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Discussion Starter · #1 ·
So I ordered the ED subs. What should I do with them? Box size is not a factor, building them might be (for pvc ports). I've made 3 slot ported boxes for car audio before but have not worked with PVC. It'll be powered with 500w/ each.
I was thinking to down fire them in a 6^3ft sealed box (6 minus displacement of subs and bracing). Would that be a bad idea? Its main purpose if for HT use, but nothing Serious.
 

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I modelled this sub a while ago and each sub in 6 cubic feet tuned to 18 hz would work for HT. Port diameter is 6 inch and length would be about 34 inches long. With 400 watts input, cone excursion is reached at 24 and 16 hz. Would you be building boxes or tube subs?
 

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Discussion Starter · #3 ·
I would be building a box/ table end (that's what I've seen people call it). But wow if its 6^3ft each, then that'll mean 12^3 for two, if thats the case i rather keep it sealed. That's the LLT idea..I've also been trying to find out what happens if a sealed box is too big, but I can't find that answer. Would it lessen output, would it hit lower...say in the 25hz...
 

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6 cubic feet sealed for 2 subs will work but you'll get less output in the 20 hz range compared to a ported box. They'll handle 600 watts with Xmax being reached around 18 hz and spl being around 106 db at 20 hz, plus the effects of room gain.
Doubling the size to 12 cubic feet, modelling shows less power to reach Xmax with minimal effect of spl and low end output, compared to 6 cubic feet.
 

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I've also been trying to find out what happens if a sealed box is too big, but I can't find that answer. Would it lessen output, would it hit lower...say in the 25hz...
Sealed is about isolating the back wave from the front and using a controlled amount of air volume to make it behave a certain way. It can't be too big, as in the case of an IB where essentially there is no box.. For the most part, increasing size will cause total output to be a bit less, but increase output a bit more in the low end. The bigger the box, the flatter the curve [FR]. Increased size makes it more efficient - requires less power. This is why it is important to pay close attention to excursion as box size is increased. The driver can exceed xmax and sustain damage if volume / power combination is too much.

The volume of air [Vb] is a compressible spring. When air is compressed, it creates heat. The smaller the volume, the more heat - can't be dissipated as fast. Stuffing makes the driver think it's in a bigger box and also absorbs, dissipates, regulates heat. You should also know that as box size increases, so does F3 - the -3db point. Sealed has more very low end output than any other alignment, but in the range where most get little benefit - certainly below the range of human hearing and it takes huge amounts of power or multiple drivers to make that felt.

Driver parameters [Fs, Qes, Qts and Vas] also play heavily into size [Vb] - how big is big and how big is too much. For example, in an IB [very large sealed] Qts becomes critical in shaping the FR. Most often, IB specific drives are going to have a Qts in the .6-.7 range...as this becomes the system Q [Qtc]. IB's typically use 4 or more drives to increase output [SPL]. The same can be done with smaller sealed boxes as well. Typically, output will rise by 3db for every driver added in the same location - ie; the same box.

So, bottom line is that system Q [Qtc] - a direct result of the volume. Smaller is tighter, louder, punchier sounding. Larger is deeper, lower, looser and more natural. Control Vb to shape the sound, increase or decrease efficiency and prevent over excursion.
 

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Great post Warmon!
 

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Discussion Starter · #8 ·
so I finished the box, outer dimensions are 15x30x30. It sounds kinda weird to me...maybe i'm more use to car audio subs. But there's not much air coming out from the port. I used a 4" PVC port found at home depot, its 24" long. Compared to my kicker L715" 4^3ft box at 40hz there's a lot more air coming out at the slot port. Maybe because the back walls are used as the port? I'll take pictures of the box and see what you guys say...interestingly enough, it does play kinda loud and low, but it's not what i wanted from it. I like tight sounding bass, and this box is making bass kinda of hummy
 

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so I finished the box, outer dimensions are 15x30x30. It sounds kinda weird to me...maybe i'm more use to car audio subs. But there's not much air coming out from the port. I used a 4" PVC port found at home depot, its 24" long. Compared to my kicker L715" 4^3ft box at 40hz there's a lot more air coming out at the slot port.
Less air from port is indeed a good thing. It looks like tune is lower than your previous sub.
it does play kinda loud and low, but it's not what i wanted from it. I like tight sounding bass, and this box is making bass kinda of hummy
Loud and low isnormally what you want, but it looks tome you're used to car bass :rofl2: Loud and low does not mean it is not tight, but it is capable of reproducing sounds your older sub can't ;)

You need to listen to a track you know very well for instance and see the improvement down low....Once you're used to deep bass, you can'y go back :T

What's the tune?
 

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Well looks like a good end table sized sub - but where are the finished pictures? You said you carpeted it - no? =D I'm sure your enjoying it too much to be bothered with talking about it. ;)

Have you experienced any major chuffing with that small port? I mean with two 12"s with a very decent amount of throw I can easily see that little 4" port getting overloaded.
 

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I was wondering that same thing and at 500w/sub, chuffing could be a high possibility. However, with as low as it's tuned and the port facing away from you, at moderate listening levels it might not be problematic with music. During movies may be the only time...and if so, could be reduced with some huge flares.

I would like to see finished pics though :)
 

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Discussion Starter · #15 ·
Can you explain what "chuffing" is...I'm more use to car audio..have a kicker 15"L7 fitted into my little trunk. But I'll explain how I like the sub. With music, I hear nothing wrong with it...With movies, sometimes its annoying when the sub plays during vocals. Like those very small details where I wouldn't want to hear the sub, I hear the sub with like a little hum..Its hard to explain...its just I wouldn't want to hear the sub, but I hear it.

Here's the setup. Sub is placed to the left of the last picture. I'm thinking about moving it to the right, (next to the TV). But since there's people under me, I don't want them complaining. LOL





 

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Chuffing is port noise. Noise from the turbulence and compression of air flowing in and out of the port.

Humming I am not sure about. There are a couple bits that can be wrong:
1) mechanical noise from the spider or vc rubbing somewhere or the tinsel leads smacking things.
2) harmonic distortion. A good test for this is to play a sine wave of 20Hz. Crank up the volume slowly. You should not hear anything. At some point you will probably hear chuffing. Another thing you might hear is 40Hz or 80Hz. If your drivers are good you should be able to get pretty high SPL before you "hear" any note.
 

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Can you explain what "chuffing" is...I'm more use to car audio..have a kicker 15"L7 fitted into my little trunk. But I'll explain how I like the sub. With music, I hear nothing wrong with it...With movies, sometimes its annoying when the sub plays during vocals. Like those very small details where I wouldn't want to hear the sub, I hear the sub with like a little hum..Its hard to explain...its just I wouldn't want to hear the sub, but I hear it.
For vocals, lower your XO point
For the hum...you'll have to diagnose it. Is it a 60hz constant low level HMMMMM whenever the sub is on? If so it's either coming from the amp due to grounding noise, or from the signal. There are a few steps to take to track down the noise, first is unplug your LFE input wire. If the hum stops, it's from your input and you then have to track it down one step at a time all the way to the source ground if you have to.
 

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Another thing that can be contributing to muddy vocals is poor EQ. I.e. your sub is at a much higher level then the mains. As looneybomber said lowering the XO may help the symptom. But to fix the whole problem you need to eq the sub and get the levels right. RoomEQ Wizzard can help. But if you don't have the equipment you can do it roughly using an SQL meeter and some sine waves. At least this will give you a rough idea.
 
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