Internal/External Slot Port

[MikeMartel 64]

Alright, so only 10 days after i built my first box iv decided that its no good an i need to build a new one. Currently i have my box only 5.5 cubes for my 18" BTL.. with it only being powered by 1500 watts this isnt the most efficient setup. For my new box, i was going to build it closer to 7.5 cubes, sub up, port up. Now what i wanted to do was have the port 5-6 inches out of the box so that i could flush mount it to the rear deck, then seal the whole thing off from the trunk.

The box designer says for 32hz my port will be 28.75" long, 8.5" wide and 13.5" tall. Now could i simply 'slide' the port out 5-6 inches or would that effect the tuning?

Sorry if thats a bit confusing..

[///M5 2,833]

You bet

[MikeMartel 64]

So now how would i compensate for something like that?.. Im not really sure how i would build the vent like that and keep the tuning i desire..

[sefugi 166]

I would say that the amount of port that is outside the box is subtracted from what would have been in the box.

For instance, you said you would like 5-6" out of the box so you subtract that from the 28.75" total and then you only have what is left inside the box. Hope that helps.

[altoncustomtech 773]

I would say that the amount of port that is outside the box is subtracted from what would have been in the box.

For instance, you said you would like 5-6" out of the box so you subtract that from the 28.75" total and then you only have what is left inside the box. Hope that helps.

^^^This exactly!!

[MikeMartel 64]

Well yes, if i was going to add on 6" to the outside i would take off 6" from the inside. So as long as the length of my port is the same, it doesnt matter for far in or our it is from the box?

[Impious 1,476]

You will need to reduce the gross enclosure volume by the amount of port volume no longer inside of the enclosure as well.

Based on an 8.5" x 13.5" x 6" section of port, you would need to reduce the gross enclosure volume by .4cuft (that does not include the thickness of the wood, which I can't calculate since I don't know the layout of the enclosure. You would need to reduce the enclosure volume by the gross volume of the port + wood thickness no longer inside of the enclosure).

[MikeMartel 64]

Alright i get it then.. Damn i didnt think id be doing so much damn work only 10 days after i built my first box. ;D

[Impious 1,476]

Well yes, if i was going to add on 6" to the outside i would take off 6" from the inside. So as long as the length of my port is the same, it doesnt matter for far in or our it is from the box?

Correct, as long as you maintain proper total port length and reduce the gross enclosure volume by the gross amount of port volume no longer within the enclosure.

[MikeMartel 64]

Thanks Impious, you and your vast knowledge base on car audio makes me jealous.