Writing the answer as Vb=121.42722053986330118675069002095 certainly exhibits a tendency towards precision!
However, keep the responses coming - I might learn something too! 🙂
I do not know if I mentioned this, but I am a programmer.
I am writing a program to perform all of my calculations.
My native storage for my values has roughly 35 significant digits.
I am simply cutting and pasting the output of my code, hence all of the precision is evident.
I am still stuck on the fact that my vb calculation produces a volume that seems extremely large to me (5' x 5' x ~5' cabinet). BTW '~' means 'roughly'.
The Celestion design for the same speaker has a gross internal volume of 1.8434242708333333333333333333333 ft3.
So clearly:
- Celestion supplied a bogus Vas (16.7 ft3) and Qts (0.777). I doubt that.
Or
- I do not understand the calculation. My Vb calculation says 121.42722053986330118675069002095 ft3.
I do not think I am performing the calculation incorrectly, I am sure someone would have pointer that out.
Or
- The Celestion design is really not based on Thiele / Small parameters. Perhaps they simply created the box, put the driver in it, decided on an arbitrary port diameter and length, did a freq analysis on the loaded cabinet, said 'that's not very good, lets stuff some polyester wadding into it'. I cannot believe this is a realistic scenario.
I am hoping for some insight here.
I fell uncomfortable containing this discussion an a thread entitled 'Port Tube, Volume Thiele / Small'.
As with all threads what we are discussing now is far from the original question.
Perhaps I should start a new thread with a different topic title?
I am writing a program to perform all of my calculations.
My native storage for my values has roughly 35 significant digits.
I am simply cutting and pasting the output of my code, hence all of the precision is evident.
I am still stuck on the fact that my vb calculation produces a volume that seems extremely large to me (5' x 5' x ~5' cabinet). BTW '~' means 'roughly'.
The Celestion design for the same speaker has a gross internal volume of 1.8434242708333333333333333333333 ft3.
So clearly:
- Celestion supplied a bogus Vas (16.7 ft3) and Qts (0.777). I doubt that.
Or
- I do not understand the calculation. My Vb calculation says 121.42722053986330118675069002095 ft3.
I do not think I am performing the calculation incorrectly, I am sure someone would have pointer that out.
Or
- The Celestion design is really not based on Thiele / Small parameters. Perhaps they simply created the box, put the driver in it, decided on an arbitrary port diameter and length, did a freq analysis on the loaded cabinet, said 'that's not very good, lets stuff some polyester wadding into it'. I cannot believe this is a realistic scenario.
I am hoping for some insight here.
I fell uncomfortable containing this discussion an a thread entitled 'Port Tube, Volume Thiele / Small'.
As with all threads what we are discussing now is far from the original question.
Perhaps I should start a new thread with a different topic title?
The Celestion F12-X200 is, of course, designed to be used with guitar amp and speaker-modelling systems.
The concept behind this driver is to make it easy for a guitarist to swap out the existing speaker in a combo or cabinet for an F12-X200.
This would suggest that the speaker has parameters that suit either an open-back cab or a closed-back cab rather than a ported cab.
The Qes of the driver is not stated in the Celestion specs, so I am unable to ascertain the EBP (Fs/Qes) which should be 50 or less for a sealed cab.
The concept behind this driver is to make it easy for a guitarist to swap out the existing speaker in a combo or cabinet for an F12-X200.
This would suggest that the speaker has parameters that suit either an open-back cab or a closed-back cab rather than a ported cab.
The Qes of the driver is not stated in the Celestion specs, so I am unable to ascertain the EBP (Fs/Qes) which should be 50 or less for a sealed cab.
Galu.
The parameters for the F12-FX200 are stated on page 18 of the Celestion Guitar Speaker Catalog.
Qes: 0.831.
the calculation you are doing is going to tell you that the F12-FX200 is suitable for a sealed cabinet or a ported cabinet (you pick it).
Page 18 of the Catalog also contains a mini depiction of the Celestion suggested ported cabinet for the F12-FX200.
Here is the introduction page to the Celestion Ported Cabinet. Here they suggest 'to get the most from the speaker's full range capability, we recommend loading it into a bass reflex cabinet.'
Here is the 'design document'.
It is within the design document that 'polyester wadding' is referenced.
Again. when I asked Dr. Decimal about the polyester wadding, they replied 'it fools the speaker into thinking it is living in a larger cabinet'.
(BTW: I mentioned awhile ago 'Dr.Decibal' is a moniker used by Celestion for their technical support group).
I am still at a loss!
The parameters for the F12-FX200 are stated on page 18 of the Celestion Guitar Speaker Catalog.
Qes: 0.831.
the calculation you are doing is going to tell you that the F12-FX200 is suitable for a sealed cabinet or a ported cabinet (you pick it).
