At what spls are those drivers in the speakers going to effectively poop out or have excessive distortion compared to the subs, though? I'll have to do some reading on f3 efficiencies and typical distortion levels, that the f3 is the primary power point is something I'd not latched onto before (any literature suggestions?). Agree with not using something as high as a 200hz crossover generally but wonder what he is using specifically, too.
I'm confused what you're referring to, if you're referring to bass coming from the loudspeaker vs a subwoofer with a lower crossover frequency that's obviously going to depend on the speaker and crossover point and the speaker itself. Almost any medium sized bookshelf can reproduce between 80-120hz without breaking a sweat. For lower frequencies such as below 80hz, assuming the speaker is capable of full range or close to it, that will also depend. What causes distortion in low frequencies has to do with the physical characteristics of woofers vs subwoofers regarding suspension stiffness and weight. Both of these characteristics can be intentionally manipulated to adjust and optimize the frequency response of a driver, similar to how cabinet volume changes response. Woofers are generally lightweight, with medium stiff suspensions, this makes it easy for them to reproduce a broad range of frequencies. Subwoofers are heavier with much stiffer suspensions, they also generally have significantly more xmax. Bass requires a lot of movement. At 500hz, a driver is moving back and forth 500 times a second. At 50hz, 50 times a second. Even at the exact same spl this gives the driver 100x more time to extend and retract at 50hz during 1 cycle, meaning its going to travel more distance in the same amount of time. This is where suspension and weight factor into distortion and frequency response. At low frequencies, the driver must move a lot, at high frequencies, it must move very quickly, you can't get both without one or the other ends of the spectrum distorting. A lightweight driver with a looser suspension can move faster, assuming equal xmax, it too can move more and reproduce low frequencies, but lightweight drivers are typically thinner and less rigid, allowing the cone to flex as it is forced in and out over large distances, introducing distortion. This is the same distortion one gets at high volume, but this distortion becomes more readily apparent at lower spl with low frequencies. This is going to depend on the size of the woofer and the material from which it's made. Thankfully, this isn't the 70s and 80s anymore and apart from some ultra cheap htibs and all in one shelf stereos the majority of designers do not use paper cones, which are very flexible and often made thin due to weight concerns. 90% of modern day speakers use newer materials, even cheap polypropylene woofers are more rigid while being lightweight. A larger driver is going to be able to move more air with less excursion, a stiffer cone will distort less than a more flexible cone. Generally at 80hz and above a 5.25 inch woofer isn't going to see a lot of excursion.
Ported speakers should experience significantly less distortion near the port frequency because at and near the port frequency there will be almost no movement of the driver as the port will be producing most of the sound. If you've got ported speakers, play a sine wave at the f3 of the speakers and you'll notice that there is hardly any movement of the woofers. The main concern here is going to be port noise, and this will depend entirely on the diameter of the port.
Like I said, it's more likely you'll have distortion from playing the sub too high. A heavy woofer with a tight suspension is great at controlling the drivers movement and damping flex at low frequencies, it's also great at making the driver struggle to produce higher frequencies. The main reason a sub driver has extreme rolloff at high frequencies is exactly related to a stiff suspension and heavy driver. It just can't move as fast. Try playing a 120hz-200hz tone through a subwoofer at high volume then play it through your mains, decide which one sounds better. Every sub I've had has sounded worse than the speaker. Just like trying to run speakers at full range with bass, trying to run a sub at the upper end of its operating range is going to make it struggle. Unless you've got tiny speakers that begin rolling off at 100hz, 120hz or even 80hz should play just fine even at higher volume, especially if it's ported. Floor standing speakers with multiple woofers will struggle even less.
https://en.m.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers
A quick Google search turns up a wiki article.
A voice coil doesn't just receive power, it can also generate it as the driver reverses in the opposite direction. In a solid state amplifier, a majority this is reduced by damping factor, this is the reason speakers have much louder (although sloppier) bass when connected to a valve amplifier, because there is little damping factor due to a higher output impedance. Solid state amplifiers aren't completely 0, but damn close. That's also one of the reasons speakers sound much flatter on solid state amps. Nevertheless, this can't be completely eradicated. At fs, a speaker resonates almost on its own in free air. Put it into a box and you get f3, which can be altered by the box or a port. A box can also produce back pressure of its own on a driver, even outside of low frequencies. Big boxes have better bass because the distance is long enough to pick up those larger wavelengths. Ports can pick up those frequencies and emit them. The reason the impedance dramatically rises at these frequencies is because of back emf on the voice coil as the resonance moves the driver on its own. At the port tuning frequency, the resonance from the port tries to push the driver in the opposite direction, creating an opposing current and increasing resistance.
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