Trelja wrote: "Could you shed a bit more insight into how you landed on your assertion, and potentially provide some specifics, please?"
I assume this is the assertion you’re talking about: "I disagree that there is a correlation between parts count and how difficult a speaker is to drive."
Well my wording was imprecise; here is what I should have said: "I do not think there is a causal relationship between crossover parts count and how difficult a speaker is to drive." (There can be a correlation without causation.)
I have designed many speakers specifically to work well with high-damping-factor tube amps (such as the Atma-Sphere S-30 mentioned above). Here are four things that make for good synergy between such amps and a speaker: High efficiency; fairly high impedance curve; fairly smooth impedance curve; and if the impedance curve is not smooth, then the target frequency response should take the amplifier’s output impedance into account.
Smoothing an impedance curve calls for additional crossover parts. I have tried it both ways: Tailoring the response specifically for the high-output-impedance tube amp and not caring what the impedance curve looks like; and using additional crossover parts to smooth the impedance curve. Not only is the latter sonically superior when done right (in my opinion as the crossover designer), it also results in compatibility with a much wider range of amplifiers.
Most of my work is in prosound. Among other things, I build high-end bass guitar cabs. Many of my designs use bypassable notch filters for response shaping to give the bassist at least two distinctly different voicings from the same cab. With the notch filters bypassed (via a switch on the back of the cab), there is no filtering of any kind on the woofer. I do not hear any difference in dynamics between filters engaged and filters bypassed. But more significantly, neither do any of my customers, to the best of my knowledge. However what my customers CAN hear is, the cab starting to compress at high power levels, regardless of how the switches are set. So this is anecdotal evidence that thermal effects have a more audible impact on dynamics than crossover parts do (at least at the quality level of the crossover parts in my bass cabs).
I am friends with a recording engineer who has asked me not to drop his name. He has for decades been testing the dynamic compression of various loudspeakers that he has had access to. What he looks for is, how much does the speaker compress the peaks? This would be a short-term effect, which has not been studied in nearly as much depth as have long-term compression effects. (Had an interesting exchange with Floyd Toole on the subject once - details if you’d like.)
Anyway my recording engineer friend sets the volume to his reference level and then hits the speaker with what should be a 20 dB peak, to see if the speaker delivers the full 20 dB. Most deliver less, maybe 16 or 17 dB. A few deliver the full 20 dB. His observation is that loudspeaker efficiency is the best predictor. And among those speakers with less efficiency that still do well, power handling tends to be unusually high. This doesn’t PROVE that crossover type and/or parts count makes less of a difference than power compression, but it does indicate pretty good correlation between good dynamics and drivers that are just loafing along.
Note I would agree that, all else being equal, a time-coherent loudspeaker should have superior dynamics because the fundamentals and overtones are all arriving at exactly the same instant. Time-coherence implies first-order acoustic crossovers, if we’re talking about passive loudspeakers. A first order electrical filter doesn’t necessarily give us a true first order acoustic rolloff, so to achieve that target response, additional crossover parts are usually required.
Driver compression mechanisms (thermal, mechanical, flux modulation) are documented. They are real. I cannot think of anything about a series crossover that would mitigate any of these effects. I’ve owned two Frieds and spent a fair amount of time with an IMF speaker, and imo they didn’t begin to compete with the likes of Klipsch Heritage Series in dynamics (though they were imo superior in other areas). A first-order series crossover topology may be the theoretical ideal from a dynamic range standpoint (assuming it results in true time coherence), but if driver compression effects dominate, it may not matter very much.
@trelja, can you tell me what the actual mechanisms are by which crossover parts count and/or conventional crossover topologies constrain dynamics? There may be effects I’m unaware of that are worth taking into account, even if they aren’t necessarily the primary cause of compression. You may be correct that a steep crossover slope constrains dynamics, but can you tell me why? The "why's" interest me a great deal.
Thanks!
Duke
