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<blockquote data-quote="T3mpest" data-source="post: 8247988" data-attributes="member: 560148">Depends on the type of compression There are 2 main types of compression, hopefully going over both will explain the issue well enough..First type is thermal compression.&nbsp; As the voicecoil of a woofer heats up, the impedance of the coil rises, the reduces the wattage that the amplifier can produce.&nbsp; So the strength of your motor has no real effect here..&nbsp; Essentially the bigger a a coil is, the more energy it takes to heat it up, the better it will handle power compression.&nbsp; It&#039;s why when you get over 1500 watts, I&#039;d MUCH rather have a 4inch coil than a 3inch one.&nbsp; Regardless of all the cooling tricks you can put in a motor, you may be able to stop the coil from frying, but stopping it from heavily compressing from 1500 watts to say the 2500 rms of a top line 3inch coil, not so much.&nbsp; A 4inch coil is just better at taking high power.The second type of compression, less talked about is BL compression.&nbsp; As the coil begins to leave the gap, their is less force acting on the coil, so BL drops and the Q of the system actually raises when this happens.&nbsp; So for this type of compression a higher Q and compression go hand in hand, but that&#039;s not the static T/S parameter you see on a spec sheet, this is what happens to those T/S parameters when the speaker actually sees power.&nbsp; The key to controlling this isn&#039;t necessarily starting with a low QES, but having a high xmax.&nbsp; Xmax is a measurement of how far the cone can move before the BL product drops to 70% of it&#039;s resting value (if it&#039;s klippel measured xmax anyways).High QES subs generally don&#039;t go in ported boxes because they produce irregular frequency response.&nbsp; They have weaker motors that do have trouble resonating the port.&nbsp; This leads to a very wide frequency range that they see gain in, but at a very reduced magnitude. Instead of the port producing lots of extra output where it&#039;s tuned, you just get a bit more output everywhere.&nbsp; Pretty hard to design a ported box around that, especially when it unloads below tuning.&nbsp; This is great for a 4th order bandpass where you can tune it higher and have the sealed side to keep the cone under control below tuning, but for a standard ported box, just leads to a rough response.</blockquote>

[QUOTE="T3mpest, post: 8247988, member: 560148"] Depends on the type of compression There are 2 main types of compression, hopefully going over both will explain the issue well enough.. First type is thermal compression. As the voicecoil of a woofer heats up, the impedance of the coil rises, the reduces the wattage that the amplifier can produce. So the strength of your motor has no real effect here.. Essentially the bigger a a coil is, the more energy it takes to heat it up, the better it will handle power compression. It's why when you get over 1500 watts, I'd MUCH rather have a 4inch coil than a 3inch one. Regardless of all the cooling tricks you can put in a motor, you may be able to stop the coil from frying, but stopping it from heavily compressing from 1500 watts to say the 2500 rms of a top line 3inch coil, not so much. A 4inch coil is just better at taking high power. The second type of compression, less talked about is BL compression. As the coil begins to leave the gap, their is less force acting on the coil, so BL drops and the Q of the system actually raises when this happens. So for this type of compression a higher Q and compression go hand in hand, but that's not the static T/S parameter you see on a spec sheet, this is what happens to those T/S parameters when the speaker actually sees power. The key to controlling this isn't necessarily starting with a low QES, but having a high xmax. Xmax is a measurement of how far the cone can move before the BL product drops to 70% of it's resting value (if it's klippel measured xmax anyways). High QES subs generally don't go in ported boxes because they produce irregular frequency response. They have weaker motors that do have trouble resonating the port. This leads to a very wide frequency range that they see gain in, but at a very reduced magnitude. Instead of the port producing lots of extra output where it's tuned, you just get a bit more output everywhere. Pretty hard to design a ported box around that, especially when it unloads below tuning. This is great for a 4th order bandpass where you can tune it higher and have the sealed side to keep the cone under control below tuning, but for a standard ported box, just leads to a rough response. [/QUOTE]

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