Members black sphynx Posted September 10, 2003 Members Share Posted September 10, 2003 I have no clue about how to match ohms with my bogner head. I have two 16 ohm cabs , so I know to run the amp at 8 ohms (this was what I was told) I dont know how to come to this conclusion so I was hoping someone here will help me out. Thanks Link to comment Share on other sites More sharing options...
Members bunnies=dead Posted September 10, 2003 Members Share Posted September 10, 2003 use...search...button Link to comment Share on other sites More sharing options...
Members Darth Balls Posted September 10, 2003 Members Share Posted September 10, 2003 Two 16 ohm cabs = 8 ohms, as you know, so if you have two 8ohm jacks use those, or if you have an ohms selector, set it to 8 ohms, then plug in both cabs. Link to comment Share on other sites More sharing options...
Members black sphynx Posted September 10, 2003 Author Members Share Posted September 10, 2003 what if I want to run just one eight ohm 4x12 cab in mono? I would set the amp to eight ohms I would assume? these are the only two scenarios I will deal with. Link to comment Share on other sites More sharing options...
Members El Grinder Posted September 10, 2003 Members Share Posted September 10, 2003 Ok, short electricity lesson. Matching Impedance: Impedance is measured in Ohms. Two loads in series have the impedance added togehter: ex. 2x 8 Ohm loads in series configuration will have a 16 ohm total load, but only if they're wired like: + - | | 8----8 Two loads in parallel have the impedance reduced: ex. 2x 8 Ohm loads in parallel configuration will have a 4 Ohm total load, but only if they're wired like: + - | |8----|| |8----' If you check out the two diagrams, you see that in series (the top diagram) the electricity has to flow through one speaker, then a second speaker. There is more resistance to the flow of electricity. In the bottom diagram, the electricity has two paths to travel. Imagine if it were like cars on a road. Series would have your car running through two traffic lights in a row, slow, right? The traffic lights would impede your progress. In parallel configuration, you have two routes possible to take, so there would be less traffic at each traffic light. This means that you would have less traffic to deal with at either light you go to. This equals lower impedance. And for the last point. If something is wired as single load in a circuit: + - | | L_8-' It will have the impedance listed on that load. A single 8 ohm speaker will simply carry an 8 ohm load of impedance. That ends the lesson. I hope this helps you out a little bit. Link to comment Share on other sites More sharing options...
Members El Grinder Posted September 10, 2003 Members Share Posted September 10, 2003 : my drawings came out wrong... stupid auto-formatting!!!edit: Ah, HTML saves the day! btw, the above stuff is often referred to as Ohm's law. There are some math equations that define it, but that is the general gist of it. Let me know if you have any other questions. Link to comment Share on other sites More sharing options...
Members H535 Posted September 10, 2003 Members Share Posted September 10, 2003 To calculate Ohm loads for speakers of different ohms. First you must find the comon denominator EX1 You have (1) 4 ohm speaker cab and (2) 8 ohms speaker cabs and you want to know what is the ohm load when you hook them up to your amp. Fist write them out as a fraction- 1/4 + 1/8 + 1/8 then find the comon denominator (8) 2/8 + 1/8 + 1/8 then add your fractions 2/8 + 1/8 + 1/8 = 4/8 then invert your fraction and divide the bottom number into the top number 4/8 becomes 8/4. 8 div/by 4 = 2 answer- you now have a 2 ohm load Lets do another one what if you have a 16 ohm cab and a 4 ohm cab 1/4 + 1/16 4/16 +1/16 = 5/16 16/5 = 3.2 ohms How about (2) 8ohm and a 16 ohm 1/8 + 1/8 + 1/16 2/16 + 2/16 + 1/16 = 5/16 16/5 = 3.2 ohm Simpler example (2) 8 ohm cabs 1/8 + 1/8 = 2/8 8/2 = 4 = 4 ohms (4) 8 ohm cabs 1/8+1/8+1/8+1/8 = 4/8 8/4= 2ohms Link to comment Share on other sites More sharing options...
Members Darth Balls Posted September 10, 2003 Members Share Posted September 10, 2003 Originally posted by black sphynx what if I want to run just one eight ohm 4x12 cab in mono? I would set the amp to eight ohms I would assume?these are the only two scenarios I will deal with. You really have only 5 possiblilities: One 4 ohm cab = 4 ohmsOne 8 ohm cab = 8 ohmsOne 16 ohm cab = 16 ohmsTwo 8 ohm cabs = 4 ohmsTwo 16 ohm cabs = 8 ohms All amps I've seen do not have a 2 ohms selection, so you shouldn't run two 4 ohm cabs ever.Don't run unmatching cabs at the same time, like one 8 ohms, the other 16 ohms, because the amp selector would need to be 5.33 ohms. Might not hurt the amp, but just not good practice. Link to comment Share on other sites More sharing options...
