Need more subs- 2 more si18 or 4 - 8 infinity 1262? - Page 3 - AVS Forum | Home Theater Discussions And Reviews
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post #61 of 74 Old 10-23-2014, 07:47 AM - Thread Starter
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Originally Posted by Mfusick View Post
This was the one I was thinking in emails - But with the SI 15" BLEM drivers.

8 15's with 500 rms each?
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post #62 of 74 Old 10-25-2014, 02:29 PM
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Originally Posted by Pain Infliction View Post
Four Si18's over the eight 1260w's any day!

To answer how the 8 1260w's are near field.....they are really awesome! I have 8 of them behind my seats powered by two inuke 3000dsp amps.
Pain,
Why do you say 4 SI18's over 8 1260's? Looks like you chose the 1260's, was there a reason? Size, cost? Btw, great looking theater!

I am trying to decide whether to go with 4 1260's or 2 SI18's up front with my UM18's. I believe I am doing 4-1260's for my nearfield.
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post #63 of 74 Old 10-25-2014, 02:37 PM
 
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The only problem with infinity is extension because of the excursion. They play plenty loud as long as you keep it 20hz and up. The SI will take a lower tune if you wanted something like a 15 or 16hz tune.
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post #64 of 74 Old 10-25-2014, 10:50 PM
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Thanks @Mfusick ! Such tough decisions. I think I am leaning towards the 1260's so I can do smaller cubes just in case I decide to move them to another room. I have 2 UM18s tuned to 16Hz for the HT room and started on boxes today for 2 - dual 1260's for nearfield but I am thinking I might as well go ahead and build 4 more cubes to add across the front with the UM18's while I am at it! Why not right?
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post #65 of 74 Old 10-26-2014, 12:20 AM
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"The only problem with infinity is extension because of the excursion. They play plenty loud as long as you keep it 20hz and up. The SI will take a lower tune if you wanted something like a 15 or 16hz tune."


why can't the infinity be tuned to 16hz???


8 of them for ~$500 in big cabs tuned to 16hz look to produce 123db+ before room gain and that is at 13mm which is overhang only.

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post #66 of 74 Old 10-26-2014, 05:46 AM
 
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Big cabs, less flat. If cab is that big might as well load it with an 18".
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post #67 of 74 Old 10-28-2014, 07:23 AM
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Quote:
Originally Posted by Bud Heavy View Post
Pain,
Why do you say 4 SI18's over 8 1260's? Looks like you chose the 1260's, was there a reason? Size, cost? Btw, great looking theater!

I am trying to decide whether to go with 4 1260's or 2 SI18's up front with my UM18's. I believe I am doing 4-1260's for my nearfield.
I went with the 1260's because of the size. I cant really fit 18's behind my seats and if I could I would have for sure.

I would get the si18's up front if I was in your situation.

The Thompson Theater

RIP William Alexander
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post #68 of 74 Old 10-28-2014, 09:36 AM
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Originally Posted by LTD02 View Post
"The only problem with infinity is extension because of the excursion. They play plenty loud as long as you keep it 20hz and up. The SI will take a lower tune if you wanted something like a 15 or 16hz tune."


why can't the infinity be tuned to 16hz???


8 of them for ~$500 in big cabs tuned to 16hz look to produce 123db+ before room gain and that is at 13mm which is overhang only.
@LTD02 can you explain the overhang comment, i would like to understand. thanks

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post #69 of 74 Old 10-29-2014, 12:07 AM
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what is xmax?


in a typical subwoofer, the voice coil is taller than the gap created between the pole piece and the top plate.
the distance that the coil "overhangs" the gap is called the "overhang". :-)
when the sub is powered with a signal and starts to move forward, the overhang descreases until the coil is flush with the gap. that is where some companies specify the "xmax"--the amount of the overhang.
however, at that point, the entire gap still has coil in it, so there is plenty of room to "keep it moving further". as the coil continues to move forward, it will eventually leave the gap altogether. when there is no longer any coil in the gap, there is no magnetic interaction, so it is completely out of force at that point. force = 0% at that point.
somewhere in the middle, usually when the coil is about 1/3 of the way into the gap, the force = about 70% of the level where the coil is completely filling the gap. based on distortion measurements that point also correlates to about 10% distortion. so that point is about where xmax is specified for many drivers.


