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Ohms FAQ
- Thread starter IvanMike
- Start date
mr tea said:
No, you can't. Basically, you can never put two amps at one time into a mono cab. Just don't do it. Put it out of your mind.
mr tea said:
In order to connect both power amp outputs to the same (mono) cab, you have to connect them both to the same point (the cab's input connection). So, you've effectively tied the outputs of the two amps *together*.
Speakers and impedance notwithstanding, think about what would happen if you plugged one end of a 1/4" speaker cable into the back panel (speaker output) of one amp, plugged the other end of the same cable into the back panel (speaker output) of the other, then turned one or both on.
Yes, it would end in tears.
+100000. It would be like mixing a 110v power line with a 220v power line. Can't be done. Safely.Richard Lindsey said:
You will likely damage one or both of the amps.
Don't try this with your favorite amp.
Randy
Actually a bit off, but sort of on the right track.frankie said:
Actually its the 4 ohm cab looks like 2 8 ohm cabs in parallel. So you do have the equivalent of 3 8 ohm cabs, not 3 4's.
That error results in the part you got backwards, its the 8 ohm cab that gets 1/3 the power, and the 4 ohm cab gets 2/3 the power.
Randy
Here is a workaround for you.
First of all, if you bass head is solid state, it is not
a '8 ohm' head. Heads are rated down to their lowest
safe operating impedance. For example, my Eden WT300
head is rated at 175 watts with an 8 ohm load and 300 watts
with a 4 ohm load. Its performance is based upon the
load you put on it.
The majority of SS amps can operate safely at 4 ohms today,
and amps that operate safely at 2 ohms are more common
now than they used to be. Check your amp documentation
to verify its safe operating limits.
Valve or tube amps often have switches to select to the
load value that is going to be placed on them, and operate
safely at the selected value. Without going into specific
detail, the output of the 'output' transformer is changed.
However, if your tube amp has a line out function, you could
use it as a preamp.
Run your bass into the valve amp input. Take a speaker cable
and run it from the line out of the valve amp to the line in of
the bass head. Then connect the bass head to the 4 ohm cab
as normal.
Power up and play with the dials and settings till you get the
tone you like, assuming you can get it with this rig.
Like Richard said, forget about running 2 amps in parallel unless
you are interested in a barn burning.
First of all, if you bass head is solid state, it is not
a '8 ohm' head. Heads are rated down to their lowest
safe operating impedance. For example, my Eden WT300
head is rated at 175 watts with an 8 ohm load and 300 watts
with a 4 ohm load. Its performance is based upon the
load you put on it.
The majority of SS amps can operate safely at 4 ohms today,
and amps that operate safely at 2 ohms are more common
now than they used to be. Check your amp documentation
to verify its safe operating limits.
Valve or tube amps often have switches to select to the
load value that is going to be placed on them, and operate
safely at the selected value. Without going into specific
detail, the output of the 'output' transformer is changed.
However, if your tube amp has a line out function, you could
use it as a preamp.
Run your bass into the valve amp input. Take a speaker cable
and run it from the line out of the valve amp to the line in of
the bass head. Then connect the bass head to the 4 ohm cab
as normal.
Power up and play with the dials and settings till you get the
tone you like, assuming you can get it with this rig.
Like Richard said, forget about running 2 amps in parallel unless
you are interested in a barn burning.
just to make sure I won't buy weird things here:
I have two Peavey cabinets (115BX 15", 350 Watt RMS and a 210TX 2*10", 175Watt RMS), and I was thinking to buy a Peavey Max 450 bass head (450 Watt in 2ohm, 300 Watt in 4 ohm and 170 Watt in 8 ohm), am I doing a good thing here? And what would be the total output in Watt I would get?
Just to make sure I don't buy this head to realize it's not the optimal amp, or I don't get the 'desired' output.
I have two Peavey cabinets (115BX 15", 350 Watt RMS and a 210TX 2*10", 175Watt RMS), and I was thinking to buy a Peavey Max 450 bass head (450 Watt in 2ohm, 300 Watt in 4 ohm and 170 Watt in 8 ohm), am I doing a good thing here? And what would be the total output in Watt I would get?
Just to make sure I don't buy this head to realize it's not the optimal amp, or I don't get the 'desired' output.
