gtr1963

Hey guys... I've got a question some of you here may be able to answer. I'm currently running a JCM 900 4100 dual reverb head into a Park(Marshall made) 4x12 cabinet and it sounds great. The Park cabinet is rated at 8 ohms. I am considering getting a 1960 marshall 4x12 cab in the future and wanted to attach my 900 head into both Park and 1960 head.

Will I be able to do this without lowering the impedance and blowing my output transformer? The 1960 4x12 has 4-or 16 ohm mono or 8-ohm stereo operation.

Thanks guys,

Andy

Marshall Amps

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Marshall Amp Forum

American Viking

If you want to continue using your amplifier you need to look for an older Marshall cabinet with an 8ohm impedance.
The newer Marshall cabs will take 8ohm's in Stereo but you would only be using 2 out of four speakers in the cab.
There are older Marshall and other cabs that you can get hardwired to 8ohms. Avatar is another company that you may want to check out, their new cabs are the same price as used 1960 cabs plus you can get them with whatever speakers you want.

__________________


Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

gtr1963

thanks Viking for the info. That really helped me out. I may look for another older 8 ohm cab out there, as I don't really want to modify my head for that.

thanks again,

Andy

American Viking

Right on, and when you do get two 8ohm cabs be sure to set your amp to 4ohms when running both of them.

__________________


Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

woodddj

the 4100 will only work in 8 or 16 ohm. you will see (4)16 on you head. but only the combo's run 4ohm not the heads. i did a reserch and you can mod the head to run 4ohm, but i think that would be a waist of time and money. the park cab will work fine as long as you have the amp set on 8ohm, later if you want to get a 1960 you will have to wire the park cab to 16ohm,( you can find wireing diagrams all over the net). that way you will have two 16ohm cabs running at 8ohms on your head. 2x16=8ohm 2x8=4ohm. its kind of confusing but once you figure it out it will all make sence. oh, i almost forgot. the 8ohm stereo on the 1960 is only used if you have two heads, the 4100 is not a stereo head. if im wrong someone please tell me, but im almost sure this is the correct way.

American Viking

He's right about the head, I didn't realize that. The only way you can run two cabs with a 900 is if both cabs are 16ohms and you set your impedance to 8ohms on the head.

Where he is mistaken is that you can't rewire that Park cab to 16ohms no matter what. A 4x12 with 8ohm speakers can't be wired to 16ohms.

So damn, maybe you're better off buying a newer Marshall cab and ditching the Park for another one. What kind of speakers are in the Park? I know you'll hate to part with it but it may have the same type of speakers as a regular Marshall cab.

__________________


Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

woodddj

i figured i was dead on the info about the 900. but i questioned myself on the cab, thats why i wanted someone to correct me if i was wrong. i thought you could raise or lower the ohms of a 4x12 cab by wireing them in series or parallel. i had a 4ohm 2x12 and rewired them in series to get a 16ohm for my 900.

V-man

I am running my 4100 through an Avatar 4x12 at 8 ohms myself, since my Marshall 16 ohm 1960A is out of state. In other words, same fix you're in: 2 cabs of different impedence and the 4100. The solution for now is to make due with the Avatar (certainly don't need more than a 4x12 right now as is). When the time comes for more air movement, the Avatar goes off to another rig or it's sold and the difference is applied to a 1960B at 16 ohms.

So, ask yourself if it's worth a sale and 2 purchases for 2 compatible 4x12s or if you have enough for your needs now.

__________________
Gibson: '88' Explorer 90, Flying Vs - '02' V-Factor, '06' RI, '07' RI
Jackson: '92' Rhoads Tribute, '92' Rhoads PCS, '02' KV2
'92' ESP/Hill King V
'04' Epiphone Goth V

'84' Marshall 1992
'93' Marshall 4100
'97' Crate Blue Voodoo BV-60 Combo

woodddj

in order to have a 8ohm 4x12, what ohm would each speaker have to be, 8ohm or 16 ohm ? now i know and under stand a 2x12 but the 4x12 confuses me. i know if you wire two 8ohm speakers in series it will up the ohm to 16 and if you wire two 8ohm speakers parallel it will drop them to 4. so how does it work with a 4x12?????

jaze70ss

lots of wiring configs for enclosures.. Four 4 ohms all in series =16 ohms or Four 16 ohms series parallel = 16 ohms Four 8 ohms does not always mean it wont work due to actual impedance being less or more than stated...Its a reactive load and can be more forgiving than you think... (8 can actually be more like 6 ohms) Just check impedance with a good meter after you wire it and if it shows 14ish ohms.. then plug that mother in and let it rip.. Jay

American Viking

You can make a 4x12 with 16ohm speakers come out to be 4 or 16ohm and the same with a 4x12 with 4ohm speakers. The equation just doesn't work with 8ohm speakers, they're kind of a one trick pony at that point. I really believe that the only reason all manufacturers don't just stick to a universal impedance is because they don't want their stuff to be compatible with everything else. Marshall is one of the few companies that tries to make it's heads work with any and everything, but doesn't always work.

Here are some easy wiring diagrams that can explain how it works a little better than I can. The bottom one goes over 4x12 and 2x12 wiring. The diagrams of course apply to any size speaker not just 12". Take care

Wiring a 4 X 12 Speaker cabinet
Jumbo Sunshade - Speaker Wiring Diagrams

__________________


Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

woodddj

thanks for the info.

American Viking

Just glad to help out and learn more from the fellow Marshall player!

__________________


Transformers inside amplifiers were not originally designed to be in there, and the tube was not created for the guitar amp.
ANY recommended idle current is a guideline and in no way a necessary requirement. There is no skeleton key for any tube amp.

ProfChaos

I have a modified Marshall 1960 Classic cabinet through which I play my Marshall 6100 (the EL34 version). The 1960 Classic is nice because it uses the 25-watt green-back speakers, like the classic Marshall cabinets had. A studio engineer helped me to modify my stock 1960 Classic in two ways:

1.) The engineer had access to high-quality, three-ply birch plywood from a boat manufacturer, so we replaced the cheesey fiberboard back panel of the 1960 Classic cabinet, using a real piece of wood. Man, oh, man, what a difference! The highs are more articulated, and the lows are a little beefier, the midrange tones now show a less overwhelming, more balanced relationship to the highs and lows. The cabinet also projects the sound wave in a noticeably superior manner. It just fills even the smallest of rooms in a way that is noticeably better than the sound projected before the mod occurred. (This makes sense, since it was merely for the reason of making a bigger profit per cabinet that Marshall started using fiberboard back panels with all closed-back cabinets; the original, old-school Marshall cabinet after which the 1960 Classic was designed had a plywood back panel.)


2.) The sound engineer and I also performed a series-parallel wiring modification for the speakers.

The second Marshall cabinet pictured at the following hyperlink (the lower--hard-wired--cabinet with the greenback speakers) shows a series-parallel wiring setup in a Marshall cabinet:

(Newer, "Hard-Wired" Marshall cabinet [the one with the 25-watt green-back speakers] illustrates series-parallel wiring)

With this mod, you lose the 16-to-4 ohm switching capability and you must replace the back jack-plate with a generic jack-plate of the same size, but the mod is worthwhile, nonetheless.

cheers,
--Professor Chaos