Question:
OKay, I"ve got a 16Ohm Celestion speaker in my combo amp now and I have put my old Sheifield into a singe 12" cab. It is rated at 8Ohms.
My extra speaker jack in my amp is connected in Parrelel (half the ohms) however my amp can only be set for impedences of 4, 8, 16 ohms.
How would I connect my other speaker and my new one in my amp and set the impedence to 12ohms? Or am I doing the math wrong here.
The real question is, because I'm connencting in Parrelel, what would I set the impedence of the amp to be?
Thanks!
-Deren
Answer:
i have never heard of an amp or speaker using 12 ohms. i don't even think it's really done.
Answer:
Exactly my point!
If you have to "half" the impedences of the two speakers (connected in parrelel) then you'd have a 16ohm speaker plus a 8ohm speaker divided by two, which equils 12ohms.
This is why I'm asking the question, because I don't know if I'm doing this right. How to you connect two speakers in parrelel and set the impedence for the amp?
one speaker is 8ohms, the other is 16ohms.
Thanks,
-Deren
Answer:
Wait, you're trying to use an 8 ohm speaker with a 16 ohm? I could be wrong, but I think you usually try to use speakers of all the same ohmage. Of course, if I were you, I wouldnt trust my advice as certain and I'd wait till Tom comes in and once again puts everyone in their place. I am fairly certain there is no 12 ohms though.
Answer:
hmm I think your right.
I hope tom comes soon, perhaps there is a way to do this. Mabye I should just forget trying to run two different impedences.
-Deren
Answer:
See the site below for some info:
http://www.rexc.com/services/ohms.htm
I think your best bet is to match the impedances of your two speakers, maybe at 8 ohms each and set your amp to run at 4 ohms. Or, if you have two different resistance speakers, you may have to do the bi-amp setup. I agree that Tom is the expert.
Answer:
ok. so you have an 8 ohm and a 16 ohm speaker.
if you use the forumal to find impeadance (ohms) in parallel (its on the website listed above jfyi) is 1/((1/x)+(1/y)....ect)
so this means to find the impeadance for your 'set-up' it would be 1/((1/16)+(1/8)). which reduces to 1/(3/16). which reduces to 16/3, or 5.333... ohms.
which isn't the 12 ohm that it sounded like it would be before.
now, im *pretty* sure that you could use this impedance at the amp's 4 ohm. this would normally be fine on a ss amp. but on a tube amp, im not 100% sure. but yea. major tom would hopfully have a better idea. but as long as you put them in parallel you would *probably* be ok.
-will
Answer:
Originally Posted by wng ok. so you have an 8 ohm and a 16 ohm speaker.
if you use the forumal to find impeadance (ohms) in parallel (its on the website listed above jfyi) is 1/((1/x)+(1/y)....ect)
so this means to find the impeadance for your 'set-up' it would be 1/((1/16)+(1/8)). which reduces to 1/(3/16). which reduces to 16/3, or 5.333... ohms.
which isn't the 12 ohm that it sounded like it would be before.
now, im *pretty* sure that you could use this impedance at the amp's 4 ohm. this would normally be fine on a ss amp. but on a tube amp, im not 100% sure. but yea. major tom would hopfully have a better idea. but as long as you put them in parallel you would *probably* be ok.
-will
That's it, 5.3 ohms total for 1) 16 ohm, and 1) 8 ohm in parallel. WNG is correct - Set the amp for the 4 ohm setting, the 5.3 will be a bit more load but its pretty close, It will be fine. In theory, your amp will put out a bit less power than its max, but I don't believe it will be enough to be noticeable. The 16 ohm speaker will get less power than the 8, so depending on the efficiency of the speakers, the 8 will probably be a bit louder.

Answer:
yes, my understanding is to always use the amps ohm selector equal to or less than the actual speaker ohms...4 will work as Maj Tom said... also as to volume, sensetivty of the speaker-speakers are to be considered as well(loudness of speaker measured in db) best thing to do is get a closley set matched speakers, but being poor, we use what we find... the other thing, use each as one speaker ... not combined....