New cab impedance question

  • Thread starter Thread starter meathman
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meathman

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Hi

I just received my new diezel cab. Its a front loaded 4 by 12 with v30s. Ill be using this with a herbert (mono, only one cab)

My question is, the cab has no impedance labeled on the back. I dont know whether to use 4 ohm , 16, ohm, 8 ohm , etc

Does it matter? If so, which one should I use.....

Just want to be extra sure I dont screw up my new rig...

Thanks
 
Actually... can you take a pic of it or remove one of the speakers and look at the ohm rating (8 for 8 ohm 16 for 16 of course)? My Diezel cab came wired for 16 ohm mono. Mainly because it was one a customer wanted that way and they backed out so I got it, didn't really want it that way but it really doesn't matter to me, they offered to replace the speakers too but I opted to keep them. Point is all Diezel cabs may not be 8 ohm. The rearloaded at Eddies guitars is 16 ohm too. It usually tells you on the plate though, if it has a 16 ohm over both jacks and one 8 ohm over the red jack then it's an 8 ohm mono cab.(if it's this plug into the red jack and one of your 8 ohm jacks on the head)


Later on,

-Nick
 
Thanks.....It does say 8ohm on their website, but as you mention nick, you never know..

My cab has nothing written where the ohm symbol is on the back....its just blank

Ill take a look at the speakers, but Im gonna have to assume the mono input (red one) is 8ohm like it says on their website.
 
Or just hang a meter set to ohms across the terminal ring and tip. If it's a 8 Ohm cabinet, you should read something around 7 Ohms +- if it is a 16Ohm cabinet something around 15+- Ohms...
 
dam, my meter just broke last week....

It looks like a stock fl cab with v30s...i dont see any reason to believe this would be anything other than the factory 8ohm spec...

i just wish they would have labeled it on the cab!
 
Even if it wasn't an 8 to 16 ohm load is safe.
 
Just buy a cheap dmm and measure. Dmm always comes handy and it is the easiest way ;)
Mismatching impedances won't damage your amp (as long as you use standard cabinets in the 4/8/16 Ohm range) but does alter the tone...
Best,
Stefan
 
No, Stefan!
You have to be at least at the same or a higher Ohm value on the amp side. That means, connecting an 8 Ohm cab to the 4 Ohm speaker output on the amp COULD damage the amp. Plugging into 8 or 16 Ohms on the amp is ok, though.
Tube amps will eventually take damage if no proper load is connected to them, transistor amps won't. That's why every manual tells you to always connect a speaker before turning on the amp.
 
well i dont think any of the diezel cabs work under 4 ohm so if i connect a 8 ohm out from the amp, i should be safe
 
I respectfully disagree. A proper designed tube amp (or its OT) will drive a 16 Ohm cab on your 8 Ohm output happily. No problem there. Impedance is not the same thing as resitance as it changes with frequency. Just take a look at the impedance chart of a standard speaker. It will have different impedance through the whole spectrum. You can easily reach 100Ohm of impedance around the resonance frequency.
Of course, you'll never have just one freuquency in real life.
Even 16 Ohm on an 8 Ohm output will load the secondary of the OT enough to prevent voltage sparks that could damage tubes and or the OT.
Tube amps in general are much less delicate when it comes to drive different loads. Of course you will lose some power and a proper termination is always the better way to go, technically, as a improper load will also cause higher distortion, ect.
Take a look at a typical transistorized power amplifiers load line. Dividing the load by 2 often results in a diveded by 2 power....
Best,
Stefan
 
Ok Stefan,

I must confess, after talking about this years ago with my amp tech, I always took it as a basic rule, without real technical insight or double checking of the matter.
Problem is, I killed my output transformer in my Laney because I plugged into the wrong output. It was obvious that it was the reason and my tech told me so as well. That's why I'm a firm believer in the mismatching-kills-your-OT stories.
But great to hear a different voice after all these years. I'll do some research to get a fresh view on this.
Thanks, dude!

Cheers,

J
 
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