marcin93
hispls
5,000+ posts
CarAudio.com Veteran
increasing radiating area means you need more length for the same freq tuning.
Moble Enclosurs
10+ year member
Box Designer/Builder
Because by adding another port of the same size, you increase port area. Increasing port area increases tuning frequency. So to control the tuning frequency to the desired resonance as before, longer ports are needed. So, if you decrease the area of the aeroports (to something less than 4" in your case) and using two of them, you can keep the length around the same. You just have to figure what area will work (which will be around half of the original port area) for the two to keep the same length. Hope that helps!
Moble Enclosurs
10+ year member
Box Designer/Builder
Need driver specs first: fs, qts, vas, xmax, max power rating, resistance, etc. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Moble Enclosurs
10+ year member
Box Designer/Builder
Now, are you saying you want to use a single 4" aero for (4) sa8s? I just want to make sure that is correct......if so, then it is highly likely you will have undesirable noise at high output levels, yes. I would recommend no less than (1) 4" port for each. It's also dependent on the sound that you want to achieve as well. But to keep it simple, 1 for each driver is the min I would do. You might get other recommendations as well, just so you are aware.
Moble Enclosurs
10+ year member
Box Designer/Builder
My personal opinoin......go with slot ports. My professional opinion.....let me design you a new box for less than $20 for the blueprints. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Moble Enclosurs
10+ year member
Box Designer/Builder
But let me add to that so your not left in the dust.........As far as the slot ports, I do recommend those, but if you already have the box built (I hope not), then you do not have much of a choice but to deal with a higher tuning frequency. Some would recommend using bends in the aeroports. That, to me, is too much work for what you get out of it. So, you do not have many options if the box is already built. But if you are just putting things together, again, I highly recommend using one of my designs. I can have someone do the build as well if you like. Just let me know. Other than that, without actually doing some calculating further, I cannot say too much about what should be done vs what can be done. Slot ports, are very versatile. If you have the ability to utilize them, do it.
OP
marcin93
10+ year member
Senior VIP Member
- Thread Starter
- #12
Hey man, thanks I just notice that ive heard of you before hahah. I live pretty close to you and I have seen some nice work done by you. This box is just a temporary that I decided to build myself, at first i thought the aero ports where a great idea but i guess not :/ I will contact you whenever I will be making a better box, thanks for the help!
Moble Enclosurs
10+ year member
Box Designer/Builder
You are very welcome. I will be glad to help you, and even if you do not purchase a design, ask me questions if you have em. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Thank you for your support!
audioholic
5,000+ posts
not a moderator
The key to understanding tuning versus port area is to understand that its all based on resistance.
Imagine blowing through a straw. Now blow through a straw that's twice as big around. Its easier to blow through it, less resistance. You must increase the length of that bigger straw before it provide the same resistance when you blow through it. Makes sense right? In a vented enclosure, the subwoofer is blowing through a straw. How much resistance there is to blowing through that straw affects enclosure tuning (along with the enclosure's internal volume).
Port area is important because it affects air velocity inside the port. The more air the sub can displace, either through cone area or excursion, the more air is traveling through the straw. So the bigger the cone, and/or the greater the excursion you expect to see (based on wattage, efficiency, enclosure size, etc), the more port area you need to have to keep air velocity inside it low enough to not create its own noise.
One last comment, lets remember that a round port with flared ends, while still an effective port mechanism, is technically not an aeroport. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
Imagine blowing through a straw. Now blow through a straw that's twice as big around. Its easier to blow through it, less resistance. You must increase the length of that bigger straw before it provide the same resistance when you blow through it. Makes sense right? In a vented enclosure, the subwoofer is blowing through a straw. How much resistance there is to blowing through that straw affects enclosure tuning (along with the enclosure's internal volume).
Port area is important because it affects air velocity inside the port. The more air the sub can displace, either through cone area or excursion, the more air is traveling through the straw. So the bigger the cone, and/or the greater the excursion you expect to see (based on wattage, efficiency, enclosure size, etc), the more port area you need to have to keep air velocity inside it low enough to not create its own noise.
One last comment, lets remember that a round port with flared ends, while still an effective port mechanism, is technically not an aeroport. //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif
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