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Author Topic: port tuning  (Read 5478 times)

David Parker

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port tuning
« on: July 15, 2011, 03:06:06 pm »

when you calculate the size, number, and length of the ports, do you subtract the volume of the ports from the overall volume of the cabinet?
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Ales Dravinec

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Re: port tuning
« Reply #1 on: July 15, 2011, 03:36:46 pm »

when you calculate the size, number, and length of the ports, do you subtract the volume of the ports from the overall volume of the cabinet?

Absolutely !

w/r
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Alan Sledzieski

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Re: port tuning
« Reply #2 on: July 16, 2011, 08:42:45 am »

when you calculate the size, number, and length of the ports, do you subtract the volume of the ports from the overall volume of the cabinet?

Are you using a program to do this?  Or doing your own math?  What ya building?
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David Parker

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Re: port tuning
« Reply #3 on: July 16, 2011, 11:21:48 am »

Are you using a program to do this?  Or doing your own math?  What ya building?

I built four 2-15 subs a few months back, using eminence Kappalite 15 drivers. I used a design on the eminence website, specifically for that driver. They gave the volume of the cab, and the number, size, and length of the ports. It has six 6" ports 11.25 long, to reduce port velocity. I've been well pleased with the performance of the subs, but just got to thinking, those port's volume adds up to about a cubic foot. So I used a port calculator to see how much difference it made in the tuning to deduct the volume of the ports from the volume of the cab, and it's significant. It appears that I can plug one of the ports and pretty much get back to the suggested tuning of the cab without changing the length of the ports, which would be very difficult at this point.
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Alan Sledzieski

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Re: port tuning
« Reply #4 on: July 16, 2011, 03:12:01 pm »

I built four 2-15 subs a few months back, using eminence Kappalite 15 drivers. I used a design on the eminence website, specifically for that driver. They gave the volume of the cab, and the number, size, and length of the ports. It has six 6" ports 11.25 long, to reduce port velocity. I've been well pleased with the performance of the subs, but just got to thinking, those port's volume adds up to about a cubic foot. So I used a port calculator to see how much difference it made in the tuning to deduct the volume of the ports from the volume of the cab, and it's significant. It appears that I can plug one of the ports and pretty much get back to the suggested tuning of the cab without changing the length of the ports, which would be very difficult at this point.



I use eminence software to build cabinets at time to time, I know changing the port configuration also has a lot to do with how much power the driver will handle at certain frequencies down low.

So what are the changes? By plugging 1 port in responce?
What driver are you using exactly?
I thought they usually give a box design with dimensions??????
Whats your internal box volume?
Did you compensate for the area the speaker takes up in the box?

Plus 6, 6'' ports seems like a lot of area for a dual 15', given the x max and the kinda power they handle they handle. 
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David Parker

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Re: port tuning
« Reply #5 on: July 16, 2011, 05:56:14 pm »



I use eminence software to build cabinets at time to time, I know changing the port configuration also has a lot to do with how much power the driver will handle at certain frequencies down low.

So what are the changes? By plugging 1 port in responce?
What driver are you using exactly?
I thought they usually give a box design with dimensions??????
Whats your internal box volume?
Did you compensate for the area the speaker takes up in the box?

Plus 6, 6'' ports seems like a lot of area for a dual 15', given the x max and the kinda power they handle they handle.

http://www.eminence.com/pdf/Kappalite_3015LF_cab.pdf
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Alan Sledzieski

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Re: port tuning
« Reply #6 on: July 17, 2011, 10:22:36 am »

http://www.eminence.com/pdf/Kappalite_3015LF_cab.pdf

When I get a chance I'll plug all the numbers in and see what I get.
 I did look at port velocity graph listed, its very low, they are not running all those ports for reducing port velocity, its for other factors.
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Alan Sledzieski

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Re: port tuning
« Reply #7 on: July 17, 2011, 12:17:18 pm »

http://www.eminence.com/pdf/Kappalite_3015LF_cab.pdf

Ok 

6 ports   vs    5 ports

 Power handling
40.1 hz, 897w, 900w
39.4 hz, 648w, 900w
38.7 hz, 472w, 900w
38.0 hz, 348w, 900w
37.3 hz, 280w, 756w
34.7 hz, 90.1w, 215w 

Port velocity

6 port 10.2 m/s @ 38.7 hz
5 port  12 m/s @ 34.1 hz.

6 port, fb 44, f3 41.01
5 port fb 40.58, f3 41.01

6 port is + 1 db from 133 hz to 70.3 hz over a 5 port.

Conclusion, leave as 6 port, engage the 40 hz low cut on the crossover.  From the way the 6 port handles power I see why they went with the design, simply cutting the frequency below 40 hz, gains a 1db out put in the sweet spot.  Port velocity was never a factor.
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Alan Sledzieski

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Re: port tuning
« Reply #8 on: July 17, 2011, 12:23:46 pm »

http://www.eminence.com/pdf/Kappalite_3015LF_cab.pdf

6 port is yellow.  Graph is showing output, you can see the 1 db loss in the 5 port
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Gary Weller

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Re: port tuning
« Reply #9 on: July 17, 2011, 01:13:44 pm »

6 port is yellow.  Graph is showing output, you can see the 1 db loss in the 5 port

What program is that?
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Alan Sledzieski

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Re: port tuning
« Reply #10 on: July 17, 2011, 01:23:43 pm »

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David Parker

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Re: port tuning
« Reply #11 on: July 17, 2011, 02:36:06 pm »

Ok 

6 ports   vs    5 ports

 Power handling
40.1 hz, 897w, 900w
39.4 hz, 648w, 900w
38.7 hz, 472w, 900w
38.0 hz, 348w, 900w
37.3 hz, 280w, 756w
34.7 hz, 90.1w, 215w 

Port velocity

6 port 10.2 m/s @ 38.7 hz
5 port  12 m/s @ 34.1 hz.

