Flared port question

[4BangerStanger]

OK, I have the dimensions of my new enclosure roughly figured out and have it just about where I want it. The design calls for a 4" port that's 17 inches long. I've never used a flared port before, so I'm trying to figure out how deal with it. In my situation, would the whole port, including the flares be 17" long?  Or would I need a 17" long "pipe" and add the flares?

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[4BangerStanger]

Also, how much does the location of the port matter?  The box will be roughly 25w x 15h x 12d.  The sub will be on the front side and the port will be on the left side. I'm thinking that I'll put the port halfway up and as far forward as I can without getting in the way of the sub. 

 

[THATpurpleKUSH 5,000+ posts]

The length includes the flares. Usually the flares require you to add 1 inch to the total length. 

 

[4BangerStanger]

The length includes the flares. Usually the flares require you to add 1 inch to the total length. 

So, the total length would be 17" or 18"?  Sorry if my brain's not working. I blame the whiskey. 

 

[4BangerStanger]

Just to clarify, the Torres box calculator says the port needs to be 17" long. But, doesn't have the ability to specify that you're using flared ports. 

 

[THATpurpleKUSH 5,000+ posts]

Just to clarify, the Torres box calculator says the port needs to be 17" long. But, doesn't have the ability to specify that you're using flared ports. 

Add 1 inch if it doesn't give you the option of a flare. This is a better calculator for flared ports:

http://www.psp-inc.com/tools2.html

 

[4BangerStanger]

Got it. Thank you. 

 

[4BangerStanger]

Any thoughts on the second part of the question regarding placement of the port?  Obviously I need to be able to place it somewhere where it won't hit the sub. What's the best placement?  Is ok to have it ported on the left side?  Or should I port it out the front and use an elbow?

 

[THATpurpleKUSH 5,000+ posts]

I would put it on the same side as the sub, keep the port opening as far from the sub as you can and try to keep the port at least a port width away from walls. Use a sewer and drain elbow if you have to bend it. 

 

[4BangerStanger]

I would put it on the same side as the sub, keep the port opening as far from the sub as you can and try to keep the port at least a port width away from walls. Use a sewer and drain elbow if you have to bend it. 

OK. That's kinda what I was thinking. How does one go about accounting for the elbow when determining port length?

Also, I'm planning on using the Precision port from Parts Express. Can I use a regular ABS elbow from HD?

 

[THATpurpleKUSH 5,000+ posts]

OK. That's kinda what I was thinking. How does one go about accounting for the elbow when determining port length?

Also, I'm planning on using the Precision port from Parts Express. Can I use a regular ABS elbow from HD?

Measure down the middle of the elbow. You  want to use an elbow for sewer and drain, not sch 40. Most Home Depots should have them in stock for around $5. 

 

[4BangerStanger]

I would put it on the same side as the sub, keep the port opening as far from the sub as you can and try to keep the port at least a port width away from walls. Use a sewer and drain elbow if you have to bend it. 

THATpurpleKUSH, I read another post from you where you said that the port needs to fire off a hard surface and I'm wondering if I may need to change up my design a bit. The box is going in the trunk of a Mustang. My plan was to have the sub firing toward the back of the car.  The rear of the trunk if probably 12-15" from where the sub will be. Is that going to present a problem?  Would I be better of having the sub and port on the side of the box, firing into the other side of the trunk, which would probably be 6-8" from the sub?  I might not be able to fit the sub and port on the side, so maybe I should go back to the rear firing sub and side port?

 

[THATpurpleKUSH 5,000+ posts]

THATpurpleKUSH, I read another post from you where you said that the port needs to fire off a hard surface and I'm wondering if I may need to change up my design a bit. The box is going in the trunk of a Mustang. My plan was to have the sub firing toward the back of the car.  The rear of the trunk if probably 12-15" from where the sub will be. Is that going to present a problem?  Would I be better of having the sub and port on the side of the box, firing into the other side of the trunk, which would probably be 6-8" from the sub?  I might not be able to fit the sub and port on the side, so maybe I should go back to the rear firing sub and side port?

12-15" from the rear isn't an issue for daily listening.The closer you move the port to the rear (but no closer than a port's width), the better overall performance you will have because its coupling the rear wave in phase with the front wave. 

Have you considered using an external port like these?

 

[4BangerStanger]

12-15" from the rear isn't an issue for daily listening.The closer you move the port to the rear (but no closer than a port's width), the better overall performance you will have because its coupling the rear wave in phase with the front wave. 

Have you considered using an external port like these?

Appreciate the reply. The external ports would be a no go. The car is my driver for now and I routinely have to carry sports and/or workout equipment back there. In addition to taking up too much space, I feel like there'd be a high likelihood that they'd get damaged. Maybe I'll just slide it back when the trunk is empty. 

 

[Buck 5,000+ posts]

With 4" flared black ports, the port physical length is 18" but the effective port length is 17".  Each flare loses .5" of effective port length due to increase of surface area of port line.  So if you need a 17" effective port length, just buy a 4" flared and stick it together, don't cut any of it and you should be fine.