What causes increasing harshness as the volume goes up?

[Saurav]

Just wondering what the various factors are that would contribute to this.

The most obvious one would probably be the drivers themselves compressing and distorting, right. I wonder if that's the case with mine though - they're 97dB sensitive and use pro audio drivers, and I was barely reaching 90dB peaks.

I guess it could be the amp running out of steam (it's only 3.5W) - would that be the next most likely cause?

I'm also wondering if my speakers are brighter than they should be, and this is the Fletcher Munson curves coming into effect - the tonal balance in the treble sounds better when the volume is turned down, but the treble starts to become relatively too strong as I reach more realistic volume levels?

What else? Increased vibrations affecting exposed microphonic tubes?

I just noticed this last night, with one particular CD. So maybe it was more psychological than anything else. I was playing at the same volume level I usually play my music at, and I haven't felt the sound to be too harsh before. Could it be something in the recording that makes one specific CD behave this way?

Any insights would be most helpful.

Thanks,
Saurav

 

[sreten]

I guess it could be the amp running out of steam (it's only 3.5W) - would that be the next most likely cause?

IMO yes, its how often its clipping, which goes up with apparent volume.
(average volume is ~ 25dB below peak levels that cause clipping)

🙂 sreten.

 

[sreten]

I'm also wondering if my speakers are brighter than they should be, and this is the Fletcher Munson curves coming into effect - the tonal balance in the treble sounds better when the volume is turned down, but the treble starts to become relatively too strong as I reach more realistic volume levels?

Sounds perfectly sensible to me, the treble level
should be adjusted to suit normal listening levels.

A flat resonse at 86dB to 88dB for one watt, typical for
speakers isn't the same as a flat response at 97dB/watt.

🙂 sreten.

 

[Elso Kwak]

Increased Harsness????

Huh, increased harsness????
Just have a look at this post!:
http://www.diyaudio.com/forums/showthread.php?postid=281991#post281991

 

[Saurav]

Are there any easy ways to determine if I'm sending my amp into clipping? And I guess I can tone my tweeters back down some more.

 

[sreten]

try this :

http://sound.westhost.com/project23.htm

🙂 sreten.

 

[Saurav]

Hmm... I'm not sure if that will work for a tube amp. My grasp of this is very feeble, but I think the flyback effect in the output transformers allows the output voltage to rise above the supply voltage. AFAIK, that is not considered clipping.

 

[sreten]

I'm certain the design doesn't suit valve voltage rails.

Literally you can hear clipping in a valve amplifier, though
its not as painfully obvious as a transistor amplifier.

A simple LED/Zener/resistor/capacitor circuit can be
used to monitor output level set at 3W into 8 ohm.

🙂 sreten.

 

[Saurav]

OK, so implement one of the more conventional comparator circuits that he was talking about? That could be done.

Thanks for the help.

 

[sreten]

You don't even need a comparator.

do a web search - you should find something.

'amplifier power output indicator'

assuming symmetrical voltage swing

The zener or diodes + LED forward drop determines the
threshold, the resistor limits LED current, the capacitor
lengthens the indication so you can see it.

🙂 sreten.