Building another 5F1 - is there any disadvantage in going 16 Ohm output?

[leevc5]

8 Ohm seems to be the standard but my xfmr has a 16 Ohm tap. The reason I ask is that used 16 Ohm speakers are at bargain prices compared to their 8 Ohm equivalent.

[shooter]

each tap available can be used without effecting operation, were it does effect operation is when you hang a 16ohm speaker on a 4ohm tap.  I have made up 2 2X12 cab that both have 16ohm wired || for 8ohm cab.  I've found that musician types can do this easier than figuring out series connected speakers

[jjasilli]

To play devil's advocate:  some believe that lower ohm taps (into a matching speaker load) sound better, or at least different.  The theory seems to be that use of a low ohm tap causes the OT to saturate or compress more.  (I'm not taking a position, and am unaware of any scientific proof.)  E.g., this is supposed to contribute to the magical tone of the '59 Bassman with its 2 ohm output.

[sluckey]

Something to ponder... You will have more NFB when using a 16Ω tap. May need to increase the size of the 22K NFB resistor to compensate. Let your ears be your guide.

[leevc5]

Thank you all once again! Picked up a Celestion 12" Greenback for 70 bucks. Not doing the NFB anymore, like the response and smoother overdrive gain without. Also as you all advised am using .1 coupling caps with the bigger speaker and although unChampy much prefer these small but significant changes.

[ginger]

Yes... use a different value feedback resistor , or remove it entirely

[ginger]

I always have a switchable negative feedback resistor on 5F1 builds , as they have no tone control... switching the resistor out , as you may know, adds high end and gain .

[92Volts]

To play devil's advocate:  some believe that lower ohm taps (into a matching speaker load) sound better, or at least different.  The theory seems to be that use of a low ohm tap causes the OT to saturate or compress more.  (I'm not taking a position, and am unaware of any scientific proof.)  E.g., this is supposed to contribute to the magical tone of the '59 Bassman with its 2 ohm output.

It definitely could matter! A normal OPT with one secondary and multiple taps leaves part of the winding unused if you don't use the highest tap available. 16 ohms needs twice as many turns as 4.

The 4 ohm section may use thicker wire to accommodate higher current, so not quite "half the secondary" is left unused (if the unused windings are thinner, they take up less area/volume/weight of copper). It still makes a difference, though.

Of course, that's not what's going on if an amp only has a low-ohm tap like older Fenders compatible with 2 ohms or 3.2/4 ohms only. There are plenty of reasons those OPTs might saturate sooner than modern ones, based on size and materials though, so using a modern one (with multiple taps available) might be a way to get closer to that sound.

[jjasilli]

Yes, that's the theory!  Don't know if it's possible to do a scientific tone test, because it may be impossible to isolate variables.  The problem is you'd have to use a different speaker to match the different OT secondary taps, so there always seems to be more than one variable at play. 

[sluckey]

Please don't put that poor little champ through any scientific study.   

[shooter]

+1!

build it as designed, play it through a 4 X 12 populated with bigger than 97bd'rs, be happy

[PRR]

Scaling winding impedance is simple geometry. More/less turns of thin/fat wire.

Not-using ALL the copper on an OT is not a large sin. Especially in guitar amps, which don't attempt 70KHz or really huge inductance.

The scaled-out difference, loading at 4r or 16r, is a small difference in winding resistance. Which is already small relative to the marked impedance.

In some Ideal World, you pick your speaker impedance not-too-small and not-too-large. On the low end: Speaker impedance should be much larger than speaker-line resistance. Even if the line is short, the "tinsel" lead-ins from speaker terminals to voice coil must be light yet flexible, so are thin, and add a few tenths of an Ohm. At the high end, many-turn voice coils cost more to wind and rot-out quicker. Most 300r speakers and many 45r speakers died young. So 3.2r DC (4r audio) was common for in-box (short line) speakers. In theaters with 300 foot speaker lines, two 16r speakers were wired for 32r total load, so the long line did not have to be expensive fat-gauge. This was a general state of affairs until the early AR speakers which were still 4 Ohm nominal. Soon after, transistor amps appeared in hi-fi, but some of the early ones did not stand-up in 4 Ohms. (And theaters gradually changed-over from amps in the booth to amps behind the screen.) 8 Ohms became the common impedance.

I don't see 16r speakers being generally cheaper. If you have found an over-stock in 16r, yes, use them.

