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Fuses


joeydingo
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I just got my 8th pair of Pro speakers that have fuses. Thought I'd post a quick "word to the wise" as every single pair I've gotten (from dedicated Klipsch nuts to people who had no idea what the speakers were) have had the 20 amp test fuses that were factory installed in them. From split LSIs to KP3002s to KP301s, KP 250s, you name it, EVERY single speaker has come with a 20 amp factory test fuse. I'm no expert on what fuse goes in what cabinet, but think there isn't much below MCMs that calls for more than a 4 amp fuse. And I'm no electronics expert, many of you post things that are WAY over my head. But I know one thing----fuses cost far less than drivers. So if you're buying pro gear, even stuff 20+ years old, do not assume someone else ever changed out the fuses to be correct for the drivers.

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we were looking at a few of the pro schematics recently and many of the pro stuff that have lots of resistors on the xover use 20 amp fuses. We we looking at one of the subs which had 4 20 watt resistors on the board and it used a 20 amp fuse. So basically, some do show 20amps in the schematic's.

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To clarify the fuse issue on Klipsch Pro, I was a huge proponent of fusing all our speaker systems. We tested out prototypes of most all the Klipsch Pro speakers. Klipsch decided to put fuse holders on all their pro input panels which I was very pleased about. BUT, they did not want the hassle of dealing with people blowing fuses, etc., so they shipped ALL of them "nailed". The 20 amp fuse essentially eliminated a protective fuse. They did ship a sheet with recommended fuse values, though. I spent years tweaking Klipsch's formula for getting the right AGC fuse value. The idea is that you want the fuse to blow on a continuous level before the driver, but due to the fuse's time to respond, peak vs. average, etc. it's not an exact science.

Here's the concept of AGC fusing we have used for 39 years with Klipsch speakers in actual professional use. With an AGC fuse, you want to fuse at a continuous value that would be less than or equal to 3dB down from the maximum continuous wattage recommended. Exceeding that value likely will result in the driver protecting the fuse. Example: for a 300 watt rated driver, 3dB down would be 150 watts. A 4-amp AGC fuse would be the correct value as a 5-amp fuse would exceed the 150 watts (Ohms law, W = I(squared)R: 4 amp fuse squared = 16 x 8O load = 128 watts; 5amp fuse squared = 25 x 8 = 200 watts).

In all of our Klipsch PRO speakers with 15" woofers, we use 4-amp fuses for the low and 1.5-amp fuses for the highs. Most of the 1" or 1.5" drivers in the Klipsch Pro speakers, I consider 30-50 watt drivers for the frequency range they cover. The 1.5 amp fuse would come out to 18 watts for an 8O driver. You can't go to 2 amp (32 watts - too high) and a 1 amp fuse is too small (8 watts).

So, in all of our passive network Klipsch boxes (KSM-15s, KP-456s), as well as some extra KP302s and KP320s, we use a 4A low and 1.5A high fuse. Klipsch's recommendations are a little more conservative than ours on some models, but no one probably has more of a practical working record with the speakers than we do. For smaller Kipsch and non pro speakers, the low may need to be a 3A and many of the small single fuse systems need to be 2.5A (or 3).

We also fuse all of our KP600 system drivers and have an unbelievable track record on protecting those. That would be a whole different topic.

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To clarify the fuse issue on Klipsch Pro, I was a huge proponent of fusing all our speaker systems. We tested out prototypes of most all the Klipsch Pro speakers. Klipsch decided to put fuse holders on all their pro input panels which I was very pleased about. BUT, they did not want the hassle of dealing with people blowing fuses, etc., so they shipped ALL of them "nailed". The 20 amp fuse essentially eliminated a protective fuse. They did ship a sheet with recommended fuse values, though. I spent years tweaking Klipsch's formula for getting the right AGC fuse value. The idea is that you want the fuse to blow on a continuous level before the driver, but due to the fuse's time to respond, peak vs. average, etc. it's not an exact science.

Here's the concept of AGC fusing we have used for 39 years with Klipsch speakers in actual professional use. With an AGC fuse, you want to fuse at a continuous value that would be less than or equal to 3dB down from the maximum continuous wattage recommended. Exceeding that value likely will result in the driver protecting the fuse. Example: for a 300 watt rated driver, 3dB down would be 150 watts. A 4-amp AGC fuse would be the correct value as a 5-amp fuse would exceed the 150 watts (Ohms law, W = I(squared)R: 4 amp fuse squared = 16 x 8Ω load = 128 watts; 5amp fuse squared = 25 x 8 = 200 watts).

In all of our Klipsch PRO speakers with 15" woofers, we use 4-amp fuses for the low and 1.5-amp fuses for the highs. Most of the 1" or 1.5" drivers in the Klipsch Pro speakers, I consider 30-50 watt drivers for the frequency range they cover. The 1.5 amp fuse would come out to 18 watts for an 8Ω driver. You can't go to 2 amp (32 watts - too high) and a 1 amp fuse is too small (8 watts).

So, in all of our passive network Klipsch boxes (KSM-15s, KP-456s), as well as some extra KP302s and KP320s, we use a 4A low and 1.5A high fuse. Klipsch's recommendations are a little more conservative than ours on some models, but no one probably has more of a practical working record with the speakers than we do. For smaller Kipsch and non pro speakers, the low may need to be a 3A and many of the small single fuse systems need to be 2.5A (or 3).

We also fuse all of our KP600 system drivers and have an unbelievable track record on protecting those. That would be a whole different topic.

I would agree with the -3db formula. The only problem with Pro speakers is you really do not know how much power is getting to the speakers once you consider the dcr of the cheap inductors used and the large bank of power resisters added to soak power.

