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running 8 ohm speakers with a 4 ohm amp?
- Thread starter Lonesomedave
- Start date
Hey there, thanks for the link. I was getting really curious as I was reading this thread. I know all about Ohm's law and all that nonsense (because I went to school for it years ago) but I was pretty sure that the situation was going to be much different with amplifiers because they are far different than ideal circuits.
Much obliged for the info.
But look at the modern schematic, they added more amp protection and a relay which confuses the owners when the amp cuts out. This extra protection still ships on new Ampegs.
Most all modern SS amps offer short-circuit and thermal protection, but it's hard to trip this on higher load impedance. Carvin even offers a power supply switch on some amps to prevent over current on lower impedance loads. This switch also provide more power at higher load impedance.
okcrum
in your chest
Well, I think the confusion came from one thinko: the line voltage at which the relay circuit itself would drop out. It's an easy fix and Ampeg implemented it, at least in the SVT-CL. The rest of the regime in which the protection circuits work is pretty easy to understand.
You'll notice the Class D amps also have impedance switches in some cases. That sets a limiter threshold for the power amp.
You'll notice the Class D amps also have impedance switches in some cases. That sets a limiter threshold for the power amp.
I have a Peavey Tour 450. It says it's "4 ohm total minimum amplifier load". Is that considered a 4 ohm amp? I'm planning on using it with a GK 410MBE(8 ohm)and sometimes the 4x10 along with a 210MBE(8 ohm). It is a SS amp though.
4 ohm amp with 8 ohm speaker: not the best idea but it won't hurt anything. (If you have a tube amp it MAY wear out sed tubes faster than normal.)
8 ohm amp with 4 ohm speaker: Don't do it. That's the end of it.
Some amps have different ohmage outputs and/or switches to reduce/raise the ohms.
Example: I have a Musicman 65 head (Great distortion channel. I use it for keyboards. Sometimes for bass.) that can be switched from 4 ohms to 8 ohms. Again, if the speaker is higher than the amp, you're not risking anything.
8 ohm amp with 4 ohm speaker: Don't do it. That's the end of it.
Some amps have different ohmage outputs and/or switches to reduce/raise the ohms.
Example: I have a Musicman 65 head (Great distortion channel. I use it for keyboards. Sometimes for bass.) that can be switched from 4 ohms to 8 ohms. Again, if the speaker is higher than the amp, you're not risking anything.
Where did you find that mello? I've been looking at a Tour 450 locally and there aren't too many 4 ohm cab options, could you send me a link to whatever source you got that spec from? I couldn't find an 8 ohm rating anywhere!
Invalid Link Removed
I Googled...."peavey tour 450 owners manual".
This is on page 12.
It is better to match impedances. Many tube amps have an impedance transformer on the output. If this doesn't match with the cabinet impedance it may distort and eventually overheat, if used at or near maximum power. These impedance transformers often have taps for 4, 8 and sometimes 16 Ohms. So I'd have a look at a technical manual, or inside the amp.
I kinda posted in the middle of this thread. Is your post here regarding tube amps mainly?
I have a 4x10 8 ohm cab and I have a 2x10 8 ohm also. I wanted to try the 4x10 with the Tour 450 and see how it sounds. Do you think that is okay to do with this amp head? I know I can use both of the cabs and get 4 ohms. I thought I'd just try the 4x10 and see what kind of volume I get from it.
You wrote: "The specs for the Tour 450 say 300 watts at 8 ohms and 450 at 4 ohms", which basically answers the question. It just delivers more power in a lower impedance, but 8 Ohms doesn't hurt the amp. And yes this regards tube amps mainly, as they usually are fitted with an impedance transformer.
