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8 ohm and 16 ohm speaker in paralel?

peter_heijnen

Member
Messages
2,100
Hi, i have two Celestion G12H Anniversaries catching dust. I recently realized i never played a 212 with Anniversaries before, so i'd like to check both speakers out in a 212. However, both speakers have different impedances, 8 and 16 ohms.

It got me thinking, if i'd wire the speakers in paralel, would the correct calculation for the cabs impedance be like this? 1/8 + 1/16 = 3/16 = 1/5,3

And if so, resulting in 5,3 ohm, could pairing be done without harming either speaker or amp, running the amp at 4 ohm? And when pairing, could one speaker possibly overpower the other one because of the mismatching?

Thx in advance.
 

Johndh

Member
Messages
388
Its not real good. Its not matching what the amp wants to see, and , the 8 will take 2/3 of the total power.

Other than changing one speaker, the best work-around is if yr amp has a full set of output sockets, 4, 8 and 16 ohm. does it?
 
Messages
15,618
Figure out which one you like the sound of most & buy a matching driver. Mixing drivers in a single cabinet is just a bad idea, especially with an impedance mismatch.
 

MoBigBro

Gold Supporting Member
Messages
380
I have never put impedance mismatched speakers in the same cab, but I have paired impedance mismatched speakers in separate 1X12 cabinets as follows:
8ohm G12V70 with 16ohm Alnico Gold
8ohm Creamback 65 with 16ohm Alnico Gold
I've played this pairing with a Port City Pearl on both 4ohm and 8ohm settings; a Bassbreaker 15 on both 4ohm and 8ohm settings and a '66 Bandmaster at 4 ohms.
I prefer the G12V70/Alnico Gold pairing and I prefer the 4ohm settings. This is particularly nice with the Bandmaster, but many of the tones are interesting and quite usable.

(BTW, you are correct that the resulting impedance is 5.33ohms).

I have paired a 16ohm G12H30 Anniversary with many other 16ohm speakers with varying but generally usable results.

I would not recommend permanently loading a 2X12 with mismatched speakers but why not have some fun and see what you come up with while choosing a permanent speaker for your cabinet!
Cheers,
MoBigbro
 

peter_heijnen

Member
Messages
2,100
Thx everybody. I just want to test the two anniversaries together in a 212, it's pure curiousity and definetly not for keepers. Most important for me to know is wether or not i would damage amp or speakers by mismatching.
 

pdf64

Member
Messages
7,055
It may be simple to apply equal power to both speakers; please respond to post #2 in order to determine this.
 

MKB

Gold Supporting Member
Messages
8,199
Its not real good. Its not matching what the amp wants to see, and , the 8 will take 2/3 of the total power.

Other than changing one speaker, the best work-around is if yr amp has a full set of output sockets, 4, 8 and 16 ohm. does it?
It may be simple to apply equal power to both speakers; please respond to post #2 in order to determine this.
If you mean plugging a 16 ohm speaker into the 16 ohm jack, and a 8 ohm speaker into the 8 ohm jack, both at the same time, that will give you an impedance mismatch if all of the taps are on a single secondary, and all are referenced to the same ground. Most OT's I've seen are like this. I'd have to crunch the math to be exact, but in essence the above configuration would effectively apply less than 8 ohms to that section of the winding. I would not do that unless the amp builder approves such a load.

A 16 ohm and 8 ohm speaker in parallel would be 5.3 ohms, I'd be comfortable running that on a 4 ohm tap, but again it might be best to ask the amp manufacturer to be sure.

In some cases a 16\8 speaker pair mismatch might work very well, if say the 16 ohm speaker has a higher efficiency than the 8. For example, if you had a 16 ohm V30 and an 8 ohm G12M-25 Greenback, those two might be a better aural match as even though the V30 is getting less power, its higher efficiency would compensate for it.
 

peter_heijnen

Member
Messages
2,100
It may be simple to apply equal power to both speakers; please respond to post #2 in order to determine this.
As stated above already it doesn't seem to be a good idea. Besides that i don't have separate outputs, just a pair of outs and an impedance selector.
 

edgewound

Member
Messages
5,646
Since they're the same model speaker with different impedance voice coils, you can pretty much assume they will sound similar.
 

pdf64

Member
Messages
7,055
If you mean plugging a 16 ohm speaker into the 16 ohm jack, and a 8 ohm speaker into the 8 ohm jack, both at the same time, that will give you an impedance mismatch
Correct, but it would equalise the power to each speaker.
However, no, I was thinking of
...if you connected an 8 ohm speaker to the 4 ohm tap, and a 16 ohm speaker to the 8 ohm tap, the reflected impedance would be correct
from http://www.aikenamps.com/index.php/technical-q-a
And each speaker would get an even share of the power.

 

gldtp99

Member
Messages
3,755
Just plug any speakers in any way you feel like.

Turn the amp up all the way and play it.

If/when something breaks...…………. take amp to a tech.

Maybe nothing will ever fail.

Maybe it will.

These impedance and mis-matching threads are getting boring.

So much bad info and pseudo-tech put forth in these threads.

If a tube, OT, or other failure occurs take the amp and have it fixed.

Go ahead and run any crazy mis-match you want to.

You already know that you're supposed to match amp/speaker impedance.

If you choose to run some mis-match then assume the risk involved and pay one of us to fix the amp if something fails.

Us real techs don't know if/when a failure will occur because you're running some crazy mis-match------- We don't have Crystal Balls, Gypsy Women with Tarot Cards, or any other way to see into the future.

If you choose to run a mis-match it is a risk to some degree.

If you choose to run a mis-match then man up and assume that risk------ and back it up with money for repairs in the event some failure occurs as a result of your decision to run this mis-match.

Maybe no failure will ever occur in your amp.

There's only one way to find out.
 
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peter_heijnen

Member
Messages
2,100
Mismatching impedances between amp and speakers never harmed my amps, in the old rack days i even played a german tube stereo power amp who's designer trusted his OT that much that he dared anybody to blow it under what circumstance imaginable. I once played one side of that amp unloaded during hours on full power, by mistake of course, but nothing blew up.

However, using two speakers with different impedances is something i never heard of before. I can't see a problem in informing a little about it. I think it's plain stupid to just dive in and risk to burn anything effortlessly.
 
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pdf64

Member
Messages
7,055
Since they're the same model speaker with different impedance voice coils, you can pretty much assume they will sound similar.
Yes, but (all else being equal) a 2 x 12 will tend to sound different to a 1 x 12, perhaps due to acoustic effects such as mutual coupling and comb filtering (due to phase cancellation).
 

Johndh

Member
Messages
388
ok so you dont have all the outs. But if you did, youd plug 16 ohm into 8 ohm jack and 8 ohm into 4 ohm jack. Amp is correctly loaded and each speaker gets equal power.
 

PushedGlass

Member
Messages
609
If you are interested in assessing how they sound, be aware that you're not giving the speakers a fair shake in that regard. The 8 ohm will be the one you hear the most of; it is getting twice the power of that going to the 16 ohm one.
If they're in parallel this will be the case (parallel = same voltage, so P=V^2/R); if they're in series (series = same current, so P=I^2 * R) it's the other way around.
 

edgewound

Member
Messages
5,646
Yes, but (all else being equal) a 2 x 12 will tend to sound different to a 1 x 12, perhaps due to acoustic effects such as mutual coupling and comb filtering (due to phase cancellation).
Yeah...3 to 6 dB louder will do that.
 




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