Tuesday, May 15, 2012

Deep Bass: Volume 1

My wife and I have a push-pull, love-hate sort of relationship when it comes to bass response. She loves bass; the more the better, flabby or thin, as long as it's loud and dominant. I on the other hand have a more selective slant on this topic and prefer little (read no) bass over flabby bass. Allow me to explain.

Several manufacturers over the years have found ways to get deep bass from small speakers. While this is doable, what results is long cone excursions for any kind of sound pressure level. This means that to go loud, these small drivers must be pushed to their limits and you can see the little buggers flapping in the breeze trying to reproduce very low notes. To me, this is not music; this is noise and categorized much like the tinniness and lack of dynamic range I hear in 16/44 CDs.

Acoustic suspension speakers, prevalent in almost every commercially available design, use a cone edge that also permits long cone excursions. This half-round foam or rubber roll lowers the distortion of the cone but the characteristic sound of such speakers is boomy. It is only once you hear what other designs can do is when you understand how much distortion you are listening to.

The sound of bass reflex speakers leaves me mixed in that the colorations are lower but the flabbiness and tuning seem to be more prone to temperature, barometric pressure, and humidity sensitive. Ports and enclosures reveal the tuning issues after prolonged (weeks worth) listening.

Infinite baffle designs seem more accurate than the above but the compromise is the last octave (very deep bass under 40Hz).  Properly controlling the rear wave from a dynamic driver gets one closer to accurate sound at the expense of huge cabinets (read refrigerator sized).

My first real love with low bass was when I heard the Klipsch corner horn (K-horn) for the very first time. Besides transforming whispers into roars (1 Watt sensitivities typically exceeding 100dB), horn loaded speakers do not demand long cone excursions thereby keeping the amount of movement each driver has to an absolute minimum.

But there is always a tradeoff when it comes to clear, undistorted bass and the K-horns have their own: PHASE.  The time it takes for the sound to emerge through the labyrinth and arrive at your ear is tens of milliseconds behind the time it takes for either the midrange or tweeter sound to arrive at your ear. What you hear is a musical disconnect much like the chronic audio/video sync problem plaguing HD TV today. A classic example of this problem is to listen to a tap dancer: you hear the metal cleats and a moment later you hear the thud of the leather shoe. Listening further you come to the realization that everything is just a bit "off" and again you find yourself in search for that ultimate low distortion and phase coherent bass.

Fortunately, bass is the part of the audio spectrum to which human ears (especially male gender ears) are the most tolerant to such distortions.  So where does one turn when all other speakers have compromises that make their sound muddy or weird?  Enter the planar speaker.

Back in the 1980s, I ran across an ad in the back of Audio magazine that summarily read, "Full-range planar speaker." Intrigued by its possibility, I always held hope to hear such a speaker knowing that other planar transducers such as EMIT and EMIM tweeter and midrange drivers did very well. Even the Magnaplanar panel speakers showed promise for this technology but none could attest true full-range bass. All other models needed some sort of woofer to get into the basement (notes under 100Hz).

One day a friend bought a pair and set them up in his Boulder, CO, listening room. With his Moscode amps warmed up and tubes aglow, we spun some jazz and for the first time I heard what real bass could sound like. Now these Apogees also were not perfect, but they were definitely a step in the right direction. They required massive power to drive and careful attention to placement and room treatment. There was a small sweet spot from which to fully appreciate their potential, but the sound that reverberated through the room was unique in itself. But the sound...that unmistakable sound was for the first time there. I lusted after a pair but their price was beyond my reach.

I still think fondly back to that day when I first heard what good bass sounds like. Despite their drawbacks and quirks, properly designed planar speakers sound to me more accurate than others. I think of all of the audiophiles who probably share my view but cannot put up with their inherent compromises. Oh well, I'll just have to be satisfied with what my Bozaks do right and dream of the day that a pair of full-range planars appear in my own listening room.

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.


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