Page 18 of the Catalog also contains a mini depiction of the Celestion suggested ported cabinet for the F12-FX200.
Here is the introduction page to the Celestion Ported Cabinet. Here they suggest 'to get the most from the speaker's full range capability, we recommend loading it into a bass reflex cabinet.'
Here is the 'design document'.
It is within the design document that 'polyester wadding' is referenced.
Again. when I asked Dr. Decimal about the polyester wadding, they replied 'it fools the speaker into thinking it is living in a larger cabinet'.
(BTW: I mentioned awhile ago 'Dr.Decibal' is a moniker used by Celestion for their technical support group).
I am still at a loss!
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Here is some more information relating to the F12-X200.
Mission cabs has a cabinet built for the F12-FX200.
This design clearly does not follow the Celestion specification (as it has two square ports). Take a look at it's dimensions at the bottom of the page. Yes these are external. this is clearly no where near the 121.42722053986330118675069002095 ft3 my calculation has come up with.
Here is there dual F12-FX200 model.
Zilla Cabs (out of the U.K) produces a cabinet that follows the Celestion design.
Here is a youtube video. The Celestion design cab is displayed at 9:18 of this video.
So in the end I can ensure (at least myself) that I am not a complete idiot here. I simply cannot understand at this point as to why my Vb calculation end up with such a large value, where all of the cabinets I have linked to here are nowhere near this size.
Mission cabs has a cabinet built for the F12-FX200.
This design clearly does not follow the Celestion specification (as it has two square ports). Take a look at it's dimensions at the bottom of the page. Yes these are external. this is clearly no where near the 121.42722053986330118675069002095 ft3 my calculation has come up with.
Here is there dual F12-FX200 model.
Zilla Cabs (out of the U.K) produces a cabinet that follows the Celestion design.
Here is a youtube video. The Celestion design cab is displayed at 9:18 of this video.
So in the end I can ensure (at least myself) that I am not a complete idiot here. I simply cannot understand at this point as to why my Vb calculation end up with such a large value, where all of the cabinets I have linked to here are nowhere near this size.
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> Dr. Decimal
> Dr.Decibal
They (and the unit) honors Alexander G. Bell, and should be "Dr Decibel"
I thought Tim already explained why 121.4272205...... is NOT correct.
Caveman tip: box volume is rarely much more than Vas. If Q is low, box volume should be much less than Vas. (A primary design factor is small box.)
Dumb caveman tip: "most" speakers (ordinary efficiency), you can size a box as (D*1.2)^3, where D is advertised diameter. So 12"*1.2= 14.4, cubed is 3,000 cubic inch, 1.7 cubic feet base size. Then multiply by 0.7 for a small thumpy sealed box, to 4 for a large deep duct-box. The maker-proposed box is small, about 1.1X nominal, with a huge duct. But I could picture a good Twelve in 15 cubic feet, if maximum bass extension for driver dollar is desired and space is no object.
> Dr.Decibal
They (and the unit) honors Alexander G. Bell, and should be "Dr Decibel"
I thought Tim already explained why 121.4272205...... is NOT correct.
Caveman tip: box volume is rarely much more than Vas. If Q is low, box volume should be much less than Vas. (A primary design factor is small box.)
Dumb caveman tip: "most" speakers (ordinary efficiency), you can size a box as (D*1.2)^3, where D is advertised diameter. So 12"*1.2= 14.4, cubed is 3,000 cubic inch, 1.7 cubic feet base size. Then multiply by 0.7 for a small thumpy sealed box, to 4 for a large deep duct-box. The maker-proposed box is small, about 1.1X nominal, with a huge duct. But I could picture a good Twelve in 15 cubic feet, if maximum bass extension for driver dollar is desired and space is no object.
There are 28.317 liters per cubic foot. Rounded 😉
47.3 liters is 1.67 cubic feet
Everybody makes mistakes.
I cannot believe I have spent the last week pestering you people about this!
I am furiously hyper ventilating as I am typing this!
Yes, I am aware that 121.4272205...... is NOT correct. Yes, Tim's explanation was understood.
Being State-side I am not conditioned to think in terms of metric, euros, Celsius or dog years. There is no way I would ever have noticed the apparent decimal misplacement on Celestion's documentation.
I will email Dr. Decibel (AKA Dr.Decibal) and inform them of the misplaced decimal point.
Tim, you the man!
I am furiously hyper ventilating as I am typing this!
Yes, I am aware that 121.4272205...... is NOT correct. Yes, Tim's explanation was understood.
Being State-side I am not conditioned to think in terms of metric, euros, Celsius or dog years. There is no way I would ever have noticed the apparent decimal misplacement on Celestion's documentation.
I will email Dr. Decibel (AKA Dr.Decibal) and inform them of the misplaced decimal point.
Tim, you the man!