xmax discussion

[dadydolas 10+ year member]

so most companies list xmax and audioque lists usable throw

difference and input on the importance of the formentioned

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[jmanpc 5,000+ posts]

xmax = one way linear travel

usable throw = linear peak to peak

 

[JohnEJanowitz 10+ year member]

Unfortunately there isn't a standard out there for either. Xmax used to just be looked at as the physical overhang or underhang of the coil. Then DUMAX testing came around and they determined Xmag to be the point at which BL drops to 70% of the value at rest. This is pretty much the standard, but not everybody rates things this way. The "usable throw" could be either a peak to peak value, or could just be the one way suspension limit.

John

 

[BrianChia 10+ year member]

Well, the truth is that even non-linear excursion can be considered useable so it can be vague.

 

[ItalynStylion 10+ year member]

Well, the truth is that even non-linear excursion can be considered useable so it can be vague.

Am I ignorant or does non linear excursion sound like it's a bad thing for a subs' livelihood //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[dadydolas 10+ year member]

good start

so discuss how it should affect ur decision on choosing a driver

 

[bose301s 5,000+ posts]

Am I ignorant or does non linear excursion sound like it's a bad thing for a subs' livelihood //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

You're ignorant. Nonlinear excursion just means that the BL has dropped below 70% of its maximum.

 

[ItalynStylion 10+ year member]

You're ignorant. Nonlinear excursion just means that the BL has dropped below 70% of its maximum.

Got it. The way he worded it made it sound like the sub was moving side to side and not in and out.

 

[dadydolas 10+ year member]

bump

 

[JohnEJanowitz 10+ year member]

bose301s,

Is that a michigan tech husky on your pic?

John

 

[dadydolas 10+ year member]

not relevant but thanks for the bump

 

[audioholic 5,000+ posts]

Why are you still bumping this, you've gotten your answer already.

 

[Kyle_Keating 10+ year member]

xmax standards are all over the board, the most honest if all mfr's simply embrassed this (but none the less inaccurate) is simply to take the coil height and subtract the gap height and the divide by two (overhung) or do the reverse of that for the underhung. This works better for overhung because it has better behavior as the coil leaves the gap (the current sky rockets in an underhung motor when it leaves the gap and the EMF drops and it accelerates the voice coil out causing an oil can effect that has lots of distortion (its bad to over driver underhung drivers), but underhung drivers have a higher total linear stroke. The total linear stroke would only a few % BL deviation and standard overhung drivers wouldn't even be beyond a few mm each way before they start to drop off in BL, some are better than others of course. The linear drivers work to correct that of course, there are a few different well known types i wont dive into right now...

total usable thrown is a useless figure but is more or less a mechanical limt you hope never to reach! By the time you go beyond xmax for any driver, you're into not only audible distortion, but heavily reduced sensitivity and compression. In other words, you may have pour multiple times the mount a power simply to get a little more SPL and it will be very non-linear and distorted. Now of course, the system itself will heavily affect how much SPL and displacement you can get given an mount of voltage at a given frequency, but basically you don't want to go beyond xmax, in theory even for SPL contests, but of course thats not always practical or possible when even 0.1dB makes a difference! Best to give it the extra power and break something //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Papermaker85 5,000+ posts]

xmax in a design should be designed around power handling, freuqnecy response, alignment and desired output. so in other words if you want a high output lowend monster sealed you would opt for more xmax/larger boxes

ported on the other hand ESP subs like DD 9500 has 18-20mm xmax and you rarely exceed this firgue even with 3kw and huge boxes! the woofer is designed to have a narrower more limited bandwidth and designed to use the port over a wider bandwidth as well futher decresing excursion...

most woofers with 25mm xmax in 2.25 cubes tuned to 35 need in axcess of 3KW to reach peak xmax.. this variers from woofer to woofer and excursion increase above tuning and lower tuned boxes require more excursion above tuning to reach the same output, but in general ported box woofers rearly exceed there xmax rating with rated power...

i have learned over the years using the standad 2 cubed box with a 35hz tune 16-18mm xmax takes about 2kw to be reached and by this time a pair do 12" drivers are doing well into the mid to high 140s...

exceptions like the mag D2s which are often tunded low benfit from the higher xmax becasue they are designed to get low and sound great in smaller very low tuned boxes.. the result is above tuning 60-70hz teh increased xmax means increased output when power input is applied... this takes right at abut 1800 per driver to reach its limits, in 2 tuned to 30... xmax is so over hyped its not even funny..

 

[snoopdan 5,000+ posts]

xmax is so over hyped its not even funny..

I think its mainly because people can understand a tangible link between a measured number and movment of a woofer cone in their head in relation to driver output. IE: You see a sub moving in and out with great lengths and the uneducated individual wants to correlate that with a number they can easily understand.