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What's with these 15 ohm speakers I'm seeing these day? Please splain it to me.


GAS Man

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So if you're doing a 16 ohm out from the amp, aren't you supposed to be going into a speaker that is at least that ohm rating or higher?

So why do they have speakers that are just 15 ohms?
http://www.sweetwater.com/store/detail/G12H-HER5515

That's one less idn't it?

images?q=tbn:ANd9GcRliKC7naoJu2sVe4MUPOp

I'm thinking about upgrading some 16ohm speakers in some cabs to that 15 ohm model, but that confuses me confused.gif

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The short answer? Tradition. 15 is close enough to 16 it won't cause any problems. It's my understanding the classic Celestion speakers from back in the day were labeled as 15 ohms, and at some point they changed. The impedance didn't change, but the label did.

One thing to keep in mind is an impedance rating is a dynamic rating whereas resistance is a static rating. The two are often confused, but impedance changes with frequency the speaker is reproducing. Due to this dynamic response, an amp built to handle 16 ohms won't see any difference with 15.

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Quote Originally Posted by Deadbeat Son View Post
I know, right? Have you tried Dave @ Avatar? He has pretty good Celestion prices.

Hope you're doing well GAS Man!
Yes, right after making my last post here I did do just that. I haven't bought anything from them yet, but I have gotten one or two quotes from them and I indeed have been impressed with the offers they can make. I just never went ahead yet with those other contemplated mods. Sometimes speakers get better with time so I don't follow through, and sometimes I just don't follow through. biggrin.gif

Best wishes to you too wave.gif
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Quote Originally Posted by GAS Man View Post
So if you're doing a 16 ohm out from the amp, aren't you supposed to be going into a speaker that is at least that ohm rating or higher?
No. That would only apply to SS amps.

A tube amp is actually more likely to be damaged by too high an impedance, but anything within a factor of 2 either way is not going to be an issue.

Now, the nominal impedance of a speaker is a very imprecise thing. A speaker is not a resistor, there is resisive, inductive and capacative impedance which vary with the excursion of the coil. It is also an active component in that the cone also forces the coil to move when it tries to return to its center point. Combined, these factors mean that the instantaneous impedance of a speaker can vary wildly about the nominal value - it can even show negative impedance.

So, difference between 15 and 16 is purely down to what the manufacturer decides they want to put on the babel.
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Thanks for the other posts above as well

Quote Originally Posted by ugameus View Post
Thanks for the link. The speaker I'm looking at is a different one though. I mostly have a "hate" relationship with my Marshall JCM2000/DSL1000 and the cheapo MC (note, not MG, the MC was still made in the UK - but uses a manufactured board) 4 x 12 cab. It was a good "package" deal at $1200 complete, but I want to add more warmth, like Bassman-ish tones to it. I'm hoping it won't be throwing good money after bad (but I can always pull the speakers back out for a later application) but the speaker I'm looking at is the Heritage version. It's still made in England and is apparently designed after what was once considered a bass speaker. But it's got the lowest frequency rating (down to 55HZ) and is said to thicken the tone to "syrupy" character. My amp could sure use that. Plus I also want the cab upgraded for all the other heads I have kicking around that could then ride that beeyatch wink.gif

G12H-HER5515-xlarge.jpg
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