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tweeter protection

 
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Eugene
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Joined: 02 Oct 2004
Posts: 8
Location: Edmonton Canada

PostPosted: Wed Apr 20, 2005 4:37 am    Post subject: tweeter protection Reply with quote

It looks like I found a pair of T-52's for my Cantatas , so to protect them from blowing again , it was sugested that I use fast acting .5 amp fuses . The problem with this idea is that they might blow during program peaks , that might not harm the tweeters . It was also sugested poly switches , now do these things suddenly , at the rated amperage , open up , or is there an increse of resistence before this happens ? I was looking on the internet and found a protection circit that is just a lite bulb in series with the tweeter . The idea is that under low volume there is just a low resistence of the light bulb in the path to the tweeter . when the volume goes up the light bulb starts to light up , heating up the filament , increasing the resestance of the light bulb , and lowering the amount of jucie going to the tweeter . At very high volumes , light bulb burns out , hopefully before tweeter . The light bulb could be very easy installed in the Cantatas , at the tweeter level control . The problem is the only values I found for the light bulb is 18W 24V ,this is for a PA speaker system . I was thinking that a 12V 5W pilot light might just work . What do you guys think ? Please excuse my spelling and grammer.
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ColinR
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Joined: 31 Jul 2004
Posts: 1175
Location: Staffordshire

PostPosted: Wed Apr 20, 2005 9:54 am    Post subject: Reply with quote

If you are concerned about blowing fuses or operating some other form of protection circuitry on musical content whilst playing it "loud" you simply have the wrong speakers. You therefore need to find something else which will offer the ear shattering spl's that you desire, like vintage Klipsch, JBL or Yamaha or a modern ATC.
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Eugene
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Joined: 02 Oct 2004
Posts: 8
Location: Edmonton Canada

PostPosted: Thu Apr 21, 2005 4:46 am    Post subject: Reply with quote

I feel like I have just been scolded and sent to my room without supper . I bought these speakers used in 1982 , the factory .5 amp fuses blew with in the fist year , I put in 1 amp slow blows then . I had no problems with them exsept for that one time in 84 when both the Cantata T-52 and the T-27 that are in the Chorales I use for rear surround on the Left channel blew . I had the surrounds hooked up to the amp with the negative leads of the speakers connected to each other , and not the amp . My room mates at the time declaired innocence . I was running a Halfler DH200 ,100W@.001% per channel . The problems did not start untell I got another Halfler DH200 and briged them both for 250W mono . I also have a pair of JBL CF-120's (Just Big and Loud) They sound fantastic for DVD's , Explotions and gunshots just shake the house , but they sound crappy for music . I am still looking for feed back on the light bulb or polyswitch , if I use the polyswitch sholud I put a shunt resister with it , 10K ohm ? This will prevent an accedentall install of a three amp fuse , which is what happened . Usally after a night of Darts . Must be all that aiming juice .
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ColinR
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Joined: 31 Jul 2004
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Location: Staffordshire

PostPosted: Thu Apr 21, 2005 10:42 am    Post subject: Reply with quote

Right Eugene get a pair of 0.5amp Polyswiches and solder them across the rears of the fuse holders, remembering to remove the holder caps and Blue-tack them somewhere behind the metal panel for safe keeping. Polyswitches operate by suddenly offering a large resistance when they warm up, reducing the signal to the T52. Regarding a shunt resistor the value you require is 5 to 10 Ohms ("ten to twenty times cold resistance of 0.5 Ohm"), if in doubt I would recommend that you email Malcolm Jones at Falcon Acoustics as he knows a thing or two about Cantatas from his time with KEF. The light bulb is an alternative but it will offer a steadily rising resistance before it blows. You need a 5 watt 12volt job, remember these are plain vanilla Tungsten filament jobs not Halogen. Check out your local bicycle shop if you wish to go down this particularly precarious route. Test it out with your spare T33A's first. A packet of 20*0.5mm 0.5 Amp quick blow fuses would avoid any soldering or mathematics though.
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Eugene
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Joined: 02 Oct 2004
Posts: 8
Location: Edmonton Canada

PostPosted: Fri Apr 22, 2005 2:34 am    Post subject: Reply with quote

I ordered some .5 amp poly switches from a local electronic parts store and will hard wire them in the Cantatas .
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Eugene
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Joined: 02 Oct 2004
Posts: 8
Location: Edmonton Canada

PostPosted: Fri Apr 22, 2005 5:31 am    Post subject: Reply with quote

Went to the Falcon web page and they have the information I was looking for . http://www.falcon-acoustics.co.uk/SpeakerProtection.pdf I have been on there web sight before and I never noticed it . I wonder if it is a new addition .
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Wouter
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Joined: 18 Jun 2004
Posts: 60
Location: Ramsel (Belgium)

