Siphon speed does stack, but the most you'll be able to stack is 3, and only for a little while. perma hasten isn't possible, it's not a 100% buff.
Defiant 50's
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@Miss Chief
25% attack rate buff and debuff, 3 stackable but most of the time you'll run with 2, Permahasten not possible.
DON'T eat muffins while I'm developing you.
Pants! Turkey Magnates! A man in a box! Rogue AI! Come one, come all, to arc ID 10107 - It's [i]'Not as long as some other arcs'[/i]!
Is perma hasten possible with SB + stacked siphon speed?
Might be able to do it with 2xSB, seems more likely. With stacked siphon speed, of course.
I'd say SB and 3 siphon speeds should bring it pretty close to perma, and 2*SB definitely should make it perma.
I'm sure I read somewhere that a SR scrapper, running hasten and quickness would need 20 Speed boosts to make hasten perma.
Defiant 50's
Many and varied!
@Miss Chief
[ QUOTE ]
I'm sure I read somewhere that a SR scrapper, running hasten and quickness would need 20 Speed boosts to make hasten perma.
[/ QUOTE ]You read wrong.
Hasten was perma with 6 SO's, which was around 200% recharge buff. AFAIK, both siphon speed are either 20, or 25%, so combined with 3 RechRdx in hasten you'd need 4 or 5 siphons/speed boosts to make hasten perma.
I remember doing a test... when I was stacking 3 x siphon speeds and a controller was throwing speed boost on me Hasten was perma (as far as I remember anyway, we did the test just after ED hit).
It's not too far from perma with 3-stacked Siphon Speed but it's really hard to keep Siphon Speed stacked like that.
Well... if I might add my comment as a hardcore kinetic: 
If you have hasten and syphon speed 3-slotted with recharge reductions and keep hitting things it´s not that hard to keep it stacked like that (leaving hasten with a nearly nonexistent hard-to-notice downtime).
But the necessary playstyle will eat away at you sanity quickly. You will hate any pause, be it because of your (or your teammates´) natural needs for food, drink or other things, just because it takes some time to "get going" again. You will find yourself quite often being the first to charge a new enemy spawn (with or without elite-boss/AV) if your tank/brute (depending on your religion) is not accustomed to not resting anytime. And you will have a one-attack-attack-chain.
In short: It´s absolutely sick.
Well. I guess I have worked enough for today. Will be on with one of my kinetics shortly. 
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
[ QUOTE ]
Well... if I might add my comment as a hardcore kinetic:
If you have hasten and syphon speed 3-slotted with recharge reductions and keep hitting things it´s not that hard to keep it stacked like that (leaving hasten with a nearly nonexistent hard-to-notice downtime).
But the necessary playstyle will eat away at you sanity quickly. You will hate any pause, be it because of your (or your teammates´) natural needs for food, drink or other things, just because it takes some time to "get going" again. You will find yourself quite often being the first to charge a new enemy spawn (with or without elite-boss/AV) if your tank/brute (depending on your religion) is not accustomed to not resting anytime. And you will have a one-attack-attack-chain.
In short: It´s absolutely sick.
Well. I guess I have worked enough for today. Will be on with one of my kinetics shortly.
[/ QUOTE ]
Kinetics FTW 
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theRegulator Empathy/Energy/Soul Defender
Total Inertia Ice Blast/Kinetics/Psy Corruptor
Total Inferno Ice Blast/Thermal/Leviathan Corruptor
[ QUOTE ]
I remember doing a test... when I was stacking 3 x siphon speeds and a controller was throwing speed boost on me Hasten was perma (as far as I remember anyway, we did the test just after ED hit).
[/ QUOTE ]
Almost - I was playing the other day with another Kin defender and with 3 Siphon Speeds and Speed Boost I had about 10 seconds downtime on Hasten.
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[ QUOTE ]
You will hate any pause, be it because of your (or your teammates´) natural needs for food, drink or other things
[/ QUOTE ][ QUOTE ]
You will find yourself quite often being the first to charge a new enemy spawn
[/ QUOTE ][ QUOTE ]
And you will have a one-attack-attack-chain.
[/ QUOTE ]
Kudos, Sin, those are three of the truest statements about Kin I've read.
DON'T eat muffins while I'm developing you.
Pants! Turkey Magnates! A man in a box! Rogue AI! Come one, come all, to arc ID 10107 - It's [i]'Not as long as some other arcs'[/i]!
Just tested:
Kinetics defender: Siphonspeed 3xSO recharge, Hasten 3xSO recharge.
Got Hasten down to 30 seconds (therabouts) downtime.
This isnt stopwatch perfect, but was fairly accurate.
Which is pretty good - Hasten is up 2 mins, down 30 seconds. So whats that, about 80% of the time hasten is up?.
Had neurtino bolt recharged before I was through the animation . Not that a like neutrino bolt, but given its very short activation time, felt pretty amazing.
What is the recharge rdx rate of Siphon Speed for Kinetics defenders?
Does it stack?
I'm sitting here attempting to achieve perma Hasten, and finding myself 20 seconds short of the next hasten. If Siphon Speed rech rdx is 100% like I beleive, then it can't stack. Anyone got numbers/facts about it?