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Discussion Starter · #1 ·
Hello,

I a couple of days hopefully my new sub will arrive finally. I am looking to build a enclosure for it. It is an Sundown audio e8 v4 sub. The sub will be placed in my room which is quite small and I will use the sub for both music and movies, so I would like it to go pretty low if that is possible, maybe around low mid 20s? The sub itself is 300 rms and will be driven by a 400 watt rms amp. I have no idea what type of enclosure is best for my situation, I thougt maybe a transmissionline, but the subs fs is pretty high because its an 8.

I hope someone could help me out on this, I will really appreciate it.


Abdullah,
 

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I would suggest looking at a 3db extended bass shelf enclosure for this driver.
It gets down to 30 Hz and doesn't go over the manufacturers maximum box size specifications.
The box size is 0.62 cu ft (17.5 l) tuned at 29 Hz with a 4" port that is 63 inches long (this could be an issue for such a small box)

Sundown Audio e8v2d2.PNG
 

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Discussion Starter · #3 ·
Thank you for your reply Robbo.
After I saw your reply I started to design something, this is what I came up with.

The box size is 17,5l and the portlength is 1600mm. I did let the port start at the side of the box and let it bend around halfway its length to come back againt to make it its full length. Around that I will make another box, you can see it as one giant box with a divider baffle in between. My question though is, the port starts really close to the sub, will this have any effects on the sound produced?
 

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Discussion Starter · #5 ·
I know, its just an idea sketch. There will be bracing added to the port. As if now it is impossible to make it because the box would be made from one solid peace :) I will design and detail it further later on, just want to know how you think about this design.
 

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That is what winisd comes up with, a 100mm port would need to be 1.6m long.

What you have sketched would certainly work if you added the bracing that you mentioned.
I look forward to seeing your progress on this. :T

You need to keep a minimum of 100 mm to prevent port "chuffing"
 

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Discussion Starter · #9 ·
I played around with winISD my self for a bit because I am thinking that the other box is tuned a bit to high, how about something like this? (white graph is the old one, pink graph is the new one)
the box is 25l, about 3-4 liters more than the factory recommended boxsize. Port length and diameter stays the same which sould tune it around 24Hz. Will this be realistic for an 8'' sub at 400 rms? or should I keep with the original design?
 

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I would check cone excursion and port air velocity to see if it's all ok. First port resonance of 107hz is still and issue since you will most likely use the subwoofer at this frequency unless you lowpass at 80hz with something like 4th order.

Also I wouldn't care about manufacturer enclosure size. All the mather is the transfer fontion magnitude, cone excursion and power handling of the subwoofer. If all these are good looking and within spec I don't see why a smaller or bigger box would be an issue.
 

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Discussion Starter · #11 ·
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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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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Discussion Starter · #13 ·
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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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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Discussion Starter · #15 ·
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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Discussion Starter · #17 ·
I fooled around witht the 6db extended bass shelf but the port becomes above the 2m which I find is pretty long. :nerd:
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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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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Discussion Starter · #20 ·
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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