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Is my vintage receiver underpowered for JBL speakers?

toddalin said:
When someone "uses it" and the speakers can't take it and burn out.

The thing is, if you are running the speakers at even 1/10th the rated power, they are already undergoing dynamic compression and this compression can be well in excess of 3 dB at the top of the speaker's power handling capability. When you turn them up using that extra power, they don't go 3 dB louder and you may not even hear the increase in volume.

Then the tweeter breaks up (maybe) and goes mute and you wonder where the highs went.
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Yeah, but compare the heat build-up in a voice coil from a few db increase of clean power to the heat build-up from a clipped signal. Clipped signals are much more destructive.
 
toddalin said:
The 9090 is very unstable into some loads including some Infinities, my brother's included, that burned it out.
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I’ve never heard this before. My 9090DB has happily powered everything I hooked up to it including stacked Advents, JBL L110s, BA A200s, Celestions, etc.
 
z-adamson said:
Yeah, but compare the heat build-up in a voice coil from a few db increase of clean power to the heat build-up from a clipped signal. Clipped signals are much more destructive.
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https://sound-au.com/tweeters.htm

"6 Bigger Amplifiers

A persistent myth in the audio industry is that clipping damages tweeters, so you should use a bigger amp to ensure more headroom so the amp won't clip. This claim is simply bollocks! Take the 100W amp described above, and replace with an amp big enough to prevent clipping ... even with the additional 12dB input signal as shown in Figure 7. Since a 100W amp was just below clipping with an average output of 16W, if we add 12dB that takes the peak amp power to 1.6kW (near enough) and the average power will be 254W.

Do you imagine for an instant that this amp won't blow the tweeters (and everything else) if the input level is increased by 12dB (until it's just below clipping)? Everything will fail, and usually fairly quickly if the speaker was designed for a 'nominal' 100W input. It is simply nonsense to imagine that the loudspeaker drivers in a 100W speaker can survive an average power of over 250W and peak power of up to 1.6kW.

If a user often turns their amp up to beyond clipping levels, they will probably do the same with a bigger amp. They might even turn it up more, because it won't have the distortion component which increases apparent loudness until the average power is a great deal higher. Such users will never hear signs of speaker distress if they can't even hear gross clipping. Speaker failure is a certainty, even if their 1.6kW amp only ever clips a few transients. They can expect the tweeter to fail, and the woofer to catch on fire.

So, while it's perfectly alright to allow perhaps 3-6dB or so of headroom for the power amps, that relies on that fact that it is reserved as headroom! If you use the extra power then there's no headroom any more, and all the effects explained will still happen, but at even higher power levels than described above."

Based on the above if a user has enough power with 60 watts there is no advantage to buying 120 watts just to add another insignificant 3 dBs.
Turn it down a little or get a more capable system.
 
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z-adamson said:
Yeah, but compare the heat build-up in a voice coil from a few db increase of clean power to the heat build-up from a clipped signal. Clipped signals are much more destructive.
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If the amp is clipping, there is a pretty good chance you may hear it before it burns something out. OTOH, if you have too much power, you can fry your speakers in an instant with a tone arm drop.
 
Yeah that link doesn't convince me of anything. Of course you can blow your speakers with too much power.

Realistically tho, your 100w amp is rarely going to be pushing all 100watts. If you're listening to 95db speakers at 98db, you're not feeding it 100w continuous.

Kind of a flawed argument IMO.

The people I know who blow speakers also indicate that too much power has never been an issue, but clipped signals have.
 
opnly bafld said:
I must be missing something in your post.
Not using all the power, but tweeters are failing because of clipping? o_O
What if they are listening to 87dB speakers at 98dBs?
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If you have lots of power, you're less likely to drive said amplifier to clipping than with a small amplifier. Just because I have a 100watt amp doesn't mean I'm using all 100watts, but it's there when I need it for large transient spikes etc and that overhead protects me from the amp going into clipping. The odd clip may not cause damage but sending a clipped signal to a speaker consistently over time is not a good thing IIRC.

Pushing a speaker beyond its physical limits will also blow it regardless of whether the signal is clipped. Voice coils burn up etc

Maybe I'm wrong in my understanding and if so, please someone correct me, and I apologize for misleading.
 
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