Help diagnosing a damaged KG-4

[erdric]

Hi all. I have a KG-4 in a 2 channel system that has developed a problem. When playing certain music, mainly bass-heavy and at a medium to high volume, I get this sound coming from the speaker. It sounds kinda like a high pitched pop/squeek you hear from a sneaker on a indoor gym floor, but definitely electronic in nature. I've tried two different amps (NAD and Denon) with the speaker and get the same results. I've tried the same CD at high volume in my HT system and the sound is not there. The other weird thing is that I can repeat it over and over again with this bass-heavy CD, in different parts of the track, but it doesn't always occur with other music. It's something about how this CD sounds that causes the speaker to freak out.

Does anyone care to guess what it might be? I THINK it's the tweeter but that's a 100% guess. It just seems like the logical thing given how high-pitched the sound is. However, for all I know it's the crossover. I've never diagnosed a speaker problem until now. I guess I've been lucky so far.

TIA

[erdric]

BTW, why can't I get paragraph breaks?! Is this a Safari thing?

[WMcD]

In the past I've pointed out that bass drivers can make some very odd noise when overdriven. IMHO it is when the active bass driver bottoms out and the diaphragm structure hits the magnet. I have heard a clanking sound. I think that what other people describe as a crackle is a lower form of the same. I would not have believed the woofers can make these treble like noises until it happened to me.

I don't know about the KG-4. Maybe the squeek is an air leak. Hard to tell.

I would suggest that you take off the front grill and look at the driven woofer while you're playing the passage. Take some care with level because, again, I think it is a mechanical overload situation. And also look at the passive.

These bottoming out effects are easy to do when you hit a sealed speaker system a system resonance. But below system resonance, the sealed box prevents excursion.

In a ported system this is not much of a problem at resonance because the port loads it. The problem with the ported system occurs when you hit it with bass below resonance. The port is not limiting excursion and there is no sealed box. The port is a hole.

With a sealed system with a passive, there might be some complications. This is because (I think) the passive is set to resonate somewhat below the active radiator. I haven't figured that out.

In any event, modern bass heavy recordings are really challenging the speakers. It is not a matter that they have bass down at about 41 Hertz, which is the open string on a bass guitar. Rather, they have infra sonics down around 20 Hz at high levels. That is dangerous to the mechanical systems.

Gil

[erdric]

Thanks for the reply. I think you nailed it with the bass. I had the house to myself for the last hour so I put a number of cd's through the system at low and high volume. Not a single one caused the sound to occur except for the one CD I mentioned. I could get it to repeat over and over again. It starts at a point where the bass really kicks in. The CD is Kodo "Ibuki", which is Japanese drumming and very bass intensive. There is something about this CD that my KG's hate because it plays beautifully on the Forte II's. I would have never thought a bass driver could make that sound. Anyway, I feel relieved that there appears to be no problems with the KG-4's. I plan on handing them down to my son once he gets a little older. Thanks.