[jjasilli]

I think it's a European thing, to save on materials.  Things were tough in Europe during & after WWII.  16 Ohm speakers can use thin speaker wires.  Thin wires have higher resistance.  A couple of Ohms of resistance is small percentage of 16 Ohms but a significant 50% of 4 Ohm speakers.  This affects speaker response.

Literally the same idea with the kitchen sink.  American sinks of the 1950's were heavy cast iron, porcelain coated.  Very wasteful by European standards.  Euro sinks were thin metal, with fluting to give strength to the thin metal walls (and a bit more artistic design). 


@sluckey & shooter.  C'mon guys, don't cry.  It's for science!

[PRR]

The amount of copper is the same at any impedance.

Higher Z means pounding the copper out thinner, and winding more turns more gently. This suggests low-Z is most economic. But not too low. Hence 4r was normal for decades.

There was a short Philips flirtation for tube transformerless outputs and 300r speakers. This saves a heap of copper in an OT, though you make up for it with more cash to Philips for another fat tube.

Nearly all US intercoms were 45r speakers to reduce loss in long-long lines. The extra care in winding is paid-back by using thinner wire in long runs.

The in-betweens were instructive. Theater system speakers were carefully made, and 16r wasn't so very thin in high-power voice coils. Seriesing to 32r makes cheap #16 wire perfectly good to beyond the length+width of a large theater.

[shooter]

Very wasteful by European standards.

somewhere in my cobwebbed mind isn't there a law that states you cannot create nor destroy, only change (and up norte' heat is NOT waste)

It's for science!

if you're an aspiring geek, have meter, scope n sig-gen, the 5F1 might be a good place to start.
gain, asymmetry, phase shift, frequency shift, harmonics............then plug in, play til you get it outta your system

[92Volts]

Jensen is the only company I've seen the acknowledge any difference between the "same" speaker at different impedances: https://www.jensentone.com/vintage-alnico/p12q That example shows 16 ohm being most sensitive, with a big loss (3.8db) from 16 to 32 ohms.

Obviously, something doesn't scale perfectly. I wonder if this is a "less efficient speaker" or an impedance/measurement issue (if you feed a "1 watt" signal based on the speaker's rated impedance, actual power will vary as it's above or below rated impedance).

The 32 ohm model is actually rated for more power so it's possible the voice coil is thicker than electrically needed, for durability or ease of production. This might make it heavier or stiffer than a perfect adaptation of a lower-ohm speaker would be.

[Ed_Chambley]

A good Transformer will have the correct gauge wire for the 4 ohm current and if it is multi-tap, the gauge will reduce between the 8 and 4 ohm for the lower current and if it has a 16, again a good transformer company will reduce the gauge more to be equivalent.  The idea is no matter which tap is used, you have the same core and the proper primary current handling for each tap.


This is fine for guitar amps.  There are also secondaries in some transformers that have seperate windings, whereas each section is wound for proper usage.  This is the best choice for HiFi, but I really do not think frequency response suffering on guitar amps is a problem.


I have a Champ with multitap OT and a original Tweed Champ with a replaced 8" Weber Alnico 4 ohm.  I just built a 2, 8" cabinet for the Champ Head and used 8ohm so I could have either 4 ohm or 16 ohm.  Plug it in either way, sounds the same.

[jjasilli]

QuoteVery wasteful by European standards.

somewhere in my cobwebbed mind isn't there a law that states you cannot create nor destroy, only change  (and up norte' heat is NOT waste)


Shooter: the "waste" is in the amount of copper in the speaker lead wire between amp & speaker.  A 16 Ohm speaker allows the use of thin wire without substantially changing the load impedance as seen by the amp. 

[shooter]

the amount of copper in the speaker lead wire

If I already have fat wires for my 8ohm speakers, and I hook up a 16, changing taps, where's the waste

[PRR]

Yes, the P12Q data is odd.

Transformers are easy. In speakers you also need an even number of layers (you prefer to go out and back all-winding, not bring the far-end back direct because that means clearance loss). Between standard wire gauges and the need for even-number layers, sometimes it just does not work out well at all scales.

But there's other oddities. The 32r mass is least, yet the Fs is lower. Yes, the compliance is higher. But that is about the cloth and paper, not the coil. Do they really press a different cone and spider for 32r? Or is this within the production spread of pulp and varnish? That they just grabbed a looser-batch cone when they went to get numbers on the 32r?