building sub....... please help a first timer (1 Viewer)

[Joe Meissner]

thanks guys.

a twelve it is. at least now i can cut the holes. not sure when i will order it, but i appreciate all the help.



is that correct? the same lenght for one 4" or 2 3" ports.

also what is the hole size for each port. i would like to cut that hole too.

thanks

Joe

 

[Dustin B]

Just double checked in LspCAD. Two 3" ports need to be 49.4cm long to tune to 22hz and a single 4" port needs to be 49.6cm long.

The cut out will depend on the exact dimensions of the PVC you buy, or which flared port kit you buy. I wouldn't make it until you have what you are going to use.

I don't think you could fit the 6.25" cutout required for Adire's FP4 kit on your baffel. And the FP4 kits max length is 17". Check on the flares avialable on PE, and what PVC pipe is avaialable locally and decide between the twin 3" and single 4" from there.

 

[Joe Meissner]

does it matter where the port goes. IE on the bottom or front firing. would i be able to do 2 4" ports in the front? I only have 15" depth to work with in the front.

thanks

joe

 

[Joe Meissner]

kinda like this.......

 

[ThomasW]

Port placement isn't critical. They can be mounted anywhere that isn't obstructed when the sub is operating.

 

[Dustin B]

It doesn't matter where the port goes. Only rule of thumb is leave a least a port width from the end of the port to the nearest surface (that goes for both ends of the port).

Twin 4" ports would need to be 38" long each to tune your enclosure to 22hz.

With the 3" both ports have to be 19.5" long.

There are three things that need to be considered in order to tune an enclosure to a particular frequency. What the net volume of the enclosure is, what the diameter of the port is, and how long the port is.

As examples, assume the other two variables are kept the same.

If you make the enclosure larger, the tuning goes down, make it smaller the tuning goes up.

If you make the port wider (adding more ports is making the port wider), the tuning goes up, if you make the port narrower the tuning goes down.

If you make the port longer the tuning goes down, if you make the port shorter the tuning goes up.

 

[Joe Meissner]

if this is the case, why not use 2 inch ports and make them shorter? or does port noise come into play when using something to small?
also I just saw the thread about the Link Removed web site. $91 bucks for the 1201 sounds good.? is this a good driver for my size box? or am i better of sticking with the dayton?

 

[Robert_Gaither]

The BPD is a bad choice based simply on the box size limit that you're restricted to (I modeled on WinISD and the box size was 192.2 litre ported {6.79 cubic feet} and 91.4 litre {3.23 cubic feet} sealed, but you don't seem to want sealed). I would go with the Dayton DVC simply because of the way it seemed to model in WinISD for the box size limitation you're restricted too. I would recommend a single 4" port over dual ports assuming you are going to cut a similar size hole in the braces to support it, it would mean less cutting and thus less time (and a single 4" port should cost cheaper than 2 3" ports).

 

[Dustin B]

The 1201 would be fine.

And yes that's the catch. The more air the driver can move the larger the port has to be in order to prevent compression and port noise.

 

[Jon Torres]

Regarding the DVC 15, getting a qtc of 0.707 in a sealed box heavily stuffed using Unibox, it says you need 64.3l or 2.27 cubes. I was lucky enough to pick up the DVC 15 on sale for $99. It should go on sale again. If you ever want to upgrade, there's more room w/ the 15. IMO

 

[Joe Meissner]

Dustin,

I was just looking at the shiva recomendations and it says to add 5" to the port length when using straight pipe with no flare. does this hold true for the dayton 12? so does your recomendation of 19.5 inch port for a flared port or straight pipe.?

thanks

 

[Dustin B]

You need to reread those instruction for the flared port kits a little more carefully.

They say cut the center tube 5" shorter than your calculated port length. Then when assembled, the over all length of the kit with the flares attached will be 1" longer than your calculated port length.

So you would cut the center tube to 14.5", then the overall length of the port including the flare would be 20.5".

Problem is the center tube that comes with the FP4 and FP3 port kits is only 12" long. And it isn't a standard PVC or ABS pipe size. Or at least I haven't heard of anyone successfully replacing the center tube in one of those kits. You could ask about getting another 12" peice of the center pipe and two more couplers though.

Edit: Ok, I need to read your post more carefully :p)

Yes, the 19.5" is for a straight pipe. Box tuning is not affected by which driver is used (unless there is a huge difference in the amount of air the driver physically displaces in the box). Tuning is only dependent on the dimensions of the port and the net volume of the box.

 

[Joe Meissner]

I need to put a 90 degree bend in my box. do you think a 4" pvc 90 would fit on the pipe in the port kits ? and would the bend give me enough length to get what i need? if thats the case i could order one of the PRECISION PORT 4" FLARED PORT TUBE KITs from PE.

if guys are using standard pvc pipe, what are they using to flare the ends? or are they?

sorry for all the ?'s but i really am a newby at this and just want to get it right the first time.

thanks

Joe

 

[Patrick Sun]

Highly doubtful because the thickness of the straight section of a precision port is around 4 1/8" (at the most), while a PVC elbow has to accept a pipe with outside diamter of around 4 1/2". The elbow will be loosey goosey when mated to the thin precision port straight section.

How long do you need to make the port? If you can't fit the port inside the enclosure, it's time to think sealed or use a passive radiator (though that's the most expensive option).

 

[Joe Meissner]

dustin says about 19.5 inches for my box. i can put the port on the bottom if i have to. to keep it a straight pipe.

but i like the look of your(Patrick's) box with the twisted tube in it. with the driver and port on the front. how was the flare created on that box? and how was the pvc attached to it?

thanks

 

[Patrick Sun]

I didn't make that box. But the flare is made from using a roundover bit on MDF for the front baffle. On the inner side of the front baffle, there was a hole that allows the pipe to mate with the outside layer of the baffle (like a ledge) so the port is seated in the inner layer's port hole.

 

[Joe Meissner]

i think i can do that.

thanks