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conig
Dodge Dakota
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5/07/2003
10:54:15
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 Subject: downfireing/simulateddownfireingworthit?
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I wrote a post on this last night but can't seem to find it today.
anyway what are the benefits of downfireing a sub? is it sound quality or spl? what I would rather due would be to have a 1/2inch piece of plexiglass or 1/4 glass, to somewhat simulate downfireing and still alow the sub to be seen.
I built an isobaric enclosure 1 cuft slot loaded because I thought my amp couldn't handle a 2ohm load. I tried it with one 12 port plugged up with towels as the port is not tuned right for 1 12 and I will probable get port huffing. I have since started closeing off the port for 1cu ft sealed. I will be adding some polly fill, but any suggestions to increase spl would greatly be appreciated.
I may just biuld a 2cuft ported enclosure but would like to see if theres any options for what I have now.
also there is no place to get my rta tested in my area so I can't tune to resonancy frequency unless anyone can give me a rough idea.
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JMII
Dodge Dakota
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5/07/2003
15:41:47
|  RE: downfireing/simulateddownfireingworthit?
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wow your all over the road... way too many things at once!
Downfiring the subs (slot-loading) causes the bass waves to move slower thus it's mostly a SQ thing, but can sometimes increase the SPL slightly too. I'd down fire them at a piece of 3/4" MDF, anything else would rattle badly I'm afraid. If you still want to see the sub put a mirror over the MDF. If you do that, then do it at a slight angle for a better effect with the mirror.
- Porting increases the SPL (if the subs are designed for it)
- Adding more power increases the SPL
- Adding more surface area increases the SPL (larger subs)
- Adding more subs increases the SPL
Isobaric enclosure are not effecient designs, they only look cool.
What does the manufacture of the sub recommend: sealed or ported? You could be wasting your time building the wrong box for the wrong kind of speakers. Just sticking ports into various boxe sizes is a good way to make swiss cheese, but not bass.
I do not build ported enclosures because of the complex nature of calculating the res freq of the ports. There is software that will do it, but if the box is not built perfectly it will not matter. Often during construction you have to make mirror changes which might effect the end result in ways you can't predict.
- John
http://home.mindspring.com/~jntmoore/truck/home.html
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conig
Dodge Dakota
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5/07/2003
17:48:12
| RE: downfireing/simulateddownfireingworthit?
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xtant recommends 1.0cuft sealed or 2.0cuft ported the ported is only 2db's higher. I have built a ported box for these subs before they were a little bit more "peakey" then I would have liked but they (2at thiat time no backseat) beat hard as hell. my eyelids would shake and vibrate, which i liked but sq did suffer not as bad as I thought it would.
I have almost a good comprimise right now just need a tad bit more. I've been told by another user on this forum the qts suggests sealed, but when I did equations myself I got they would be best ported.
xtant is more about clarity so I would assume sealed is what they would want. I have some mdf laying around so I'll try makeing a baffle with that. the other thing I just thought about would be cutting the logo into the mdf that could be seen through and then putting lexan across that.
how far off should the slot loading be? I could only find one post on the net on some random forum were someon stated they got 5db's from doing this but can find no other info on slot loading or down fireing. any ideas were to look.
sorry for the long reply. I'm basically trying to use one of my subs and get the most I can from it. I've built plenty of boxes so I can build one ported just never had slot loaded before so I'd like to try it.
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JMII
Dodge Dakota
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5/07/2003
19:24:52
|  RE: downfireing/simulateddownfireingworthit?
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Not sure about the distance... I've always used like 3" since most down-firing home theather subs (like my own Infinity 10") is about that much.
I just know it works because I built a truck box once for an xtra cab Mazda and it did not hit that hard, so we gambled, flipped the box over and built supports to raise it up (again about 3 or 4") and let it fire at the floor instead of the roof. Then it slammed nicely. So, I built my competition system in my Civic hatchback with the subs were very close to the rear glass and fired 'em backwards on purpose to get the same effect. Once again it made a difference that was noticeable. Now how many dBs? ...I have no idea.
BTW I just want to make sure we are not confusing our terms here - slot loading is just having a sub's output fire thru a "slot" as described above with the Mazda box. However the box itself could be sealed or ported. So you could do a slot-loaded ported enclosure if your really adventersome :) My guess is that would thump big time.
Sounds like you know what your doing anyway. As stated above I do not mess with ported (or vented) designs so your on your own there - good luck.
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conig
Dodge Dakota
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5/07/2003
22:55:36
| RE: downfireing/simulateddownfireingworthit?
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appretiate the help man all you have stated was what I was thinking. in my old svt contour I had both subs sealed faceing forward sounded alright I then fired them backwards and they got so much louder tried turning boxes(ive had 3 sealed one slot ported) in my truck around backwards upwards forwards to backwards wasn't that different. so i wasn't sure it was worth it.
since I already have a sealed box built i'll try it with this one first as I'm out of mdf. when this isn't loud enough for me I'll try it the other way around.
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conig
Dodge Dakota
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5/09/2003
10:19:23
| RE: downfireing/simulateddownfireingworthit?
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tried it slot loaded wasn't all that inmpressed. so I'm gonna build a box 2.07 ported I have the port length figured out for a 5inch port, however I want to use a square/rectangular port.
I'n opinion what would be better a port 6x3.27 square or a slot running up the whole box 16.5x1.19 hey box have almost identical surface area.
or should I just use pvc the square should be cleaner sounding. in theory.
both of these are based on 3.14r2 which with my calculations comes out to 19.625for area.
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