Glass Fuse/bulb Protection
Printed From: Speakerplans.com
Category: General
Forum Name: Electro Frying Forum
Forum Description: Talk about drivers, processors and mixers
URL: https://forum.speakerplans.com/forum_posts.asp?TID=60227
Printed Date: 26 March 2026 at 10:13pm
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Topic: Glass Fuse/bulb Protection
Posted By: CHAMPION
Subject: Glass Fuse/bulb Protection
Date Posted: 07 December 2011 at 4:00pm
Whats the point in putting a Quick Blow Glass Fuse on the cross over network of a mid/high speaker when it can not prevent the Compression Diaphragm from shorting out !      ------------- Sticks n Stones |
Replies:
Posted By: cravings
Date Posted: 07 December 2011 at 4:25pm
| they're bulbs, not fuses. |
Posted By: cravings
Date Posted: 07 December 2011 at 4:25pm
| but you're right, should protect them really... |
Posted By: JohnnyPyro
Date Posted: 07 December 2011 at 5:00pm
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wrong wattage lamp me thinks .. lamps should blow way before the comp ... had them from new?
------------- Pyrotechnics... its not rocket science, well.... actually it is !! :o) Powered by MC2 & XTA |
Posted By: Herb-i
Date Posted: 07 December 2011 at 5:15pm
Correct fella...........
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cravings wrote:Posted By: lgosdset
Date Posted: 07 December 2011 at 6:38pm
they are fuses weather they can be used as a light bulb or not, it performs the same function, as well as very basic limiting. Stop nit picking. fuse
clearly they were not the correct rating. |
Posted By: chris_k
Date Posted: 07 December 2011 at 7:00pm
Not a bulb. People in the know call them lamps! 
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Posted By: MessyM2k8
Date Posted: 07 December 2011 at 7:10pm
this, you plant bulbs in the garden, ah how many times have we heard that one? |
Posted By: chris_k
Date Posted: 07 December 2011 at 7:21pm
| Whenever I'm in the wholesalers and a member of the public comes in asking for bulbs, one guy behind the counter always says that. Every bloody time. |
Posted By: kedwardsleisure
Date Posted: 07 December 2011 at 8:08pm
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I think it's an age thing. I call those bulbs and I call decorative table fixtures 'lamps' as in 'standard lamp' or 'bedside lamp'. But this is well-trodden nonsense. Those limiter lamps are meant to afford limiting. If they blow, you've ridden the limiter once too often. Some manufacturers use fuses, some use bulbs, some use PTC thermistors (polyswitches), some use thermal breakers and some use sweet FA. I don't think they're designed to be fool proof, which is ironic in a way. Yes, I have customers who think they have novel sound-to-light loudspeakers that are actually meant to flash to the bass beat as an attractive feature of their speakers. Honestly. ------------- Kevin North Staffordshire |
Posted By: Centauri
Date Posted: 07 December 2011 at 11:29pm
Agreed - by the time there is enough voltage to blow the lamp / bulb / illumination device, it has well and truly gone past its limiting capability. By the look of the shattered diaphragms. these boxes have been pushed way past what they were designed to do - simple abuse..... |
Posted By: cravings
Date Posted: 08 December 2011 at 12:17am
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ev diaphragms aren't cheap either.. are the bulbs blown? |
Posted By: service dept Steve
Date Posted: 08 December 2011 at 9:37am
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They are designed to work as "dynamic resistors", that is to say they show one resistance cold and a much higher one when hot. The problem comes when the "hot" resistance still isn't enough to overcome an overload, using 2 or more in series will help assuming that the hf still sounds ok with the effect of the "cold" resistance. Some systems use proper light bulbs, these would typically be 12v 22w brake light bulbs or 20w halogens, a 24v 22w would offer higher resistance whereas a 12v 50w halogen would offer lower resistance without decreasing the lamp life. ------------- We are not "They", We are "The others" http://www.servicedept.co.uk" rel="nofollow - http://www.servicedept.co.uk - |
Posted By: tweeter box
Date Posted: 14 December 2011 at 9:43am
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so if one wanted to put a fuse/bulb just before a comp to act as protection which fuse would be used? would there be different fuses for diff watt intake? ------------- PRECISION SOUND SYSTEM. Feeding the peoples needs for Roots Music. Strictly premium grade reggae and dub steppers from the early 70's to present day. |
Posted By: Art Welter
Date Posted: 16 December 2011 at 3:06am
The value of a fuse/lamp/bulb is dependent on the impedance curve and power rating of the driver used, crossover frequency and design, and is only going to provide about a 3 dB reduction in power when lit. If the "fuse" handles too little voltage, it will pop on peaks that the driver could handle. If it handles too much voltage, the result is like the OP's picture. The OP's driver shattered the diaphragm before the voice coil burnt up. It would have started to sound terrible at a much lower volume than needed to cause the destruction. |
Posted By: wayward91
Date Posted: 18 December 2011 at 9:10pm
| i have some hk crossovers/speakers with a 18w 24v bulb on them . when its removed the horn is reduced in volume by a fair bit. im yet to discover if they work as a fuse. |
Posted By: kedwardsleisure
Date Posted: 18 December 2011 at 9:29pm
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At the end of the day a bulb limiter is better than nothing, if it's sized such that it doesn't cause a nuisance anyway! I had a pair of nearly-new HiSys2 brought to me by a very glum chap who said they'd set up at a gig and the mics on stage had been allowed to squeal for 2 seconds during the sound check and the horns had popped before they could dive for the mixer. I examined them and the horns were fine, it was the lamps blown. 2 lamps later and he was a happy chappy. ------------- Kevin North Staffordshire |
Posted By: shagnasty
Date Posted: 18 December 2011 at 11:32pm
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Gotta say here, the lamp PTC limiter does work to a point, but if you've let the input signal clip you could have a waveform so loaded with harmonics the driver can never hope to re-produce the thing is gonna cook and die anyways....
