I've just been informed that to use ALL capital letters is a SIN
@PMental :
That is wide band program content AES/double (burst) power.
Try that at 50Hz(acoustical load) or at port tuning(low displacement, no cooling to speak of) and see what happens.
The RMS thermal capacity will be in the 500W ballpark, give or take. So the driver eating 1kW at Xmax by itself already gives you 3dB crest factor by just force to get there ignoring acoustical or other loading. That thing will run hot in there. It is still workable, but I´d be getting two 18"s or 21"s for the price any day. Don´t get me wrong, it´s an awesome fully functional speaker, but borderline, "stunt piece" for many of us. There is little good reason behind deploying em for our usage.
@cowanaudio:
Given that they provide Klippel figures beyond 20mm one way, and given the construction of modern neo drivers, it is doubtful it could be bottomed out before coil burns down, and it is most probable that 40mm Xmech is one way here. Those 10 year old B&Cs got this specs pulled away from their specs sheets for the reason of "unreachability" unless you are out to purposefully destroy them, And they were specced to 60mm Xmech for normal high end models and 70mm for 18IPAL I think(peak-peak). 80mm on much newer bigger speaker is very expectable value. Sure, it deserves better presentation of such data. Not just Celestion bugs me with this.
@5th element:
There is still good merit to the oldschool Xmax, but no wonder that specified Xmax is going beyond the mathematical one. At times we had 6mm pole pieces, 2mm "outside the full pole piece coverage" by the coil was 33% direct magnetism loss. Now with 14-20mm pole pieces, it is between 10-20%, causing much milder Bl decay, allowing us to use these beyond x-max excursions with favourable THD figures. More so with split winding voice coils.
That is wide band program content AES/double (burst) power.
Try that at 50Hz(acoustical load) or at port tuning(low displacement, no cooling to speak of) and see what happens.
The RMS thermal capacity will be in the 500W ballpark, give or take. So the driver eating 1kW at Xmax by itself already gives you 3dB crest factor by just force to get there ignoring acoustical or other loading. That thing will run hot in there. It is still workable, but I´d be getting two 18"s or 21"s for the price any day. Don´t get me wrong, it´s an awesome fully functional speaker, but borderline, "stunt piece" for many of us. There is little good reason behind deploying em for our usage.
@cowanaudio:
Given that they provide Klippel figures beyond 20mm one way, and given the construction of modern neo drivers, it is doubtful it could be bottomed out before coil burns down, and it is most probable that 40mm Xmech is one way here. Those 10 year old B&Cs got this specs pulled away from their specs sheets for the reason of "unreachability" unless you are out to purposefully destroy them, And they were specced to 60mm Xmech for normal high end models and 70mm for 18IPAL I think(peak-peak). 80mm on much newer bigger speaker is very expectable value. Sure, it deserves better presentation of such data. Not just Celestion bugs me with this.
@5th element:
There is still good merit to the oldschool Xmax, but no wonder that specified Xmax is going beyond the mathematical one. At times we had 6mm pole pieces, 2mm "outside the full pole piece coverage" by the coil was 33% direct magnetism loss. Now with 14-20mm pole pieces, it is between 10-20%, causing much milder Bl decay, allowing us to use these beyond x-max excursions with favourable THD figures. More so with split winding voice coils.
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The TSQ2460's graphs reference *"Simulated data", not Klipple verification.
I'd agree that the TSQ2460's progressively stiffening suspension with progressively reduced BL would make coil burning more likely than reaching Xmech, but the Celestion "Ten Squared" brochure with specifications for this "TS" series of drivers specifically states the 40mm Xmech is the "Maximum peak-to-peak excursion before damage."
The 21 IPAL has 80mm peak to peak Xmech/Xdamage, twice that of the TSQ2460.
That's what they say...
Celestion probably included enough pole piece depth that the suspension would brake (or break..) before the coil former smashes the back plate, but suspensions at the end of their mechanical limits definitely let out some distress calls 😳 .
Art
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@weltersys:
Good catch! Maybe it is time to ask Celestion directly? I still hope I am actually right with the Xmech/Xdamage, and it is a mistake in presentation of Celestion data.