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To clarify the fuse issue on Klipsch Pro, I was a huge proponent of fusing all our speaker systems. We tested out prototypes of most all the Klipsch Pro speakers. Klipsch decided to put fuse holders on all their pro input panels which I was very pleased about. BUT, they did not want the hassle of dealing with people blowing fuses, etc., so they shipped ALL of them "nailed". The 20 amp fuse essentially eliminated a protective fuse. They did ship a sheet with recommended fuse values, though. I spent years tweaking Klipsch's formula for getting the right AGC fuse value. The idea is that you want the fuse to blow on a continuous level before the driver, but due to the fuse's time to respond, peak vs. average, etc. it's not an exact science.

Here's the concept of AGC fusing we have used for 39 years with Klipsch speakers in actual professional use. With an AGC fuse, you want to fuse at a continuous value that would be less than or equal to 3dB down from the maximum continuous wattage recommended. Exceeding that value likely will result in the driver protecting the fuse. Example: for a 300 watt rated driver, 3dB down would be 150 watts. A 4-amp AGC fuse would be the correct value as a 5-amp fuse would exceed the 150 watts (Ohms law, W = I(squared)R: 4 amp fuse squared = 16 x 8Ω load = 128 watts; 5amp fuse squared = 25 x 8 = 200 watts).

In all of our Klipsch PRO speakers with 15" woofers, we use 4-amp fuses for the low and 1.5-amp fuses for the highs. Most of the 1" or 1.5" drivers in the Klipsch Pro speakers, I consider 30-50 watt drivers for the frequency range they cover. The 1.5 amp fuse would come out to 18 watts for an 8Ω driver. You can't go to 2 amp (32 watts - too high) and a 1 amp fuse is too small (8 watts).

So, in all of our passive network Klipsch boxes (KSM-15s, KP-456s), as well as some extra KP302s and KP320s, we use a 4A low and 1.5A high fuse. Klipsch's recommendations are a little more conservative than ours on some models, but no one probably has more of a practical working record with the speakers than we do. For smaller Kipsch and non pro speakers, the low may need to be a 3A and many of the small single fuse systems need to be 2.5A (or 3).

We also fuse all of our KP600 system drivers and have an unbelievable track record on protecting those. That would be a whole different topic.

I would agree with the -3db formula. The only problem with Pro speakers is you really do not know how much power is getting to the drivers once you consider the dcr of the cheap inductors used and the large bank of power resisters added to soak power.

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Then I certainly stand corrected. Guess I was thinking more about the tweeters I've looked into where they call for a 1 1/2 amp and the mids where they call for a 3 amp. And KP 4000 subs called for a 4 amp.

I don't necesarily agree that if the schematics show a 20 amp, that it means it should be a 20 amp. One of the problems is trying to figure out how much power gets to the drivers and how much is soaked by the large power resisters. I don't think 100% of the power actually makes it to the drivers.

post-22082-13819691869184_thumb.jpg

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Some MWM cabinets were shipped with a 5-amp label, later changed to 4-amp. I have a copy of a Frequency Response (white paper) 'A K43 woofer will protect a 5 amp fuse' (not Klipsch sense of humor) , therefore the company's stance was to recommend using a 3 amp. More conservative as you have said. I have that chart here somewhere. I also have a bag of 20 amp fuses that I've accumulated in years of buying blown up speakers. Seems no one read or cared about using the proper value. However, I've had lots of issues with the 1 or 1.5 blowing in HF of pro monitors due to a single blast of feedback, that's not very convenient. ALso blew ALL of the HF fuses in 4 KP362 cabinets at one gig. Yeouch. Carry bags of them with me any more or cheat slightly. Another reason for the 20 amp fuse that I've heard is that many of the later products were installed, sometimes high in ceilings of churches and auditoriums where changing a glass fuse would be time consuming and expensive, therefore the decision was made to install basically a 'non-fuse' and leave it to the end user whether a value that would protect the speaker should be installed.

MWMfuse3amp.pdf

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After 39 years of using Klipsch speakers in a professional environment (driving the pi#& out of them), it is very cut and dry EXACTLY what's the best AGC fuse to use for protection out of what's available. We have already proven what works and what doesn't. The AGC fuse values available are limited and we've used them all - even 3.5A, if you can find them.

I pushed very hard to have the fuse holders on Klipsch Pro speakers and didn't disagree with their decision to leave fusing up to the user. The KP600 series did not have fuse holders on the cabinets. One, they were intended for the highest end professional and two, they were designed to flown in the air, as well as stacked. We designed our own custom EP connector panels (built by Whirlwind who also built the 600 input panels) on the back of our 600 amp rack that have fuse holders for each amp output. Normally, we parallel two stacks and run 4O loads. If we use single stacks, the fuses have to be changed (1/2 value) to protect the 8O loads.

Using the best fuse value may require changing in some cases where it would have been ok, but going up eliminates the protection and it's worth it. Doing this for a living, you need to be able to fix things quickly and it has to be working the next show. Fuses cost a whole lot less than drivers and diaphragms, and take an instant to change. We rarely blow any fuses, but carry plenty of all the values we use.

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Fuse values shown on the schematics in no way indicates best value to use. It only shows exactly how the crossover was shipped from Klipsch (nailed with a 20 amp fuse). They did enclose a suggested value sheet with the pro speakers explaining how to use the fuse protection, if you desire.

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here's a chart. if you know your ohms and know your watts, it will give you the amps. keep in mind that the ohms changes across the speakers range as the hand off from woofer, mid and tweets occurs.

post-22082-13819691917222_thumb.png

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