Marshall 4x12 Cabinet Wired Improperly.wmv

A Marshall cabinet with four (4) 15 ohm speakers wired in series for 60 ohms. This caused the amplifier to dead short one of the EL34's. The cabinet was rewired properly for 16 ohms.

[@Wardell43]

Good video. When ever buying used equipment you should always check the ohms before attaching an amplifier to it. Even if it's from a friend. If you don't know what you're looking for get someone that does. If you're using 2 cabinets, they must be wired in phase(The same) or they will cancel each other out. There's wiring diagrams all over the internet and there's plenty of demo's on you tube like this one. A problem with buying used equipment is people stealing out the good speakers and replacing them with something cheaper, which in this case could have been 8 ohm speakers in a cabinet that says 16(or 15). you must hook the amp up to the proper load!

[@wesdavis7371]

That.....is awesome. "There's a little thunderstorm outside...." Hell, there was one in that tube too!

[@sdownfallband]

Good video. I have a Peavey Windsor Amp Head, that is oscillating at RF when all tone & texture controls are turn off. All the last EL34 tube red plates pretty quick. I've tried different tubes and check many compnents (out of circuit, and no luck. I have not tried it with a differnt cabint. Your video here, made me think of a similar possibillity.

[@ElPasoTubeAmps]

If you have four (4) 16 ohms speakers you can wire them as I did in the video or you can put them all parallel (+ to + and - to -) for all speakers and end up with 4 ohms. Not sure what would be best for your Marshall. Hope this helps.

[@ElPasoTubeAmps]

This may or may not have anything to do with your problem but I have seen on several occasions where the reverb tank and/or reverb circuit can cause oscillation. I just fixed a really nice Fender Deluxe Reverb (pair of 6V6) that had a bad 25uF/25v cap across an 820 ohm cathode resistor. Turning up the reverb just slightly sent it into a 4 kHz squeal. Similarly I just sent out a Crate VooDoo with a bad reverb tank that would squeal very high (didn't measure the frequency) with a little reverb on.

[@kaipo1444]

To properly wire a Marshall 412 cabinet the total impedance should amount to 16 ohms! This is the typical impedance for Marshall cabinet. So in essence two of the 16 ohm speakers should be wired in series on each side and then the output of the paired series connected in parallel. So you will have the series connection of two speakers at 32 ohms and then connect each series of two in parallel with a final impedance of 16 ohms. The whole reason for the 16 ohm speaker being used in the UK is in the early days of building speaker cabinets for PA use they tended to attach several cabinets together, but they made the mistake of using small gauge wire and ended up having impedance problems. Marshall output section does not do well at low impedance speaker loads.

[@basspig]

Low or no-load conditions with high amounts of drive generally cause excessive screen grid current. Unchecked, this could lead to tube failure. Good catch on the speaker impedance and wiring!

[@FireicerCooper]

The cable you used is called a figure of 8 twin just so you know, nick named bell wire.

[@claytonaustin9955]

Marshall amps were routinely 8 OR 16 ohms. (the true vintage ones were very often 8...same is true for Hiwatt). HOWEVER, for those of us who toured using 4 cabinets per head ...this was the correct way to wire it if you wanted to set your amp to 16 ohms using 4 cabinets without much other monkeying around. Since it was internally done without having the polarity incorrect on any of the four, it may have been that way on purpose.??? By the way, this gives you a very nice sound on stage. Not so nasty up close...but you don't loose it as you get farther away either. And yes, you will blow some tubes if you only have one speaker cabinet plugged in at 60 ohms. You do need all four or you are asking for it

[@kaipo1444]

I’m afraid your comment is a little confusing. You said that, “Marshall amps were routinely 8 OR 16 ohms.” Were you talking about the speaker cabinets? Or the amplifiers themselves? Marshall Amplifiers since 1966 have had a selectable impedance of 8 & 16 ohms (and later on 4, 8 and 16) with the pin selector. So you set the impedance according to what speaker cabinet you’re using or how many. I have never seen a 4 x 12 stock Marshall cabinet that had impedance of other than 16 ohms. Hiwatt amplifiers also have a selector switch for the speaker impedance of 4, 8 and 16 ohms, along with most of the Fane purple loaded 4 x 12 speaker cabinets were also 16 ohm. I’m a little curious how you connected 4 Marshall speaker cabinets to one head? Most Marshall amplifier heads only have two output jacks with the exception of the model 1967 Major 200 watt amplifiers.

