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Old 29th March 2011, 10:01 AM   #21
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Car drivers any brand. My preference is for paper cone pioneers.
I will post a picture of the one I made later.

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Old 29th March 2011, 10:22 AM   #22
jazd is offline jazd  Australia
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Car drivers any brand. My preference is for paper cone pioneers.
I will post a picture of the one I made later.

Shoog
Hey you must have missed the second page of the thread. I already have purchased four 8" drivers.
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Old 29th March 2011, 11:02 AM   #23
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Does that look right? 73.2L with 34.77Hz tuning and a 10cm port that is 20cm long. Last thing I want to do is build a box that is totally wrong.
Tuning is way too low. You have to remember the excursion limit is +/-4mm so it will bottom out at very low volumes with that tuning frequency. The tuning Q is also too low for outdoors use. Even in a large room the optimum Q is 1, outside the relative equivalent of medium size room Q of 0.7 is a Q of 1.2. Luckily it's pretty easy to calculate when you have the Q 0.7 tuning; divide volume with Pi and multiply Fb with SQRT(2).

Even then it's going to be pretty big, and a fair bit larger than my Boominator I fear.
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Old 29th March 2011, 11:47 AM   #24
jazd is offline jazd  Australia
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Where do I set that in WinISD? Do you have a link to some information about this Q?

I'm not sure what you mean by divide volume with Pi as this works out to 23.3L which is smaller. 34.77 * sqrt(2) = 49.17Hz makes more sense though. Is 10cm port diameter still OK?
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Old 29th March 2011, 12:13 PM   #25
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Where do I set that in WinISD? Do you have a link to some information about this Q?

I'm not sure what you mean by divide volume with Pi as this works out to 23.3L which is smaller. 34.77 * sqrt(2) = 49.17Hz makes more sense though. Is 10cm port diameter still OK?
It's not something you can set. The calculation I described above transform a normal Q 0.7 tuning that you can get from WINISD to an exactly Q 1.2 tuning. Both parts of the calculation are needed, you have to both lower the Vb AND increase Fb, otherwise it doesn't work.

10cm port is fine but you can probably get away with a smaller diameter port if needed.
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Old 29th March 2011, 01:28 PM   #26
jazd is offline jazd  Australia
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So 23.3L and 49.17Hz is right? That seems real small.

Thanks for all your help so far Saturnus.
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Old 29th March 2011, 01:36 PM   #27
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No worries.

Remember to plot those figures, ie. the new Vb and Fb, into WINISD to check the response curve. It should have a precisely 3dB peak @ Fb*2.
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Old 30th March 2011, 06:14 AM   #28
jazd is offline jazd  Australia
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I've uploaded a drawing of the box I am going to make. Hopefully its all OK.

Volume on each side is 25.3L which allows for the port volume and driver displacement. Port will be 6.6cm long.

Center section holds the batteries and amp, will make the side come off on one side.
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File Type: pdf Box.pdf (60.1 KB, 45 views)
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Old 30th March 2011, 03:08 PM   #29
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by jazd View Post
I've uploaded a drawing of the box I am going to make. Hopefully its all OK.

Volume on each side is 25.3L which allows for the port volume and driver displacement. Port will be 6.6cm long.

Center section holds the batteries and amp, will make the side come off on one side.
Hi,

IMO:Your design is OK and will definitively deliver more appreciated SQ than a typical boom-box ever would do.(See the picture)

Suggestion: Test with different port lengths: 1.2-6.6 cm, 6.6 cm is Hi-Fi but not necessarily best for open air 2Pi venues.

b
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Old 30th March 2011, 03:51 PM   #30
bjorno is offline bjorno  Sweden
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...IMO:Your design is OK and will definitively deliver more appreciated SQ than a typical boom-box ever would do.(See the picture)..b
To good to be true,I've posted a picture using bad data.
I'll later be back with a revised picture.

b
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