16 OHM speaker with the 5:25 ? ? ?

[fredm]

I'd like to clarify something if possible regarding using a 16 ohm rated speaker with the 5:25 Express.

OK, on page 19 of the owners manual it states under the heading "Mis-matching",

"When running a higher resistance (for example: 8 ohm output into a 16 ohm cabinet", a slightly different feel and response will be eminent. A slight mismatch can provide a darker smoother tone with a little less output and attack."

Now then, I have a 16 ohm Celestion G12H 30 watt speaker which I really like the sound of and would like to try it in my 5:25, in place of the standard fit 8 ohm V 30.

OK, now if we look at page 21 of the owners manual there is diagram number 5 showing a "Safe Mismatch", a 16 ohm cabinet plugged into the 8 ohm socket. My concern is that diagram number 5 shows a partial back view of an amplifier where there is a 4 ohm socket an 8 ohm socket and a 16 ohm socket.

My concern is that the 5:25 only has two 4 ohm sockets and one 8 ohm socket. It is not the same layout as the picture in the owners manual.
Is it really ok to do this with the 5:25 ? Does anyone here do this?

The reason I ask is because I have a Blackheart Little Giant BH5H that has a 16 ohm output two 8 ohm outputs and a 4 ohm output. I connected up the 16 ohm celestion to one of the 8 ohm outputs and swiched the amp on. About 2 seconds after I started playing a horrible high pitched squeal came from the speaker so I quickly switched it off. It definately did not like it.

I guess not all amps are wired the same way.

 

[soundchaser59]

I've had 16 ohm California and Tone Tubby and now a 16 ohm Texas in mine, and it sounds and plays great. I always plug it into the 8 ohm jack, it's just as they say...... a slight bit darker and slightly less crisp, but nothing that untrained ears ever notice. My non-musician friends cant tell the difference. If I crank the master up then I cant tell the difference either.

I am wondering about using a 16 ohm speaker and an 8 ohm speaker at the same time, both plugged into the two 4 ohm jacks. The jacks are, I believe, wired parallel, and a 16 and 8 in parallel is about 5 ohms......and I assume that would be safe for the 4 ohm jacks? Or should I plug the 16 into the 8 ohm jack, and the 8 into the 4 ohm jack?

 

[Trea]

Soundchaser59: This would give you a 5.33 Ohm load which would be fine. As long as your total ohm load does not go below 4 you are safe.

fredm: Yes that is perfectly fine to run a 16ohm load out of the 8ohm jack. You can always go higher then rated, just not lower.

Hope this helps.

Trea

 

[soundchaser59]

I would assume that the amp doesn't know and doesn't care if the two 4 ohm jacks have either a 8 ohm +16 ohm =5.33 ohm load, or if there are two 8 ohm cabs connected, as long as the pair of 4 ohm jacks "sees" a total impedance of no less than 4 ohms.

So if I wanted to use an 8 ohm and a 16 ohm cab at the same time, I should plug them both into the two 4 ohm jacks.

 

[J.J]

According to the manual you can use go lower than 4 Ohms. 2Ohm on the 4Ohm outlet is fine. Mesa just state that your output tube life will be reduced.

SoundChaser, I would put your 16Ohm speaker on the 8Ohm outlet and your 8 Ohm speaker in a 4Ohm outlet. If you put them both in the 4Ohm outlets, the 8Ohm speaker will be much louder as it will get double the power. You may even like it that way (so experiment with that), but doing what I mentioned will keep things in balance.

 

[soundchaser59]

According to the manual you can use go lower than 4 Ohms. 2Ohm on the 4Ohm outlet is fine. Mesa just state that your output tube life will be reduced.

SoundChaser, I would put your 16Ohm speaker on the 8Ohm outlet and your 8 Ohm speaker in a 4Ohm outlet. If you put them both in the 4Ohm outlets, the 8Ohm speaker will be much louder as it will get double the power. You may even like it that way (so experiment with that), but doing what I mentioned will keep things in balance.

Good point, I will try it both ways and see what I hear. (I have a good eye!)

 

[soundchaser59]

Well, I decided to play it safe and I simply called Mesa Boogie tech support.

The word from them is plug the 16 ohm cab into the 8 ohm jack, and the 8 ohm cab into one of the 4 ohm jacks, if I want to use both 8 and 16 ohm cabs at the same time.

 

[J.J]

Yes, thats the way to do it. I was playing with an extension cab and just trying all possible combinations when I realised this.

Keen to see what your eye hears :wink:

They way it works, is that the Ohm Jack will delivery double the voltage and half the current that a 4Ohm output will. Both outputs can deliver the same amount of power (which is a total output of about 25 watts for the 5:25).

Another interesting thing to note is that the 5:25s Dynawatt circuitry helps to protect our output tubes. If you do run a 2 Ohm speaker load from the 4Ohm outlet, the Dynawatt kicks in and limits things. It's still not great for the tubes, but would be worse without it.