4344 doghouse & ports sizes?

[jarrods]

I am drafting up my final plans for the 4344 cabinets based on all the information I see on this forum and just need confirmation on a few things:

The two ports: from measurements I have taken on images/internal cabinet photos etc I think they are 110mm ID and 150mm long. (That’s 4.3” by 6” in those other funny units). A local supplier here sells a port that is 110mm ID and has an adjustable sliding length of 160mm – 280mm. Good?

The 2122 doghouse (sub-enclosure): I read it is a volume of 14 litre (0.5 cubic feet). Now is that the volume of the inside of the box with no driver or the volume of the air left in the box after the driver is fitted? Does that level of anal obsessiveness actually matter?

Again from plans/images etc I measure inside dimensions:
4345: W 368mm x H 254mm x D ?? (D would be 150mm for 14l)
or 14.5” x 10” x 6”
4343: W ?? x H 248mm x D 125mm (W would be 455mm for 14l)
or 18” x 9.75” x 5”
4344: ???

I would assume it is best to place the doghouse so the driver is off-centred in it to the left or right. What about up/down off-centring as well or are we getting back into the realms of nympholepsy again? From what I can deduce in the 4345 it is some 75mm (3”) off-centred in the left/right plane.

thanks,
Jarrod

[Robh3606]

Hello Jarod

That volume on the 2122 enclosure is before the driver fill ect. I am using a sono tube so it is a cylinder. As far as the box tunning you using the same volume?? I am under a bit myself. Just tune to your volume. You can always adjust.

Rob:)

[jarrods]

I am using internal dimensions:

1000mm x 600mm x 325mm - 195litre
(approx 40" x 24" x 12.75" - 7cu ft)

less the 2122 enclosure of 14litre and other guff that takes up space. I think this is very close to the original JBL 4344.

My problem is I don't know how to tune a port, so I was after a port length of the original to copy.

I am trying to understand what the word 'tuning' means in this context. I am guessing there is some lower frequency of the driver that the hole/s and length of the port offers no resistance to the movement of the cone. If you make the hole smaller or make the pipe longer then the displaced air can't fit though as fast so pressure is built up and a resistance is felt. Is the frequency where the resistance to cone moment starts the tuned frequency?

I have purchased four of the adjustable ports. 110mm inner diameter and a sleeve withing a sleeve to make it adjustable from 160mm - 280mm. I could cut the lengths of the tube down to say 100mm so it could adjust from 120mm to about 200mm (if the original design was 150mm so the range can be either side of this).

jarrod

[Ian Mackenzie]

Jarrod,

You must be getting close.

There are plentry of good references on the www and also in the Heritage site regards tuning.

Giskard is the one to guide you here.

Bassbox and other programs will assist the alignment...do you have this?...we can help.

Do you have an audio signal generator?..........if not when you are ready I can help with the fine tuning and glass of nice red (or a port).


Ian