbar protection is the way to go.
Logged

Joseph D. Macry

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 425
  • Austin TX
Re: fusing horn drivers.
« Reply #18 on: May 08, 2014, 11:25:10 AM »

When I used to sell retail PA gear, some Community speakers (thinking specifically of CPL46 3-way) would come back with the complaint, "I see sparking coming from the inside." I would explain that the crossovers have a small lamp for tweeter protection; the flashing light was the protection circuit working.
Logged
Joseph Macry,
Austin, TX

John Sabine

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 255
Re: fusing horn drivers.
« Reply #19 on: May 08, 2014, 11:29:48 AM »

The amp has been gone for 2 years. I placed non polarized capacitors inline with the horn drivers to block DC in the event of some future calamity but feel that they effect the sound quality of the horns. Looking for an option that would allow me to protect the horns from a random mishap (such as the amp that went nuclear and fried 8 horn drivers on the night before a festival) but won't effect the sound of the horns.

Every bit of this sounds like an exercise in futility.

Discard the amplifier that "goes DC". Replace with modern amp. Bring enough rig for the gig. Forget about fuses.
Logged
"I think it needs more barn"

ProSoundWeb Community

Re: fusing horn drivers.
« Reply #19 on: May 08, 2014, 11:29:48 AM »


Pages: 1 [2] 3  All   Go Up
 



Site Hosted By Ashdown Technologies, Inc.

Page created in 0.033 seconds with 24 queries.