Amp Cabinet Ohmage Ratings

[Jenesis]

Looks like an Arabic 30 to me...

[Ironbird13]

google image Ohm and thats what comes up

[Jenesis]

Personally I would have posted the pic where the girl has it tattooed on her bum.

[Rog]

I've loaned my little Fender 1x12 to a friend for a couple of gigs. He's using his 15" bass cabinet instead of the combo speaker and reckons the sound is incredible. I guess the proof is in the pudding, as they say.

One thing to remember with a parallel circuit is that the total will always be less than the lowest value. So even if you stuck a high value cabinet in the second jack, total load would still be less than the 8Ω optimum load.

[robnobcorncob]

google image Ohm and thats what comes up

Buddhism - OM

Impedance = Ohm

[rickenbackerkid]

SO much for giving the guy a straight answer!

Your amp has two speaker outs, in parallel.
The total impeadance for both is 8 Ohms. The single internal speaker is 8 Ohm, so thats a match.
You could run two 16 Ohm cabs, making 8 Ohms.

Now ohm ratings tend to be fairly conservative, Bogner, Mesa/Boogie and others state that up to a 100 percent mis match is safe for their amps.

(I can't speak for the quality of Fender's OT's, so proceed with caution!)

Therefore, while not recommended, you can almost surely run a 4 - 16 ohm load. This could be two 8 ohm speakers for a 4 ohm load, or 4x 16 ohm speakers for 4 ohms. Or even a single 16 Ohm speaker.

Your DRRI internal speaker + your 4x10 classic 50 speakers would be would be 5.333 Ohms, in my mind fairly safe. However, you DRRI would have to work a lot harder to achieve the same volume it does on it's own, meaning faster tube wear, higher chance of overheating, more chance of blowing fuses, ECT. At the same time the extra projection of four more speakers will make it feel louder even when it's not

Hope that helps, feel free to hijack the thread again.

Ben

[mr_sooty]

Cool, thanks bro. I was really just curious as to how it would sound, but I wanted to make sure I wouldn't blow the amp before I tried it. I'm kind of wondering what it might sound like to run a 2x10 cabinet under the 1x12 DRRI. I'm thinking maybe I could build one to match the amp. Could be cool.

Everything I've read online suggests the DRRI can handle 8ohms in each speaker jack easy enough.

[Rog]

let us all know how you get on. There's several threads here about good amp techs who can fix it afterwards...

[RobRoyMcCoy]

The point of having to unplug the internal speaker (8 ohms) and plugging in an extension cab (also 8 ohms for the sake of the point) is that a 4 x 12 cab (8 ohms) will be much louder than a 1 x 12 cab or speaker (with the same speaker type) and will sound different due to the dimensions and type of the enclosure (sealed, open, semi-open etc).

Whilst some manufacturers say that a 100% mismatch is permissible, it is not a good idea to run the amp into a lower than designed load if the bias is set such that it will, on average, spend more time in the over dissipation region of its operation that it can handle. Basically if you run the amp into too low a load you increase the risk significantly of destroying the power tubes, shortening their lifespan if they do not melt, and increasing current through the output transformer beyond the design limits.

Increasing the load on the other hand is a good way to overdrive the amp at lower power. The tubes will saturate before they cut-off as the slope of operation becomes more shallow and this will effect the tone both in class A and class AB (i.e. all valve guitar amplifers) however it may be a change that sound good so it is always worth a try.

[mr_sooty]

The point of having to unplug the internal speaker (8 ohms) and plugging in an extension cab (also 8 ohms for the sake of the point) is that a 4 x 12 cab (8 ohms) will be much louder than a 1 x 12 cab or speaker (with the same speaker type) and will sound different due to the dimensions and type of the enclosure (sealed, open, semi-open etc).

But if you have to unplug the main speaker, why not just plug the extension cab into the main speaker out? Why have a seperate extention speaker out?

[rocklander]

The point of having to unplug the internal speaker (8 ohms) and plugging in an extension cab (also 8 ohms for the sake of the point) is that a 4 x 12 cab (8 ohms) will be much louder than a 1 x 12 cab or speaker (with the same speaker type) and will sound different due to the dimensions and type of the enclosure (sealed, open, semi-open etc).

But if you have to unplug the main speaker, why not just plug the extension cab into the main speaker out? Why have a seperate extention speaker out?

have a look at the socket.. it may be a TRS type thing that disconnects the main speaker anyway... at least, that's how I'd design it..

[RobRoyMcCoy]

The point of having to unplug the internal speaker (8 ohms) and plugging in an extension cab (also 8 ohms for the sake of the point) is that a 4 x 12 cab (8 ohms) will be much louder than a 1 x 12 cab or speaker (with the same speaker type) and will sound different due to the dimensions and type of the enclosure (sealed, open, semi-open etc).

But if you have to unplug the main speaker, why not just plug the extension cab into the main speaker out? Why have a seperate extention speaker out?

It does depend oh how it is wired as RL says. The schematic would show this clearly I would imagine.

Say the OPT has an 8 ohm winding. If you plugged a 16 ohm cabinet in the extention jack and left the 8 ohm speaker in the original jack you would be presenting a 5.3 ohm load to the 8 ohm winding. This may be OK but you would need to measure the operation of the amplifier into this load to determine if it is a safe bet over time or not. You could plot this on paper if you can get the correct characteristic curves for the tubes in question and draw the load line onto it.

Alternatively, as a previous poster said (I think) you could plug 2 x 16 ohm loads into the two jacks presenting an 8 ohm load to the secondary winding.

I suggest checking the schemativ to see how the jack is wired.