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Basic question about impedance and watts

I just bought a pair of Thiel cs3.5's and am now looking for an amp. If the impedance is 4Ohms (i think this is the correct value, i didn't get the owners manual) and the recommended power is 50-150 watts (once again, a guess), how much power should the amp have? Do i need an amp that is 50-150 watts at 8ohms, or do i need an amp that is 25-75 watts at 8Ohms (assuming the amps watts double as the impedance halves)?
I guess the reason i had no luck searching for this is because its so basic.
if anyone knows the specs for these speakers, could you let me know? the owners manuals are available on Thiel's website for most, if not all, models except the 3.5s.
ketchup
plato
1,543 posts
 
Ketchup, it's really not that critical, but I'd err towards the higher power side if you have a large room and like to crank it up now and then. If I recall, I think the 3.5s use active bass equalization, and if that's the case, the bass will tend to drain a lot of power from the amp...

Did they come with any kind of electronics that plug into an AC outlet?
ketchup OP
692 posts
 
they did come with the bass EQ that you mentioned, and it does plug into AC. when i hook it up, a hum/static comes out of both speakers. i got a little bit of a deal because of this, hoping that thiel could fix the unit at a reasonable cost. i've only heard great things about their service, even if the 10 year warranty is up. we'll see!
anyway, i will call them tomorrow and ask about the eq and their power recommendtion.
marakanetz's avatar
marakanetz
5,473 posts
 
if amp produces 50W to 8Ohms than to 4 ohms it should double the output current or have a transformer's secondary coil stable to 4 Ohms.
Not neccessarily the wattage will double. The output power is rather dictated by peak capabilities of the output devices.
plato
1,543 posts
 
I've heard great things about Thiel's service as well. Good luck to you!
elevick
2,636 posts
 
1-you should get as much wattage as you can afford. Thiels will suck your amp dry. Don't get me wrong, I love thiels. However, anyone buying that level of speaker must match it with an equal amp.
2-a little help with wattage:
Doubling the power will get you a 3db gain
Every 10db will double the perceived listening volume
Therefore, a 94db speaker, 8ohms, will produce about 110db at 50watts. An 87db speaker will require about 150 watts to get the same volume.
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