PostPosted: Tue Apr 26, 2005 7:25 pm    Post subject: Reply with quote

Hello all,

I have been following the two discussions on the forum about the tweeter protection.
Of course I am convinced that a fuse MAY protect the tweeter in some cases.
But the thing I don't understand is: if you know your hifi system well (mainly the power handling of the speakers and power output of the amplifier), it is easy to do the 'protection' of all speakers yourself. Or am I wrong?
I have a pair of modern Cresta's and an older pair of Concerto's, connected to an Arcam Alpha 7. For me, it is clear when the maximum power is reached for the speakers and I will always give the volume a little turn to the left when this critical point has been reached.

For all the years, I have never had a damaged tweeter (of other speaker unit).

Or is there another reason or advantage of the fuse?


Thanks for the feedback,
Wouter
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proffski
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Joined: 22 Aug 2003
Posts: 1297
Location: Tewkesbury UK

PostPosted: Fri Apr 29, 2005 9:16 pm    Post subject: Re: tweeter protection Reply with quote

First congratulations on finding replacement units for your loudspeakers!

Bulbs are ok for copmressors for PA use, but have no room at all in Hi-Fi!
Have a look here:
http://www.falcon-acoustics.co.uk/SpeakerProtection.pdf

Their main site is: http://www.falcon-acoustics.co.uk/

Polyswitches do make more sense than non linear bulb filaments!
You may also wish to try Wilmslow Audio: https://secure.wilmslow-audio.co.uk/acatalog/

If you wish to try fuses starting at about F0.5A is probably ok.
I'd stick with Polyswitches if I HAD to use speaker tweeter protection...

Andy.
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adam_audio
Intermediate Contributor 50+


Joined: 07 Jul 2005
Posts: 53
Location: Land Of The Lost

PostPosted: Sun Jul 10, 2005 1:01 pm    Post subject: Reply with quote

ColinR wrote:
If you are concerned about blowing fuses or operating some other form of protection circuitry on musical content whilst playing it "loud" you simply have the wrong speakers. You therefore need to find something else which will offer the ear shattering spl's that you desire, like vintage Klipsch, JBL or Yamaha or a modern ATC.


Exactly.


If your primary concern is the delicate and musical rendering of explosions and gunshots, then protection circuitry isn't necessary. However, if you are hell bent on "shaking the house" with 250wpc....there are 100 speakers that would do so with much more slam and skull splitting 'realism' than the KEF Cantata....and do so naturally without the concern of blowing up anything. I would in this case, be inclined to back up Colin's suggestions and also add Tannoy 15"s or Altec Voice of Theater/Valencia to the list of speakers that would probably work better for your chosen application.

I just don't understand what it is that most people consider to be "loud", I suppose. I love to crank the volume just as much as anyone else....AC/DC, Queen, The Who, Motorhead, Pink Floyd, Bowie, Judas Priest, etc....and I've never blown a fuse or tweeter on my Cantatas or any other speaker I've owned, including Quad 57s. That is because I find that most speakers will play loud enough to be pleasurable in the context of reproducing the actual musical event without well before getting to the point of damaging my ears or contributing to the repulsive noise pollution that seems to be accepted as the norm in our society.

When I reach the point that I can feel the music hit me in the gut, I sit back and enjoy without having the urge to push it to see if I can knock a tile off the ceiling. I think it all boils down to what works for me personally. I think I'd rather get lost in the music and listen to the melodies than be kicked in the face. Clearly the Cantata wants to take you on a journey, but you are obviously in search of something more than where this speaker wants to take you and that is why, I believe, Colin suggested the other speakers and made the comments he did.

If you simply MUST continue to slap your Cantatas around with Stallone DVDs and what not....I therefore offer you the most simple solution to your problem that I can think of: install in-line fuses in your speaker cables. I actually do this myself because the Music Hall cd player I use is known for having the defect of emitting a loud pop from time to time and I want some extra protection. Also, every once in a while I'll grab a cd that's cut exceptionally loud and forget to turn the volume down from the previous disc. I started with .5 amp fuses, but had to increase to .75 and I haven't blown a single one yet. "Dr. Quad" recommends 1 amp in-line fuses as a temporary solution to the Quad 57 panel-arcing issue in a pair of ESL speakers that don't have the protection circuits installed, and I guarantee those rickety electrostatic jobs are significantly more fragile than your KEF Cantatas.

Good luck.
-adam
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