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Post by Hohn on Jul 25, 2006 20:50:51 GMT -7
I just assumed that it's two 16 ohm drivers in parallel-- correct??
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Post by combo800 on Jul 26, 2006 0:40:03 GMT -7
Yours has 2x16-ohm speakers?
Hmmm...
The 1st combos that folks posted about in here had 2x8-ohm speakers... some wired in Series to 16 ohms, others wired in parallel to 4 ohms--like mine.
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Post by Hohn on Jul 26, 2006 18:30:02 GMT -7
I'm talking about the cab &head, not combo.
I suppose I should have checked this earlier! I have an 8ohm Hot Plate, and I need cab impedance to be 8ohms.
I could always wire it for 16 ohms, I suppose and be OK. I don't like the idea of speakers in series, though--failsafe isn't there to protect output trans.
jh
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Post by combo800 on Jul 27, 2006 0:36:45 GMT -7
I'm talking about the cab &head, not combo. A thousand pardons... I saw "Ray 2x12" in the subject line and thought of a combo. I'll shut up, now...
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Post by Hohn on Jul 27, 2006 15:31:31 GMT -7
Well, it was my fault for the misleading title.
Besides, why would the cab have different impedance than the combo??
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tuna
New Member
"Ain't Nothin to it"
Posts: 23
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Post by tuna on Aug 6, 2006 3:41:16 GMT -7
I just bought a head and cab from Dave Thomas over at Richmond Music and the cab is 8 ohm. I was in Richmond Music on Friday and they had just gotten in a red head and cab and that cab was 16 ohm. (?) It didn't last long though, Ol' Dave sold it to a young fella that had a big smile on his face as soon as he hit that 1st chord.
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Post by billyguitar on Aug 6, 2006 7:43:52 GMT -7
I think what this shows is Z uses what he can get. So long as there is an impedance match between the head and the cab it'll sound great.
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Post by benttop (Steve) on Aug 6, 2006 8:35:33 GMT -7
I was surprised when my 2x12 came and it was 4 ohms. I hadn't specified any particular impedance, but 4 works fine and I don't plan on using any extension cabs, so it really makes no difference here. ESPECIALLY when I hit that first chord every time I play - makes me grin too!
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Post by brando on Aug 6, 2006 11:13:48 GMT -7
I was surprised when my 2x12 came and it was 4 ohms. I hadn't specified any particular impedance, but 4 works fine and I don't plan on using any extension cabs, so it really makes no difference here. ESPECIALLY when I hit that first chord every time I play - makes me grin too! +1 My exact experience.
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Post by Hohn on Aug 6, 2006 18:31:52 GMT -7
Mine came and the cab is 16 Ohms-- 2 eights in series.
Sound like a dream and works fine with my 8Ohm Hot plate, so I don't care.
Besides, I can now make another cab with 16 ohm impedance, and run BOTH of them with the HOt plate:)
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Post by rockstok on Sept 17, 2006 6:58:31 GMT -7
After reading the discussion on impedence-parallel/series issue etc., I am more perplexed about how it all adds up. I have been using 2 1x12 cabs with a Radio Shack mono Y splitter (the only way I could find since a stereo Y isn't the ticket). I have been running it from the 4 ohm out of my RxES. Of course the bottom line is what it sounds like but I still would like to understand how the wiring is set up in S vs P and if I'm doing it right. Thanks for you feedback. Bill
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Post by benttop (Steve) on Sept 17, 2006 8:43:20 GMT -7
After reading the discussion on impedence-parallel/series issue etc., I am more perplexed about how it all adds up. I have been using 2 1x12 cabs with a Radio Shack mono Y splitter (the only way I could find since a stereo Y isn't the ticket). I have been running it from the 4 ohm out of my RxES. Of course the bottom line is what it sounds like but I still would like to understand how the wiring is set up in S vs P and if I'm doing it right. Thanks for you feedback. Bill Hmmm... I'm not exactly sure what your question is here, but the bottom line is this. For speaker impedances, you can typically use Ohm's Law for resistance. Ohm's Law states that two resistances in series are additive, while two resistances in parallel divide. Some examples: Two 8 ohm speakers in series end up being 16 ohms total. Two 8 ohm speakers in parallel end up being 4 ohms total. As long as you're always working with two speakers, and they are the same impedance, you can get by with that example. But when you add in more speakers and different impedances, it gets more complicated real quick. It is generally not a good idea to use different impedance speakers in a multi-speaker setup, so if you keep to all the same, you can say that for parallel, you just divide by the number of speakers. In other words: 4 16 ohm speakers in parallel equals 4 ohms. 16 ohms/4 speakers=4 ohms If you insist on using four speakers of different impedances, you end up having to do algebra to determine the impedance. Here's the formula for that: That image should have a ... at the end, because it goes out forever. You could have 27 speakers in parallel and use that formula to determine the impedance. There are a dozen other considerations - series/parallel wiring, speaker phasing, and don't get me started on frequency... Series/Parallel is just that - some speakers in series, others in parallel. For example, lets say that you have four 16 ohm speakers in your cab, but you want a total impedance of 16 ohms. Well you could wire the left two speakers in parallel (16/2=8 ohms) and the right two speakers in parallel (16/2 = 8 ohms) then wire those two sets in series (8 + 8 = 16 ohms). By now, you should see that if you want a 4x12 cab to come out at 8 ohms, you have to start with either 8 ohm speakers, or 2 ohm speakers, or 32 ohm speakers. I guess it's obvious what the solution would have to be there... Hope that all helps some...