[@claytonaustin9955]

Kai Po Let me clarify, I realize few people are technicians looking through these vids. Obvious (or not), I was referring to the speaker cabinet, not the amp. My bad. 16 ohms was by far most common. But if you were in music in the 70s, you shouldn't even be arguing with me. There were plenty of 8 ohm cabinets out there at that time. I've been mostly out of music for close to 20 years, and I know if you didn't specify you usually got a 16 ohm cabinet. I still have most of my gear, My hiwatt cabinet I bought mid 80s is definitely an 8 ohm, although my oldest hiwatt cab. (1970ish) is 16...which is the reason it was never used for touring. (For the most part, we used marshall cabinets for touring, Hiwatt heads) I do not own any 16 ohm marshall cabinets, they are all 8. Last cab. I bought was in the 80s and it was made in the 70s. I don't recall ever buying a 16 (although most folks had 16ohm ones), although the 8 ohm ones were getting harder to find as time went on. The ONLY reason I always needed 8 ohm ones was because that was what we started with and the idea of replacing all of them was irritating. As far as how to wire them, you already should know if you are versed on impedence. But I will humor you. In my rig, rather than running 4 cabinets at 32 ohms each and using an adapter for 4 (some marshalls had 4 outs,...I don't think I ever had a Hiwatt with 4), I had 2 or three adapters made,..they have one input (from the amp) and 4 outputs, the outputs HAD to ALL be plugged into 8 ohm cabinets...and they worked in a similar way you would wire 4 speakers up in a cabinet. Once in a while we would use 8 cabinets each, which is why I have more than one of those adapters (when using 8, obviously we were set to 4 ohms at the amp. Even though we had quite a few heads, stage volume just gets wayyy too loud if you are actually using more than one head. The only problem with 8 cabinets was you needed your guitar amp mic a long distance from the drummer, since you'd get a lot of bleed, I seem to remember keeping a single 8 ohm speaker (in a single cabinet) and turning it sideways away from the drummer so that snare drum was not always going into the guitar mic louder than the guitar was. By the way, just because you read somewhere that only a marshall major had 4 speaker outs, does not make it so. It was less common for sure. But I've seen wayyyyy too many with 4 for me to think the one I had was some sort of mistake.

[@monkeyrocks5150]

thankyou so much i was just looking for this solution

[@crunchchannel9391]

Drugs were hard on equipment in the 80s

[@monkeyrocks5150]

Holey smokes! just wired it with lamp cord too and it changed the sound dramatically !!! I was all scewed UP !!!!!!!!!!!!!!!!!! before!!! .................THANK YOU !!!! so throw amp switch to 16 ohms ? will work?

[@rsweetjr16]

THANK YOU ,THANK YOU.

[@rjake61]

The only speaker terminal with two wires landed on it are the + and - going to the cab jack, at least when I do a series/parallel cabinet job...

[@ElPasoTubeAmps]

Do the plates of the EL34's turn red with no drive (i.e. in a static state?) If so, as you say, it is oscillating or the bias is off a good bit. Good luck.

[@bigbird9794]

I have a very Similar vintage Marshall 4x12 cab. I need it to go to my Mesa triple rectifier which has only options of 4 or 8 ohms. Is there a wiring diagram I can use to make this work?

[@carrollledscarrollleds2032]

Hello I have a 1970 revival earth sound research amp, it has four speakers, should I wire it like you did the Marshal?

[@PROGITAR]

hi, i have ibanez soundwave SW100 that can produce 100w. The original speaker is 8ohms 200watt ( according to the suipplier ). it is possible to add one more 8 ohm speaker in parallel ( it has 2 output jack ). Question : can i change the original speaker to 2 x 400watt RMS ?

[@jks2]

probably a lot louder after rewiring. die hard output transformer on that marshall, he probably never cranked it.

[@pillarsofserpents]

man, is it me or are those wires REALLY REALLY thin? My old Marshall has some big, thick wires. I feel like you gotta replace those. they can't be giving enough juice.

