Is Cerwin Vega accurate with their xmax numbers? (re: V15DV2)

Poking around at 12" and 15" woofer specs, Cerwin Vega has a couple of models that report unusually high xmax for their price. For example, the XED12 for $60 is stated as having 17.8mm, and the V15DV2 which can be found for around $175 has 24mm. Is this even half way realistic?
Since WHEN is *price* a Thiele Small Parameter? :confused: :rolleyes:

If you knew anything about speakers you would be well aware that Cerwin Vega for decades held the huge X-Max crown for the very good reason they became a large company (in the 70´s :rolleyes:) by inventing and manufacturing nothing less than the "Earthquake" movie sound effects speakers.

Where they did shake people and buildings to the limit of structural failure.

Some theater installations:

65338f28769f5c03a64884521735a927.jpg


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kipman725

Member
Paid Member
2007-06-10 12:41 pm
Warrington
I would say no at first guess. Xmax is a number defined by geometry:
Driver TS Parameters: Xmax >> speakerwizard.co.uk
so looking at pictures of the XED12 you can see its top plate is only a few mm thick which means to have 17mm of xmax almost all the voice coil would be hanging out of the magnetic field and the driver would be very inefficient and have low power handling. The low power handling would be because the top plate removes heat from the coil and most of the coil would be hanging out in free air. This is also why you shouldn't use high xmax drivers in situations where they see high power without excursion as the ends of the coil can burn.

If you want to verify xmax you can chop the driver up or use an oscilloscope and distance measurement sensor:
measuring excursion - Bass Gear - Data-Bass Forums
 
I would say those are probably peak to peak values. The VMAX 12 lists 14mm of xmax which sounds perfectly reasonable for what the driver is presenting as.

It doesn't really make sense for the XED12 to have more than this but then again I could be wrong. It would also mean they are breaking the convention they use to define xmax across the website. Email them and ask.
 
Cone movement yes but not linear excursion. Cerwin even have their Stroker series, amongst their others, these are a different beast altogether and are clearly built for maximising travel.

These only have 16.4mm of xmax.

[IMGDEAD]https://cerwinvegamobile.com/wp-content/uploads/2018/04/st122d-2.jpg[/IMGDEAD]

Now if that doesn't have 24mm of linear, one way, excursion, I'd be very surprised if the other one did.
 

kipman725

Member
Paid Member
2007-06-10 12:41 pm
Warrington
Rotfl.......

b:)

So your estimating the maximum excursion using the maximum amount the half roll surround can move back and forth?

*the Pyle drivers 15" I tested had every t/s spec wrong apart from xmax but they where only claiming 8mm ;) I would seriously recommend the optical sensor method that I used and linked in as they are very cheap sensors. You could even use a PC sound card to record the sensor signal if you didn't have a scope .
 
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Examples of Scrutinizing of ex-aggregated Advertised x-max and Sd Parameters by estim

So your estimating the maximum excursion using the maximum amount the half roll surround can move back and forth?

No, that's what the Advertised Sd implied when Mapping on the Posted Driver Picture, x-max is Cone Excursion Max and x-max is in Reality always < as the Cone Excursion Max is the limit where above stretching and shrinking(Sd) effects occur.
The Advertised Pictures are often somewhat skewed: Often resulting in less than 1% error that can be ignored.

*the Pyle drivers 15" I tested had every t/s spec wrong apart from xmax but they where only claiming 8mm ;) I would seriously recommend the optical sensor method that I used and linked in as they are very cheap sensors. You could even use a PC sound card to record the sensor signal if you didn't have a scope .
[/QUOTE]

I vote for simple Distortion Measurement to set the Limit( Fidelity Experience) for usable Driver Cone Displacement ~1 % for a Mid-bass at 100Hz and as low as possible above or Max.<= ~10 % for a Sub at f-3dB, lower at the upper cut-off, all within the System Pass-band.

b:)

PS:Submitted Pictures

Examples:
Estimation of Rubber Surround Stretch Point or for corresponding Accordion Surround
 

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Estoy sorprendido porque Bjorno ha agregado texto a sus adjuntos....
Tengo una duda que me carcome el cerebro y no me deja conciliar el sueño ....

Sr. Bjorno, usted tiene prejuicios hacia nosotros los sudamericanos o quizás especialmente hacia los argentinos ?

Pregunto esto porque en una oportunidad usted me "facilitó " unos de sus ya famosos gráficos tan completos, pero ante mi agradecimiento y una pregunta muy simple al respecto no se tomó la molestia en responderme.

Entonces, usted solamente quiere hacer alarde de sus conocimientos ?
No considera que compartir informacion técnica tan abundante pero sin un minimo de explicación de lo que quiere significar es desconsiderado hacia los miembros de DiyAudio ?


I am surprised because Bjorno has added text to his attachments ....
I have a question that eats my brain and does not let me fall asleep ....

Mr. Bjorno, do you have prejudices towards us South Americans or perhaps especially Argentines?

I ask this because on one occasion you "provided" me with one of his already famous graphics so complete, but to my thanks and a very simple question about it, he didn't bother to answer me.

So, you just want to flaunt your knowledge?
Do you not think that sharing such abundant technical information but without a minimum explanation of what it means is inconsiderate towards DiyAudio members?
 

kipman725

Member
Paid Member
2007-06-10 12:41 pm
Warrington
Estoy sorprendido porque Bjorno ha agregado texto a sus adjuntos....
Tengo una duda que me carcome el cerebro y no me deja conciliar el sueño ....

Sr. Bjorno, usted tiene prejuicios hacia nosotros los sudamericanos o quizás especialmente hacia los argentinos ?

Pregunto esto porque en una oportunidad usted me "facilitó " unos de sus ya famosos gráficos tan completos, pero ante mi agradecimiento y una pregunta muy simple al respecto no se tomó la molestia en responderme.

Entonces, usted solamente quiere hacer alarde de sus conocimientos ?
No considera que compartir informacion técnica tan abundante pero sin un minimo de explicación de lo que quiere significar es desconsiderado hacia los miembros de DiyAudio ?


I am surprised because Bjorno has added text to his attachments ....
I have a question that eats my brain and does not let me fall asleep ....

Mr. Bjorno, do you have prejudices towards us South Americans or perhaps especially Argentines?

I ask this because on one occasion you "provided" me with one of his already famous graphics so complete, but to my thanks and a very simple question about it, he didn't bother to answer me.

So, you just want to flaunt your knowledge?
Do you not think that sharing such abundant technical information but without a minimum explanation of what it means is inconsiderate towards DiyAudio members?

Perhaps a misunderstanding working out whats going in the pictures is part of the fun :)