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So i had an argument!

 

Silver Member
Username: Ishkabobble55

Erie, Pennsylvania

Post Number: 129
Registered: Jul-05
ok i went to this local audio shop today that mostly sells memphis and alphasonic. i ask the guy how much xmax this one memphis sub has and he says to me, " Xmax doesnt matter, it only matters for a spl application. you only need a lot of xmax if you are going to be playing your sub at one tone." so i say, "well, it does matter. how do you think a sub moves air, surface area alone cant do it. so your telling me a sub with 1mm of xmax can compete with a sub that has 32mm of xmax? he said back, "well ya because you only need alot of xmax if youre going to be playing ur sub at one tone." then he proceeded to lecture me on how long hes been in car audio, 12 years, and how its not worth arguing with him cause hes right and mr bigshot gots 2 trophies for bein an idiot. then he says how dare you tell me how a speaker works! and he continuse to inform me that the sub has 4 spiders and dual voicecoil and a dual motor structure. I THINK ITS A BUNCH OF BS!!!!!!! this really ticked me off cause i know im right but he just didnt want to admit it because im only 16 and hes been in the buissness for 12 years!!! tell me if im right, or if you even understand the argument, please!
 

Silver Member
Username: Ishkabobble55

Erie, Pennsylvania

Post Number: 130
Registered: Jul-05
thanks.
 

Gold Member
Username: Mikechec9

Http://www.cardomain.c...

Post Number: 1856
Registered: May-05
gotta go pick up these kids from the auditorium, but real quick-i'm not going to presume his ignorance b/c i didn't hear the entire discussion.
from an sq perspective: although dumax is a more accurate suggestion of a subs quality reproduction at high excursion/volumes, xmax can at least suggest it. tell the salesman that how "linear" a sub is means how accurate and true it remains even at high excursion. excursion equates to volume as, like you said, you are moving more air. of course, with additional surface area, there is less need for excursion because the piston uses displacement to move more air.
this is all past the basic misunderstanding made by the salesman. most basically, true xmax is going to be a key determinate in how loud the sub plays. i.e., how much air it can move. how far the piston moves doesn't relate to frequency (tones). he is referring to how many times moves in and out per second. if it moves in/out 50 times in one second, it is playing 50hz for that one tone. if it plays this same tone at 20mm over 5mm, it's playing 50 hz LOUDER.
 

Gold Member
Username: Mikechec9

Http://www.cardomain.c...

Post Number: 1857
Registered: May-05
i think he is referring to a nonlinear sub that moves a bunch of air, but sounds like trash. these are your typical SPL subs.
tell him there have been many innovations in the last 12 years:-)
 

Silver Member
Username: Rob_preg

Royal oak, Michigan United states

Post Number: 282
Registered: Sep-05
^^^ well put
 

Silver Member
Username: Ishkabobble55

Erie, Pennsylvania

Post Number: 131
Registered: Jul-05
thanks alot guys. i dont think we should have even had the stupid argument in the first place, waste of time.
 

SPL sub
Unregistered guest
^^^ well put
 

Silver Member
Username: Baseball1187

Columbia, SC

Post Number: 342
Registered: Dec-04
well.. it does matter, but not as much as people like to say. Xmax mainly comes into play with sealed enclosures, ported, well it doesnt matter as much. At tuning frequency the subs movement will be minimized. if you've ever seen a high excursion sub, or any sub for that matter, play at or slightly above the tuning frequency of its box, it doesnt move much at all!

SPL with ported has a lot to do with the BL and suspension of the driver, mostly BL. A high BL driver, like the RE MT, can change the direction with a lot of force... yada yada, F=Ma... the faster you can change directions, accelerate in the opposite direction.. the more output you can potentially gain in a ported box. A driver with 32mm of xmax will never reach 32mm of excursion in a ported box above it's tuning frequency, with a resonable amount of power. below, sure.. but that's pointless. The videos you see online are generally below tuning to exploit the excursion, yes, because it looks cool...

but to answer your question, he was right to some degree. xmax is not nearly important as people like to say. for instance, the SX has an xmax of 21mm, the XXX 32mm. The SX will get louder, with less power in a ported enclosure. however in sealed, the XXX will get louder (the SX has a stronger motor, but less xmax)
 

Silver Member
Username: Baseball1187

Columbia, SC

Post Number: 343
Registered: Dec-04
"thanks alot guys. i dont think we should have even had the stupid argument in the first place, waste of time"


no well I think it's a good post, people are looking too much at xmax to determine what a sub can do. it's important, but not nearly the all important parameter people make it out to be
 

Gold Member
Username: James1115

Wilton, Ct

Post Number: 4380
Registered: Dec-04
http://www.bcae1.com/ go to skeakers it elaborates a little more on this.
 

