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Quick Amp Question about Ohm

C

Chunkyzz

Mar 1, 2012
55
0
#1
Heya guys!
simple question!
i have a trace elliot vintage GP11 simple 4 12"
i think its a 250W,its old late 70's and all the marking on it is gone,vanish,disappeared....

Since it was 2 heavy i took it apart,so i got a Head(built into a box yes) and 2 cabinets of 2 12".
the speaker says its an 8 Ohm

MY 2 Tiny Question are!

1.Can i use only one cabinet of 2 12"?(its the same speakers as there were before i took them out of the Regular amp)
for lets say smaller gigs? when there is no room for the 2 cabs.

2.i might buy a new Head (TC BG250 or the bigger one) and it says on the amp minimum 4 Ohm,can i use my Cabinets?the trace 8Ohm?

so! can i drive half the amount of Speakers with the same head?
and can i use my old Speakers with a new Head?

thanks alot!
if u did not understand feel free to ask =)
 
#2
You can power an 8 ohm speaker load with an amp that is rated at 4 ohm minimum load. You just cannot go below 4 ohms or the amp will overheat and possibly burn up.

I am not sure how your original 412 was wired, but if you are saying each speaker is 8 Ohm, than each 212 cabinet is probably now 4 ohms (and your original 412 was 8 Ohms- as a guess). Which would be fine. I don't think you would want to run both of your 212s together anymore though, unless you have a series cable, or you will be running at 2 ohms.

The confusion is how you are using the term "speaker" - the correct way is each cone is a speaker, all the cones together in a box is a "speaker cabinet" or "cabinet". Calling the entire box a speaker is misleading for this very reason.

What you really need to do is determine the"nominal impedance" - the ohm rating - of each of your 212 speaker cabinets. If it's the case that each of these cabinets is 8 ohms then you would be ok using just one of them, because running 8 ohms in a 4 ohm minumum amp is ok, or you could use both them, as the two 8 ohm cabinets together would be 4 ohms, still ok with your amp.
 
#4
HolmeBass said:
You can power an 8 ohm speaker load with an amp that is rated at 4 ohm minimum load. You just cannot go below 4 ohms or the amp will overheat and possibly burn up.

I am not sure how your original 412 was wired, but if you are saying each speaker is 8 Ohm, than each 212 cabinet is probably now 4 ohms (and your original 412 was 8 Ohms- as a guess). Which would be fine. I don't think you would want to run both of your 212s together anymore though, unless you have a series cable, or you will be running at 2 ohms.

The confusion is how you are using the term "speaker" - the correct way is each cone is a speaker, all the cones together in a box is a "speaker cabinet" or "cabinet". Calling the entire box a speaker is misleading for this very reason.

What you really need to do is determine the"nominal impedance" - the ohm rating - of each of your 212 speaker cabinets. If it's the case that each of these cabinets is 8 ohms then you would be ok using just one of them, because running 8 ohms in a 4 ohm minumum amp is ok, or you could use both them, as the two 8 ohm cabinets together would be 4 ohms, still ok with your amp.
Click to expand...

+1 ditto
 
#5
ok so lets see if i got it =)

I had a Combo amp with 412 speakers whice i took apart, and made 2 cabinets of 212
now! on the amp head the huge heavy block(transistor i think its called) is written with a stamp 8Ohm whice means the head is 8 ohm(as far as i know)
and on each speaker whice is wired in series every amp has a stamp 80hm on them.
so! what should i do?
run 212 and its ok? or run all of them together? or go to someone who knows and check the amp?
 
#10
ImageUploadedByTalkBass1358279552.570947.jpgImageUploadedByTalkBass1358279565.814842.jpg
2 more 2 come
 
#13
sorry for the wait, I was researching this amp.

In pic #2, there looks to be just "holes" is this true?

when in the combo, were the speakers wired directly to the amp, or plugged with a cord?
 
#14
thats true,its just holes since the amp was a combo the amp had 2 lines going out from the amp head part to the 412 in a series connection.
the head section is a 2 piece which is connected together by a cable,the transformer and power socket to the head-plate with the EQ and the vol and so
 
#16
Chunkyzz said:
ok so lets see if i got it =)
and on each speaker whice is wired in series every amp has a stamp 80hm on them.
Click to expand...

I am glad Andyman is on this, because a sentence like this is just confusing. Actually, meaningless. There are no amps on speakers.

But from the pics the speakers are 8 ohms (the space between "8" and "ohms" helps a lot, doesn't it?) and if you really wired them in series than each of your 212's is a 16 ohm cabinet, and running them together in parallel (the way 99.99% of speaker cabinet jacks and amplifier jacks are wired) then you'll get 8 ohms net.

If you amplifier can only go as low as an 8 ohm load, this will be ok. If you actually wired the speakers in the cabinets in parallel then you will break your amp.
 
#17
lets see if i understand parallel VS series.
what i did is the the - of the 2 speakers is connected to the - of the Amp Head to the same place together and not Speaker to speaker and then to the Amp.

got it?
same for +
 
#18
and Yea this is my Amp the one in the pic.
it was a combo so no Jack connected to the Plate.

and just to let you guys know, i am not going to connect any other speaker/cab/cabinet other then the ones that was in the combo,lets say i took the combo and splitd it into 3 boxes =)
 
#19
Chunkyzz said:
lets see if i understand parallel VS series.
what i did is the the - of the 2 speakers is connected to the - of the Amp Head to the same place together and not Speaker to speaker and then to the Amp.

got it?
same for +
Click to expand...

So both negative speaker terminals ( - ) are wired together and to the negative amp terminal, and both positive speaker terminals ( + ) are wired together and to the positive amp terminal? That's a parallel connection!! Have to go right now, will come back later, don't run your amp like that!
 
#20
oh ****... i did already play with the amp for 2-3 hours at low Volume... thank god the gig was canceled...
guess i go to my friend who builds amps and stuff.... to check the things i did... and i will get a punch to the head lol
thanks!
 

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