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Mighty Favog

How much can a K-57-K handle??

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Does anyone know the maximum power a K-57-K can handle?? I’m using Bob’s replacement CD53P (non-Ti) diaphragms and I’ve blown 3 (yes – THREE) of these things in a month in my 84' Cornwalls! I’ve also got his B-3 networks, cast woofers and CT125 tweets.

My system is listed below and here are the conditions:

Preamp at 39% volume (around 2.5 watts on the amp’s meters)

EQ set at 1-2 db above flat in midrange area although they sound fuzzy with or without it engaged at the preamp.

Program was Manhattan Transfer’s Christmas SACD playing a boy’s choir track (can’t remember the track title).

It seems that when they start to "break in" that's when they "let go" and sound horendously raspy and fuzzy.

At first I thought I wasn't aligning them correctly on the driver pins but these last two times they've snapped with no wiggle room at all.

Is the K-53-K diaphragm really interchangable with a K-57-K??

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Did the original diaphrams toast? If not, you might try swapping them back in. There may be something wrong with the current ones Bob has or the crossover. Also, remove the eq and see if that helps. Maybe something is wrong there.

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I've taken the EQ out of the loop and it didn't seem to change things.

A couple of days ago I was playing the system a bit on the loud side (not concert levels) and all of the sudden BAM! The left channel put out this hugely horendous staticky buzz coming from the midrange. I turn the volume down and it went away but when Iturn it back up (but not as high) it came back. From that point on the mids from that speaker can have a slight rasp but not all the time but more pronounced at higher volumes.

I found this thread and my Corn 1's do fall under the suspition since they came with K-57-K mids, K601 horns and B3 networks.

http://forums.klipsch.com/forums/t/48399.aspx?PageIndex=1

I can't keep ordering new diaphragms from Bob at $42 a pop and I can't afford to order the rest of the parts needed to make a Cornscala II (A) project out of the cabs. Shoot, I don't even have the last diaphragm paid for yet on my Visa and it's already toast.

Here is a pic of what one of the diaphragms looked like when that channel started making a buzzing noise (but not the horendously loud staticky buzz). It is the only one I found so far that had this mark on it. Resistance measures anywhere from 11.3 to 11.9 ohms.

post-5564-13819634897916_thumb.jpg

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I don't really know how much power a Cornwall II can handle, but my customers never had any problems with 200W rated amplifiers.

One time the bored salesmen bridged a pair of Adcom GFA555 into a pair of Cornwall II, that's about 900W per side. They got a bit 'scared' sounding in the bass, but the mids and HF sounded OK. (note: I wouldn't recommend this for long term use)

The Carver M1.0 was hard on woofers, but again, no problem with the mids and HF.

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I would get the amplifier check, probably passing DC. Double check your wiring in the crossover to speaker to make sure everything i wired properly.I do have a 200 watts per side amp pluged to a 20 watts tweeter in a Tri-amp set up and i never blown a tweeter in 5 years and trust me i did run my system stupidly extremly loud(way pass concert level did hit +130 db @ 8 feet away in the basement) to impress friend couple time when drunk [<:o)]

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I also owned Cornwall IIs a while ago and powered them with a GFA555 II (not bridged as DJK but still 200+ watts a side). I would crank them to stupid levels, never a problem. If the original diaphragms failed and you are still cooking new ones, there is a problem elsewhere, amp or crossover.

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" I would get the amplifier check, probably passing DC."

Please explain, in great detail, how the DC gets though the capacitor into the autoformer, and how it gets through the autoformer to the driver.

Capacitors and autoformers do not pass DC.

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Maybe i should have been careful with my wording, the amp can be bias improperly and present ''excessive'' voltage at the output and be enough to burn the tweeter, can be clipping too early from being over driven in early stage/defective. Burning tweeter at this rate is not normal so i would check the wiring in the speaker/crossover to make sure everything is ok and if no joy get the amplifier bench check, hope this is better for explanation.

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One of the possibilities that Bob came up with was that the crossover point may be set too low from the woofers to the mids. Makes sence to me. Back when the first one blew I noticed a fuzzy sound instead of the keyboards coming from the mids while playing the beginning of Dire Straits' "Walk of Life". Albeit not a sign wave, it is kinda close to that 400-600Hz mark.

I'm sending the networks back to Bob so he gan give them a look see.

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"Maybe i should have been careful with my wording, the amp can be bias improperly and present ''excessive'' voltage at the output and be enough to burn the tweeter, can be clipping too early from being over driven in early stage/defective. Burning tweeter at this rate is not normal so i would check the wiring in the speaker/crossover to make sure everything is ok and if no joy get the amplifier bench check, hope this is better for explanation. "

You should have quit while you were ahead.

Improper bias does not cause "excessive" voltage at the output and cannot burn the tweeter. Besides he is having problems with his mids, not the HF.

Clipping doesn't hurt drivers (no matter how many time this lie is repeated) unless it exceeds the long-term thermal limits of a driver (usually an HF device) or mechanical damage (usually the woofer).

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