You don't really give us the full infornmation here, which is
what is required to answer your question.
According to a spec sheet I accessed off a link on the
Peavey website
[Invalid or Expired Link Removed]
the 115BX comes in a few versions.
The 115BX BW with a "Black Widow' driver. This is rated at
700 watts and comes in 4 or 8 ohms.
The 115BX also comes with a Scorpion Driver rated at 400 watts at 4 ohms.
Kindly check your specs or cab and verify the impedance.
However, we can discuss the situation as it stands for
the 4 ohm cab, assuming that is what it is.
The 2 cabs hooked up together will run at 2 ohms
( 4 ohms each) and the Max 450 will deliver peak 450 watts
at that impedance according to the website specs. I note the
2x10 is rated for 175 watts, 350 peak at 4 ohms.
The amp will deliver power to each cab equally, ie 225 watts
to each at peak at 4 ohms per cab, (2 ohms system total). At that point the amp may start to clip. A slightly larger amp like the Max 700 may be a better choice if you intend to play
consistently at very high volumes or at outdoors venues.
That would give you a bit more headroom. There are also
a lot of other amp choices in that size and price range.
For lower volume applications, smaller rooms or non metal
bands, you should not have an issue and it should be a nice
setup, tight and punchy top and lots of fat bottom.
what is required to answer your question.
According to a spec sheet I accessed off a link on the
Peavey website
[Invalid or Expired Link Removed]
the 115BX comes in a few versions.
The 115BX BW with a "Black Widow' driver. This is rated at
700 watts and comes in 4 or 8 ohms.
The 115BX also comes with a Scorpion Driver rated at 400 watts at 4 ohms.
Kindly check your specs or cab and verify the impedance.
However, we can discuss the situation as it stands for
the 4 ohm cab, assuming that is what it is.
The 2 cabs hooked up together will run at 2 ohms
( 4 ohms each) and the Max 450 will deliver peak 450 watts
at that impedance according to the website specs. I note the
2x10 is rated for 175 watts, 350 peak at 4 ohms.
The amp will deliver power to each cab equally, ie 225 watts
to each at peak at 4 ohms per cab, (2 ohms system total). At that point the amp may start to clip. A slightly larger amp like the Max 700 may be a better choice if you intend to play
consistently at very high volumes or at outdoors venues.
That would give you a bit more headroom. There are also
a lot of other amp choices in that size and price range.
For lower volume applications, smaller rooms or non metal
bands, you should not have an issue and it should be a nice
setup, tight and punchy top and lots of fat bottom.
Yes Thor you are right, I didn't give you all the specs because I didn't realize there were two 115BX cabinet editions. Well the one I have is equiped with a Scorpion Speaker (it looks a lot tighter than the new model, mine still has the 'old school' Peavey logo) rated at 400 Watt and 4 ohm. I was just wondering: the amp will deliver 225 Watt to each cab, but the 2*10" is rated 175 Watt, this won't damage the speakers right? (I mean I think the amp doesn't supply 225 Watt continuous)
About the volume applications: I don't play in a metal band and very high power is not really required here. I come from a Rickenbacker BR-35 (1979 - 75 Watt amp through a 15" speaker), but the volume was not sufficient for small gigs (gigs at birthday parties from friends etc.). You said the Max 700 would allow more headspace, but lets say my financials don't allow the extra 120, and I don't think I will need that much more power.
PS: I think this stack will look so tight, I just love Peavey
About the volume applications: I don't play in a metal band and very high power is not really required here. I come from a Rickenbacker BR-35 (1979 - 75 Watt amp through a 15" speaker), but the volume was not sufficient for small gigs (gigs at birthday parties from friends etc.). You said the Max 700 would allow more headspace, but lets say my financials don't allow the extra 120, and I don't think I will need that much more power.
PS: I think this stack will look so tight, I just love Peavey
Timebutt said:Yes Thor you are right, I didn't give you all the specs because I didn't realize there were two 115BX cabinet editions. Well the one I have is equiped with a Scorpion Speaker (it looks a lot tighter than the new model, mine still has the 'old school' Peavey logo) rated at 400 Watt and 4 ohm. I was just wondering: the amp will deliver 225 Watt to each cab, but the 2*10" is rated 175 Watt, this won't damage the speakers right? (I mean I think the amp doesn't supply 225 Watt continuous)
About the volume applications: I don't play in a metal band and very high power is not really required here. I come from a Rickenbacker BR-35 (1979 - 75 Watt amp through a 15" speaker), but the volume was not sufficient for small gigs (gigs at birthday parties from friends etc.). You said the Max 700 would allow more headspace, but lets say my financials don't allow the extra 120, and I don't think I will need that much more power.
