Loudspeakers Lament

by Nelson Pass


CLASS A or CLASS A/B……… will Audiophiles ever evolve to a Classless Society?

Is Class A amplification superior and preferred to A/B?

The answers to these two questions are a definitive:

Not Likely
Not Always

And the slightly longer answer:

We prefer Class A, because it usually sounds better.
We appreciate Class A/B for it’s practicality.

To illuminate; a very short discussion, not about amplifiers but about one of our other favorite topic, loudspeakers!

When a speaker designer sets about to design a loudspeaker they have a number of physical constraints that they have to work within, and being engineer types we have all sorts of buzzwords that describe those constraints and their effects.

Speaker designers massage those constraints, hopefully to a happy compromise where the speaker achieves various targets, such as frequency response and polar dispersion in your room.

Salient to this discussion would be impedance and “Q”. Most audiophiles have a grasp on impedance, so lets talk very briefly about “Q”.

“Q” describes how a system stores and releases energy and what sort of acoustic artifacts are present at release.

“Q” from a speaker designer perspective has two major subsets:

Qe are the various electrical components of the function
Qm are at the various mechanical components of the function

Collectively they form a loudspeakers “Qts”, the total system “Q”; it’s “Quality Factor”.

The only thing you need to come away with from this is that “quality factor” and “impedance” interact in ways that dramatically shape how a loudspeaker responds to an amplifier and ultimately what we hear from that loudspeaker. As a result some loudspeakers demand wattage, others “not so much”.

And happily we have amplifiers that match to a wide spectrum of speaker characteristics and we can usually predict which amplifier class (A or A/B) behaves best with what speaker……… and so can you.

A moment of audiophile empowerment

When thinking about amplifiers, pick a musical selection that has a combination of great dynamics and inner detail.

My favorite is a Tom Jung (DMP) recording “Tricycle” by Flim and the BB’s (on vinyl) . Old audiophiles will remember this recording! If you have a well recoded personal favorite by all means use that. Maybe something with a great brass section and dramatic dynamic contrast in the lower registers.

At the opening measures of “Tricycle” there is a delicate little instrumental with space and layering; followed by a tremendous crescendo that comes unexpectedly on an up-beat and then falls right back to delicate detail with space and layering.

If upon first listen that crescendo doesn’t startle you, terrify the dog or send the cat and kids scurrying for cover you likely need to pair those speakers with a healthy A/B amplifier (or a much more powerful Class A amplifier)

On the other hand, if there is a lack of space, fine detail and inner depth in that recording, plenty of impact and no emotion; then you and your speakers may just need a healthy infusion of Class A amplifier power.

If your speaker is efficient and has low impedance (4 ohms or less), you might want to consider Class A first.

IF your speaker is not terribly efficient and is of more conventional impedance (6 ohms or greater) you might want to consider A/B amps first.

It’s about synergy folks…..but you already knew that, right!

Class A amplifiers bring delicate control to the listening experience. Class A/B amplifiers bring a certain speed and jump to the listening experience in a smaller package.

Having a choice between Class A and Class A/B amplification is another tool to optimize your listening experience……

Our Customers Opine!

We have our favorites, and so do you! Call us at +1.530.367.3690 if you have specific speakers you want to discuss with us.

Without mentioning names:

Electrostatic panel aficionados adore amplifiers with output voltage to spare. Big voltage in a practical amplifier, the logical choice is A/B and for those duties the Pass Labs X600.5 and X1000.5 reign supreme.

Planar magnetic speakers, another panel speaker, but very unlike most electrostatic designs in their amplifier requirements. Planar speakers appreciate power, but they do not absolutely demand power. What you are going to want is at least 100 of the best watts you can afford. Class A power preferred, it simply sounds better. If XA100.5’s are outside of the budget, then the X350.5 or X250.5 can be used to good effect. For the smallest planar magnetic panels in either a surround or small second system an X150.5.

Highly efficient large floor standing conventional paper cone loudspeakers; we’ve been frequently informed that “Magic Happens” when these speakers are driven by the XA-60.5 Class A monobloc’s. An XA-30.5 stereo amp is another excellent choice, but typically does not deliver quite as deep a soundstage or quite as much bass foundation as the XA60.5

Contrasted to cone loudspeakers that are not so large, those with multiple small to medium size woofers a couple of midrange drivers, metal dome tweeters. Loudspeakers of very low efficiency, frequently difficult to drive beyond 105 dB, in room. Usually these sound best when they have high wattage amplifiers at their disposal. The cognoscenti opt for either the X600.5 or XA200.5 Those with the wherewithal overwhelmingly prefer the Xs-300.5. The Xs-300.5’s having the spatial richness of Class A and the drive normally reserved for Class A/B amplifiers.

Legendary in the UK, and once again gaining popularity worldwide, moderately large easy to drive box speakers of modest power requirements. What too choose, anything XA.5 or Xs from the diminutive Xa30.5 on up.

Studio monitor loudspeakers, those with professional recording studio pedigree’s usually demand power. At minimum Xa-160.5 monobloc’s. For a big room and the ability to listen at concert level, X600.5 monobloc’s may be a better choice at an equivalent price-point.

At the end of the day all speakers require power to behave as intended. Some require all the power you can muster, others more modest.

We prefer the sound of our Class A designs. IF the space or budget will not support our Class A designs the A/B product will supply the power in a smaller more affordable package without giving up too much in the way of performance.

Class A watts are hardware heavy, not all systems and budgets will support that level of hardware. For those systems we have very high performance A/B amplifiers.