Fusing Speakers that where not fused

cudaken

Active Member
I blew up my KEF Q 75.2's along with some other speakers. Most died due to age not the power I gave them. But then again 600 watt's 8 ohms RMS a side will blow some stuff up Real Good.

You would think $1200.00 speakers would be fused, but the KEF's where not?

KEFs are rated at 200 watt's a side, not sure if 6 Ohms or 8 Ohms. KEF manual blows chunks. Just got them back and sound better than ever, but getting sick of going to DR HI FI ever weekend so I intalled some in line fues's.

KEF's are not Bi Post Mounted at this point. I used a in line fues on the + side of speaker cable at the speaker termail. Is that all I need to do, or should there be one on the - side as well? I was told that when I go BI Wire that I can use the same sizes fues on both termails.

Is there ruel of thumb on Max watt's, dB sensitivity, OHM and fuse. My Dahlquist DQ 10's have 3 amp in them. DR HI FI said the KEF would handel a 5 amp fues, but not much proteck there. Useing a 2.5 at this time, and think I just lost a F--king tweeter in one of the KEF's.

Not sure yet. Any help?

Cuda Ken
 
You ever think its a fault of the amp and not the speaker ?
 
How about turning it down a little bit, or finding a pair of speakers that can take your abuse?
 
http://members.aol.com/phasetek/faqgeneral.html

Phase linear site has formula for calculating fuse size (they should know). According to this you should be using a 2.5 or 3.0 amp fast blow fuse (depending on whether you are 6 or 8 ohm. But as fast as you are blowing and destroying you might as well get some higher power handling speakers. It is unlikely with your history to expect that you will be able to control your volume hand to protect 200 watt speakers with 600 watt amp. No clipping and that kind of power difference can get you in trouble nearly as fast as severly underpowering speakers and having a fast volume hand. Good luck.
 
FYI...fuse protection for speakers is pretty unreliable, but better than nothing I guess. Certainly they would do little to protect a tweeter, so bear this in mind.

Here is a chart of a couple of 'fast-acting' fuses. Note that, even at 210% of rated capacity, it would take 30 min for the fuse to open. At 400% of rated capacity, it may take as long as 1/3 of a second. I just pulled these up quickly, but all fuses exhibit much the same behavior.

The solution is to get speakers that can handle what you are doing.
 
Grumpys right.

Usually the reason speakers get fried is a problem in the amp. Not always, ....but many times.

I use "test speakers" that I have added a fused protection.
After finished going through a unit, I give the amp/receiver a final listening test with speakers.

Fuses are cheap protection... I every case.
 
Hey, thank you all for the answers. First set of speakers I fried where my Dahlquist DQ 10's.God, I hate to tell this story but I will. Bought them new in 1984 and where under powerd with the ADCOM GFA-1A. When they got rocking, pop went the fues. Called the shop I bought them from and was given a cheap fix that worked then.

Then system slept for 10 years, wife and I got back togather and got tired of hearing her bitching over Mozart. Fast foward, Cuda Ken got the Bug and dragged all the equipment to the garage and did the Amp up grade. Blew the foam of the DQ 10's, well 30 years old now. Did the refoam, blew them off again and some hard parts, voices coil, and cone off the other one. One night, I then rememberd I did the cheap fix that stopped pooping the fuse with the GFA-1A Amp? Picked up the DQ 10's from Dr Hi Fi, after reconeing and open the fuse holder! Yep, 5 AMP slow blow from 1985 where still there. I have the DQ's back for 10 weeks, have replaced some 3 amp fuse's but no drivers. :banana: Sound like 1984 again :banana:

Now, the KEF Q-75.2's. No idea what killed them for sure. I do seem to blow right speakers first. I did send the ADCOM 555 right Amp to be ckecked for DC leaks. I recived the KEF Q75.2's while I was have the right 555 tested. So I was only running stereo off one 555 200 watts 8 ohm RMS. Blew the right tweeter, KEF sent me a new one, then blew the right mid range and both cross overs.

OK, KEF Q 75.2's ratted at 200 Watts, Adcom 555 stereo 200 watts, no flutter from the speakers. Amp led's alert nerver flickerd, just dead speakers?
Right ADCOM passed from 16 OHM to 2 OHM and no DC leaks stereo and mono, speck's where better than new. All speakers just die with out a wimper.

Was told it could be the ADCOM GFP-1A Preamp it self going into clip but was told that is very un likely. BUT, it seem's the right side does out power the left channel some what?

I thought I was deaf, old drag racer, rock band and run a body shop for 22 years. KEF Q75.2's ratted at 114 dB. Guess what I asked for Christmas? Yep dB metter. Found I like the toons at 95 dB, at 105 dB I turn it down pretty quick.

Also, I did not blow a teeter, just a 2.5 Amp fuse. :banana:

One more thing, lenght of speaker cable, could that have something to do with the Spekers going Boom? Right side cables are shorter than the left one's. I was going to ask this question about speaker timeing for best sound stage but came up here.

Cuda Ken, belch :D
 
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