They do help, my main experience of these is the Turbo TXD-530 (FK-88 is very similar) and I have replaced a lot of lamps but never a slot tweeter.....
:-)
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Posted By: Audio-kid
Date Posted: 21 December 2011 at 6:18pm
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i f i remember correct didnt peavey used to use a 2 way x over with a lamp type limiter fitted in them. sure they used to fit the same in the rcf/mackie pro touring rigs to. Made me laugh that the customer in the ralier post thought it was some form of sound to light show. oh my dayz lol pmsl. honest. great stuff
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Posted By: _djk_
Date Posted: 21 December 2011 at 9:09pm
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The EV drivers with the 1-1/4" coils usually use a 0.5A PTC to protect them in their factory crossovers. The Speaker Exchange crossover shows a pair of 211-2 lamps in parallel, way too much current. One 211-2 would be more appropriate. The #1141 looks to be a better choice. #211-2 I^2=1 works well with 8Ω drivers with 1" coils #1141 I^2=2 works well with 8Ω drivers with 1-1/4" ~ 1-1/2"coils #1156 I^2=4 works well with 8Ω drivers with 1-3/4" ~ 2"coils ------------- djk |
Posted By: Tekasis
Date Posted: 22 December 2011 at 10:20am
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http://forum.speakerplans.com/light-bulb-in-mid-tops-cabs_topic57133.html" rel="nofollow - http://forum.speakerplans.com/light-bulb-in-mid-tops-cabs_topic57133.html ------------- **Heavy Weight-Line** A home without books is like a body with no soul. |
Posted By: CHAMPION
Date Posted: 22 December 2011 at 11:37am
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Heres some from Peavey Impulse 200 series... http://imageshack.us/photo/my-images/233/img2011121400608.jpg/" rel="nofollow">  http://imageshack.us/photo/my-images/525/img2011121400609.jpg/" rel="nofollow">  Blown Poly-switch, Hi Freq Capacitor, and damage to the high power Resistors, Fuse was in tact ! No damage to the Mid or Compression . ------------- Sticks n Stones |
Posted By: portapartyman
Date Posted: 22 December 2011 at 12:01pm
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I've blown my lamps in my Wharfedale Lix Monitors a few times while ringing the system out. VERY annoying but atleast its only the lamp that blows!!! I now make sure I have plenty of lamps and my soldering iron at the ready.....hasn't happened for some time now but happened this summer at two consequitive gigs and had to adapt (bodge) some lamps out of the van.
------------- Festival Asylum. Providing PA, Decor, services and entertainment to the UK festival market www.festivalasylum.co.uk |
Posted By: jj naz
Date Posted: 14 October 2016 at 4:11pm
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Hi, I am not much of sound geek, need help, I have sound used in gig, passive Custom speakers 350w RMS 2 way, HF of 40w RMS, my crossover network don't have light fuse( bulb), hence had blown coils many times, need info. of the follow: 1). Could automotive bulb of 12v ....? W...amps? Do, if yes specify amps and watts Also what is the calculation for above bulb type??. 2). Would DC protection circuit work for safe guarding speakers??? 3). Read a post here for halogen bulb in series, how would one use it? Voltage? watts? Thanks for all help rendered. |
Posted By: Sparky02
Date Posted: 25 August 2017 at 7:00pm
| The instrument panel lamp types I have seen to protect tweeters are Festoon glass tube types, that fit in a glass fuse holder, rated 12.8 Volts and 2.1 amps. These have about a 6 ohm resistance when they are heated to full temperature of 2800 degrees Kelvin. A cold lamp has between 10 and 15 times lower resistance. A 100 Watt amplifier provides 28.3 Volts into an 8 ohm speaker. If a tweeter in a 2 way cabinet receives 30% of the signal, on average, from a full frequency range source, then it gets about 15.5 volts on average at almost 2 amps, producing 30 watts. At the maximum volume from the amp, the lamp would heat up and limit tweeter voltage, so you may hear a slight volume reduction, but the tweeter would be saved from destruction. A cold lamp will have 10 to 15 times lower resistance than a fully hot bulb, so at low volumes a human would not be able to notice the loudness reduction. These lamps work well in a full range speaker cabinet, however, if the signal coming from the amp has mostly high frequencies, then the tweeter could see higher voltages, which could push it over its 30 Watt long-term power rating, or over its diaphragm excursion limit, and it might or might not survive, depending on the safety factor the manufacturer used. Failure modes are 1) Mechanical, due to over-travel of the diaphragm causing fatigue cracks, or immediate tears, and 2) Thermal, overheating which melts the voice coil wires. The lamps can be put in parallel for higher wattage tweeters, or multiple tweeters. The best way to prevent tweeter damage is DO NOT DISTORT THEM. If you hear distortion, turn it down. Do not let idiots run your PA board in a band, turning the volume up until it distorts. If it sounds bad, it IS bad. Use a power amp slightly higher rated than your speakers, as too small an amp will clip voltage at its DC power supply limit, stopping the speaker cone or diaphragm motion momentarily, reducing the reactive component of coil impedance, sending large DC overcurrent spikes into the speaker. This will eventually destroy the speakers, and may blow the output transistors in the amp. Or, set a smaller amp gain low enough not to clip. If a larger power amp is used, set the gain low enough that the pre-amp or mixer will never drive the speaker over its mechanical or thermal rating. Overdriving the tweeter can also cause the same output stage failure on the amp. Most of this also applies to woofers, in a similar manner, although they are more robust than tweeters. I welcome comments. Thank you. |