6 port, fb 44, f3 41.01
5 port fb 40.58, f3 41.01

6 port is + 1 db from 133 hz to 70.3 hz over a 5 port.

Conclusion, leave as 6 port, engage the 40 hz low cut on the crossover.  From the way the 6 port handles power I see why they went with the design, simply cutting the frequency below 40 hz, gains a 1db out put in the sweet spot.  Port velocity was never a factor.

The reason I was considering plugging one port is because I think I'm about a cubic foot smaller than the plans call for, if I deduct the port volume from the cab volume. All your calculations are based on the cab volume in the plans. If my cabs are a cubic foot less than what the plans call for, then all your calculations are off. That's what my original question was about, whether I should deduct the volume of the ports from the volume of the cab. The inside dimensions of my cabs are 21.25x26.75x42 inches.
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Alan Sledzieski

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Re: port tuning
« Reply #12 on: July 17, 2011, 03:48:13 pm »

The reason I was considering plugging one port is because I think I'm about a cubic foot smaller than the plans call for, if I deduct the port volume from the cab volume. All your calculations are based on the cab volume in the plans. If my cabs are a cubic foot less than what the plans call for, then all your calculations are off. That's what my original question was about, whether I should deduct the volume of the ports from the volume of the cab. The inside dimensions of my cabs are 21.25x26.75x42 inches.

Your internal volume is then 13.816
The volume of the box that I used was 13.36, the program actually figured that internal volume out.  Your box is actually bigger.
I used your internal box volume and ploted it with 6 and 5 ports.  Same results, handles more power, 1 db less out put with 5 ports.
 Not seeing huge differences that you are.
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Alan Sledzieski

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Re: port tuning
« Reply #13 on: July 17, 2011, 04:00:01 pm »

The reason I was considering plugging one port is because I think I'm about a cubic foot smaller than the plans call for, if I deduct the port volume from the cab volume. All your calculations are based on the cab volume in the plans. If my cabs are a cubic foot less than what the plans call for, then all your calculations are off. That's what my original question was about, whether I should deduct the volume of the ports from the volume of the cab. The inside dimensions of my cabs are 21.25x26.75x42 inches.
 

Just reread your earller posts, your port length is 11.25.

Re did it all with your port length, same findings, but nothing huge.
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Alan Sledzieski

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Re: port tuning
« Reply #14 on: July 17, 2011, 04:01:22 pm »

What is the significant value change you are seeing?
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David Parker

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Re: port tuning
« Reply #15 on: July 17, 2011, 04:56:14 pm »

What is the significant value change you are seeing?

The difference I am seeing is when I do the calculations with 12.8 cubic feet, the volume of my cab if you deduct the volume of the ports. Am I supposed to deduct the volume of the ports from the volume of the cab before doing the calculations?
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Alan Sledzieski

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Re: port tuning
« Reply #16 on: July 17, 2011, 05:54:53 pm »

The difference I am seeing is when I do the calculations with 12.8 cubic feet, the volume of my cab if you deduct the volume of the ports. Am I supposed to deduct the volume of the ports from the volume of the cab before doing the calculations?

Yes

Again, what are the differences???, flying blind here.
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Alan Sledzieski

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Re: port tuning
« Reply #17 on: July 17, 2011, 07:14:48 pm »

The difference I am seeing is when I do the calculations with 12.8 cubic feet, the volume of my cab if you deduct the volume of the ports. Am I supposed to deduct the volume of the ports from the volume of the cab before doing the calculations?


 And subtract the volume of what the drivers displace.
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David Parker

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Re: port tuning
« Reply #18 on: July 17, 2011, 08:04:10 pm »



 And subtract the volume of what the drivers displace.

depending on the volume of the cab, the port sizes and number changes for the same tuning. My question has to do with how to come up with the  volume of the cab. I know you deduct for the displacement of the speaker and handles and bracing, but do you subtract the volume of the ports to come up with the volume. If you do your calculations with a 12' cab vs. a 13' cab, you'll come up with different port lengths.
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Elliot Thompson

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Re: port tuning
« Reply #19 on: July 18, 2011, 12:19:24 am »

depending on the volume of the cab, the port sizes and number changes for the same tuning. My question has to do with how to come up with the  volume of the cab. I know you deduct for the displacement of the speaker and handles and bracing, but do you subtract the volume of the ports to come up with the volume. If you do your calculations with a 12' cab vs. a 13' cab, you'll come up with different port lengths.

You can direct this question to Harristech since Eminence Designer is Bass Box Lite.

Have your serial number handy for the company will ask for it before answering your question.

http://ht-audio.com/pages/Support.html

Best Regards,
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ProSoundWeb Community

Re: port tuning
« Reply #19 on: July 18, 2011, 12:19:24 am »


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