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Post by DRZ on Sept 17, 2006 14:20:01 GMT -7
Hohn, No currant Z 2x12 cab loaded with Blues is 8 OHM.
When I started in January to release the StangRay I purchased 260 Celestion Blue speakers. That's right guys 260 of them, with shipping over $36,000 worth of them. This way I could offer a deal on the head cab combo, and lock my price up for the year. BTW I have less then 40 left, thank you guy's very much.
All the Blues I bought were 8 OHM, so the cabs were either 16 ohm ( two 8's in series ) or 4 OHM ( two 8's in parallel ).
I have found that 2 series connected 15 watt Blues can fail in the StangRay. So I have connected all 2X12's to 4 OHM, that's cab and combo both.
On some days I like the sound of two Blues in Series at 16 OHM ALA VOX, but they are just TOO expensive to put in harms way. All StangRay's will be wired for 4 OHM.
DR.Z
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Post by combo800 on Sept 17, 2006 20:27:16 GMT -7
...I purchased 260 Celestion Blue speakers... I have less then 40 left, thank you guy's very much. Well, glad to have helped you out with 2 of 'em... And they sound just fine to me in parallel.
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Post by rockstok on Sept 18, 2006 5:46:03 GMT -7
Thanks benttop, and Doc! I think I'll leave the wiring to the pros.
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Post by benttop (Steve) on Sept 18, 2006 5:51:41 GMT -7
Thanks benttop, and Doc! I think I'll leave the wiring to the pros. Well depending on your setup, you probably can do exactly that. But if you use a head/cab configuration, and you have multiple cabs, you need to figure out what is allowed and what is not. Or you could end up causing some preventable problems. A good example is my Stingray. My cab is 4 ohms as the Doc just mentioned, but adding a second cab would drop the impedance to 2 ohms if I hooked it up in parallel, and that would definitely be bad. I would have to wire up a special cable to get the two 4 ohm cabs in series with each other, arriving at a nice safe 8 ohms. So you should become familiar with at least the fundamentals...
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Post by guitarstan on Sept 18, 2006 9:53:57 GMT -7
benttop, as I understand resistance/impedance and tolerances, an 8 ohm speaker may measure only 6 ohms or 8.6 ohms on a VOM under static conditions ie no load. If you are using a 4 x 12 cab with some speakers at 6 ohms and some at 9 ohms and of course amp designers know this basic fact, then it seems to me that we just want to stay in the ballpark but not worry about adding resisters to our speakers to provide exactly an 8 ohm load to the 8 ohm speaker jack on our amps? Did that make any sense? In other words could we not mix and match 8 ohm with 16 ohm speakers in whatever configuration with however many speakers as long as we could deliver approximately 8 ohms +/- to the 8 ohm amp jack? Yes I know it would probably totally screw up certain frequencies with inductance hot spots or whatever but theoretically is my thinking more or less "correct"?
BTW...I flunked out of Electrical Engineering ;D but never lost interest in the field.
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Post by dock66 on Sept 18, 2006 11:56:15 GMT -7
Electrical Engineering was my other major , but didn't quite make it in life.Took a different route instead.
dock66
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Post by guitarstan on Sept 18, 2006 16:01:59 GMT -7
other major, what was your main major?
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Post by guitarstan on Sept 18, 2006 16:10:44 GMT -7
benttop...how about this line of thinking....the 8 ohm jack of an amp could read 6.8 to 9.2 ohms? And we would know that the output transformer would be safe with a static load within that range!?
Please don't hit me ;D.
