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Unread 03-31-2008, 11:05 PM   #1 (permalink)
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please help a retard... 8 & 16 ohms = ?

hi, everybody! Yes, I am basically a retard. what I do not know about inductance, etc. has filled volumes. Literally. Here's the problem... I have a Marshall cab, model 8412. It came with 4 Celestion G12L (8 ohm) speakers in it. I believe they are 25 watts, but don't know for sure. they only say G12L on the back. the frames are inked 8 ohm.

They sound nice, but not great, IMO. I bought a pair of vintage Heppner 16 ohm alnico magnet speakers. Nice and light, they sound more mellow & fuller to me than the Celestion G12L's, more like Greenbacks. For the sake of this exercise, let's say all the speakers are rated the same for wattage (they probably aren't, but... close enough for rock & roll). I want to put the Heppners in the cab & still have it be 8 ohms. Can this be done?

Can I wire the 2 G12L's in series to get 16 ohms, and the Heppners parallel to get 8 ohms and then... magically... not blow up my 100W RMS tube amp head and get... let's see... 8 + 16 = 24 / 2 = 12 ohms??? do you see my conumdrum? maybe if I add 2 - 4 ohm tweeters and hide them inside the cab & rip out their cones I could balance things ohm-wise?

I know a TUBE AMP IS HAPPIER PUSHING A GREATER OHM LOAD (EX: 8 oHM OUTPUT HEAD, 16 OHM CAB = OK; 8 OHM OUPUT HEAD, 2 OHM CAB = FIRE) OOPS - SORRY FOR CAPS...

here's what I did so far (really!)... I took one G12L out and put it in my Fender Deluxe 112 that had a blown 65 watt 8 ohm stock speaker. The Fender sounds great now, but I really want to use the Heppners in my Marshall cab. So far I have replaced the one G12L with the Heppner & wired it as the cab was originally. My knowledgable friend Krishna who refins & builds guitars said that it would be something like 12.5 ohms if I left it as is.

... could someone who speaks Retard help me? thanks!!
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Unread 04-01-2008, 02:57 PM   #2 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

double post, sorry.
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Unread 04-01-2008, 03:06 PM   #3 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

There is no way to wire a pair of 8's and a pair of 16's so all 4 equal 8 or 16.

No way, no how.

This can be explained easily....if you're not afraid of a little high school math.

In parallel, resistances (close enough to impedance) combine like this:

1/Rtotal = 1/R1 + 1/R2

In series, they combine like this:

Rtotal = R1 + R2

I don't have the energy to finish this, so just read this thread:
SPEAKER WIRING
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Unread 04-01-2008, 08:48 PM   #4 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

Quote:
Originally Posted by Adwex View Post
There is no way to wire a pair of 8's and a pair of 16's so all 4 equal 8 or 16.
No way, no how.
This can be explained easily....if you're not afraid of a little high school math.
In parallel, resistances (close enough to impedance) combine like this:
1/Rtotal = 1/R1 + 1/R2
In series, they combine like this:
Rtotal = R1 + R2
I don't have the energy to finish this, so just read this thread:
SPEAKER WIRING
Thanks for your reply. I read thru the link, plus I've been researching online about parallel/series. I think the usual Marshall cabs (for 8 ohms) are wired series/parallel, 2 sets of speakers Parallel equalling 4 ohms, then hooked together in Series to equal 8 ohms.

What if I just leave 1 - 16 ohm speaker in with 3 other 8 ohm speakers? No harm, no fowl (sic)? It might be a little quieter, but no adverse load on my tube amp, right?

BTW, my cab is an 8 ohm cab, so I assume it's series and parallal to get that ohm rating.

I know I could just buy another set of Celestions that are 16 ohms and wire it to equal 8 ohms, and that is very tempting, if more expensive than my preference - noted above, of just having one 16 ohm in with 3 - 8 ohm speakers.

How about the 16 ohm alnico Webers? Utahs? JBL's? any suggestions? I'd like a speaker with the capability to reproduce sound (best as possible) at the human hearing level of something like 50-16000 Hz.

