Current optimized or voltage optimized speakers?


Just read a recent post from an old thread, and an old question, that has kicked around the Forum for some time. Back in "09," a member wrote:

"Read Atmasphere's posts and white paper. Amp choice [is] highly dependent on whether your speakers are current optimized or voltage optimized. Which strongly suggest[s] that at least a part of 'system synergy' can be predicted."

The question for the Forum is how can one know whether speakers are "current optimized or voltage optimized"?

My layman's understanding of Ralph's whitepaper is that most solid state amps are based on the "voltage paradigm" (voltage is constant and watts change with load) and that most tube amps are based on the "power paradigm" (voltage changes with load, but watts don't change very much) [or is it the other way around?? LOL]

The old post quoted above suggests that some speakers will work better with solid state amps and others with tube amps -- let's leave electrostats and maggies out of the discussion. I'm thinking about the vast array of dynamic speakers out there.

So . . . restating the question, how do we know whether dynamic Speaker X will work best with a tube amp or a solid state amp?
bifwynne
Others w more technical knowledge than me will have more/better answers, but I think that one way to "know" (besides listening) is to look at the impedance characteristics of the speaker. Higher overall impedance and a relatively constant impedance over the audible bandwidth is a good clue that the speaker will match well w tubes. OTOH, a significant reduction in impedance, esp. in the bass, indicates that the speaker will require more wattage at those frequencies, which a tube amp is not designed to/is not able to deliver, resulting in a bass-weak presentation. An amp that "doubles down" ( delivers twice the output wattage) with a halving of the load impedance) will be better able to drive that speaker in the lower frequencies and will have a more robust bass presentation.

Considering the issue further, constant voltage sources (SS amps) deliver less power into a higher impedance load, so speakers with a high impedance SHOULD mate better with tube amps. Conversely, a tube amp will not be able to deliver steady wattage to a speaker with wide swings in impedance; hence the generalization that speakers w a flat impedance curve mate well w tube amps.
Couldn't have said it better than Michael (Swampwalker) did, except that in the last sentence change "wattage" to "voltage."

Also, although it doesn't directly relate to the question, it's worth mentioning that Ralph (Atmasphere) has also stated that solid state amps, as well as tube amps, will generally perform better into high impedances than low impedances. This assumes, of course, that they are not asked to approach the limits of their power capability when doing so.

One final point, although it is a fairly obvious one. Researching what amplifiers others use with a given speaker can often be helpful in determining whether to go tube or solid state.

Best regards,
-- Al
Then there is the issue of phase angle:.............
Impedance phase angles which are severely negative (i.e., capacitive), especially at frequencies where the magnitude of the impedance is low, will make life difficult for the amplifier in terms of how much current it has to supply. Also, the efficiency of the speaker will most likely be less than it would be if the phase angles were more benign, everything else being equal. That will further increase the power demands on the amplifier.

I don't think, though, that highly capacitive phase angles in themselves are necessarily an indication that a suitably high powered tube amp would not be sonically compatible. Although, of course, high quality high powered tube amplification does not come cheaply.

Best regards,
-- Al
Phase angle has nothing to do with whether the speaker is Voltage or Power Paradigm.

I am always amused by the idea that 'this speaker is hard to drive so get a transistor amp that can double down.' The speaker got the reputation of being 'hard to drive' for a reason; you can count on the fact that a hard to drive speaker will never sound right with any amp, as the amp has to work hard to drive it (equals more distortion, which contributes to harshness).

The simple answer to the OP is look at the designer's intention. For example Coincident Technology uses tube amps for reference- Power Paradigm technology.

Planar speakers of all types tend to be Power Paradigm also. I know these weren't to be in the conversation per the OP, but there it is. Planars don't have an impedance curve based on box resonance, and it is resonance that drives the impetus for the Voltage Paradigm.

An example is a box resonance due to a woofer in the box. When an amplifier that is a voltage source encounters the box resonance (impedance peak) it throttles back its power. This gets flat frequency response in theory.

But just because you have box resonance does not mean the speaker is on the Voltage Paradigm. An example of Power Paradigm box speakers was already mentioned, another is Audiokinesis, where Duke has built speakers that take advantage of the amplifier's power response in a way that allows the speaker an extra 1/2 octave of response in the bottom octave, without coloration. There are many other examples.
Ralph, Al and others -- thanks for your responses, but I'm still not sure the question has been answered.

As I said, my speakers -- Paradigm S-8 v3's -- have some pretty wild impedance and phase angle curves. At one point (100Hz I think), impedance is as low as 4 ohms. But above and below that point, it's roller coaster land. Phase angles are weird too. Nevertheless, the speakers are nominally rated at 8 ohms. How Paradigm came up with that number, I'll never know.

