12" Tapped horn |
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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Posted: 30 August 2010 at 9:38am |
Cone motion has to increase at a 12dB/oct rate.
53hz * 0.707 (one half octave) = 37.5hz Therefore the maximum output for a given cone displacement must be 6dB less for a half octave of bass extension. Note: You must be comparing apples with apples, ie: tapped horn vs tapped horn, or sealed box vs sealed box. A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB). A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB). A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB). |
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djk
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Djim69
New Member Joined: 29 August 2010 Location: Benelux Status: Offline Points: 6 |
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JDCutta
Registered User Joined: 24 June 2010 Location: North Lincs Status: Offline Points: 555 |
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DJK do you have the plan for the above?
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tomschute
Old Croc Joined: 15 May 2006 Location: Mid Wales Status: Offline Points: 1817 |
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many thanks Centuri. It does get confusing when threads meander! |
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Out to lunch... stableaudio@hotmail.co.uk
www.stableaudio.co.uk Speaker Building Services |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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Yes, I can see that, but some others have assumed that particular sim was for the box in question, which it clearly isn't.
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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My sims are of designs that looks good, similar to what is being discussed.
It is easy to see the length and mouth areas from the data field on the sims.
They are meant to be a suggested design, and it is up to the user to decide what he wants to build.
Hornresp liter volumes may be used to estimate overall bulk by dividing by .8, ie: 200L net will probably end up around 250L gross. Edited by _djk_ - 12 August 2010 at 2:48am |
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djk
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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djk seems to like throwing the odd arbitrary TH sim of a mentioned driver into the mix, even if it does not represent the box being discussed........
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tomschute
Old Croc Joined: 15 May 2006 Location: Mid Wales Status: Offline Points: 1817 |
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how confusing! so what is the plan for the above HR data?
sorry if i'm confusing the thread just all seems a little disjointed. |
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Out to lunch... stableaudio@hotmail.co.uk
www.stableaudio.co.uk Speaker Building Services |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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From what I can see, that sim is just a design that djk threw up last December, and is not a sim of the actual MTH-30. If you look at the FSP discussion page on the MTH-30, it specifies -3dB at 52Hz.....
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tomschute
Old Croc Joined: 15 May 2006 Location: Mid Wales Status: Offline Points: 1817 |
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a late night crude sketch...
.. am I just over tired or what? I make it more like 163cm for s2 to s3... |
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Out to lunch... stableaudio@hotmail.co.uk
www.stableaudio.co.uk Speaker Building Services |
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_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
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"please tell me i'm wrong and all these HR and Akabak sims are correct......."
Yes, you're wrong and the sims are correct.
The 1/4W of 140cm is 62hz, how could it possibly hit 38hz if it was that short?
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djk
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