I'd like to keep the weight down, and some of the ceramic magnets are HUGE!

comments welcome.
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Unread 04-02-2008, 10:16 AM   #5 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

If you have one 16 ohm speaker with three 8 ohm speakers, in series/parallel, the resulting impedance is this:

1/Rtotal = 1/(8+16) + 1/(8+8)

1/Rtotal = 1/24 + 1/16
1/Rtotal = 2/48 + 3/48
1/Rtotal = 5/48
Rtotal = 48/5

Rtotal = 9.6 ohms

Unless your amp has a setting for 9.6 ohms, which I doubt it does, I wouldn't do it. I suggest you have all 4 speakers of the same impedance, 16 or 8.
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Unread 04-02-2008, 12:08 PM   #6 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

Based on your comments in here, I would recommend taking your cab somewhere to get it wired. I don't think you should be wiring anything.
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Unread 04-17-2008, 06:27 PM   #7 (permalink)
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Re: 4 speakers at 16 ohms = 4 ohms

well, I appreciate you comments about me not wiring anything, but perhaps I'm not a total retard... I wired in the one Heppner, it sounds nice, but... rather quiet, and seems to "quiet-out" 2 other speakers. only the top left speaker (as you view the cab) sounds like the correct volume. I just got a replacement 8 ohm Fender speaker for my Deluxe 112 and I'm going to put that in, take out the Heppner from the Marshall cab and replace the Celestion from whence it came, and then... wire 4 - 16 ohm Heppners into another Marshall cab so they run at 4 ohms and run that cab off the line out from my Fender Champ... heh heh... tube amp heaven... rock on, kids. Peace.
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Unread 04-18-2008, 10:53 AM   #8 (permalink)
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Re: 4 speakers at 16 ohms = 4 ohms

Quote:
Originally Posted by bosrocker51 View Post

... wire 4 - 16 ohm Heppners into another Marshall cab so they run at 4 ohms and run that cab off the line out from my Fender Champ...

.
You cannot run a speaker from a "line-out". I think you meant "speaker out". There's a big difference.
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Unread 04-22-2008, 12:33 PM   #9 (permalink)
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Re: 4 speakers at 16 ohms = 4 ohms

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Originally Posted by bosrocker51 View Post
well, I appreciate you comments about me not wiring anything, but perhaps I'm not a total retard... I wired in the one Heppner, it sounds nice, but... rather quiet, and seems to "quiet-out" 2 other speakers. only the top left speaker (as you view the cab) sounds like the correct volume. I just got a replacement 8 ohm Fender speaker for my Deluxe 112 and I'm going to put that in, take out the Heppner from the Marshall cab and replace the Celestion from whence it came, and then... wire 4 - 16 ohm Heppners into another Marshall cab so they run at 4 ohms and run that cab off the line out from my Fender Champ... heh heh... tube amp heaven... rock on, kids. Peace.

I don't know if you are a troll or if I should take you seriously. If you are not a troll, read back what you said and tell me if that seems logical to you. You wired in one speaker that is mismatched and it lowered the volume of your other speakers. At some point would a light go off telling you there is a problem? When you blow up your amps, please come in and tell us about it.
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Unread 05-04-2008, 04:20 PM   #10 (permalink)
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Re: 4 speakers at 16 ohms = 4 ohms

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Originally Posted by ZoomZilla View Post
I don't know if you are a troll or if I should take you seriously. If you are not a troll, read back what you said and tell me if that seems logical to you. You wired in one speaker that is mismatched and it lowered the volume of your other speakers. At some point would a light go off telling you there is a problem? When you blow up your amps, please come in and tell us about it.
I ran my amp about 10 minutes with the higher impedance Heppner. I was assured by a credible amp fiend that I woud not eff up my amp, and I didn't.

sorry to disappoint, chum, but my amps are fine and the 4 - 16 ohm speakers I wired for my Fender Champ are wired in perfectly (by me). Try dismounting from your high horse... the weather down where I am is sunny and with a fine promising future in sight... thanks for your condescending comments, I had a good laugh from them!
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Unread 05-05-2008, 10:33 AM   #11 (permalink)
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Re: please help a retard... 8 & 16 ohms = ?

Well I am happy to hear you did not blow up your amp and I am hardly being condescending. You stated yourself that you did not know anything about imepdance, and you had no idea how to wire it. Based on your lack of knowledge of wiring and impedance, I recommended you allow someone who does know what they are doing help you out. My comment on telling you that you will blow up your amp was to discourage you to not do it. While what you are doing will NOT blow up your amp, you will NOT get optimal sound from it. It is a bad mismatch and will not sound good. I would have thought the fact that you know that you speakers do NOT put out the same volume might have been an indication that something was not right. If you feel I am on a high horse, so be it. Your amp friend is correct when he told you that it will not mess up your amp. It won't but it wont sound good either. You are basically defeating the purpose by mismatching ohms. But hey, if you like the way it sounds, more power to you.
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