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Post subject: Ohm questions about extension cab
Posted: Fri Apr 15, 2011 8:26 am
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i just bought a super champ xd....I have a B-52 AT-212

The B-52 fried itself at practice the one night.

My question is concerning using my B-52 as an extension cab until I get the amp fixed...if I ever do...

The B-52 has two 12" cones with HUGE drivers. The speakers are rated at 16 ohms at 120 watts. The XD says in the manual 8 ohm/25 watt minimum for the speaker out.

I don't remember enough from high school physics to get my ohms and wattage straight. Can I plug both or one of the B-52 speakers in to the XD or do ohms measure backwards as 16 is less than 8 and 8 less than 4?

If I'm using an amp that calls for 8ohm/25 watt minimum that is pushing 15 watts out with the amp and I want to use two speakers that are rated 16 ohms at 120 watts....am I going to destroy my amp or under power the speakers with plenty of head room for the speakers to handle?


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Post subject: Re: Ohm questions about extension cab
Posted: Fri Apr 15, 2011 9:04 am
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Hi hyde_81,

No problems using the speakers from the other amp. Impedance matching is only about amp efficiency, to get the most power out. Your SCXD amp can easily handle an impedance mismatch of 2 to 1 either way, so you can use 16 ohm or even 4 ohm speaker load with it, but power out will be max with 8 ohm. In fact, too high an ohm load is not good, I wouldn't go above 16 ohms myself, and never run the amp without a speaker, or sufficient load connected. And the two 16 ohm speakers in the B-52 amp are likely wired in parallel, so that will be 8 ohms if you use both anyway. Also, as long as the speaker wattage is equal to, or greater than the amp wattage it will work fine. The amp will produce x-amount of power, so the speaker has to be able to handle at least x-amount of power, or more.

So, you can use one, or both speakers from the B-52 with your SCXD just fine, and the sound with the other speaker/speakers will likely surprise you as to how much louder it can be than it is with the stock speaker. Just make sure that the speakers you use are only connected to one amp, and don't power up either amp without speakers connected. :)

Edit:
Is each speaker in the B-52 16 ohms, or do you mean 16 ohms total for both?

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Post subject: Re: Ohm questions about extension cab
Posted: Fri Apr 15, 2011 9:24 am
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each speaker is 16 ohms. They are wired together in the cab. I took the B-52 head out of the cab and will be using it a paper weight for a while or forever.

But yes....each speaker is 16 ohms...so would that make an 8 ohm load if they are wired in parallel? And more importantly....how would I tell if they are wired in parallel or series?


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Post subject: Re: Ohm questions about extension cab
Posted: Fri Apr 15, 2011 10:58 am
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Yes, if two 16 ohm speakers are in parallel, the total is 8 ohms. If the positive (+) terminals of both speakers are connected together (usually white or red wire), and the negative (-) terminals of both speakers are connected together (usually black wire), then they are wired in parallel. So, the speaker cable from the amp has both wires to one speaker, then two wires connected from there to the other speaker. :idea:

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Post subject: Re: Ohm questions about extension cab
Posted: Fri Apr 15, 2011 12:47 pm
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shimmilou wrote:
Yes, if two 16 ohm speakers are in parallel, the total is 8 ohms. If the positive (+) terminals of both speakers are connected together (usually white or red wire), and the negative (-) terminals of both speakers are connected together (usually black wire), then they are wired in parallel. So, the speaker cable from the amp has both wires to one speaker, then two wires connected from there to the other speaker. :idea:


+1

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Post subject: Re: Ohm questions about extension cab
Posted: Sat Apr 16, 2011 7:32 pm
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shimmilou, thank you very very much for the info. I also got off my lazy keister and did a little research and found some info on calculating ohms and wattage. Physics class started coming back to me. haha. I now have enough know how to keep my head straight where these things are concerned.

I checked my gutted B-52 cab and the speakers are indeed wired in parallel. I haven't had a chance to fire up the amp with extension speakers. I'm like a kid at Christmas now, all I wanna do is fire the damn thing up and see what she can do!


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Post subject: Re: Ohm questions about extension cab
Posted: Sun Apr 17, 2011 1:05 am
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Your SCXD should really roar with a pair of 12's -- let us know how it sounds after spend an hour or two with it.

Arjay

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Post subject: Re: Ohm questions about extension cab
Posted: Sun Apr 17, 2011 5:49 am
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Believe me I will let you know. I'll see about getting some sound clips up. I'm psyched. I'll take some pics too so everyone can get an idea of the size of the drivers on the b-52 speakers. I just know the wife will be yelling at me to turn it down. Grounds for divorce if you ask me. :lol:


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Post subject: Re: Ohm questions about extension cab
Posted: Sun Apr 17, 2011 9:47 am
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hyde_81 wrote:
Grounds for divorce if you ask me.


"Counselor, on what basis does your client seek dissolution of this union?"

Your Honor, on the grounds of irreconcilable SPL's."

:lol: :lol: :lol:

Just buy her some earmuffs, Hyde.

:mrgreen:

Arjay

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Post subject: Re: Ohm questions about extension cab
Posted: Sun Apr 17, 2011 9:54 am
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:lol: Earmuffs?!? Talk about grounds for divorce! That may only work if you pair the earmuffs with some jewelry, or shoes or something for her. The earmuffs so she can't hear you, and the jewelry so you won't have to hear her. :lol:

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Post subject: Re: Ohm questions about extension cab
Posted: Tue Apr 19, 2011 1:02 pm
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Well I wanted to get pics of the rig and a sound clip or two, but that will definitely happen at a later date. Either way I got to fire up SCXD through the B-52 cab. It was most definitely louder through a 2x12 cab. I can't wait to open it up at practice. One thing I was really impressed with was the warmth and sustain on the overdriven channels. Things definitely have the smoothness of an analog signal even though its a digital amp voice.

All in all a very good buy with a TON of options. It's like a sore d*ck...you can't beat it.


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Post subject: Re: Ohm questions about extension cab
Posted: Tue Apr 19, 2011 1:31 pm
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Improving a speaker array is one of the easiest and most effective ways to open up an amp and let it "breathe". Just be mindful of the recommended impedance load.

Arjay

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Post subject: Re: Ohm questions about extension cab
Posted: Tue Apr 19, 2011 3:17 pm
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Congrats!

Been thinking of playing around on the same manner myself...lots of speaker cabs, most with speakers, for sale on CL. 4x10, 4x12, 2x12...not much money either unless it's an old Marshall or Fender...

Hmmmmm... :!:

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Post subject: Re: Ohm questions about extension cab
Posted: Tue Apr 19, 2011 5:13 pm
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In the interest of impedance...does that go hand in hand with ohms, is that another way of measuring ohms or is it completely different from the amount of ohms that the amp can handle? I made sure the speakers are wired correctly as the amp requires an 8 ohm load minimum and the wattage of each speaker is I believe 120 watts.

But, is there more I have to take into consideration?


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Post subject: Re: Ohm questions about extension cab
Posted: Tue Apr 19, 2011 7:01 pm
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Impedance is represented in ohms, and means an opposition to current flow or resistance, just as current is represented in amps. Generally speaking, the word "impedance" implies and AC circuit, such as the output of your amplifier, as its "opposition" to changes in current will vary with changes in frequency. That's why we refer to the "nominal" impedance rating for a speaker or amp. Technically, impedance and resistance mean the same thing and both are represented in ohms. :idea:

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