example: let's assume the coil is 20mm long and the gap is 10 mm high. 20-10 = 10mm, 10mm/2 (because of overhang on the top and the bottom) = 5mm. that is the amount by which the coil will overhang the gap on each side. so using the overhang method, xmax = 5mm.
however once the coil moves 5 mm in either direction, it is still in the gap. so it can keep going about 1/3 of the gap before it starts to decline in force and increase in distortion. 30% of 10mm is 3mm, so in addition to the 5mm it can go another 3mm for a total of 8mm xmax.
so one company could say the driver has xmax = 5mm and another could call the same driver xmax = 8mm. however, they could both be describing the same driver. so it is important to know which method is being used to describe the xmax when making comparisons.




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Last edited by LTD02; 10-29-2014 at 10:30 AM.
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post #70 of 74 Old 10-29-2014, 12:12 AM
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"Big cabs, less flat. If cab is that big might as well load it with an 18"."


not sure what flat has to do with anything, but here is an 18" (Dayton HO) loaded in a 5 cubic footer tuned to 16hz and the 1262 in the same cab. the 1262 has much less rolloff.


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post #71 of 74 Old 10-29-2014, 05:40 AM
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LTD ,does the 18"HO example above lose so much SPL because of the Low Tune,.. compared to the MartyCube Design ??
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post #72 of 74 Old 10-29-2014, 05:41 AM
 
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I was talking about the 1260 vs SI. If you are going that big on the cab might as well throw an 18" in there.
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post #73 of 74 Old 10-29-2014, 09:44 AM
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Quote:
Originally Posted by LTD02 View Post
what is xmax?


in a typical subwoofer, the voice coil is taller than the gap created between the pole piece and the top plate.
the distance that the coil "overhangs" the gap is called the "overhang". :-)
when the sub is powered with a signal and starts to move forward, the overhang descreases until the coil is flush with the gap. that is where some companies specify the "xmax"--the amount of the overhang.
however, at that point, the entire gap still has coil in it, so there is plenty of room to "keep it moving further". as the coil continues to move forward, it will eventually leave the gap altogether. when there is no longer any coil in the gap, there is no magnetic interaction, so it is completely out of force at that point. force = 0% at that point.
somewhere in the middle, usually when the coil is about 1/3 of the way into the gap, the force = about 70% of the level where the coil is completely filling the gap. based on distortion measurements that point also correlates to about 10% distortion. so that point is about where xmax is specified for many drivers.


example: let's assume the coil is 20mm long and the gap is 10 mm high. 20-10 = 5mm. that is the amount by which the coil will overhang the gap on each side. so using the overhang method, xmax = 5mm.
however once the coil moves 5 mm in either direction, it is still in the gap. so it can keep going about 1/3 of the gap before it starts to decline in force and increase in distortion. 30% of 10mm is 3mm, so in addition to the 5mm it can go another 3mm for a total of 8mm xmax.
so one company could say the driver has xmax = 5mm and another could call the same driver xmax = 8mm. however, they could both be describing the same driver. so it is important to know which method is being used to describe the xmax when making comparisons.




Thank you for that, I thought I understood xmax, but the way you explained it makes it much more cleared now.

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post #74 of 74 Old 10-29-2014, 10:40 AM
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"LTD ,does the 18"HO example above lose so much SPL because of the Low Tune,.. compared to the MartyCube Design ?? "


generally, the lower the tune and the smaller the cab, the less efficient it will be at making spl. at some point though, there is a golden matchup between xmax, power handling, and tuning. for the Dayton 18/si18ht that is around 10 cubic feet, tuned to 17hz and powered by about 1100 watts as that takes the driver to its usable excursion limit. that was more or less the original martysub concept in a simple to construct package. going smaller and/or tuning it differently can give a little more or less spl in different regions.


mf, that example was simply to show that the 1262 driver does just fine in a cab tuned to 16hz. (fwiw, the si18 driver models the same as the Dayton ho18). I didn't mean to just call you mf, but that is your callsign.
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