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NEW CELESTION 24" DRIVER |
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taurusty 
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Joined: 09 January 2007 Location: Jamaica Status: Offline Points: 504 |
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 Posted: 11 October 2025 at 6:31pm |
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Hi Lev, What efficiency spec would you be comfortable with? |
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Crashpc
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Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 539 |
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Posted: 11 October 2025 at 7:51pm |
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@taurusty: See B&C Speakers 21DS115 specs.
I might not have time right away, but the TSQ2460 is coming on monday.
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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APC321
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Joined: 24 August 2013 Location: West Midlands Status: Offline Points: 797 |
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Posted: 11 October 2025 at 8:09pm |
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That Celestion datesheet for their new 24" driver is interesting:
Moving mass is quoted at 717.2 grams...thats almost three quarters of a kilo. For comparison for a PD 2450 is 424 grams. |
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Lucasdude
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Joined: 16 March 2013 Location: London Status: Offline Points: 986 |
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Posted: 11 October 2025 at 9:58pm |
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Could anyone quickly knock up a model of this driver in a simple reflex cabinet? Tune to 27hz with 2 x 100mm ports and a volume equivalent to VAS? A 70cm cube will give 350 litres.
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Crashpc
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Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 539 |
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Posted: 11 October 2025 at 11:45pm |
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2x100mm ports is utterly underported for such driver.
Given what the papers hold, I'm not trying. I might measure real T&S on monday or tuesday, and then.... @ACP321: it is needed for the robustness. 424g cone on a 24" will not make it in demanding/specialty high density solutions.
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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taurusty
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Joined: 09 January 2007 Location: Jamaica Status: Offline Points: 504 |
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Posted: 12 October 2025 at 7:42pm |
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Morning All
Thank you Crash:3.4% Which brings me to another ques. F orgive me for going off topic, but how can one spkr be 2% no & another 3.4% but both are 98db SPL??? |
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DMorison
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Joined: 14 March 2007 Location: Aberdeen Status: Offline Points: 1740 |
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Posted: 12 October 2025 at 8:11pm |
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Most likely different impedance. Although they're both nominal 8ohm speakers, it looks like the PD has a higher average impedance. So, if we feed them both a standard 2.83V test signal, that speaker will draw less power from the amp. So, it can be producing the same SPL for less power, hence more efficient and possibly an easier load for the amp to drive.
NB this is based on a quick glance at the manufacturer.'s curves, not proper modelling as I'm only on my phone right now - you should always model drivers to verify rather than trusting the single number specs which often do not show the full details.
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fudge22
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Joined: 26 July 2022 Location: UK Status: Offline Points: 263 |
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Posted: 12 October 2025 at 8:44pm |
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From his quote, he is not sure.
At 3%, is this an example of an acceptably efficient loudspeaker?
The efficiencies are likely to be calculated and thus a nominal figure. The spl or sensitivity figures are probably measured on axis using a refernce voltage not power. Also a drive unit with a higher directivity can be less efficient but have a higher spl figure. Neither the efficiency or sensitivity of a drive unit is constant across its frequency range and can’t be truly represented by a single figure. A rather simple way of calculating a reasonably accurate value of the absolute maximum efficiency of a loudspeaker (at low frequencies) is dividing the effective diameter of the drive unit by the wavelength being reproduced. No practical real life loudspeaker will match this because it assumes an ideal situation such as a cone with no mass. At 40Hz, the Celestion driver discussed would be 0.53/6.8 = 0.078. Multiply by 100 gives 7.8% You can play with the driver parameters as long as you like and not improve on this. It is useful for checking that more thorough calculations are not wildly wrong. It is a reasonable assumption that manufactures will use what is sometimes referred to as Small’s reference efficiency (given by the following equation) to calculate the published efficiency.  This calculation will always be larger than the real efficiency. Inserting the parameters for the Celestion drive unit gives a result of 2.1%. Perhaps, having done the calculations himself, Lev was actually highlighting that Celestion had got their calculations wrong? For those not happy with such low efficiency, using the following formula given on the speakerwizard website produces larger numbers.  This uses proper parameters like Vas and Qes, none of those pesky electro-mechanical parameters. It is however wrong, and gives the Celestion an efficiency of over 13%.
It has probably been copied from some other source that may have copied it from some other source that copied something wrong. It helps to be able to understand the equations and how they relate to the performance of a real device. The correct version of this equation has the numerator: 8 * PI^2 * Fs^3 * Vas This simplified equation (as in it makes more assumptions in the interest of an easier calculation) gives an efficiency of 4.25%, which although closer is still too high. It should be noted that of these equations assume the load is resistive. The load of a real drive unit is partially reactive, which means that the current passing through the coil is out of phase with the voltage. That is a whole other topic. |
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levyte357-
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Joined: 27 July 2012 Location: UK, South East Status: Offline Points: 8517 |
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Posted: 13 October 2025 at 12:12pm |
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Firstly, ignore efficieny/sensitivity specs in dB. Is mostly lies/BS. I only respect reference efficiency, specified by nO, as that can be verified from T/S Parms. If 18"/21" subwoofer has nO of approx 2.3% or above, that alone implies decent sensitivity, with FS/vas/qes, dictating, sub sub response in correct cab. Void V18-1000 - approx 3.0% PD1850 MK1/2 - approx 2.88% Orig PD1852/1851 - approx 2.4% 18sound 18nlw9601 - approx 2.28% - my fav 18" driver of all time B&C 18DS100 - approx 2.1% Give the 18nlw9601, sufficient power, it will easily outperform all of the above, but at hefty price. Always wanted to try the B&C, but prefer 18s with min 5" VC
Edited by levyte357- - 13 October 2025 at 12:21pm |
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Global Depopulation - Alive and Killing.
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Crashpc
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Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 539 |
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Posted: 13 October 2025 at 9:19pm |
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The preliminary (usually miserable) results on unpacked driver: Fs: 35,6Hz Qes: 0,35 Cms = 0.029555 mm/N damn that´s a tough cookie. ETA = 2.47 % - I think we can hang somewhere around 3% when it is burned-in. Lp(2.83V/1m) = 100.14 dB Ditto Levyte357 - The heftier copper coil still does make difference, and I am very unlikely to go back to CCAW 4,5". Edited by Crashpc - 14 October 2025 at 10:21am |
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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Andylaser
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Joined: 16 April 2010 Location: Southampton Status: Offline Points: 392 |
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Posted: 03 December 2025 at 11:41pm |
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"music so loud, that if we move in next door to you; your lawn will die" - Lemmy
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levyte357- wrote: