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Discussion Starter · #1 ·
Hi all,

I recently bought an O Audio Bash 500 amp from the USA and a Shiva-X2 from my local audio Distributor for my home audio system.
I'm following the suggestion of Exodus Audio & building a 3 cu ft enclosure - tuned to 22Hz.
As no-one really wanted to assist me in a box design (with sheet cut sizes), I will happily include these for the reference of anyone else wanting to build one (aren't I a top bloke?!).

Details are as follows:
Overall dimensions:
Width - 600mm
Depth - 490mm
Height - 400mm

Gross volume - 93.2 litres/ 3.29 cu ft.

Sheet cutting list for 18mm MDF:
[email protected] 600mm x 400mm (double baffled front face & singular rear panel)
[email protected] 490mm x 600mm (top & bottom panel)
[email protected] 450mm x 360mm (side panels)
I'm having the front faces CNC'd (in the centre of the panel) to flush mount the face of the woofer.
The cutout hole required is 280mm.
To flush mount the outer edge of the sub on the double baffle (outer sheet on front), I'll having a 320mm cutout.

I'm toying with the idea of having it laminated in a black veneer look or spending the money to have it painted in a gloss black?
Anyone have any ideas on how to raise this enclosure off the ground about 100mm (4") and how to stop it sliding on my timber floors?

Will update pic's when the build starts!

Cheers.

Daz
Melbourne, Australia
 

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As no-one really wanted to assist me in a box design (with sheet cut sizes), I will happily include these for the reference of anyone else wanting to build one (aren't I a top bloke?!).
I don't recall you asking, did I miss it?

Anyone have any ideas on how to raise this enclosure off the ground about 100mm (4") and how to stop it sliding on my timber floors?
Why 4"? Is the port going to be on the bottom?
 

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Discussion Starter · #3 ·
Hey MikeP,

Not specifically from Home theatre shack - but no-one was really willing to give out sheet cut sizes to supply a Cabinet Maker!
There is no other reason apart from aesthetics to have it raised.
Is this a performance hinderance - even if 2" off the ground?
 

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Hey MikeP,

Not specifically from Home theatre shack - but no-one was really willing to give out sheet cut sizes to supply a Cabinet Maker!
There is no other reason apart from aesthetics to have it raised.
Is this a performance hinderance - even if 2" off the ground?
Boxnotes will give you a good start, but it's unlikely anyone will have a cut sheet for your exact enclosure requirements.

Does your 93L account for the volume of space taken by the driver, bracing and the port? If not, you need to subtract that from the net volume or enlarge the box to get it back. Assuming that it is 93L net, then a tune of 22Hz, allowing the full 420W of the O Audio into the Shiva will mean you need two 4" ports of 96cm long (or their rectangular equivalent) which take up nearly 20L internally.

Passive radiators would save on space vs a port.
 

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I am using their enclosure design of a "Medium ported (3 cu ft)".
http://www.audiomarketplace.com.au/pdfs/ShivaX2Apps.pdf
Exodus Audio have specifically stated that the 4"aero Port (I'm using a Precision Port with flares) only needs to be 15.98 inches (406mm) long?!
I have allowed for the volume of the driver & port - which is why the total volume is 3.29 cu. ft.
I simulated using the full 420W and the port air speed was too high for my tastes with a single port, 42.8m/s at 20Hz. I then tried it with 2 x 10.2 cm ID ports, 21.4m/s at 20Hz and that's why they needed to be longer.

I don't use the same software as Kevin, but Unibox is widely used and has been very accurate for me so I trust it. In the published sims in the app guide the results posted are similar to what I get with 250W, but the drive voltage is stated 44.7V or 500W into 4Ω.
 

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Discussion Starter · #8 ·
Just a quick question before the MDF cuts are made;

I know sealed enclosures are generally better for music and considering I use this system for 65% music - would it be a disadvantage proceeding in having it ported?
 

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I know sealed enclosures are generally better for music and considering I use this system for 65% music - would it be a disadvantage proceeding in having it ported?
Sealed enclosures are not "better" than ported for music or anything else. Each have compromises. Go ported:T
 

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Just a quick question before the MDF cuts are made;

I know sealed enclosures are generally better for music and considering I use this system for 65% music - would it be a disadvantage proceeding in having it ported?
I'm not sure where people have gotten the idea that sealed subs are better than ported ones, but it's hogwash. As long as you have a large enough port you can easily best the sealed sub in efficiency and extension. There really isn't a contest. Sealed speakers tend to be less problematic in speakers, but the issues of ported designs are vastly overstated. Consider that Harman the king of perceptual research uses a lot of ported speakers in their designs. I think much of it is psycho acoustic.
 

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Discussion Starter · #12 ·
Hi guys,

Typically - my mate had got caught up in other things & is getting the cuts made next week.
He has suggested that I do slot port it as he also had concerns with port speed with this power.
I know this is a really big ask, but would someone PLEEEASE help me in calculating a slot port size and ammending the total enclosure volume to allow for it? Dimensions can change slightly to accommodate the slot port.

Thank you very much - in advance!
 

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Discussion Starter · #14 ·
He will be using 18mm MDF, so internal dimensions are simply:
Width - 582mm
Depth - 472mm.

I am now also considering designing the 3.5 cu ft enclosure Exodus suggest - as that has a much larger port area for the power I'm running.
Here are my initial calculations:

I am trying to design the 3.5 cu ft medium ported enclosure from here:
http://www.audiomarketplace.com.au/pdfs/ShivaX2Apps.pdf

I have come up with the following external dimensions in 18mm MDF (not including double front baffle):
Width: 60cm
Depth: 60cm
Height: 40cm.
This makes the gross internal volume: 115.79 litres/ 4.09 cu ft.
They specify a port length of 75.6cm at a diameter of 13.5cm.
The port volume equates to 10.8lt. I don't know how to convert this round port to a slot port area?
Driver volume equates to: 3.7lt.
This makes a Nett internal volume of: 101.29lt/ 3.58 cu ft. Spot on!
The cutout hole on the first panel is 280mm.
To flush mount the outer edge of the sub on the double baffle (outer sheet on front), I'll need a 320mm cutout.

If I have the woofer flush mounted (with a double front baffle) above the slot port - will there be enough room for the port opening (8cm)?

Cheers again!
 

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A slot port with an opening 25cm wide x 5cm high and 65.5cm long will give you the same tuning frequency as a round port with a length of 75.6cm and a diameter of 13.5cm.

The port air speed will be under 22 m/s if you use the 20 hz hi-pass filter on the O Audio amp.

You'll have to add the 18mm thickness to the sides and top of the port to figure out how much it displaces.


 

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Discussion Starter · #16 ·
Thanks Mike - appreciate it!
The above enclosure is tuned to 20Hz, so will the HPF being exactly 20Hz be ok?
p.s. how can I calculate the 18mm MDF thickness to calculate the area it displaces?
Sorry to cause you more work!
 

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A 75.6cm long x 13.5cm wide port in 3.58 cu.ft. is a 22.2 hz tuning.

For port displacement:
250mm wide + 18mm x2 (two sides) = 285 mm total width.
50mm + 18mm (The bottom of the cabinet doesn't count) = 68mm total height.
655mm - 36mm ( double front baffle) = 619 mm length.

285 x 68 x 619mm = port displacement.
 

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Discussion Starter · #19 ·
Hi MikeP,

Thank you for the response but it has bamboozled me with mathematics (not difficult)!
With the above enclosure dimensions (bottom of post 14), will I have to make it larger to accommodate the slot port volume you have reccommended?
If so, by how much?
 
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