Sonosub owners, help me design mine

[Newfiestang50]

Hello guys, I just ordered my RL-P 15 D2 from Mike at SS and have been doing alot of reading on this forum and others about all your subs but I still have some questions.

First of all I have been modeling this driver in winISD using a 250L enclosure power by 650 watts tuned to 15Hz and I am having trouble getting the port velocity down to an a satisfactory level using a 6" port but in reading some of the construction treads most of you used a 6". My question is how is it performing, do you hear any port noise? Are you satisfied or should I go with something bigger. I like the idea that the Areo ports will fit the green 6" pipe.
Also, when you select two flared ends, is the port length that winISD states the length from flare to flare or is it the actual pipe length?

[nick77]

http://www.avsforum.com/avs-vb/showthread.php?t=681797

No port issues at all and performance is house shaking.

[SteveCallas]

Green sewer pipe is something like 5.75" in diameter, not a true 6". A larger flare will only stave away the onset of audible chuffing, whereas a larger tube will stave away the onset of output compression and audible chuffing - since no RLp15 D2 sonosub owners using 6" diameter ports with 3/4" roundovers and up to 750 watts have reported any audible port noise, I'd stick with the larger diameter port and just use a 3/4" roundover as a semi flare, it has proved itself to work well. The port length WinISD suggests is just for the pipe length.

[ThomasW]

Use of the AeroPort flares means the green pipe will effectively flow as much air as a ~7" straight port. That's the benefit of using real flares as opposed to simply using a roundover bit.

If you need to stick with a smaller overall enclosure use the green pipe and the flares. If you have space for a larger tube use 8"-10" ports and a roundover bit.

[SteveCallas]

Thomas, the aeroport will only affect audible chuffing limits, not compression limits, correct?

[Newfiestang50]

The port length WinISD suggests is just for the pipe length.

Even if you select two flared ends. Steve, when you mentio9ned going with the larger port diameter what size do you mean, and what material?

[SteveCallas]

I'm talking about 6" ID sonotube as opposed to 5.75" ID green sewer pipe. Since port noise hasn't been identified as a problem with this type of RLp15 design using a 6" ID diameter port and 3/4" roundover as a flare - and there are a fair number of them out there - I'm not seeing any need for a much more expensive aeroport flare. That it requires you to use a 5.75" diameter port as opposed to 6" only seems to strengthen that thought, as your port velocity goes up a bit and your compression threshold goes down a bit.

[ThomasW]

Thomas, the aeroport will only affect audible chuffing limits, not compression limits, correct?

Steve as far as I know those are the same thing. When one hits the compression limits, chuffing occurs.

The problem with any port is the impedance mismatch between the air in the port and the air in the outside world. That's where flares come into play. They allow a higher air speed before chuffing occurs.

If one's not concerned about box size, huge ports are great until pipe resonances start becoming problematic.

If one wants the smallest box possible with the lowest reasonable tuning, I think the AeroPorts are a great investment.

[SteveCallas]

Thomas, I'm using this work as a guide, as I don't have the means to do such thorough experimenting - his work seems legit. His calculator shows that audible chuffing comes into play before output compression, and that only port diameter will directly affect the onset of output compression, whereas port diameter and flaring can affect the onset of audible chuffing, with flares becoming less significant with larger diameter ports. It seems to make sense, as audible chuffing would be the result of air turbulence while air is moving across the openings of a port (where flares come into play), whereas output compression would be dependent on the smallest cross sectional area of the port, which when flares are used, is the port diameter itself. Does that hold any logic?

[ThomasW]

Steve,

There's a reason I don't participate in those epic debates on AVS.....

I'm very much a pragmatist, so I build what makes sense to me. If it works fine, if not it's back to the drawing board. Fortunately after doing this for 40+yrs my track record is getting better... :B

I don't doubt there are some measurable differences between the designs I use and those with 8"-10" ports. How audible those difference are I'd need to hear for myself before jumping on the bandwagon.

[SteveCallas]

Understood.

There's a reason I don't participate in those epic debates on AVS.....

Believe me, nothing has revealed to me how smart and experienced you are more than exactly this, and I mean that in a good way. You know to stay away from it and not waste your time, whereas I constantly allow myself to get sucked right in ops:

[Newfiestang50]

I'm talking about 6" ID sonotube as opposed to 5.75" ID green sewer pipe. Since port noise hasn't been identified as a problem with this type of RLp15 design using a 6" ID diameter port and 3/4" roundover as a flare - and there are a fair number of them out there - I'm not seeing any need for a much more expensive aeroport flare. That it requires you to use a 5.75" diameter port as opposed to 6" only seems to strengthen that thought, as your port velocity goes up a bit and your compression threshold goes down a bit.

Sorry guys but I'm still not clear on the port lenght in winISD when choosing two flare ends (if one was to go with the Aero ports), the length that it provides, is it from flare to flare or is it only the pipe length between the two flares? Also the diameter that winISd asks for, I assume one should put in the actual inside diameter of whatever you are using for the port, correct?

[SteveCallas]

The length is just for the pipe - use the exact ID of the port material you will use to get the closest representation. Keep in mind if your tune in WinISD comes out to exactly 15hz, in real life, that exact tuning point could be anywhere from 14-16hz.

[Newfiestang50]

The length is just for the pipe - use the exact ID of the port material you will use to get the closest representation. Keep in mind if your tune in WinISD comes out to exactly 15hz, in real life, that exact tuning point could be anywhere from 14-16hz.

Ok, so if for example my lenght in WinISD comes out to be 20", I should cut 20" inches of pipe and then add the two flares to the pipe for an over all length of something greater than 20", correct?

[collo]

The length supplied by WinISD is the acoustic length of the port.

You need to make an adjustment for the flares. The conventional wisdom is to treat half the air in the flares as belonging to the port, and half belonging to the environment.

The Aeroports have a flare radius of around 30mm or 1-3/16"" so add half this amount for each flare.

That means your overall physical length is the acoustic length plus 1-3/16"

[Newfiestang50]

The length supplied by WinISD is the acoustic length of the port.

You need to make an adjustment for the flares. The conventional wisdom is to treat half the air in the flares as belonging to the port, and half belonging to the environment.

The Aeroports have a flare radius of around 30mm or 1-3/16"" so add half this amount for each flare.

That means your overall physical length is the acoustic length plus 1-3/16"

Guys, I kept refering to winISD but in fact I am using UniBox to model the sub, so in light of this, is all the comments above still accurate.

You would think that if someone went through the trouble to allow you to select between one, two or no flare ends then the distance calulated as the port length would be from the one flare end to the other if you select two flared ends, this would make sence and keep things simple for the builder.

[Newfiestang50]

Guys, what terminal connections are most common for sonosub owners, I was looking at the ones on parts express but don't really see any there that will go through 2 layers of 3/4" MDF plus 1/4" plywood. Any suggestions would be great.

[SteveCallas]

I use and recommend these for use on a bottom cap. I cut out a binding post "section" on the inner two layers of my bottom cap to allow room for them - see my attached pictures. The third, outer layer stays solid with only two small holes to screw the binding posts into.