16ohms VS. 8ohms

[donbarzini]

I am considering a pair of Greenbacks for my JCM800 2x12 combo. I've heard from some that Marshalls sound better running at 16ohms. The amp is set for (2) 16ohm speakers wired parallel for the amp to run at 8ohms. I'm wondering if I should install 8ohm Greenbacks wired in series and run the amp at 16ohms. Any benefit from this?

[Davey]

what is the amps speaker rating?

if it's 8 ohm, buy two 16ohm ones, so you match them with the amps output.

if it's 16 ohms, buy two 8 ohm ones.

i got two 8 ohm ones for my 2x12 cos i didnt want to limit myself to only an 8 ohm cab (who in the world uses 32ohm outputs anyway?) and have it wired in paralel. and it's easy to make a 16 ohm cab out of it.

16ohm speakers are foremost used in 4x12's all wired in paralel, so you get a 4ohm cab (but with 4x12's you can go a bit nuts with the wireing, so you can mix & match a tiny bit)

i think it doesnt matter which speakers you use as long as you match the amps output (it's ok to have a 16ohm cab on an 8ohm output, but NOT the other way around) and about 16ohm speakers sounding better, i cannot comment on that cos i dont know

[Bob Johnson]

I'd be a bit cautious about changing the impedance of the speakers if the JCM800 combo doesn't have selectable output impedance like the head has.

My Traynor YGL3 is ok for 4 to 12 Ohm loads so I've tried running it into 8 (4 is the nominal impedance) and it does make the amp sound cleaner with tighter bass. That's on an amp without selectable impedance settings. On an amp with selectable settings I would have thought it would make very little difference since the conditions inside the amp wont change with the change in load.

[donbarzini]

My JCM800 has an impedance selector for 4ohms, 8ohms or 16ohms. I've heard from some, this may not be true, that Marshalls sound better running them at 16ohms so I was just curious as to anyone elses thoughts on this subject.

[Davey]

get two 8 ohm speakers.. try them in series, then in paralel. see if it changes the tone

but like bob said, it doesnt make a diference since you have the selector switch, which changes the condition of the output transformer to match the load.


unless someone proves 16ohm speakers sound better than the rest, it's all hear-say

[Bob Johnson]

My JCM800 has an impedance selector for 4ohms, 8ohms or 16ohms.

If it's got an impedance selector you're obviously not going to have any problems then. It's just an opinion, but I can't see upping the speaker impedance making much difference. I think it only makes a difference on my amp and amps like it 'cos it's not selectable so the output tranny voltages, biasing and god knows what else can change when you change the speaker impedance. This doesn't (shouldn't) happen on an amp where the impedance is correctly matched.

[Skybone]

I've got a 50w JCM800 4104 combo, and I've recently put 2 16ohm Vintage 30's in there, one to replace a blown G12M-70, the other just because I can... ;)

Basically, a 2x12 JCM800 is wired so that 2x 16ohm loads combine to make an 8ohm load (I can never remember whether it's series or parallel!), anyway, I think it sounds good like that.

What output rating are the Greenback's you're thinking of installing (they're 25w aren't they?) , as I think that the total output loading needs to exceed the total ouput of your amp so that you don't end up blowing your speakers (with rock n roll!!!). The Vintage 30's are rated at around 60w each, so that's 120w total (I think this is how it goes), as mine is only a 50w amp, the power handling of the speakers is over and above what is required.

[donbarzini]

Yes, I have a 4104 also. I am just going to get the (2) 16ohm Greenbacks and wire them parallel and run the amp at 8ohms since I have an 8ohm Hotplate already. The Greenbacks are rated at 25W each but since I don't even play the amp at 10 they should work just fine. I have G12H230's (30W each) in there now but I want the speakers to break up a bit sooner, it will be an experiment.

[Bob Johnson]

Don't want to preach but you shouldn't use speaker distortion to get the sound you want. It sounds cr@p for one thing.
Cone ripple and speech coil saturation are usually pretty destructive. Cone ripple can/will damage the cone, the cone suspension and the speech coil suspension eventually. Over driving the speech coil will cause it to over heat and burn out. I'm talking general principals here; in this case you're probably pretty safe 'cos Celestions are so bullet proof so, luckily for you, you won't see any breakup from the speakers anyway

[donbarzini]

Totally understand. Many players use a 100 watt head into a 4x12 loaded with Greenbacks so I will be using a 50W combo with 2 Greenbacks, no difference except the combo is a bit shallower and open back.

[Bob Johnson]

Yeah, should sound great.