Gold Member
Username: Mikechec9

Http://www.cardomain.c...

Post Number: 1858
Registered: May-05
i think the argument was for xmax in a practical sense as opposed to the potential or "listed" xmax numbers. the salesman saying that true/useful xmax doesn't matter is the same as saying the size of a sub doesn't matter-you can get the same volume out of an 8" sub as you can a 15" sub. although there are certainly other factors to take into consideration, the two are directly proportional; the more either increases (size or xmax), the more air that's going to be moved.
of course, i am far more concerned with bl, inductance, and transient response than spl.
but i would favor a good amount of both over compromising one over the other.
the brahma would not be an sql/HO driver if it had a 13" xmax.
 

Silver Member
Username: Baseball1187

Columbia, SC

Post Number: 345
Registered: Dec-04
yea, that's all I was trying to say, and partially what the saleman might have been trying to say.. people place too much importance on the xmax paramater...
 

Gold Member
Username: James1115

Wilton, Ct

Post Number: 4389
Registered: Dec-04
<img=>http://www.diysubwoofers.org/graphics/driver1.gif</img>

Excursion - ref. www.dictionary.com
a. A movement from and back to a mean position or axis in an oscillating or alternating motion.
b. The distance traversed in such a movement.
* In regards to a loudspeaker, this refers to the distance the cone can travel back and forth within the limitations of the driver's suspension (spider and surround.) This distance, in combination with the surface area of the loudspeaker's cone, determines how much air is moved, mechanically speaking, by that speaker (not accounting for power requirements, cabin gain, enclosure effects, and other external factors.) which is why you see speaker diameter, along with excursion discussed so frequently by forum members, and the car audio community in general. The more air you move, generally the louder the speaker is going to get, all else being equal. (Which it never is.)

Xmag = DUMAX Excursion limit due to the magnetic limitations of the driver's motor. Xmag is defined as the displacement at which the BL product has fallen to 70% of its value at the cone's rest position.

Xmech = Maximum physical excursion capability of the driver. Exceeding Xmech normally results in damage to the driver.

Xsus = DUMAX Excursion limit due to the driver's suspension. Xsus is defined as the point at which the compliance of the suspension has decreased to 25% of the value at the cone's rest position.

Xmax = Linear (one-way) travel of the cone. Xmax is used to determine the maximum linear SPL capability of the driver, and can be defined in a number of ways. The DUMAX definition is objectively the best one, and it is defined as the shorter of the Xmag and Xsus values, in each direction of cone travel. This definition is more useful than the older definition of Xmax, which was solely dependent on the length of the voice-coil vs. the length of the gap.

DUMAX = David Clark's DUMAX device is a driver measurement system that can, among other things, measure how far a driver's cone can travel while still working in a linear fashion. This gives a more consistant, and useful measurement for T/S specifications when looking at loudspeakers. Much like the new CEA ratings for amplifiers, DUMAX specs on loudspeakers level the playing field and give comparable results for products when comparing between different manufacturers, taking the "fudge factor" and hype, or misleading advertising tricks out of the equation.
From Glass' word of the week:-)
 

Silver Member
Username: Ishkabobble55

Erie, Pennsylvania

Post Number: 132
Registered: Jul-05
i realise that xmax is not the most important thing in the speaker world, but my argument was about the fact that the guy said that alot of xmax is only needed if you are going to be playing your sub at one tone. i didnt understand what he was talking about so i argued the fact with what knowledge i have. what mike chec was saying is absolutly correct. but basically what the guy said was that xmax means nothing unless your trying to win a spl comp while playing your subs at one tone, and i told him that xmax means something in the sq world too, because you have a sub for a main reason, to put bass in your trunk, and a sub with little xmax couldnt do that aswell as a sub with more xmax could, unless it was huge and made up for the lost movement with surface area. all of the items that have to do with a subwoofer would not work if even one of them was missing, they all work together to make the stuff we love, BASS. and thats all that matters
 

Gold Member
Username: Mikechec9

Http://www.cardomain.c...

Post Number: 1861
Registered: May-05
David Clark is a pretty sick genius of sound:
DUMAX- http://www.dlcdesignaudio.com/services/dumax.htm
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