#1
hey there
before you say anything, this belongs here purely because i need to modify something based on the answers i get here
I recently got a Marshall AVT150H head
I also got (in some insane deal) a couple of Laney 2x12 cabs
the speakers in the cabs are Celestion's (not that that is relevant) and they are 50watt power, 8 ohm impedance.

what i want to know is, provided i wire them for the correct impedance, will i be able to use them with the head?
someone told me that 50watt speakers will handle 100watts of power but only output 50watts of it but I'm somewhat cynical

Also, if i were to wire it so the speakers in the cabs were parrallel (giving 4 ohms impedance per cab) and then wired both cabs in series (to give 8 ohms, 200 watts) and then put them into the 8ohm jack on my head would that work perfectly well?
#3
Quote by Bigsteve92
someone told me that 50watt speakers will handle 100watts of power but only output 50watts of it but I'm somewhat cynical
You should be cynical. This is just plain wrong.

Quote by Bigsteve92
Also, if i were to wire it so the speakers in the cabs were parrallel (giving 4 ohms impedance per cab) and then wired both cabs in series (to give 8 ohms, 200 watts) and then put them into the 8ohm jack on my head would that work perfectly well?
It would make more sense to wire each cab with it's speakers in series, giving you 16 ohms. Each cab will have a separate cable. Plug them both into the amp. (you have 2 jacks on the back of your avt) You won't harm this solid state amp by having more than the recommended impedance. You won't get the full 150w output unless you have 4 ohm impedance. But you can't get 4 ohms with 4 8-ohm speakers.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#4
Speaker of the same impedance share power equally regardless of whether they are wired in parallel or series. So 2 x 50W speakers will handle 100W.
You AVT stands for Advanced Valve Technology or something does it not? And I believe they are SS output with Tube pre-amp (Hybrid). While maximum power transfer occurs when impedances are matched, SS amps are very forgiving with regards to loads and don't need to be exactly matched to prevent damage that a tube amp could incurr.
So with 2 speakers, your choice is either 4 Ohms (Parallel) or 16 Ohms (series). Pick the one that best matches what your amps user guide specifies.

EDIT just noticed you've got two cabs. So i'd aldso go for 16 Ohms per cab and when each is plugged into your amps output jacks (which are usually in parallel) you'll end up with 8 Ohms and 200W power handling.
Moving on.....
Last edited by KenG at Sep 1, 2009,
#5
Quote by SomeoneYouKnew
You should be cynical. This is just plain wrong.

It would make more sense to wire each cab with it's speakers in series, giving you 16 ohms. Each cab will have a separate cable. Plug them both into the amp. (you have 2 jacks on the back of your avt) You won't harm this solid state amp by having more than the recommended impedance. You won't get the full 150w output unless you have 4 ohm impedance. But you can't get 4 ohms with 4 8-ohm speakers.


There's an 8 ohm output and an 8/4ohm output. will i get the full 150w through the 8 ohm output?

Quote by KenG
Speaker of the same impedance share power equally regardless of whether they are wired in parallel or series. So 2 x 50W speakers will handle 100W.
You AVT stands for Advanced Valve Technology or something does it not? And I believe they are SS output with Tube pre-amp (Hybrid). While maximum power transfer occurs when impedances are matched, SS amps are very forgiving with regards to loads and don't need to be exactly matched to prevent damage that a tube amp could incurr.
So with 2 speakers, your choice is either 4 Ohms (Parallel) or 16 Ohms (series). Pick the one that best matches what your amps user guide specifies.

EDIT just noticed you've got two cabs. So i'd aldso go for 16 Ohms per cab and when each is plugged into your amps output jacks (which are usually in parallel) you'll end up with 8 Ohms and 200W power handling.


I thought it might be like that but I wasn't sure and i can't afford to experiment incase i break something as i now have £24.86 left in my bank account - thank f*** i'm living at home with the parents for free

I think i'd rather add a jack to one of my cabs and plug them both in through one output just to be sure - there's nothing to lose from that right?
#6
Quote by Bigsteve92
There's an 8 ohm output and an 8/4ohm output. will i get the full 150w through the 8 ohm output?
Probably not. The 8/4 output might have a switch in it to change an internal feedback loop or smth. You might get more output at 8 ohms by using only the 8 ohm jack, but probably not the full 150w.

Quote by Bigsteve92
I think i'd rather add a jack to one of my cabs and plug them both in through one output just to be sure - there's nothing to lose from that right?
That would be the easiest and most manageable, imo.
Wire both cabs up for 16 ohms and have 2 jacks in parallel on at least one of the cabs.
Then daisy-chain them.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#7
so basically all i need to do is drill a hole on the back of the top cab and put a jack in, and then connect the pos and neg of the new jack to the pos and neg of the current jack?

can you recomend me a specific jack for this or is a standard guitar jack fine?
#8
Quote by Bigsteve92
so basically all i need to do is drill a hole on the back of the top cab and put a jack in, and then connect the pos and neg of the new jack to the pos and neg of the current jack?
Yep. pos to pos. neg to neg.

Quote by Bigsteve92
can you recomend me a specific jack for this or is a standard guitar jack fine?
just a standard 1/4" jack, nothing special.

Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#9
SYK
*skips quote to save space*
thanks for the help dude
i should have this all sorted out tomorrow

what type of wire should i be using for this btw?
#10
Quote by Bigsteve92
SYK
*skips quote to save space*
thanks for the help dude
i should have this all sorted out tomorrow

what type of wire should i be using for this btw?


just get like 16AWG lamp cord


you can't hear the difference between anything fancier
#11
at least 18 gauge in the cabs. 16 gauge would be even better.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#12
I just got round to taking the back off and having a look -
both cabs contain two 16 ohm speakers
the reading on my multimeter across the input jack is 6.9-7.1 ohms
when i wire these in parallel i'll be getting about 3.5 right?
i'll be putting this through the 4 ohm output now right?


and the wiring on the cabs seems to have been done with the standard wire you'd find inside a guitar; is that right or is it the wrong gauge?
#13
Quote by Bigsteve92
I just got round to taking the back off and having a look -
both cabs contain two 16 ohm speakers
the reading on my multimeter across the input jack is 6.9-7.1 ohms
when i wire these in parallel i'll be getting about 3.5 right?
i'll be putting this through the 4 ohm output now right?
Yes.

Don't sweat the difference between DC resistance and the impedance of the speaker.
I've seen 8 ohm speakers read as low as 6 ohms on DC resistance.

Quote by Bigsteve92
and the wiring on the cabs seems to have been done with the standard wire you'd find inside a guitar; is that right or is it the wrong gauge?
Kinda wimpy, if you ask me. You can get away with lighter gauge wire when the speaker impedance is higher. But even with 16 ohm speakers, at 50 watts you'll have almost 2 amperes of current. the 22 or 24 gauge wire you'll find in a guitar won't melt down or anything. But personally, I think a larger gauge is appropriate.
Meadows
Quote by Jackal58
I release my inner liberal every morning when I take a shit.
Quote by SK8RDUDE411
I wont be like those jerks who dedicate their beliefs to logic and reaosn.
#14
Quote by SomeoneYouKnew
Yes.

*snip*


so in that case i can actually just use some of my spare wire to have my rig going for the time being and then when i get a chance i can get some proper wire and re-do the whole cab with it