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post #11 of 34 Old 01-18-15, 12:31 PM Thread Starter
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Re: Seeking for help,

this is how the excursion and the port air velocity looks like. the velocity peak from the old alignment (withe graph) is 23,3 m/s at 26,39Hz. The velocity peak from the new alignement (pink graph) is 25,46 m/s at 22,49Hz. The excursion graph speak for itself I think.

again, the port will be braced to reduce the port resonance.
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post #12 of 34 Old 01-18-15, 12:51 PM
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Port air velocity should be good. It is a little bit high but with a round over it will be fine.

Cone excursion is low so you have room to increase the enclosure size if you want. This will affect transfer fonction magnitude (might be better) and reduce port lenght which will increase 1st port resonance. If your port is resonsting it might ring and it will be annoying.
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post #13 of 34 Old 01-18-15, 01:01 PM Thread Starter
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Re: Seeking for help,

How much more can I increase the box? because if I will increase its size the port air velocity will also increase. For example, when I make it 40 liters, the air velocity will increase to above 30m/s with the same tuning. But the bigger box gives the transfer function magnitude an increase at around 23-24 hz, so that is always good

How much does the excursion need to be? Does it have to be x amount of % of the total excursion at the tuned freq or something?
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post #14 of 34 Old 01-18-15, 01:36 PM
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Cone excursion has to be within subwoofer Xmax. Don't go above that because xmech (true mecanical limit) is unpredictable and you can easily damage the woofer.

If air velocity go to high add more port.
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post #15 of 34 Old 01-18-15, 01:53 PM Thread Starter
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Re: Seeking for help,

How about this, added a second port of 4 inch, 40liters tuned to 24hz, port velocity is around 15m/s. But it says that the port length is 2031mm, is this 2031 for each of the port or does it has to be 2013 divided by the amout of the ports, which makes is around 1015mm per port, which is more workable than 2 2m long ports..
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post #16 of 34 Old 01-18-15, 02:37 PM
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Re: Seeking for help,

It would be the length for each section, 2 x 2m.
In winisd if you select ported and then 6dB extended bass shelf you get a smoother response without the hump in it.

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post #17 of 34 Old 01-18-15, 04:38 PM Thread Starter
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Re: Seeking for help,

I fooled around witht the 6db extended bass shelf but the port becomes above the 2m which I find is pretty long.
So I messed around the old one and this is what I came up with, (yellow graph)
25liters tuned to 24hz, with again the same port specs (4'' and 1600mm long). Excursion still a bit on the low side. The vent airspeed is 25,46 m/s at 22,51 Hz. I hope it will sound pretty nice. Any thoughts someone?
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post #18 of 34 Old 01-19-15, 02:45 PM
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Re: Seeking for help,

The Port velocity is a bit high but may be OK, don't forget that you will need a High Pass filter set around 24 Hz to prevent over excursion below the tuning frequency and I would recommend setting the crossover to the mains as low as possible, even 60Hz if the mains can go that low.

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post #19 of 34 Old 01-19-15, 07:35 PM
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Re: Seeking for help,

I would consider using a passive radiator design instead of a port.
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post #20 of 34 Old 01-20-15, 12:45 PM Thread Starter
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Re: Seeking for help,

Sinds I have no experience with passive radiators I dont have any idea what the advantages are. Would there be major difference compared to a ported box?
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