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Post by benttop (Steve) on Sept 18, 2006 17:37:28 GMT -7
benttop, as I understand resistance/impedance and tolerances, an 8 ohm speaker may measure only 6 ohms or 8.6 ohms on a VOM under static conditions ie no load. If you are using a 4 x 12 cab with some speakers at 6 ohms and some at 9 ohms and of course amp designers know this basic fact, then it seems to me that we just want to stay in the ballpark but not worry about adding resisters to our speakers to provide exactly an 8 ohm load to the 8 ohm speaker jack on our amps? Did that make any sense? In other words could we not mix and match 8 ohm with 16 ohm speakers in whatever configuration with however many speakers as long as we could deliver approximately 8 ohms +/- to the 8 ohm amp jack? Yes I know it would probably totally screw up certain frequencies with inductance hot spots or whatever but theoretically is my thinking more or less "correct"? BTW...I flunked out of Electrical Engineering ;D but never lost interest in the field. Well some of what you've said is correct, but you're forgetting some too. The "impedance" of a speaker is defined at a certain frequency. Impedance is an AC characteristic. Resistance is a DC characteristic. If you stick your ohm meter across a speaker's terminals, you are measuring the DC resistance of the coil, not the AC Impedance of the coil. That is specifically why it doesn't read the value on the label. But if the manufacturer says it's an 8 ohm speaker, you can probably rely on that. In fact, you SHOULD rely on that WAY more than a DC resistance measurement, which could be way off depending on the speaker. And you CAN put different impedance speakers in one cab, but you're going to have one dissipating more power than the other. If that's cool with you, go for it. But it would be very difficult to predict ahead of time what it's going to sound like. Plus, you'll need to do the algebra to make sure you don't overload one - a good example would be putting an 8 ohm Alnico Blue in a cab with three other hundred watt 16 ohm speakers, and trying to run a bazillion watts through there. Might not be a very good idea if you don't like replacing expensive speakers. Hope that helps a bit.
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Post by dock66 on Sept 18, 2006 18:59:03 GMT -7
other major, what was your main major? Guitarstan, It is Medical dock66
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Post by guitarstan on Sept 19, 2006 5:35:02 GMT -7
Steve, yes that helps tremendously and makes perfect sense. As an engineer I like to understand things at least a little beneath the surface and that has confounded me for decades.
So how would one test a speaker to verify its impedance, use an oscilloscope? I am most concerned about checking a speaker that has been reconed. I am a little hard core about not accepting what things are suppose to be verses what they are. A great man once said "Believe not your eyes, your ears, your mother or your father, believe only that which is verifiable".
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Post by benttop (Steve) on Sept 19, 2006 8:10:44 GMT -7
Steve, yes that helps tremendously and makes perfect sense. As an engineer I like to understand things at least a little beneath the surface and that has confounded me for decades. So how would one test a speaker to verify its impedance, use an oscilloscope? I am most concerned about checking a speaker that has been reconed. I am a little hard core about not accepting what things are suppose to be verses what they are. A great man once said "Believe not your eyes, your ears, your mother or your father, believe only that which is verifiable". Well Stan, if you really want to determine your speaker's impedance on your own, you can do it with some test gear and patience, and some algebra. But I think it's a bit beyond the scope of this thread. Check this site for the full story: sound.westhost.com/tsp.htmGood luck!
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Post by guitarstan on Sept 19, 2006 9:15:57 GMT -7
Very interesting, I am currently reading it. Although I may never actually run this test it will broaden my horizons and allow me to reframe a number of behaviors that I tend to obsess over ;D.
Thanks again Steve!
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Post by Hohn on Sept 19, 2006 12:11:12 GMT -7
OK, now I am *thoroughly* confused.
My Ray's 2x12 says "16 ohm" on the lone input jack.
Could this be an early build 2x12 that had them in series?
I've been using the 16ohm output on my head so far with no problems. I can't really see inside the cabinet to tell what the drivers' individual impedance is.
That *would* explain why my amp gets so loud so fast if in fact that cab is 4 ohms and I'm running it as if it was 16ohm!
I'd really hate to nuke the output tranny on my new head, so can anyone put this one to rest?
Why is my open back 2x12 w/Blues labelled as 16Ohm??
(To add to BT's post, impedance is sum of DC resistance and AC reactance. Reactance is product of total inductance and capacitance. Thus impedance is total opposition to current flow, accounting for AC and DC factors). You can actually calculate the time constants for given RLC circuits and thus the amount of frequency-dependent opposition to current-- or conversely which frequency will give lowest or highest reactance)
justin
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Post by billyguitar on Sept 19, 2006 13:05:04 GMT -7
If your cab says 16 ohms I wouldn't argue with the label, especially if you bought it new. If your cab was 4 ohm and you were running it out of the 16 ohm jack you would lose some volume and tone due to the mismatch. As far as your amp getting "so loud so fast" the impedance doesn't affect that. If you find the volume hard to control try the lo sensitivity input. I know what Benttop's saying about how to read the exact impedance but I've always done the VOM meter reading and it's always worked for me, the speaker's reading on the meter is about 2/3rds of it's actual value. I've never gotten any kind of wild reading but then I haven't done it very often, just to check myself when I've rewired a cabinet. Benttop's right of course, but this rough method has been good enough for what I've done.
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Post by guitarstan on Sept 19, 2006 13:14:50 GMT -7
so a 16 ohm cab might read around 12 ohms on the VOM and an 8 ohm around 6.
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Post by benttop (Steve) on Sept 19, 2006 13:37:17 GMT -7
I only said it that way because it's inexact. I hate that...
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Post by guitarstan on Sept 19, 2006 13:40:49 GMT -7
I heard you Man
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