Not sure if my amp or speakers have gone

[aaroneight]

Hi, appologies if this comes accross as very stupid...

So, own a marantz amp and a pair of kef cresta 2 speakers. They've served me well for about 12 years. However, after a heavy session this weekend while connected to my dj equipment, the speakers now sound very bassy with very little trebble coming through. My feeling is that this is unlikely to be a problem with the speakers as it would be quite unlikely for the tweeters to blow on both speakers at the exact same time so the problem is more likely to be with the amp? Am i correct in thinking this?

I've tried the speakers through different channels on the back and it sounds the same. Unfortunately, none of my freinds own seperates so i'm unable to test a different amp or speakers with my system to work out what has gone wrong.

What do you guys reckon? Any help is appreciated! Thank you!

 

[Thompsonuxb]

You may have blown the tweeters. Put your ear to them and listen.

If it was only the speakers been used logic suggests there at fault....

 

[davedotco]

Generally your logic is correct, it would be extremely rare for both tweeters to fail at the same time, but that really only applies under normal conditions.

It is well known that an amplifier, when overdriven can produce some nasty, squared off wavefoms that can give tweeters rather more power than they can handle and, since you were giving it some stick, this is most likely what happened.

Try and check, by cupping a hand over the tweeters to see if they are still working, you should be able to tell.

If you are remotely technical, remove the tweeters disconnect or desolder the leads and check with a meter, an open circuit or even a dead short will denote a blown unit, find the part number, usually on the back, get replacements and fit, easy peasy.

 

[aaroneight]

Thanks! Useful advice. cupped the tweeters and they're not producing any sound. Only coming from the sub.

Looks like time to upgrade to the Q Acoustics Concept 20... Which leads to my next dilema

 

[davedotco]

Generally your logic is correct, it would be extremely rare for both tweeters to fail at the same time, but that really only applies under normal conditions.

It is well known that an amplifier, when overdriven can produce some nasty, squared off wavefoms that can give tweeters rather more power than they can handle and, since you were giving it some stick, this is most likely what happened.

I'm quite satisfied with the explanation given from JBL Pro regarding why small amps kill speakers while clipping.

The square waves make the coil spend more time outside of the magnet assembly voice coil gap. This means there is less cooling and the driver fails due to lack of overheating its voice coil. Whether you play more continuous unclipped power or little but clipped (square waved) power, the effect is the same, more heat is accumulated.

Music is 'spiky' (we have all seen music waves on wave editors) but squarewaves are 'blocky', big chunks of continuous power either out or inside of the voice coil gap. This translates as less cooling time. DC or AC, it doesn't matter what goes through the coil. Excessive heat, rubbing and hitting the stop is what ruins drivers.

Ferro-fluid protects drivers by lubricating (less chance of rubbing), is more efficient heat transfer material than air from the coil to the driver magnet and basket, and protects from dirt accumulating. Imagine the speaker industry without DuPont. *biggrin*

Your above explanation is true of all drive units, not just tweeters, but they are particularly vulnerable as a signal with high levels of harmonically related distortion will have much more energy at higher levels than 'normal' and, relatively speaking, a tweeter has a very modest power rating, a couple of watts being typical in a decent unit.

Many amplifiers produce all kinds of nasty waveforms when overdriven and can be very distructive at all frequencies, including those way above our hearing limits. All good reasons to use bigger, more capable amplifiers.

 

[Vladimir]

The complaints about ferro-fluid is that it reduces transient response, but the benefits really outweigh the cons IMO.

 

[Vladimir]

Generally your logic is correct, it would be extremely rare for both tweeters to fail at the same time, but that really only applies under normal conditions.

It is well known that an amplifier, when overdriven can produce some nasty, squared off wavefoms that can give tweeters rather more power than they can handle and, since you were giving it some stick, this is most likely what happened.

I'm quite satisfied with the explanation given from JBL Pro regarding why small amps kill speakers while clipping.

The square waves make the coil spend more time outside of the magnet assembly voice coil gap. This means there is less cooling and the driver fails due to overheating its voice coil. Whether you play more continuous unclipped power or little but clipped (square waved) power, the effect is the same, more heat is accumulated.

Music is 'spiky' (we have all seen music waves on wave editors) but squarewaves are 'blocky', big chunks of continuous power either out or inside of the voice coil gap. This translates as less cooling time. DC or AC, it doesn't matter what goes through the coil. Excessive heat, rubbing and hitting the stop is what ruins drivers.

Ferro-fluid protects drivers by lubricating (less chance of rubbing), is more efficient heat transfer material than air from the coil to the driver magnet and basket, and protects from dirt accumulating. Imagine the speaker industry without DuPont. *biggrin*