Thursday, September 16, 2010

Can Recorded Grunge Guitars Destroy Your Tweeters?

Once often asked during the rise of Seattle Grunge movement, do playing recorded “grunge” guitars on your hi-fi kit eventually destroy your tweeters?

By: Ringo Bones

Part of the rationale of owning a really good hi-fi rig is the ability to play loud without hurting your ears with aggro of distortion. Surprisingly, I’ve just recently found out as recently as a couple of weeks ago that there are still really – I mean really – naïve audiophiles who genuinely believe that playing recordings of “grunge guitars” – i.e. highly distorted and very loud electric guitar passages can eventually result in tweeter damage of your loudspeaker. I don’t know if these naïve audiophiles ever actually heard one played live or been in a Nirvana or a Soundgarden concert, so it is yet premature to judge. But the “assumption” that such “hot guitar tone” can fry tweeters is partly based on misinformation over amplifier clipping.

Every audiophile and hi-fi rig owner knows that pushing a power amplifier into hard clipping – i.e. playing it too loud that it no longer sounds nice – will “fry” or burn out your loudspeakers’ tweeter coil because the clipped waveforms contain much more high-frequency energy than a typical music signal. Given this truism in the physics behind the workings of electronic amplifiers, one will thus be curious enough to ask: “What happens when the music itself naturally contains heavily distorted clipped sounds – like those in loudly played and distorted electric guitars played through a fuzz pedal set on high or even extremely high? Will this result in tweeter damage too?

The truth – fortunately to us rockers – is that distortion produced by electric guitars played through “fuzz” or distortion pedals being set to extreme grunge is not nearly as destructive in comparison to actual amplifier clipping. Sound quality wise, I really don’t believe that the distortion tone created by guitarists and their special equipment is nearly as rich in harmonics as the distortion produced when a power amplifier truly clips.

The upper frequency of the harmonics produced by an overdriven guitar amp is limited by the instrument amp – which is more likely vacuum tube equipped with an output transformer coupled into a single-coned electric guitar loudspeaker – and the medium in which the instrument is recorded on – i.e. analog magnetic tape running at 30 inches per second. Ultimately restricting the bandwidth of a loudly played distorted electric guitar to lows of about 75-Hz to highs of about 5,000-Hz.

Just listening to such Seattle Grunge music makes me feel that much of the distortion behind its distinctive tone occurs at midrange frequencies where our ears are most sensitive to, rising into the treble range but decreasing in amplitude as the frequencies of the harmonics rise. A typical “clean” jazz guitar track played on a vacuum tube-equipped combo guitar amp typically measures 200 to 300 % total harmonic distortion. The electric guitars in a typical Seattle Grunge rock’s total harmonic distortion figure probably lies closer to 1,000% THD or even more.

Furthermore, if tweeters were actually being destroyed during playback of such music, older audiophiles would have read about it in 1990s era hi-fi magazines. And might even necessitate labelling such cassettes and CDs back then with warnings of potential tweeter damage when played loud in addition to the PMRC Parental Advisory, Explicit Lyrics warning stickers. Fortunately for music lovers of the world, no tweeters had even been martyred alongside Kurt Cobain during the heyday of Seattle Grunge.


Heidi Gail said...

At the volume levels I tend to listen my indie and punk LPs and CDs - at around 96 to 100 dB SPL which can be too loud to most non-audiophiles / civilians - I never yet burned out the tweeters of my Tannoys yet. But I recently visited our local hi-fi dealer friendly enough to let me hang around during demos, and during one of these demos - using Veruca Salt's Eight Arms to Hold You album played at very healthy levels - it managed to make the stripped-down Infinity loudspeakers'tweeters' magnets just a bit too lukewarm. The mid-range drivers magnets too got a bit lukewarm.

Sherry said...

Even if the loud guitar parts of Seattle sourced Grunge Rock doesn't destroy your loudspeaker's tweeters, it may give them a very tough workout. The Mobile Fidelity Soundlab Ultradisc CD of Nirvana's Nevermind album that's digitally mastered from the original analog master tapes - shows treble lift in the noise floor for a few milliseconds before the onset of modulation. This is the Sony Super Bit Mapping (SBM)noise shaping's "smoking gun". The spectral analysis of this particular acoustic event was even published in an edition of Audio magazine back in 1995.

Ringo said...

There has been serious discussion whether noise-shaping digital mastering schemes - like Sony's Super Bit Mapping - could be raising analog signals deemed inaudible from analog master tapes to humanly audible levels had been much discussed during the mid-1990s. Even the germanium diode white-noise of the stompboxes used in the recording of Iron Maiden's Two Minutes to Midnight has been boosted to audibility once the Powerslave album was remastered to Redbook 16-bit 44.1-KHz sampled CD using Sony's Super Bit Mapping noise shaping technique.