figured i would try it this way first, the direct approach lol.

ok need ohms education.
i just recieved a 1x12 speaker cab in great condition, however the speaker is not so hot. no big deal cause i got the cab at asteal of a deal so i can afford a better quaity speaker and still not be out to much.
ok here the deal, i dont understand ohms and how it applies to speakers.
how do i know what speaker im gonna need? what happens if my amp and speaker dont mix? whats a good quality speaker for this turd?
the only thing about the cab is the jack socket. where is a good place to get one of these things?
ive not seen this topic on here before so here is a chance for you to hold
yet another class. "ohms and speakers 101".

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

If the amp is solidstate (probably not, I know) then don't worry about speaker resistance. Just go for as low a resistance rating as you can find.

What is really important is what speaker resistance rating (Ohm's) is your amp capable of handling?
How many speakers are you looking to put in the cab and what size?

You're better off to directly match speaker resistance to the amps ohm rating (greek omega sign). If you're in a bind, you can go higher rated by one step for a couple of hours at not much risk of damage. I.e 4ohm amp, 8 ohm speaker. 8ohm on amp, 16 ohm speaker.
I can't stress enough, it's not good practice to do that all the time. You can get away with it once in a while, in an emergency, not constantly. Never plug a speaker giving less resistance than the amp is rated for. Dont plug a 4ohm speaker into a amp needing a 8ohm load.

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No no and no

n the meantime, anybody else can join in on this topic. it takes a bit of time for the bat signal to reach across the world to niki's area of the globe.

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

must be a clear sky this evening. the bat signal traveled fast.
ok dang now i gotta rethink. the plan was to have the cab (1x12)
as a general purpose cab, one for whatever amp i wanted to use it for at the time.
ok so match the speaker with the intended amps load, got it.
ok so give me some options here on quality good speakers.
also where is a good place to get a jack to put on the cab? the cab came w/o a jack. its an eminence cab if that helps niki.

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

Back of the cab is the best place to put the input jack. Thats where it is on the back of most amps. Is it a open backed cab? If so cut some ply to run across the back and house the socket in there.

I'd suggest going with a 8ohm load then. I can't think of many amps that solely use a 4ohm cab. My Vibrochamp XD and Watkins Clubman do and their the only ones I can recall. You're better off checking your amps than chancing that solely on my say so though.
You're options regarding switching resistance are sorely diminished with a one speaker cab. If there were multiple speakers you could wire it to switch between resistance ratings. Dunno if thats possible with single speaker cabs, I've never heard of it. Maybe seeing if you could get 2x10"'s in there would be better. Nice sound out of most 2x10 configurations.

Tired now, I'll find you some links out about wiring configurations tmozza.

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No no and no

as far as the jack goes i know where to put it on the cab, there is a hole for it. i just dont know where to buy one.

i just wanted to make the cab universal to a point. i have several amps with ext cab plug in options.

any idea what speakers you would look in to for this cab?
it has open back option as well. i like the cab. i need to post up a few picks.

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

Myself I like the Celestion G12-75T but their not for everyone. Very much a decent all round speaker that doesn't really excell in any one area. Good enough for me.

Chet would tell you ScumBacks. Looks a bloody good option to me, certainly no reason to doubt Chet's judgment.

Weber, you can't go wrong with em can you?

It's like buying pickups mate, you'll get super confused just by the plethora of different units out there. Find a good one that you like and go for it, is my advice.

Again pay close attention to your amps various speaker ratings when deciding.

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No no and no

niki again i stand educated. thank you very much.

ok so where should i look for a jack for this cab? who sales them?

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

Hey waycool...As far as speakers go, I agree with niki on the celestions. I have always thought their speakers really articulate well and help bring your sound up in the mix a little. The G12H is a classic (Hendrix used 'em) it's 30 watts and 8ohms and would be a good match for a nice 20-30 watt head.

Not sure where to get jacks for the cab, but you might be able to find out from someone at your local music store.

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Check out my new FB music page!

https://www.facebook.com/TheDevilandMe.Music

Told you I was tired lastnight. I forgot something of prime importance that Tim has just kindly reminded me of.

When buying a speaker go for as near double the wattage of the amps output rating. (Sorry Tim). The reason for this is that speakers are rated for peak power. Most amps are stupidly rated at their root mean square output wattage, or RMS. The RMS output of a amp it the maximum it will deliver without causing output stage clipping (to a guitarist thats power valve breakup). Which guitarist doesn't want that?

