What determines power handling?

[jrdnhsnbrg 10+ year member]

I've been thinking about this since I made a speaker for my AP Physics final out of eBay neodymium magnets, paper plates, and some wire. It was able to handle about 30W and sounded kinda decent for paper plates. What exactly determines how much power a sub can handle? Is there a certain limit a single motor can handle? Why can bigger woofers (say an 18") generally handle more power than a smaller woofer (8", 10", 12")?

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[jrdnhsnbrg 10+ year member]

Someone has to know...

 

[bubbagumper6 5,000+ posts]

2 main limitations, thermal and mechanical. Thermally the voicecoil can only handle so much current before it will get too hot and cause damage. Mechanically the speaker cone can only travel so far before it will damage the spider (i.e. the spider isn't strong enough to handle the force generated from the amount of current supplied so too much power).

 

[T3mpest 10+ year member]

Thermal limits are mostly voice coil size. They use a certain diameter and length of coil and well as layers and that makes most of the difference. Former material, gap thickness, and pole vents and forced cooling tricks are other things that companies use that can help some. My old AV15h was rated at 1k and was a 2.5 coil, that was due to the very small gap so the the coil was always very close to the motor which has better heat conductivity than air. Other speakers use wide gaps, but force the hot air out as the speaker moves. My new speaker is rated at 2k, it uses a 6inch coil and very little in the way of special tricks, other than a HUGE pole vent (soda can size, srs) and the coil is wrapped around both sides of the former, inside and and outside wound. Also some speakers make the formers black to absorb heat better, or make them from metal that absorbs heat, mine are fiberglass, which isn't very conductive, had they went with a black coated metal former, it'd probably be rated at 2.5k.

Companies rating arent' consistent either. Anyone who puts over 3k on a powerhandling spec is at the very least being misleading. Clamp a real 3k to any speaker and it wont' hold up that long, at least not if we are talking hours, all day every day abuse. Pro audio uses a very strict standard for power handling and their 4inch coil drivers are only rated around 2k, and those are built to handle power very well for long periods, longer than we'd likely see in a car. Just as all top of the line subs claim 30+mm of xmax, I'd bet if you put them on a klippel most don't break 25mm.

 

[hispls 5,000+ posts]

I've found that mechanically it's easier to throw more power at a larger woofer but conversely since they move less with the same power they will get hot faster since the primary way heat is moved away from the coil is from the flow of air from the movement of the parts.

In general the more volume of metal in the coil the more heat it will take, and copper seems to hold up better than aluminum for long term thermal capacity. Beyond 5000W various other things start to fail. Weak cones shred or buckle, weak surrounds tear or blow out, dustcaps get blown off, glue joints fail, tinsels burn up, coil lead to tinsel connection burns up, etc. etc.

The whole thing is largely hype to con naïve consumers with small pricks that the bigger the number the manufacturer claims the better it is and the more money you should pay for it.

 

[Spldecendant 10+ year member]

Another thing people forgot to add hear is motor force plays a roll in how much power can take like a dc lvl 4 weights 40lbs can take 1500rms but an xl weights 50lbs they have same coil and soft parts but the xl can take 2500rms