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Kicker 15 Inch L7 (Ported 30 HZ Build) (THREAD)

3K views 48 replies 6 participants last post by  Noah117117 
Port velocity needs to be under 1 (Mach) (at tuning and above)

Something is wrong, I think when you took that screen shot you had a itty bitty port entered

Because the port size you show wouldn’t do that
 
What do you mean under 1 Mach is that like a conversion or something, as far as my research my went, I saw that the standard port velocity should be under 17 m/s and 23 m/s is like pushing it. If I remember correctly.
Port velocity is in Mach… ya know speed of sound , at least it is in termlab

So , idk about isd , but that port velocity shouldn’t show ms , it should show speed

And , the GD would be in ms

If I’m not mistaken
 
@oabeieo if you're designing enclosures with port velocities of 343m/s second then something is seriously incorrect. OP, Just try to keep it as low as you can in the enclosure size you choose. 17m/s is where chuffing will generally start, though it depends on the port size, aspect ratio, and flare. Mid to high 20s is where compression will generally kick in with car audio sized ports. Thin long slot ports are worse than square or circular ones. In general, if the sub is in your trunk, the chuffing will be less noticeable so you can get away with the ladder numbers. As others mentioned, using a subsonic filter is a good way to protect the subs. If you are going to apply one, you should simulate that in winisd as well because it will help tame port velocity. The final thing to consider is the first resonance of your port. A rule of thumb is you should have a first resonance of 2x your crossover frequency or higher. You can get away with lower if you use brick wall filters, but usually, the port gets so long it becomes problematic at that point anyway.

Good luck with the build. Keep it simple, and take your time. If you get frustrated walk away and come back later. The first time around is rarely perfect and it can be annoying if you have expectations too high. I still rarely get through a build without something telling me that I'll never do another one, yet I keep coming back.

In winisd , (when I use it) I keep velocities under 1

Port lengths for in box, has no port noise, idk about anything else but GD is normal, box size is normal, etc etc , port length tuned between 28-35 is usually 17-25” , so . And they sound killer

I’ll take screen shots later at work
 
^^^ obviously I would try n model a box that actually starts to roll off right below tuning , I pulled that out of my arse , and used some driver in the library for the example of velocity…. Tuned at 31 I would actually expect a f3 around 28 so that one is bad example, but you get the jist
 
What does your options and plot windows settings look like? How much power are you simulating?
hummmmmm power sims ……

I’ll try changing those parameters….at least in isd

I’m termlab , all of that is calculated…. If box is in “the green” it’s good to go…. And port Mach is below 1

maybe I need to learn isd a bit more , thanks for that
 
Yeah if you're not simulating power then in winisd you are just looking at the 1-watt port velocity. The problem is that some drivers have 100 watt power handling and some have 5000 watt power handling. The simulation is not going to account for that and I'm not sure how termlab would either. What if you wan't to know the port velocity at different voltage inputs? My hunch is that you are missing something in the equation which is why your port velocities different to what others experience. Again, I have no clue what you mean by a port mach? To me, a mach is a measure of velocity, but never one I'd use for port air flow. The value is just way too fast to get any sort of precision.
yeah yeah your making sense, okay this is all absolutely agreeable and is correct. I like it. Love learning new things, thank you.

so I’ll definitely give this a shot today. I like term pro because it’s very id10t proof. If it’s in the green the box always sounds superb. Isd I can make my way through fairly well , my shop pc has termlab and I can’t move it to a different pc so at home I use isd

so I always assumed it was Mach velocity like termpro , I kept it under 1 and apparently yes the 1w setting and have had excellent results using that as a benchmark for all my isd designs…

this definitely takes it a step further, I wish isd showed the measurement profile in the main window , it’s just labeled 1,2,3,4 etc etc

i super appreciate your time explaining that.

but for me begs the question; in termpro having a vent velocity at Mach 1 or less is optimal, as soon as the event velocity goes faster than the speed of sound or whatever it’s doing the little meter goes into the yellow, it’s above 1 and is telling you the box isn’t as good

so how many meters per sec is Mach 1 (I know the answer to that but it’s part of the riddle)? And is that the proper way to look at this? What am I missing ?
 
mach 1 is the speed of sound to my knowledge which is 343m/s. You absolutely cannot have air flowing that fast through a port. It physically won't move that fast due to the resistance created by the port walls. The sub will just act sealed. Plus, have you ever heard of a plane that breaks the sound barrier. That's not a sound you'd want to come close to in a subwoofer. termpro may just have something they call 1 that refers to the limit they recommend, but it is certainly not 343m/s.

Without power modeling, you have just gotten lucky with your method of looking at port velocity. That's really all I can say.
found this, so how many M/sec is .16 sped of sound ?

(From the free winISD Beta program)

" The mach rating determines the "breathe-ability" of the port(s). If you go with too few or too narrow ports, the box will whistle like Bing Crosby at Christmas time! The reason for this is that there is too much air trying to travel down too thin a pipe (like a flute).

Changing the number or and/or the diameter of the ports of the box also changes the mach rating of those ports. You should keep the mach rating below 0.16 in order to avoid whistling.

NOTE: The MACH rating in this example shows: Qes/Pe!. This is because the Thiele/Small specs "Pe" and/or "Qes" are missing. To remedy this, these two specs must be obtained from the manufacturer and entered into the driver data. If you can only get the power rating (125W in this case), then assume Qms = 4, and calculate Qes as follows:

Qes = 1/[(1/Qts) - (1/Qms)]

Plug in the Power rating into Pe, and the calculated Qes into Qes. The mach rating will work. It'll get you in the ball park, and it's better than nothing.

If your mach rating is too high, the only way to lower it is to either increase the number of or the diameter of the ports. Of course, here comes that dreaded "trade-off" word again! If you make your port(s) bigger in diameter, they will be able to pass more air with less effort. However, in doing this, you have lowered the "loading" of the speaker(s) in the box. This, of course, changes the -3dB point of the box. The only way to get back to your desired -3dB point is to "load" the speaker(s) again. How? Well, you gotta make the new, larger port(s) longer! This forces the speaker(s) in the box to work harder to move the air into and out of the box, and brings your -3dB back to where it should be. THE END OF YOUR PORT(S) MUST BE AT LEAST 3 INCHES AWAY FROM ANY INTERIOR WALL OF YOUR ENCLOSURE."
-end quote
 
mach 1 is the speed of sound to my knowledge which is 343m/s. You absolutely cannot have air flowing that fast through a port. It physically won't move that fast due to the resistance created by the port walls. The sub will just act sealed. Plus, have you ever heard of a plane that breaks the sound barrier. That's not a sound you'd want to come close to in a subwoofer. termpro may just have something they call 1 that refers to the limit they recommend, but it is certainly not 343m/s.

Without power modeling, you have just gotten lucky with your method of looking at port velocity. That's really all I can say.
.16%343=0.000466472303207

It must mean something else and 1 being a rating
 
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