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That is a very strange question to come from a member who joined in 2002.
Amps don't think, they turn a bass pickup signal into a speaker driving signal.
Every now and then, but not for some years now, someone asks about adding a resistance to the rig to get all the watts out of the amp
Same answer applies.
No.
Amps don't think, they turn a bass pickup signal into a speaker driving signal.
Every now and then, but not for some years now, someone asks about adding a resistance to the rig to get all the watts out of the amp
Same answer applies.
No.
I dont think it's that strange (and whatever happened to the "there is no such thing as a dumb question"). You can connect two 8 ohm speakers and end up with a 4 ohm load right?
I would think that in theory if you had a single 8 ohm speaker, there could be something that could be connected to that speaker in some manner to make a 4 ohm load (and no Im not talking about adding another speaker).
All that accomplishes is space heating. The cab still gets the same voltage applied.
I think what our friend @Downunderwonder is trying to say (and could do so with a tad more kindness 
) is that you will likely notice little or no difference in volume by "getting the most out of your amp" switching to a 4 ohm load. Even though you're tapping into "more watts" it's not enough to make a difference.... certainly not enough to "rig up" the kind of resistore it would take to get the job done. And as he also alluded to, it would get hot. That kind of dummy load (that's what it's called..... not calling you a dummy) would be large and get hot.
So, to see if we can help, how 'bout telling us what kind of gear you have and what your goals are for a potential dummy load rig. Am I correct in that more volume without adding another cab is the goal?
) is that you will likely notice little or no difference in volume by "getting the most out of your amp" switching to a 4 ohm load. Even though you're tapping into "more watts" it's not enough to make a difference.... certainly not enough to "rig up" the kind of resistore it would take to get the job done. And as he also alluded to, it would get hot. That kind of dummy load (that's what it's called..... not calling you a dummy) would be large and get hot.So, to see if we can help, how 'bout telling us what kind of gear you have and what your goals are for a potential dummy load rig. Am I correct in that more volume without adding another cab is the goal?
Yep. No more volume comes from adding resistors.I think what our friend @Downunderwonder is trying to say (and could do so with a tad more kindness
So, to see if we can help, how 'bout telling us what kind of gear you have and what your goals are for a potential dummy load rig. Am I correct in that more volume without adding another cab is the goal?
The device, which would be a very large resistance of some kind, capable of handing half the power of your amp is called, in more than one electronic dicipline one, a dummy load. I deal with dummy loads often in my work.
Here is what happens. I'll use a well known popular amp in my example. The Rumble 500.
This amp is rated at 350 watts with an 8 Ohm load, and 500 watts with a 4 Ohm load.
To keep using your 8 Ohm cab and get 500 watts would require a special resistance of 8 Ohms wired in parallel with your cab, just as you would wire two 8 Ohm cabs.
When you wire two 8s in parallel, half the amp's power goes to each. So your dummy load has to handle half of the 500 watts, or 250 watts and your cab gets the other half.
So instead of getting 350 watts delivered to one 8 Ohm cab, without the dummy load, you now only get 250 watts into the one cab. The other half of your 500 watts just gets turn into heat by the dummy load.
So if you're going for a power reduction then this is a way to do it.
BTW, the resistance you use needs to be rather special. You need a non inductive resistor and to handle 250 watts in a practical manner, you need to double the power handling capacity of the resistor.
So Google yourself up a 500 watt, 8 ohm, non- inductive resistor, and there ya go.
Be aware that in addition to the loss of power, there are other more dynamic reasons that a resistor will not act like a speaker.
Here is what happens. I'll use a well known popular amp in my example. The Rumble 500.
This amp is rated at 350 watts with an 8 Ohm load, and 500 watts with a 4 Ohm load.
To keep using your 8 Ohm cab and get 500 watts would require a special resistance of 8 Ohms wired in parallel with your cab, just as you would wire two 8 Ohm cabs.
When you wire two 8s in parallel, half the amp's power goes to each. So your dummy load has to handle half of the 500 watts, or 250 watts and your cab gets the other half.
So instead of getting 350 watts delivered to one 8 Ohm cab, without the dummy load, you now only get 250 watts into the one cab. The other half of your 500 watts just gets turn into heat by the dummy load.
So if you're going for a power reduction then this is a way to do it.
BTW, the resistance you use needs to be rather special. You need a non inductive resistor and to handle 250 watts in a practical manner, you need to double the power handling capacity of the resistor.
So Google yourself up a 500 watt, 8 ohm, non- inductive resistor, and there ya go.
Be aware that in addition to the loss of power, there are other more dynamic reasons that a resistor will not act like a speaker.
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The Epifani D.I.S.T line can switch between 4 and 8 ohms.
As the guys are saying the difference won't give you more usable volume or better tone.
Adding a second cab would do both.
As the guys are saying the difference won't give you more usable volume or better tone.
Adding a second cab would do both.
I think what our friend @Downunderwonder is trying to say (and could do so with a tad more kindness
So, to see if we can help, how 'bout telling us what kind of gear you have and what your goals are for a potential dummy load rig. Am I correct in that more volume without adding another cab is the goal?
