Most Versatile Impedance for Single 12" Speaker?

[The New Steve H]

I ordered a speaker for a 1 x 12. It arrived, and it turned out to be a 16-ohm speaker. I was about to send it back.

Then I checked my Vox AC4TV's original 10" speaker. It's 16-ohm. I also checked the current speaker (Eminence Ragin' Cajun). It's 8-ohm

I just assumed most single-speaker cabs were 8-ohm. Is this not the case? My 5F6A can handle 16 ohms, but I would like to have a speaker that's versatile.

Is there a most-common impedance?

[diagrammatiks]

it's whatever your amp has taps for.

It's really hard to say what a common impedance is...

most amps these days have taps at least for a 16 and an 8 usually.

[Firestorm]

Well, if the amp is equipped to handle different output tube types. then it also depends on which speaker impedance combined with which taps give the loads you need.

[The New Steve H]

I may keep this thing. Shipping for an exchange will cost a pile, and I can use it with the Bassman.

[David Root]

I like 8 ohms and it seems to be available in almost any speaker.

If you have old Fenders, many of which have only a 4 ohm OT secondary, put two 1x12s with 8 ohm speakers in parallel and you have not only perfect matching but also the great benefit of spreading out the sound ie sound stage, which I much prefer to a point source.

Also two 1x12 cabs are easier to handle than one 2x12, unless you're under 30 or can afford a roadie! I like EV12Ls and Altec 417s which weigh a ton or two.

[amplifiednation]

I read in one of Gerald Weber's books that using the 16ohm tap (or whatever the highest available impedance is) will use all available laminations of the transformer, and therefore produce the best tones that the transformer is capable of. I never hear much difference, but his theory does make sense.

So if you have a matching tap for the speaker, give it a try! Maybe you'all notice better tone!

[amplifiednation]

I like 8 ohms and it seems to be available in almost any speaker.

If you have old Fenders, many of which have only a 4 ohm OT secondary, put two 1x12s with 8 ohm speakers in parallel and you have not only perfect matching but also the great benefit of spreading out the sound ie sound stage, which I much prefer to a point source.

Also two 1x12 cabs are easier to handle than one 2x12, unless you're under 30 or can afford a roadie! I like EV12Ls and Altec 417s which weigh a ton or two.

David, which 417 model do you like best? I am looking for one and noticed a lot of variations

[rdjones]

The most common speaker impedance is 8Ω.
I think 16Ω is more of a British thing.

An output transformer is more efficient when it's using all of it's windings, so if a 16Ω tap is available it will transfer more power than at an 8Ω tap.
The difference is negligible for the purposes of a guitar amp, though.

There may be some pros and cons with a 16Ω speaker.
The voice coil wire is smaller and therefore lighter and possibly more efficient (?)
But the thinner wire is also not able to withstand as much heat and might not handle as much power as an otherwise similar 8Ω speaker.

rd

[Cliff Schecht]

A 16 Ohm speaker is the safest bet as far as being able to plug any amp into that speaker. It's safer to underload a PT than overload. With that said, all of my test cabs are 8 Ohms with the exception of a 2x12 that has a couple of 8 Ohm old Jensens paralleled for 4 Ohms. This really only gets used with 20W and below amps though because the speakers are lower wattage (10W and 12W IIRC).

[David Root]

Taylor, what variations have you noticed and were any of them recones?

I have run Altec 417B and C in parallel in the identical design/construction cabinets, they sound the same to me. The C might be a tad brighter, not sure of that. It had spent a lot of years in a 22W Ampeg combo so it had not been exactly stressed! Looks like new. I believe they have the same voicecoil and cone. The C has a much more rigid and I think slightly heavier basket, and is the best choice if you play out a lot. My cabs are Avatar oval open back G112s.

Besides the B & C in parallel I also have a 2x12 with early 16 ohm "Diacone" 417Bs. Also an Avatar cab, G212. The 417B is cheaper than the 417C, at least on E-Bay it is, but they have both gone up a lot in the last few years. I got my 417B Diacones for $50 each less than 3 years ago, I think you might get one with a shredded cone for that now.

I only buy original cone 417s. I'm sure there are some reconers that can do a good job, but I've also seen some less-than-stellar recones on EBay.

[Reeltarded]

The answer is 0R. A speaker with zero ohms is failed in any amp it's installed in. Versatility 100%.


King Arthur: I am your king.

Woman: Well I didn't vote for you.

King Arthur: You don't vote for kings.

Woman: Well how'd you become king then?

[Angelic music plays... ]

King Arthur: The Lady of the Lake, her arm clad in the purest shimmering samite held aloft Excalibur from the bosom of the water, signifying by divine providence that I, Arthur, was to carry Excalibur. THAT is why I am your king.

Dennis: [interrupting] Listen, strange women lyin' in ponds distributin' swords is no basis for a system of government. Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony.

[roberto]

I read in one of Gerald Weber's books that using the 16ohm tap (or whatever the highest available impedance is) will use all available laminations of the transformer, and therefore produce the best tones that the transformer is capable of.

You always use all available laminations, I think he was talking about all available turns of windings. Output transformers usually have different wire diameters for different tap: Smallest tap (usually 4ohm) needs a lower AWG number because it needs more current for the same power output, then usually 8 and 16 ohm taps shares the same AWG number wire.

At the same time, the higher current (and lower voltage) of the 4ohm tap implies an higher magnetic field into the laminations of the OT, so the output trafo goes easily into non-linearity.

Usually a crancked power amp sounds a bit more smooth at higher impedances output, and a bit more harsh at lower impedance ouput.


Back on topic, I'd use 8ohm internal cab for a 1x12" combo, and a 4ohm tap which put in parallel the external speaker with the internal one. This way if we connect a 8ohm external cab we obtain a perfect match of 4ohm, and if we connect a 16ohm external cab, we obtain 5.3ohm that is only a plus 30% mismatch with the tap, and it works.

[roberto]

But the thinner wire is also not able to withstand as much heat and might not handle as much power as an otherwise similar 8Ω speaker.

Why? Lets suppose we have a 34AWG (0.02 mm^2 = 2E-8 m^2) and a 7.6 Ohm DCR.

Cupper resistivity is 1.724 x 10^-8 ohm m, so we need:
L = 7.6 / (1.724E-8 / 2E-8 ) = 8.8m of wire

If we need a 16 Ohm of the same lenght we need an AWG38 0.01mm^2 wire (otherwise we can use a 36AWG 0.014mm2 that is long 12.4m).

Specific weight of copper is 8920 kg/m3, so the weight of the 8.8m 34AWG wire will be 1.57 grams, while 8.8m of 38AWG will weight 786 milligrams. 785 milligrams won't change anything in guitar audio range.

About heat to be dissipated, in a 8ohm speaker you have sqrt(2)=1.4142 more current flowing in the speaker, and the same area to dissipate heat (that is the area of the magnet facing the windings).