Al, you're pretty good at finding equipment specs on line. If you can find the Paradigm S-8 specs, you'll see what I mean.

I drive my S-8s with an ARC VS-115 tube amp -- output is 120+ wpc. To my untrained ears, bass slam is great, overall sound is smooth, imaging very good, and so forth and so on. And I know bass is great because my wife is always complaining about the house shaking.

I guess I'm just lucky with my dumb choices, dunno. But if I was starting from scratch and already owned the VS-115, should I have looked to match my amp with a different type of speaker; and vice versa, if I already owned the S-8s, should I have looked to match the speakers with a different type of amp.

I think that's the bottom line Q here. How does one make an informed decision?

P.S. Ralph, you mentioned that "[w]hen an amplifier that is a voltage source encounters the box resonance (impedance peak) it throttles back its power. This gets flat frequency response in theory." Ok, flip the facts, if you got a speaker with an impedance peak, I believe a Power Paradigm amp (tube) will put out the same wattage regardless of impedance peaks. Would that result in frequency response NOT being flat with a tube amp.

Sorry for my persistence. I'm just trying to get this concept down. And if I am confused, I bet other are too!

Thanks guys. I think your responses will help the rest of us ding-dongs be better buyers.
Bruce, keep in mind that there are many shades of gray in between the black and white extremes. And that applies to both speakers and amplifiers.

While there are some speakers that will clearly be mismatched when used with one or the other kind of amplifier, tube or solid state, there are a lot of speakers that will do reasonably well with either. In those cases, the two resulting presentations will certainly have different sonic characters, but the differences will be such that room acoustics, personal taste, and the intrinsic sonic characteristics of the particular amplifier will determine which is preferable.

And while ALMOST all solid state amplifiers will fall into the voltage paradigm category, tube amplifiers will fall into the power paradigm category to varying degrees, depending primarily on their output impedance (output impedances for 8 ohm taps being equal to 8 ohms divided by damping factor), and its relation to the impedance of the speaker that is being used. As a general guideline, which is applicable to the kinds of damping factors that are most commonly encountered (i.e., those greater than about 2 or so), and to the kinds of speaker impedances that are typically encountered (i.e., nominal values that are in the 4 to 8 ohm area or thereabouts), the lower the damping factor (or equivalently the higher the output impedance), the greater the degree to which the amplifier will behave in accordance with power paradigm principles. (That guideline but may not be applicable in some extreme situations where the numbers fall outside those limits). ARC amps tend not to be as far into the power paradigm category as a lot of other tube amps, I believe mainly because their use of feedback tends to result in lower output impedance.

Take a look at the impedance curve of the Harbeth M40.1. It fluctuates all over the map, yet that speaker is widely used very successfully with tube amps having significantly lower damping factors than yours.
I believe a Power Paradigm amp (tube) will put out the same wattage regardless of impedance peaks.
No, it won't eliminate variations in power delivery as a function of load impedance. What it will do is to REDUCE those variations, in comparison with a solid state amp. The degree of reduction will depend on the relation between the output impedance/damping factor of the particular tube amplifier and the impedance characteristics of the speaker.
But if I was starting from scratch and already owned the VS-115, should I have looked to match my amp with a different type of speaker; and vice versa, if I already owned the S-8s, should I have looked to match the speakers with a different type of amp.

I think that's the bottom line Q here. How does one make an informed decision?
We had a related discussion a little under two years ago in this thread. For comments that are specifically relevant to your situation, see my two posts in that thread dated 1-5-11.

Best regards,
-- Al
Thanks Al. As my system description says, I'm done with major changes and upgrades for now. Will still do some tweaking here and there, but my main focus will be on buying good quality vinyl and CDs. And then just enjoying what I have. As I've said before, ignorance is bliss, because I really enjoy whatever swill is coming out of my rig.

As I've also said before, something must be right because last night my wife came running into my man-cave/listening room and went nuts because the bass was shaking the floors. I think I was playing a new CD: T-Bone. Good music.

Funny thing is that my wife ran over to the sub and starting turning knobs and flipping switches hoping to turn the bass down. I "politely" [sic] invited her out of the basement. What she wound up doing was turning the gain on the woofer up to maximum. Ha Ha.

Well, I still find the technical side fascinating. So I hope guys like you don't mind my questions. I'm really trying to understand what makes audio sound good or bad.

Thanks to all and best wishes for Happy Holidays and a Happy New Year!!

Bruce
If you don't ask questions sometimes its harder to get answers :)

Enjoy the music.