[@ElPasoTubeAmps]

This is a number of years ago but I do remember the wires being very small. #16 or #14 wire would have been better.

[@pillarsofserpents]

@@ElPasoTubeAmps Right on. I thought they seemed small. ha

[@utubehound69]

Thx!!!

[@crunchchannel9391]

So now its a 16 ohm cabinet? how does it sound now? i hear those G12-65 speakers are good ones.

[@ElPasoTubeAmps]

I never heard it personally but the musician was much happier with it and most of all, it quit blowing his EL34's.

[@GoldenGateNum9]

*It's series parallel wiring on a tube amp, tube amps are fussy & don't like that shit, but it could have been a thousand things which blew the fuse.*

[@jymebale8464]

Sir, Your breathing sounds real labor intensive which can mean you are much larger than you should be, every move you make you breath so hard, please have your self checked, you need to stay around for sometime, please.

[@underpressureman]

Can somebody help me? I have a 4x12 marshall cab with 4x 8 ohm Celestion's and I would like to wire it up to get a total of 8 ohm's. Will series/parallel wiring work for that?

[@ElPasoTubeAmps]

Put two of the speakers in series connecting plus (positive) to minus (negative). This puts the speakers in series and in phase so they work together pushing outward and inward in sync. This will give you two speakers in series which will look like one 16 ohm speaker. Do the same for the other two speakers. Now you have the equivalent of two 16 ohm speakers so you want to connect them in parallel, plus to plus (positive) and minus to minus (negative). Now you have 8 ohms and all speakers are in phase. Hope this helps.

[@underpressureman]

@@ElPasoTubeAmps Thank you so much!!! Definately helps! I watched a video on how to do this wiring setup, but he was using all 16 Ohm speakers so I wanted to double check it would come out to 8 Ohms using 8 Ohm speakers! Im new to all this, but as a musician and a studio owner/engineer I'm trying to learn to do as much as I can buy myself for stuff like Repairs/Maintenance/Mods, and any help is always mucho valued! So, can I ask one more thing. How would I wire it up, if I wanted my 4x12 to be 16ohm's using all 8 Ohm speakers? Also I always forget but whats the rule when it comes to cab/amp impedance mismatches. If I remember correctly, it's you dont want the cabinet to be a higher impedance than your amp right?

[@ElPasoTubeAmps]

@@underpressureman You are not going to get 16 ohms using four 8 ohm speakers. Your options are 8 ohms, 2 ohms or 32 ohms. I agree with you on mismatch to go low on the speakers. The worst case I ever saw was four 16 ohms speakers wired in series (64 ohms) and it kept blowing the EL34's our of the amplifier until I had the customer bring his speaker cabinet to me and quickly saw the problem. If you had four 16 ohm speakers you could get 16 ohms, 4 ohms or 64 ohms.

[@underpressureman]

@@ElPasoTubeAmps Okay, thanks, that all makes perfect sense. Can I bother you with one last question? And I appriciate all the help so far. I actually have a pair of 16 Ohm vintage 30's that Im not using in anything, but all the other speakers I have are 8 Ohms. I really want to try mixing vintage 30's with G12M-70's but is there any way to use x2 16 OHM speakers and x2 8 OHM Speakers in a 4x12 and what would the options for wiring be if you can?

[@ElPasoTubeAmps]

@@underpressureman You could put the two 16 ohm speakers in parallel for 8 ohms then that pair in series with the single 8 ohm for 16 ohms. You could also put the two 16 ohm speakers in parallel for 8 ohms and put that pair parallel with your single 8 ohm for 4 ohms.

[@cruisingthethaiway6881]

It looks like all you did is make it worse by reversing the polarity of two speakers. Did you check it with an ohm meter to make sure the impedance is correct? Your diagram was correct, your wiring was not by the looks of it with poor video quality.

[@denniswalsh8476]

Sure was wired correctly for impedance and phasing.

[@crunchchannel9391]

Thats what i thought as well. He did right by wiring the 2 left pair and 2 right pair together parallel but then he messed up with the bottom wire in series he either needs to remove the bottom or the top wire that connects the 2 pairs together.

[@moodyga40]

some one did a boo boo

[@moodyga40]

me i use lamp cord too

[@MRgamer016]

do then Cabinets come empty