SoundSplinter RL-P15 port diameter

[JonJT 10+ year member]

For those of you running ported RL-P15's, what diameter port(s) are you using and how many do you have?

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[Lightninghoof 10+ year member]

Are you simply curious, or are you trying to figure out what you should use for your own enclosure?

Minimum or optimal cross-sectional port area (Av) will depend on the driver, enclosure volume (Vb), port tuning (Fb), and maximum allocated input power.

 

[carguy83 10+ year member]

i got two 4" aero's.

 

[JonJT 10+ year member]

Are you simply curious, or are you trying to figure out what you should use for your own enclosure?
Minimum or optimal cross-sectional port area (Av) will depend on the driver, enclosure volume (Vb), port tuning (Fb), and maximum allocated input power.

I know it does.

I'm asking because port velocities for the alignments I've modeled are very high at Xmax and I'm looking to see what everyone else is using.

I should have been a little more clear because my true impetus for this thread is port cuffing. I'm wondering if anyone can hear the port cuffing when their RL-p 15s are at full tilt.

 

[JonJT 10+ year member]

i got two 4" aero's.

Thanks

 

[Lightninghoof 10+ year member]

Ah I see. Throw me the basic info regarding your enclosure design and I'll attempt to duplicate your findings. Sometimes the different modeling programs produce slightly different end results.

Are you using the D2 or the D4 version?

 

[carguy83 10+ year member]

i can't hear any port noise when my sub is going all out...if that is what you meant by 'cuffing.' //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[JonJT 10+ year member]

Alrighty, I'm using the D2 version with the coils in parallel. I got teh T/S parameters off of the soundsplinter website with the exception of Re. Its given with the coils in series so that needs to be reduced by a factor of 4. Parallel waring might also change the electrical Q of the woofer, but I do believe that is an emperically determined parameter and I don't have a woofer to test or the know-how to do it.

Otherwise my Unibox settings are as follows:

Ports: 2

Port dia: 6.16

Port end correction .519

Vb: 128 l

Absorption: 5

Leakage: 30

Port Qp: 140

Fb: 28hz

Heavy FIll

No Leakage

2 flared ends

Edit: forgot to add

Program power: 1100 watts

 

[JonJT 10+ year member]

i can't hear any port noise when my sub is going all out...if that is what you meant by 'cuffing.' //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Yep, thats what I meant. Unibox is reporting average port velocities of around 140 meters per second. That seemed a little unreasonable. Good to see you can't hear anything.

 

[Lightninghoof 10+ year member]

Jon,

I'll let you do most of the final math, but here's what I came up with. According to Dan Wiggins at Adire Audio, you want to try and limit peak air velocity to below 20 m/s at 20Hz. I feel this will depend on your tuning frequency however.

You are currently calculating for 60 square inches of cross-sectional port area. Including the other specs that you listed, peak air velocity at 20Hz would be roughly 15 m/s. The highest peak air velocity occurs at about 27Hz, at roughly 19 m/s. That's completely acceptable IMO, and should not be audible by any means.

I would say the minimum port area that should be used is 55 square inches. Optimum would be 60 square inches or higher.

So it appears you are definitely on the right track.

My advice though is to use a single port rather than multiple ports. Just a personal preference, but I find it easier to implement and tune.

I didn't account for box fill. The fill will of course increase Vb by an estimated margin of 10% ~ 30%. This will in turn alter Fb accordingly. This is very difficult to precisely account for.

 

[JonJT 10+ year member]

Unibox MUST be out of its mind as its giving me a Vmax of 120m/s at box Fb. That doesn't seem right, 120 meters per second...........

And yeah, one port would be easier for smaller diameters, but I'd need a rahter large tube to get the cross sectional area I need. It would also be pretty hard to rought that thing inside the sub box without interference.

 

[Lightninghoof 10+ year member]

Yeah, there's no way vent mach would peak at anything close to 120 m/s with 60 square inches of port area. Unibox has a screw loose or something.

As far as the port design goes, I was thinking something more along the lines of an MDF slot port. They are easy to construct, easy to bend multiple times, and double as bracing for the enclosure walls.

 

[JonJT 10+ year member]

I knew you were gonna recomend MDF slot ports! I plan on glassing the whole of the sub enclosure to conform to part of my cars trunk.

I could still incorperate a slot port now that I think about it though............We'll have to see. The two ports would provide some nice symmerty though. I'll have to see.

 

[JonJT 10+ year member]

WinISD's calculations, aren't quite as bad as unibox's but are still very wrong. Do you know where I can find some forumlas to calculate average port velocities?

 

[Lightninghoof 10+ year member]

No I don't have those formulas. Try BassBox Pro and compare its results with WinISD Pro and Unibox.

What leads you to believe the WinISD's calculations are off by a large amount?