Also if the curves were simulated, there is good chance that the suspension is not that stiff. I do't know about suspension, but the mechanical clearance should not be that hard to reach 40mm one way. Looking at B&C, it looks to me that even with 60mm figure, the coil would have few mm to spare, and something else would actually bottom.
Let's get to the bottom of things. Also If that was a case, the product would make em laughing stock for pros. Xmax 1.25mm from Xdamage is just ridiculous. I am preparing a review platform to continue the data-bass legacy, and so far all pro drivers handled Xmax +4dB overload gracefully. These Celestions would be a great addition.
//Sent them an email...
Good catch! Maybe it is time to ask Celestion directly? I still hope I am actually right with the Xmech/Xdamage, and it is a mistake in presentation of Celestion data.
Also if the curves were simulated, there is good chance that the suspension is not that stiff. I do't know about suspension, but the mechanical clearance should not be that hard to reach 40mm one way. Looking at B&C, it looks to me that even with 60mm figure, the coil would have few mm to spare, and something else would actually bottom.
Let's get to the bottom of things. Also If that was a case, the product would make em laughing stock for pros. Xmax 1.25mm from Xdamage is just ridiculous. I am preparing a review platform to continue the data-bass legacy, and so far all pro drivers handled Xmax +4dB overload gracefully. These Celestions would be a great addition.
//Sent them an email...
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1.
Based on the motor geometry, what is the excursion?
2.
With a bit of hand holding I got Gemini to figure out it excursion based on Klippel’s full-range woofer criteria for 10% distortion (the lesser of the two: Bl dropping to 82% of its maximum value, and the compliance, where XC @ 75% Cms minimum), or the less conservative 20% distortion criteria for subwoofers XBl @ 70% and XC @ 50%
Reference: https://celestion.com/product/tsq2460/
With a ruler and calculator, how about it? Our diyAudio brains trust?
Based on the motor geometry, what is the excursion?
2.
With a bit of hand holding I got Gemini to figure out it excursion based on Klippel’s full-range woofer criteria for 10% distortion (the lesser of the two: Bl dropping to 82% of its maximum value, and the compliance, where XC @ 75% Cms minimum), or the less conservative 20% distortion criteria for subwoofers XBl @ 70% and XC @ 50%
Reference: https://celestion.com/product/tsq2460/
With a ruler and calculator, how about it? Our diyAudio brains trust?
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@cowanaudio
The 18IPAL has Xmech/Xdamage 70mm, and it certainly doesn´t look like it:
Given the magnet dimensions on the TSQ2460, the space is certainly there. Anyways, let´s see if they respond. I am building a 24" free air test box, and I am inclined to get it some day (would be cool to get it this year, expecially when RCF failed us with their LN19S450)
@tktran303
There are many ways and specs to get to Xmax. I would be quite demanding, and cap it at 10% THD, acceptable DC offset, sustainable power consumption, Bl drop less than 30%. With dynamic processing though, both Bl and Cms figures could be breached while holding good THD figures, Case in point - IPAL solutions.
They look too big for 20mm too.
The 18IPAL has Xmech/Xdamage 70mm, and it certainly doesn´t look like it:
Given the magnet dimensions on the TSQ2460, the space is certainly there. Anyways, let´s see if they respond. I am building a 24" free air test box, and I am inclined to get it some day (would be cool to get it this year, expecially when RCF failed us with their LN19S450)
@tktran303
There are many ways and specs to get to Xmax. I would be quite demanding, and cap it at 10% THD, acceptable DC offset, sustainable power consumption, Bl drop less than 30%. With dynamic processing though, both Bl and Cms figures could be breached while holding good THD figures, Case in point - IPAL solutions.
The published 18.75mm Xmax is exactly what Celestions Xmax formula (0.5*(Hvc-Hg) + 0.25*Hg) states, and is consistent through the TSQ series of 12",15", 18", 21" and the 24" TSQ2460.
The TSQ2460 driver was introduced January 30 of 2024 and Celestion still doesn't include any measured data, even the frequency and impedance response are "simulated data".
If Celestion's specifications for Xmech are correct, the TSQ2145 would have only 6.3% excursion left after reaching Xmax before damage.
Even if the TSQ2145's Xmech were 44.4mm, the same ratio as the TSQ1230's Xmax/Xmech, it would be considerably less than the 6" voice coil B&C drivers.
Art