1. Is the port, just the cylindrical piece of plastic or do you have to cut out more MDF and make something that looks like a maze inside the box?
2. What is vent displacement?
3. How is the vent length 22.75"? Wouldn't that go like 10 inches out of the box?
4. And last but not least, the difference between net and gross internal volume. I figure it has something to do with the vent but not quite sure how to calculate it.
If someone could explain some of these terms to me it would greatly help me. Any pics or diagrams would help a lot too... Otherwise I'll just take the easy route and go Sealed .
lol yeah sealed is the easy road. Vents can be square (built into the sides of the box) or round like pieces of PVC pipe. In this case you will have to use square(slots) because you have to achieve more vent length than you have available in length of the box. You will have to build it with the corners of the box, so yeah like a maze. Look at Jl's website (jlaudio.com) for some visuals on that. Vent displacment is the volume of your vent in cm3 or ml or L or something. It tells you how much space your vent takes up. Your gross volume is the total box area (lxwxh) but net vol is that minus the driver displacement and vent displacement. Driver displacement is how much space the woofer takes up inside the box.
So the placement of the vent is not difficult at least. It goes along the whole width and up 1.25". Does the vent length of 22.75" look correct and if so what does that mean. Is the vent really going to go 5-10" out of the box? And for the vent does it need to be made of something such as PVC or do I just use the MDF for that?
I get the vented area now. The width of the box is 13.5" so the width of the vent is going to be 13.5"-2*3/4" MDF on each side=12". The 1.25" must be the height. But if the vent length is to be 22.75" like shown then I calculate the volume of the vent to be (12"*1.25"*22.75")/1728=0.197 cu ft.... According to above, isn't this to be 0.305 cu ft? Or is the volume of the vent not the same as the vent displacement?
hmm well im not sure who gave you those dimensions. You might try a program WinISD for box building, you can download it for free and it calculated port volumes pretty well. Im not sure if there is supposed to be 2 vents or what. The vents will wrap with the corners of the box, think of it like it following the inside of the box unitll a full 22.75 inches is achieved. I think you have your width/height mixed up tho. The height should be 13.5, the width will be 18 and it will be 16.5 deep. WOW i just realized this has to be for one woofer. If your building this for 2 type R's double the width (If you have the trunk space) or yould have to change some specs yourself. make sure you separate the chambers (and make sure to compensate for the divider in the total volume so make it like .75" wider for this) and make a port for each side. I still dont know about that vent disp sorry. If i were you i would use WinISD...well i use it anyways.
Nice thanks for the help. The JL audio site helped a lot visualizing the vent kinda wrapping around the inside of the box. I think I can figure it out for 2 woofers.
The only problem is that the width of my trunk is about 36". Would it be safe to just cut off about a half inch from the width of both chambers? Or would that possibly decrease the performance?
hmm i would shorten the width and add some depth if you can,. play with the dimensions to keep the same volume but add depth and lessen width. dont skimp on the vol it will change the tuning of the box.
Ok I kept the same interior volume by changing the width to 17", height the same 13.5" and depth to 17.3". The total width of the 2 subs will be 34.75", which I think I can manage. I don't know how I'm going to get it into my trunk, but hey at least it will be able to fit inside right haha. Thanks so much for all the help Nick.
Now for the wiring of my amp, which I have even less knowledge about...
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