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 Post subject: ported basics for dummies?
PostPosted: Tue Apr 09, 2019 4:31 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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I like to think when it comes to car audio that I have nearly done it all from basic to full custom crap but there is one part I always ignored just out of simplicity. I always built sealed boxes. While the car is still far from being ready to put the stereo in I came across a good deal on one of the 2 subs I would like to use the Morel 12" ultimo titanium so I have it on its way here now. I wanted to do these because I like the low end on them and really only need them to play up to 50-60 hz where the 9's in the doors will take over. The sensitivity is lower then I might like but being that they are for SQ and only for a small portion I would like to try a pair of them and port them to get the most out of that low end extension. Enclosure specs are for 2.29cubic ft and with a 4" x 15.5" port. I am pretty sure I will not be able to make it straight so where do I measure at bends? I know its good to flare the end of the port and to be sure to keep enough space from the end of the port to the back of the box, what else do I need to know? I am not sure I will be able to fit 4.6 cubes before ports and might have to go sealed or dial it down but for now I am hoping for big and ported.



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 Post subject: Re: ported basics for dummies?
PostPosted: Wed Apr 10, 2019 3:01 am 

Joined: Sat Aug 25, 2012 9:38 pm
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Yo Scott its me Reggie Philkenz I use to be on FB.

I was told...and hopefully you can understand me.

your box require 2.29 and lets say the port requirements is 24 inches. And lets say your box is 12 inches deep from front to back. Let's also say the inner length is 11.25 in(back wall is excluded but front wall is other wise it would be 10.5in.) So basically the port from front to back will be 11.25....than with what you already know just add the 90 degree bend and add 12.75 more inches of port.

Also keep inmind that its 12-15sq inches of port for every 1 sqft of air space.... I was also told not to calculated the port displacement with the box displacement.

There are also an online calculator that helps you with the port length and frequency but not sure of its exactly right or not....but still make me smile everytime I use it



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 Post subject: Re: ported basics for dummies?
PostPosted: Wed Apr 10, 2019 4:18 am 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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Use to be on facebook where did ya go? so in the bend do you measure the middle, inside or outside length of the port? I need to play with the online calculator, which one is recommended?



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 Post subject: Re: ported basics for dummies?
PostPosted: Thu Apr 11, 2019 4:15 pm 
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Measure the middle.

The average length of the port is the port length for tuning purposes.

If you have a way to do a signal sweep, you can verify your tuning once the box is built, and then adjust your port to get back to your target.

An impedance curve will tell you the tuning point, but you can get that with graph paper, and a DMM so long as you have 0db tones at all frequencies from say 20Hz to 100Hz.



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 Post subject: Re: ported basics for dummies?
PostPosted: Thu Apr 11, 2019 6:14 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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did some research on it today. Its a little strange as I found a site with a calculator that would tell you if the sub would be better in a sealed or ported box and going on the parameters on here:

https://www.morelhifi.com/wp-content/up ... or-web.pdf

It said that it would be better in a sealed box. I am not totally surprised as it is a SQ woofer but the graph shown for the large box ported in the link above looks like a better graph to me. Putting some of the parameters into the box design program it looks like a nice graph and with the low sensitivity numbers on the sub I can't help but think the extra output would be good?

I have not seen anything for testing or tuning a port in real life but would be interested to try. If I can build the box the way I think I can the ports would be mainly external and could be tuned



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 Post subject: Re: ported basics for dummies?
PostPosted: Fri Apr 19, 2019 10:59 pm 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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its morel season here :) got this on the porch. I am sooo tempted to take the magnet off just because it is designed to be done.
Image
Its safe to say its the nicest sub I have ever owned.



Now isn't the red line a nice perty graph? that red line is the ported graph
Image

I might just have to build a test enclosure or two to hear what sound the best.



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 Post subject: Re: ported basics for dummies?
PostPosted: Thu Apr 25, 2019 2:59 am 
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The red line in the graph looks like a free field frequency response to me.
If you build a box according to that, it will sound good in a very large room or outside.

If you put that box in a car you will get a huge boost starting about 70 or 60Hz and increasing towards lower bass. It will likely sound very heavy on sub bass and kinda slow. It might suite your taste and it might not.

Sealed boxes are great in cars because bass roll-off is compensated by cabin-gain. If you want to build a ported box, make the volume much smaller so the response starts rolling off well above tuning frequency. Keep the tuning low, around 30-40Hz.



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 Post subject: Re: ported basics for dummies?
PostPosted: Thu Apr 25, 2019 4:35 am 
the Floor Sweeping Hack with Golden Ears

Joined: Fri Dec 19, 2008 9:53 pm
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after all my research into this project it looks like everything I can find tells me NOT to put this sub in a ported box. Its not a huge disappointment as I know it will still sound good and I have learned a little more then I did before. with out the port there is no issue with space or where to mount it.



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