Now let’s look at the real essence of the upgrade starting with damping. Tenor proffers that their design changes and damping specifications offer a direct correlation to the new ‘sound’ of the 350HP. Like many, I’ve often heard the term damping with little real understanding. Most regard the spec as "the higher the better" or simply, "it controls the bass". Aside from its effects in specialty amps like SETs, it is most often ignored. To understand and correlate the results of Tenor’s new design, we need a little technical discussion of damping factor and the interactions between speakers and amp. When you see an amplifier’s power rating, it is presented at specific resistances like 4Ω, 8Ω etc. Yet every speaker presents a load that varies with frequency, with an inherent combination of capacitance and inductive reactance. Mix this with the electrical effects of the speaker cables and the mechanical effects and resonances of the speaker itself and your amplifier ends up ‘seeing’ a complex electrical impedance which varies in resistance across the frequency spectrum and presents varying phase relationships between current and voltage.

Some amps deal well with the loads, others not so well. Now it gets interesting. Most people really don’t think of the speaker/amp as a dynamic interactive system. To produce sound, the amplifier provides current to the voice coil by way of inductance. This magnetizes the coil and creates a magnetic field which interacts with the fixed magnet in the driver, moving the cone or dome like a motor. Pretty basic stuff. However, there is another side to it. Speakers are both motors and generators. Therein lies the rub. Imagine that the amplifier just sent an impulse to the driver and it moves. Now what? The transducer put mass in motion. Therefore it has inertia and wants to continue moving. In the case of a driver without an input, it will continue to move and vibrate at its resonance frequency. Yes its physical suspension will dampen motions but in the time frame of the musical impulse, inertia initially wins out. So now we have a driver with its coil of wire move through a fixed magnetic field which generates current in the coil. The roles are reversed. Now the amplifier is the load and the speaker generates the power. You can test this with a small drive unit connected to a mic input connected to an amp and speakers. Tap the driver or talk into it. Sound will come out because it generates electricity. In virtually any high-end scenario, this is no good. You have a driver flopping around without active signal producing boomy bass, treble ringing and mucked-up imaging. If the speaker would just instantaneously stop when the musical impulse did, we’d be one step closer to musical nirvana.

This is where damping enters. Technically it is the ratio of the amplifier’s internal impedance to the speaker’s impedance. For example, if a speaker has an internal impedance of 8Ω at a specific frequency and the amp has an internal impedance of 0.4Ω, the effective damping factor would be 20 (8/0.4). You might ask, so what? Remember, the goal is to bring the speaker to an immediate stop when the music impulse stops. Using a generator analogy, if you want to stop or dramatically slow down a generator, short circuit its output. If you want to stop a motor from turning, apply a brake (another short circuit). The same is true for a speaker drive unit. When it generates electricity, the load the speaker sees is the internal impedance of the amplifier plus the resistance of the voice coil. The closer you get to the speaker seeing a dead short, the higher the current, the greater the stopping power and the greater the control. The lower the amp’s internal impedance (resistance), the closer it is to a dead short. It’s an inverse relationship. The lower the amp’s internal impedance, the higher its damping factor. You’ll need to accept this as a conceptual discussion because the actual mathematics are above my pay grade.

The new 350HP doubles the 350M’s damping factor from 100 to 200. There are many esoteric forum discussions as to the audibility and importance of higher damping factors. Some claim 20 or 50 as "all that is needed". I have had so-what comments about Tenor when there are many solid-state amps with damping factors of 500 or more which have existed for 40 years. Well, there’s one more piece to this discussion. In general, ultra-high damping is associated with high global negative feedback. This causes a tendency for odd harmonics, brightness, fatigue and loss of musicality. Michel also claims that high damping with high feedback causes nonlinear damping, i.e. high damping in the bass and low damping in the treble. Tenor acknowledge the competitive landscape with solid-state amps delivering damping factors of 200 and more. Jim offers a distinction for theirs. "We did not set out to do this for better bass, we set out for increased power whilst maintaining the same sound. During the design process, we discovered the paradigm between higher power and damping which led to the epiphany. It's something that no one is talking about but should. There are high-power amplifiers that do not have our bass control and definition. Michel says it's due to the linearity of the internal impedance and increased damping factor. For the 350HP, whether it's 20Hz or 20kHz, the damping factor is always 200 [if the speaker’s own impedance is linear – Ed]. For an amp of the same power but with global feedback, the damping diminishes with frequency. But you need good damping across all frequencies to control the speaker. Even the tweeter needs damping to reduce ringing."

Michel believes that the 350HP’s damping factor across the bandwidth and its linearity is fundamentally different from amplifiers with global feedback. "Ours is linear and theirs rolls off, creating sonic artifacts which are sometimes viewed as an artificial increase of resolution but in reality are distortion." Some claim that a damping factor of 200 is overkill. I’ve seen mathematical models showing the greatest effect of damping to be in the lowest ranges (1-50), with smaller percentile gains as the numbers increase. But this is not an academic math discussion. The truth is the sound. I will attempt to correlate Tenor’s claims to my listening observations which after all is why we’re here in the first place. As an aside, I recognize the passion inherent in specialty amp designs. Owners of SET, OTL and transformer-coupled valve amps discuss and debate the importance and/or need for damping. I get it. I’ve owned OTL amps and high-impedance tube amps with output transformers, each with certain magical traits. I also recognize that the frequency response of certain speakers can and does form a synergistic match with certain amplifiers. However, we are at another level here. The 350HP is an all-out assault on the state of the art, which combined with the best speakers attempts to take us one step closer to the real event.  With the new HP, we are not talking of the illusion of bass or added warmth. Tenor have taken a significant step forward for bass depth, bass power and bass resolution.