This guy probably didn't



One of the few!

The peak power of a amps output is around 80-90% greater than it's RMS power. So a Blues Jr for example, capable of giving 15watts RMS is actually delivering nearer 27watts.
RMS is a great way of rating output for a electrical engineer, but your typical modern guitarist operates more in the peak end of the scale.

Thats why you find a 60watt speaker in that amp. It's more than capable of handling anything the amp throws at it.
There are a few people (me and I suspect Tim included) who love to hear the sound of a speaker about to tear its hair out and jump out of the cab, just so it stops suffering. What we crave is a attribute called 'Cone Cry' where the speaker will literaly howl because it can't handle the power being thrown at it. Hendrix and Clapton both owe a lot of their best sounds to this phenomenon. 100watt RMS stack (though it only delivers around 76watts RMS because of speaker resistance) into a couple of 120watt cabs. Or just one 120watt cab for recording. Dangerous.

Doing the above will blow your speakers quickly, but it sounds utterly fantastic until that happens. It's why a few years back there was so many ex Hendrix, Clapton, ex whoever cabs on the market. They were largely either destroyed during gigging and repaired or fakes.

If you look on the back of a Fender amp, it's a absolute lesson in accurately rating a amplifiers output for an electrical engineer. It really is a work of art and should be law that all amp makers do it. Even the back of my cheapo VibroChamp XD reads 5 watts RMS @ 4 ohms. So up the speaker resistance and you'll hamper all of the 5 watts getting to the speaker.
Although as a guitarist the amp is typicaly operating near peak power and kicking out closer to 8/9 watts.

Back in the 80's you used to see ratings on the back of ghettoblasters that would read 30watts RMS/53watts Peak. (example).
Modern high end valve audio power amps don't bother with a peak rating at all because the things are designed to never clip.

Funny old world eh? Bet thats clear as mud now.

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No no and no

just got a email from the guy that sold me the cab. he said he ran across
a celestion Rocket 8ohm speaker still in the box. he said he believed it was
50 watt. he will let it go for $25. is that a good deal? i dont know anything about this model speaker niki.

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

I dunno if thats a good deal mate, like I don't know the best place for you to buy spares. I don't live in the same country as you, pricings are different over there. Despite the currency differences, you get things priced without tax and all sorts.
I think the Celestion Rocket was the budget Celestion that went on to be the design that Marshall used for their own brand speakers in the MG and AVT cabs. Not a bad speaker by any means, also not the best by a long shot. A good choice for a first build, that you may want to swap out later. As for the price their about £30 in the UK, rough conversion to $50 US, though you need to check that new price yourself and make your own mind up.

Anyway good speaker cab reading here (not all info is applicable to your situation)

http://www.duncanamps.com/technical/speaker_cab.html
(Take whatever that site says about amps as law)

http://www.usspeaker.com/speaker%20wiring-1.htm
(good clear simple wiring diagrams)

http://colomar.com/Shavano/spkr_wiring.html
(good but more complex wiring diagrams. Decent explanaition or resistances too. Recommended)

Anyways now you've got me at it again I have to go try and find a couple of 12" speakers that will deliver 34watts between em for my 18watt.

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No no and no

Bit more "handy" info i posted previously lol

If you want to use speakers connected together (in parallel) use this formula.

Connect 2 x 8 ohm speakers in parallel to give 4 ohms total load on the amp.
This is because resistances in parallel are calculated as 1 over 1/R1 + 1/R2

eg The reciprocal of 0.125 + 0.125 = 0.25 easier to write than type on here. ie 1 divided by 0.25



Another way of doing the same calculation and easier to type is

8 x 8
______ = 4 ohms

8 + 8

so use 2 x 8 ohm speakers in parallel as stated in my previous reply.

easy eh

As for a speaker i have a webber blue pup and it sounds sweet, webber are based in the US so ashould be easy find.

lol your lessons can sometimes leave one with even more questions than he started with, but this time im seeing through the mud.

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63supro
"The good thing is in a club situation, most of the patrons are trashed and really can't tell the difference."

Excellent info Al.
Everyone remotely interested in getting inside speaker cabs should commit this to memory. Myself included, I just stick to series wiring.

WCJ, not a bad thing, asking questions and looking for answers is how we learn.

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