Getting a 16 Ohm Speaker down to 8ohm

[greg]

I have purcheased a 1x12 cabinet with a 16 ohm Celestion G12H30 which was accidentally overlooked while shopping on Ebay. Unfortunately, the head that I bought the cabinet to go with only has an 8ohm tap on the OT. While I understand that it should be safe to run this head with the 16 ohm load, I don't think it sounds particularly good. It seems much less punchy.

I'd just sell it and buy a new one, but this speaker has been broken in by Avatar (the Hellatone line) and does sound noticably nicer than a new G12H30 I have A/B'd it with. I'd work on breaking a new one in myself, but, well, you know - I have this one now and want to see if I can make it work for me.

I am assuming that I could put some kind of an 8 ohm load in parallel with the speaker to bring it down to 8ohm, but a) is that going to sound different than going straight to the speaker? and b) if this is a viable option, what is the best thing to use? A resistor? A speaker with no cone?

Thanks in advance.

[Enzo]

Well first you would need a 16 ohm second load to parallel with the other to make 8 ohms total, not an 8 ohm one.

If you do this, of course half the power of the amp goes to the dummy load.

Really the way to do this is to swap speakers in the cab.

[greg]

Yes - 16 ohm. Whoops.

That is what I expected (that I'd be wasting power). Oh well.

Thanks for the reply.

Greg

[Ray Ivers]

Greg,

What kind of head are you using with this cab?

Ray

[greg]

It is the little 6 watt amp I have been talking about on the Mods and Tweeks board (the Solen cap thread, on which, by the way, I just posted a question for you specifically - please take a look when you get a chance). It is a West Labs Pico Fire using their 6 watt PT/OT set. A little monster!

Thanks
Greg

[Ray Ivers]

Greg,

Oh, OK - I was hoping it was a four-power-tube amp that you might be able to pull two tubes from, and thus match up to your 16 ohm load. I couldn't find a schematic to the Pico-Fire at Dave's site, so I don't know what the circuit is.

Ray

[greg]

No he hasn't posted the circuit and would only give it to me upon purchase of the PT\OT set. I think is planning on offering a kit for it. It is a single ended amp utilizing a single EL84. Sounds like a new speaker is my only good option here.

Thanks
Greg

[tboy]

Sounds like a new speaker is my only good option here.

Well... You could get another 16 ohm cab and use the two in parallel.

[Sock Puppet]

Sounds like a new speaker is my only good option here.

You might also consider a 2:1 impedance matching transformer.

S.

[Enzo]

A 2:1 SPEAKER transformer?

[R.G.]

They exist, but are possibly not a good choice.

I'm surprised that no one has mentioned the obvious: using an output transformer with 8 and 16 ohm taps as a stepdown autotransformer. You get what is probably a good enough frequency response, and the power/sizing is easy - just pick one rated at enough or more output power. Tape off the primary leads - those will have hundreds of volts on them.

[Tom Phillips]

My 2 Cents:

Enzo: Weber sell's impedance matchng transformers. See https://taweber.powweb.com/store/zmatch.htm
I never heard one and the concept doesn't sound like a tone preserver or enhancer to me so Greg, I'm not recommending that you go that route.

However, if you are considering buying transformers, I'd put my money into a new OT for the amp and replace it with one that has 4, 8 and 16 Ohm taps. Then you can match your current speaker and any future speaker cab.
Tom

[Enzo]

OK, I only think of those things when matching into 70v systems. No reason it couldn't be used otherwise I guess. But when we buy the thing, then arrange it into the amp, it seems like just replacing the OT with a multitap would be cheaper and simpler.

[Albert Kreuzer]

Auto transformer?

They exist, but are possibly not a good choice.

I'm surprised that no one has mentioned the obvious: using an output transformer with 8 and 16 ohm taps as a stepdown autotransformer. You get what is probably a good enough frequency response, and the power/sizing is easy - just pick one rated at enough or more output power. Tape off the primary leads - those will have hundreds of volts on them.

Hi all,

just a thought: What about using a real autotransformer (117/230V)? It should work impedance-wise (tone is another matter), no?
You could transform your speaker impedance one notch up or down as you need it...
Has anybody tried this?

Cheers,
Albert

[R.G.]

Hi all,

just a thought: What about using a real autotransformer (117/230V)? It should work impedance-wise (tone is another matter), no?
You could transform your speaker impedance one notch up or down as you need it...

If you had the correct tap. The impedance is transformed by the square of the voltage ratio. So to transform 16 ohms to 8 ohms, you need a voltage ratio of 1 to 0.7071. A 4 ohm tap on an output transfomer is half the voltage of a 16 ohm tap.

Yes, an autotransfomer would work, and that's what I rejected mentally before realizing that the secondary of an OT is already the correct set of voltage ratios.