I was actually just doing some early morning thinking/brainstorming thats all as I'm thinking pulling the trigger on either a Demeter Bass 400 or 800. My cabs are both 8 ohms, an eden 2x12 and a Bag End 1x15, so if I went with the smaller amp I was just thinking it would be nice to have the option to run it on a 4 ohm load (seems to me there are actually guitar amp heads that have this ability by the way), hence me asking the question in the O.P.
Sounds like my only option though is to run 2 cabs.
OP, these guitar amps you speak of.... Are you thinking that because they have 16, 8, 4 ohm outputs? That is not what you think. Those outputs are for using with those loads, not for changing the output of the amp.
The device you are looking for is called a matching transformer. These are few and far between for good reason. They are bulky and very expensive. As was mentioned in post #5, the difference in volume would be minimal.
Tube amps have output transformers that have taps to match different loads. Some SS amps have switches that change the amps’s electronics for a lower load impedance. This is to protect that amp from over dissipation from such loads.
Tube amps have output transformers that have taps to match different loads. Some SS amps have switches that change the amps’s electronics for a lower load impedance. This is to protect that amp from over dissipation from such loads.
Technically, the answer to the OP's question is yes - a transformer would do what he wants, but it'd be big, heavy, and likely expensive. An 8 ohm resistor strapped across the amp (in parallel with the speaker) would also make the amp "see" a 4 ohm load, but I don't think you'd want to do that - you'd just be wasting power and adding stress to your amplifier, which I don't think was what you really wanted.
There's nothing wrong with running a solid state amp rated for a 4 ohm load with just one 8 ohm speaker - I do it all the time, and your amp will likely last longer if that's loud enough, as you're stressing it less. If you're fighting for every last bit of power, granted, running a 4 ohm cabinet of similar efficiency will get you a bit more, but the real solution there is probably running 2 8 ohm cabinets, so you get the efficiency bump from more coupled cone area.
There's nothing wrong with running a solid state amp rated for a 4 ohm load with just one 8 ohm speaker - I do it all the time, and your amp will likely last longer if that's loud enough, as you're stressing it less. If you're fighting for every last bit of power, granted, running a 4 ohm cabinet of similar efficiency will get you a bit more, but the real solution there is probably running 2 8 ohm cabinets, so you get the efficiency bump from more coupled cone area.
. . . . or upgrade your cabs to an 8 ohm 112 Barefaced cab (there are other makes) that can push out a lot of SPL in a small and light format.
Suitable transformers are more available than you think, but the ones I know of may not have the power rating the OP needs. Hard to say since he doesn't specify the power. As you say tube amps often have output transformers with multiple impedance taps. If you bought one of those you could connect the amp to the 4 Ohm tap and the speaker to the 8 Ohm tap, leaving the primary and any other taps open. That would do the job but the biggest output transformer I have run across while looking for parts to build my own tube amp was 135 Watts and about the same number of dollars. Bigger transformers may be available but if they cost as much as a second 8 Ohm cab....
I do not consider an audio output transformer with the primary left open as suitable. That primary would carry a lot of voltage from the step up action. Dangerous voltage!!! There are many OPTs available that are rated above 135W. What I wrote was correct.
Yep, as mentioned in the above posts, the extra 30-ish% of power you get from dropping to 4 ohms is not enough to make a noticeable difference in volume, and with a dummy load, it's counterproductive. You need at least 2-3 times the power to get any noticeable volume improvement.
Bob Lee (QSC)
In case you missed it, I work for QSC Audio!
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Yes, if you add a second 8-ohm cabinet you have a net 4-ohm load, and you have two loudspeaker cabinets putting out sound.
If you use just one 8-ohm loudspeaker and put a big 8-ohm resistor in parallel across it you can make a 4-ohm load, but there's no advantage in having a 4-ohm load. Your amp will probably clip into 4 ohms at a somewhat lower output voltage than into 8 ohms, so you'll actually have a little less power available to the loudspeaker. And about half of the power the amp works to produce will just turn into heat in the resistor and not produce any sound.
Yup! run 2 cabs if you want 4 ohm load and more watts that actually translate into more volume. Even if you could put a dummy load on your amp to push it to 4 ohms, half the watts would go to the dummy load and your single cab would get the other half. That means your one 8 ohm cab would get fewer watts and produce less volume than it would without the dummy load.
Normally, Solid State (SS) amps automatically adjust for the ohms load on them. If you hit them with a lower ohms load than they are designed for, protections kick in and turn it off, or they melt. Some SS amps have a switch to specifically change the load. All-valve (all-tube) amps usually have a switch to adjust their impedance match. NONE of these will change the load seen from your speaker cabinet.
In both cases, specifying a 4 ohm load by using a switch while trying to put it into an 8 ohm load just makes for an impedance mis-match and in some circumstances can actually cause damage to the amp. You won't get anymore volume out of it. Just DON'T do it! Just run the Eden 212 without the Bag End 115 if you want to use only one cabinet and be done with it. Since the 115 is the lighter of the two, use that for small gigs, use the Eden 212 for medium gigs and both of them for large gigs. Actually that 212 will handle most gig situations all by itself and will certainly have more volume than the 115 does by itself.
Just because you would in theory double your power to the cab with another 8 ohm load in parallel to the existing one, that existing 8 ohm load is going to perform just the same as if you'd done nothing at all.