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I'm looking at getting a new blender, basically the main things I want to be able to do with it are make curry pastes, ultra smooth restaurant quality purees and soups and grind small amounts of spices (I'm talking 1-2 teaspoons). This leaves me with two choices (possibly three of which I'll get too): the Blentec or the Vitamix. The former goes to 27,000rpm and the latter goes to 37,000. I'm wondering is there much of a difference once you get up to crazy speeds like that.

The other option is a Thermomix, which from my reading only hits speeds of 11,000rpm. Unfortunately, given that many Thermomix owners also sell them, it's pretty hard to get unbiased information online so I'm wondering if a speed drop of nearly two thirds will make a difference to the smoothness of my purees. From demos I've seen it think the Thermomix will do a better job with curry pastes and spice grinding as the blades nearly touch the base of the container unlike the other two units: my thinking being that however high the rpm of the Vitamix/Blentec, if the teaspoon of spices can't come into contact with the blades, it's useless.

I read the What to look for when purchasing a blender? question and found no mention of rpm so maybe it's a parameter that isn't very useful, if so then it would be nice to know that at least.

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I believe this answer is most accurately described as 'it's hard to find a blender that doesn't easily hit the maximum RPM you are likely to need, thus it is not important'. I only suspect, not know, so I'm just commenting. –  Myrddin Emrys Mar 30 '12 at 3:06
    
tiny spice grinder might be best bet (why stain up blender anyway?) –  Pat Sommer Apr 1 '12 at 2:15
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speed is nice but less so than a cool running motor that can go 30min -how restaurant kitchens get super smooth results (they also strain) –  Pat Sommer Apr 1 '12 at 2:17
    
Hi I have both and I am more happy with the Thermomix. Easier to clean and for me makes a smoother end - product. –  user10994 Jul 23 '12 at 6:43
    
Related question biology.stackexchange.com/questions/7483/… –  Martin Dürrmeier Mar 10 '13 at 18:24

4 Answers 4

RPM is an important factor. Although it blends the food more smoothly and much faster if it has a higher RPM, it also uses more power and does not blend harder objects as efficiently/well. Although it is important, it is definitely not the most important factor when choosing a blender. If you have the power supply, I definitely reccomend having a high RPM blender.

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Higher RPM is better for smoothies. If you've ever been to Jamba Juice or some other smoothie shop, that great texture mostly comes from the high RPM of the blender

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How do you know it is because of the RPM of their blenders and not, say, the torque of the professional blenders' motors or the sharpness of their blades? –  rumtscho Apr 3 '12 at 9:41
    
@rumtscho good point –  Geore Shg May 5 '12 at 4:01

I've used (not extensively) both a Vitamix 500 and a Thermomix TM31. I didn't know there was a difference in RPM, but I didn't notice too much difference in end-effect when both were turned up to full power. So I think it doesn't make much difference at those speeds anymore.

If you're having trouble milling spices though, it helps to heat them a while in the oven, to get rid of humidity and therefore make them more brittle.

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With a 1 inch (25mm) radius blade, the 27kRPM blender is pulling 20412 g units at the blade tips, while the 37kRPM unit pulls 38332 times gravity. msu.edu/~venkata1/… That later value is enough to make me wonder about the bearing lifetime of the unit. 25kRPM is enough for routing wood, it should be enough for pureeing foods. highlandwoodworking.com/variablespeedrouteradvice.aspx –  Wayfaring Stranger Apr 6 '12 at 13:40
    
Has the Thermomix longer blades than the Vitamix? So the speed (and gravity pull) of the Thermomix might be similar to the vitamix? –  Sam Jan 30 at 11:37
    
The thermomix is afaik stronger than the vitamix. What I know for certain is that it is built with very high quality and will last a long time. The motors are still manufactured in Germany. –  lifesayko Jul 24 at 19:21

RPM is an important factor when selecting a blender, but it's not necessarily the most critical. A blender with high RPM will blend faster, but it may not actually be indicative of how well the blender blends. In general, a powerful motor is more critical than one that simply spins fast. The higher the horsepower, the more consistently the blender will be able to run after continuous use. The torque of the blade/motor is also an important factor to consider. Higher torque means that the blade will be less likely to stop or slow upon impact with tough or dense items like banana slices or chunks of pineapple.

So while RPM is definitely important (you obviously don't want a blender that takes forever to blend up your food), it's not the only determining factor. Most professional-grade blenders will have much higher RPM ratings than standard residential blenders, but at the professional price level, horsepower and torque are just as important when making your decision.

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