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-   -   Xmax (http://www.diyaudio.com/forums/subwoofers/46637-xmax.html)

mik 27th November 2004 06:46 PM

Xmax
 
Maximum cone displacement and Xmax are the same thing or not?
Thanks!

pinkmouse 27th November 2004 06:52 PM

No, Xmax is maximum linear displacement and smaller than maximum displacement, this is more a mechanical thing.

mik 27th November 2004 07:01 PM

Thanks pinkmouse, I was looking some Visaton drivers suitable for subwoofer but they not have listed Xmax but only maximum cone displacement,

AndrewT 28th November 2004 07:18 AM

Hi, a rough estimate of xmax is half the difference between the coil length and magnetic gap height. xmax=(coil - gap)/2 for overhung. Underhung is quite rare I think. Each manufacturer will have different ways of calculating and/or measuring xmax.
regards Andrew T.

kelticwizard 28th November 2004 07:44 AM

Maximum Cone displacement very often refers to the volume of air the cone moves. It is usually written as Vd.

It is equal to Cone Area times Cone Excursion.

The difference, of course, is that if the spec means volume, the numbers will be high and be given in cu cm, cu meters or cubic inches. If they are talking about excursion, the specs will be given in mm, cm or inches.

Very often, the linear excursion is given as Xmax. The maximum excursion the cone can travel without damage is often given as Xmech.

In hi fi speakers, Xmech is often 1.5 to 2 times the Xmax. In PA speakers, Xmech is often 3 or 4 times Xmax.

mik 28th November 2004 02:16 PM

Quote:

Originally posted by kelticwizard
If they are talking about excursion, the specs will be given in mm, cm or inches.



Than we talking about excursion because specs are given in cm.
http://www.visaton.de/english/artikel/art_476_1_19.html

BAM 28th November 2004 09:17 PM

The Visaton TIW 200 XS should be a good sub driver. It has plenty of mechanical and linear excursion and should stand up to plenty of punishment. I only wish it were available here in the US. The TIW 250 XS would be even better.

Luke (Uof Iowa) 29th November 2004 05:36 PM

28 mm seems pretty high for that driver, I'm guessing that is a two-way number so Xmax would be 14 mm. But that's only a guess, they're using ambiguous terms.

AndrewT 30th November 2004 07:13 AM

Hi,
I think that 28mm is mech peak to peak. i.e. mechanical damage limit.
xmax is more likely to be in the range 2mm to 6mm. But I could be wrong.
regards Andrew T.

kelticwizard 1st December 2004 01:53 AM

The linear throw of this unit is not especially long. Here are the specs:
Rated power 150 Watt
Maximum power 200 Watt
Nominal impedance 4 Ohm
Frequency response (-10 dB) fu - 4200 Hz
(fu: Lower cut-off frequency depending on cabinet) .
Mean sound pressure level 92 dB (1W/1m)
Maximum cone displacement 28 mm
Resonance frequency fs 22 Hz
Magnetic induction 1,1 Tesla
Magnetic flux 1400 Weber
Height of front pole-plate 8 mm
Voice coil diameter 5 cm
Height of winding 1,85 cm
Cutout diameter 28 cm
Net weight 4,5 kg
D.C. resistance Rdc 3,6 Ohm
Mechanical Q factor Qms 1,78
Electrical Q factor Qes 0,34
Total Q factor Qts 0,29
Equivalent volume Vas 310 l
Effective piston area Sd 507 cm2
Dynamically moved mass Mms 62 g
Force factor Bxl 8,4 T m
Inductance of the voice coil L 1,1 mH



I do believe "the gap", which is given in Andrew's formula, is called the "Height of front pole-plate" here. It is 8 mm.

The length of the voice coil is 18.5 mm, (1.85 cm).

So, following Andrew's formula, the linear excursion is (18.5 - 8) / 2 = (10.5) / 2 = 5.5 mm. Which is barely normal for this size woofer.

It does seem to have an Xmech of about 3 times the linear Xmax, and a higher than normal sensitivity, (92 dB).

Hi fi woofers tend to have longer Xmax but lower sensitivity, and their Xmech is generally not more than twice their linear Xmax.

PA speakers tend to have higher sensitivities, (about 95 db), and have Xmech about 3 times the Xmax, which this is.

So this seems to be a cross between a PA driver and a HiFi driver. I am guessing it's primary purpose would be for a high efficiency, (for a HiFi) speaker, and not a PA speaker. But it does seem to share some qualities with a PA driver.


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