PS: I think this stack will look so tight, I just love Peavey
You should be just fine with this rig, go for it. Speaker
damage typically is more related to clipping than to
overdriving the subwoofers.
No the amp doesn't supply 225 continous, that is the peak
rating per cab and that should be pretty damm loud! You shouldn't have to push that rig nearly that hard.
very nice, I can probably have the amp by the end of the week, can't wait
thnx for all the help, it cleared a lot of things out
thnx for all the help, it cleared a lot of things out
You'd have done the same for me, bro.
Now after you get it, start a thread on how it worked out!
And pics, no pics = no head.
This is TB and WE WANT PICS!!
Now after you get it, start a thread on how it worked out!
And pics, no pics = no head.
This is TB and WE WANT PICS!!
You bet I will provide pictures, I'm absolutely in love with the two speaker cabs I already have (just waiting for the amp to groove them). Can you imagine: every morning I wake up and right in front of my bed are two monster Peavey cabs, and I want to play them so bad. It's been like this for about two weeks now, and it's seriously time the amp gets delivered. I will get it in the middle of the examinations but that won't stop me from jamming with this rig at all
(pics following by the end of the week)
(pics following by the end of the week)
Put them on the Show your Amps thread when you get them.
Good luck on your exams. Stay off timewasting Bass sites
till you are done!
Good luck on your exams. Stay off timewasting Bass sites
till you are done!
Alright, a quick question.
with an amp head with these specs,
250 Watts per side at 4 Ohms; 170 Watts per side at 8 Ohms.
which would be safer to run,
2 4x10 cabs @4 ohms, or 2 4x10 cabs at 8 ohms?
with an amp head with these specs,
250 Watts per side at 4 Ohms; 170 Watts per side at 8 Ohms.
which would be safer to run,
2 4x10 cabs @4 ohms, or 2 4x10 cabs at 8 ohms?
Alright,apparently i couldn't make much sense of what you were saying,so I'll just ask this instead of trying to figure it out:
I have a Berhinger Ultrabass BX1200(http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/480675/)
and I might in the future buy this Gallien-Krueger 210BLX-II Cab(http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/601056/) to go with it,but will it work properly?
I have a Berhinger Ultrabass BX1200(http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/480675/)
and I might in the future buy this Gallien-Krueger 210BLX-II Cab(http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/601056/) to go with it,but will it work properly?
According to the specifications provided at the site,
the Behringer has a 4 ohm speaker, and is
capable of driving a 4 ohm extension cab according to the
.pdf file provided.
The GK is an 8 ohm cab according to the specs provided.
It will draw 1/2 as much current as the internal speaker.
I.E. the internal speaker will get 2/3's of the power and
the external will get 1/3 of the power.
A better match would be a 4 ohm cab extension unit so each gets 1/2 of the power available, IMO.
Look for one of these used. They come in 4 and 8 ohm versions:
http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/601033/
the Behringer has a 4 ohm speaker, and is
capable of driving a 4 ohm extension cab according to the
.pdf file provided.
The GK is an 8 ohm cab according to the specs provided.
It will draw 1/2 as much current as the internal speaker.
I.E. the internal speaker will get 2/3's of the power and
the external will get 1/3 of the power.
A better match would be a 4 ohm cab extension unit so each gets 1/2 of the power available, IMO.
Look for one of these used. They come in 4 and 8 ohm versions:
http://www.musiciansfriend.com/srs7/g=bass/search/detail/base_pid/601033/
Thanks IvanMike, I was having trouble remembering all this stuff. I had read it on another forum but couldn't remember how it all came together. Nice post, very clear. Just to be sure I'm getting all this.
Amp at 4 Ohms can run either:
Two cabs at 8 ohms each or
One cab at 4 ohms. Right?
Amp at 4 Ohms can run either:
Two cabs at 8 ohms each or
One cab at 4 ohms. Right?
