purplesyrup
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Posts posted by purplesyrup
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Awesome info here man, thanks for sharing.
No prob,
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Wonder why it's max velocity is at its tuning frequency, where that is where it loses a lot of power.
Does that make sense? Lol
I'm not really sure, anything else I find out I will contribute to this thread. i'm just glad I finally figured out some accurate and useful info on the subject because it is a vital part of how the sub will perform and sound.
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Ok something useful, here's a vent mach calculator. http://portsgalore.stefanhinote.com/?do=ventmach
Its amazing how difficult it is to search this subject on the net. I had to search and word this topic about 20 different ways to get enough info to fully understand., I tried to piece it all together the best I could to pass on the info in that topic above. This is a pretty importent aspect of box building that I often never see anyone mention or worry about.
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Fizzy, I will try to find a diagram, I found one somewhere, also winisd calculates vent mach when designing a vented enclosure.
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"is at"
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The vent mach's maximum velocity is at the tuned frequency,
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I'll show the box specs when its all done, the first fun fact is its not a box. I'll have step by step photos and YouTube videos of what I've been doing as soon as my dd sub is here, i'm at a hold on the project until the sub is in my hands, its 50% done. the 9512 is awaiting they're newly updated parts, but they said it will be shipped out in 4 Weeks.
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I figured it out. Having a vent mach of 0.02 will slow the subs sound waves to the point that it will be a disadvantage, the first con of the vent mach being that low is the loss of back pressure, the sub looses its ability to load, which can make the sub have a weaker power handling because its getting close to having a free air experience, the next con is that the slowed down sound waves come out so slow that sounds are noticeably delayed to where you are still hearing one sound when the sub has already started playing another blurring the different tones together due to the slow leftover soundwaves murdering the sq quality I was looking for.
I'm sure that a one tone burp box that is the perfect size for the sub through trial and error may benefit from such a low vent mach, but for music it would sound sloppy.
.04-.05 is ideal for spl/sq, (plays music.accurately while allowing the sub enough back pressure to get very loud. And then up to .10 for sq, having a vent mach this high limits the subs from its ability to release its full SPL potential because the vents airflow is restricted.
Hope this helps some one in the future.
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its the rate of speed that air flows in and out of the box. having too high of a vent mach will create horrible port noise like 16% and up, whch means 16% of the speed of sound from what i've found out, so really the difference between .04 and .02 is only a 2% difference, but small numbers can still have a big impact which is what im trying to find the answer to.
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I searched the forum, and the web, on many different occasions trying to get a complete explanation on vent mach. Ive built quite a few SPL/sq boxes over the years, I've always kept the vent mach around .04 to .05, its always worked out and performed how I expected.
I am in the progress of a specific design that is throwing me some curves, you will see why in about a month, and Anyways, I have to have about 40 sq inches of port. One port that I have figured out has a vent mach of .04 which I know will work out fine, but then I was also looking at possibly using 2 5" ports which keeps me right at almost 40 SQ inches but reduces the vent mach to .02. My question is, will it be an advantage or a disadvantage to go to .02? how will it affect the performance, will it make the sub capable of more output, or cause less output, will it go from sounding great a .04 to sounding like shit at .02, I have searched and searched the web, I have never found a single source elaborating pro's and con's explaining vent mach.
Any help on this subject would be greatly appreciated, I like to experiment, but have to get it right the first time on this project. My Goal with this design is also an SPL/SQ style box, sounds great with music, with the ability to burp a high number tone.
Sub is DD9512, will be have 2000w RMS of real amp power.
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yeah how could i seal it like with tape or what ?
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the most simple answer I can come up with, without looking up the specs on your subs is. its very likely that 1 cubic foot per sub is way way to small for those subs to function properly. it is very likely you need 1.5-2.00 per sub ported, going that small will limit the drivers output all together. you would most likely be better off selling 4 of them and building an 8 cuft box for 4 of them
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Nice work, that SPL at the low HZ is not common at all, congrats
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ditto on the ported box
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the vid says it doesn't exist?
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video has bone thugs music with it, which has some offensive language for some viewers
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Sitting on diablo 19"s, loved the look on those wheels
then went to 20"s, but these got these one off Greed lust 23"
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Doing a 20hz cycle, I've had this sub since 04, the only issue was having to repair the surround in 2 places, I need to get a new one put on it, its ported by the eclipse 7232d. I'm going to retire this stuff and do a dd9512 on am m4.
Securing box to a false floor
in Subwoofers / Enclosures
Posted
One way is to weld bolts to the floor pointing up, cut little slits for carpet so they can poke through, carfully measure how you spaced them, drill holes in the bottom of the box matching the bolts welded to the floor, take sub out, seal holes and bolt box down from inside the box, then put the sub back in. the box is officailly one with the car. Another note, some insurance companies don't cover anything not "bolted" to the car, this solves that problem. from this point, use allen head screws to mount the sub, or something else that the crackhead going around stealing stereos wouldn't have and bada-bing. Throw an extra curve by using 2 or 3 different heads on the screws, so even the most prepaired thief will be out of luck. Welded bolts will also not allow any sliding .