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12" Tapped horn

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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Topic: 12" Tapped horn
    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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Djim69 Quote  Post ReplyReply Direct Link To This Post Posted: 29 August 2010 at 6:08pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JDCutta Quote  Post ReplyReply Direct Link To This Post Posted: 14 August 2010 at 1:08am
Originally posted by tomschute tomschute wrote:

Just re reading this post and noticed something.

Have I missed something or are the horn lengths for S2 to S3 100cm too much... I make it 140 not 240.



please tell me i'm wrong and all these HR and Akabak sims are correct.......

DJK do you have the plan for the above?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomschute Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 5:10pm
Originally posted by Centauri Centauri wrote:

A quick look through the thread on FSP relating to the MTH30 revealed the HR input screen here....



many thanks Centuri. It does get confusing when threads meander!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 6:51am
A quick look through the thread on FSP relating to the MTH30 revealed the HR input screen here....

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 2:54am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 2:44am
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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Centauri View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 1:13am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomschute Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 1:08am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Centauri Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 1:04am
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 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomschute Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 12:35am
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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_djk_ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2010 at 12:25am
"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?
 
djk
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