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Discussion Starter #1
Hi Everybody.

I am hoping someone can help me with my proposed sub build.

I have a couple of empty sub bins that housed dual 18" woofers. They were originally used for commercial cinema duty and are each around 550 litres gross internal volume. Just to clarify, the 550 litres is measured without deducting the internal bracing volume or the volume of the 4 x 4" port tubes that are currently in situ. The bins are very well made and weigh enough to make a hand trolley fearful.

I want to re-purpose the cabs by cutting off the backs and reducing the volume to about 400 litres net. I will seal up one of the existing speaker holes and put an IXL 18.2.2 driver into the other. Does this make sense so far??

I have been reading up on a few threads in here that suggest 400 litres is a good size cabinet for this driver (15hz tune) so that should be quite achievable by blending these boxes momentarily with a circular saw. I don't want to throw these bins out and the work involved in volume reduction shouldn't be too difficult.

Now, I am a little short of info here because I haven't measured the internal volume of the 4 existing ports and wont be able to do that until tomorrow. However, I would appreciate some advice on what the port volume should be for this build and whether 4 x 4" ports of the correct volume (and properly flared) are OK to use. I think Steve Callas recommends 8" ID ports for these subs and while I can certainly refit an 8" ID tube, I am kind of hoping I might get away with using the 4" ones. Less work and all that....

I appreciate any assistance you guys can give here. Thanks.
 

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Discussion Starter #2
OK, a rethink on the above.

I will repurpose the cabinets and make them into a slight wedge shape so-as they fit better into the rear corners of the room. When I do this, I'm going to lose the existing port tubes so I may as well fit new a one(s).

Can someone please verify my numbers:

Cab size - 424 litres (net of bracing, port volume and speaker)
Port volume - 35 litres

I am thinking it might be easier to make a slot port. I would put the speaker driver nearer the lower end of the cabinet and the slot port at the top. Thanks
 

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OK, a rethink on the above.

I will repurpose the cabinets and make them into a slight wedge shape so-as they fit better into the rear corners of the room. When I do this, I'm going to lose the existing port tubes so I may as well fit new a one(s).

Can someone please verify my numbers:

Cab size - 424 litres (net of bracing, port volume and speaker)
Port volume - 35 litres

I am thinking it might be easier to make a slot port. I would put the speaker driver nearer the lower end of the cabinet and the slot port at the top. Thanks
Have you tried simulating this driver on WinISD using the the existing box specs to see what kind of FR it would give you before embarking on radical restructuring of the boxes? Perhaps you may find that you have to do much less and probably easier alterations.
 

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Discussion Starter #4
Have you tried simulating this driver on WinISD using the the existing box specs to see what kind of FR it would give you before embarking on radical restructuring of the boxes? Perhaps you may find that you have to do much less and probably easier alterations.
Good idea. I have just had a session with winISD and it looks as though I'll have to do very little to the box. It's too large right now but once I put in some extra bracing, that will bring it down closer to the 450 litre mark. If it's still a little too big after I've done the additional MDF bracing, it will be easy enough to add in some 2" x 4" pieces and drop the volume further. Thanks.
 

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Good idea. I have just had a session with winISD and it looks as though I'll have to do very little to the box. It's too large right now but once I put in some extra bracing, that will bring it down closer to the 450 litre mark. If it's still a little too big after I've done the additional MDF bracing, it will be easy enough to add in some 2" x 4" pieces and drop the volume further. Thanks.
:T
 

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