Members H535 Posted September 10, 2003 Members Share Posted September 10, 2003 All amps I've seen do not have a 2 ohms selection, so you shouldn't run two 4 ohm cabs ever. Quality solid state amps can run at 2 ohms and have 2 ohm selector switches. Some even dynamically sence the ohm load for you and set them selves up. You can safely run combinations of 8, 16, 4 etc as long as the ohm load of your speakers is higher than the ohm load setting/rating on your amp. This is found quite often in monitor setups. For example an amp setting of 4 ohms could run any load 4 ohms or higher. IE an 8 ohm cab or a 16 ohm cab or a 4 ohm cab. Cheap power amps might give you a 2 ohm rating but that does not mean they are stable at 2 ohms and wont clip or power down or smoke under peak performance. Link to comment Share on other sites More sharing options...
Members jimfowler Posted September 11, 2003 Members Share Posted September 11, 2003 "Some even dynamically sence the ohm load for you and set them selves up." crest audio, for one. down to 2 ohms of blisteringly hi-fi sound...whoops...must not change subject. over and out. -jim Link to comment Share on other sites More sharing options...
Members El Grinder Posted September 11, 2003 Members Share Posted September 11, 2003 My Strategy 500 (all tube) can go down to 2 Ohms, but Mesa was wise enough to HIDE the brown wires tied off inside the chassis. Basically, this beast is capable of going to 2 Ohms, but they set it up so only an experienced user would make use of that feature for the safety of the amp... Link to comment Share on other sites More sharing options...
Members Darth Balls Posted September 11, 2003 Members Share Posted September 11, 2003 Originally posted by H535 Quality solid state amps can run at 2 ohms and have 2 ohm selector switches. Some even dynamically sence the ohm load for you and set them selves up. You can safely run combinations of 8, 16, 4 etc as long as the ohm load of your speakers is higher than the ohm load setting/rating on your amp. This is found quite often in monitor setups. For example an amp setting of 4 ohms could run any load 4 ohms or higher. IE an 8 ohm cab or a 16 ohm cab or a 4 ohm cab. Cheap power amps might give you a 2 ohm rating but that does not mean they are stable at 2 ohms and wont clip or power down or smoke under peak performance. OK, I shouldn't have said all amps. I was referring to current production tube amps like the Bogner, Marshalls, Mesas, ect, ect, ect. They don't have 2 ohm outs. Link to comment Share on other sites More sharing options...
Members gambit Posted December 27, 2003 Members Share Posted December 27, 2003 i'm looking at cabs right now. but my head only has 4 ohm speaker outs (its solid state) i've read several times that it IS safe to run an 8 or 16 ohm cab with only 4 ohm amp head, but some of the statements talk about "a degree of power loss".what does this mean in real terms? a 300w cab running at 4 ohms instead of its 8, means i only get half - 150watts with my head? if anyone can answer this question asap, i'll be very grateful, coz i might be egtting an amp as early as tomorrow or monday.. or this afternoon..cheers Link to comment Share on other sites More sharing options...
Members chrisaxeman Posted December 27, 2003 Members Share Posted December 27, 2003 Originally posted by black sphynx I have no clue about how to match ohms with my bogner head. I have two 16 ohm cabs , so I know to run the amp at 8 ohms (this was what I was told) I dont know how to come to this conclusion so I was hoping someone here will help me out.Thanks Hey Black, Lets simplify this,it's getting out of hand.My job is an electrician,so I'll handout the no BS approach to amp and speaker impeadence before you get confused and break something.......... Rule 1.your amp of x impeadence can run cab of x impeadence or higher. Rule 2.don't do the opposite of rule one unless you like smoke shows from your amp. Suggestion 1.If you use multiple cabs,for amp purposes use the same impeadence cabs so that they will be of equal volume-in a real world they will not be spot on but the difference will be trivial. Rule 3.Most amps use a parallel outs for multi cabs.Check your manual,it should show the connections,and will be marked clearly on the back panel-I have a Laney GH50L that has dedicated multi out's(1x16,2x16/1x8,2x4/1x8).My TSL100 has a 1x16,1x4/2x4,1x8/2x8,with a selector switch. Your pair of 16 ohm cabs will indeed = 8 ohms,you just have to connect them to the appropriate outputs.I'd have a suspicion that the Bogner would have dedicated jacks for connection in full stack mode(2x16ohm quads)....... Rule 4.Impeadences in series are added together-eg 8ohm + 8ohm =16 ohms. Impeadences in parallel(if the same value)-divide the value by the number of speakers.eg 2x16 ohms = 16/2 = 8ohms 4x16 ohms = 16/4 =4 ohms 16 ohm cabs most often use 4 x 16 ohm speakers wired in series/parallel.eg a pair of speakers each are wired in parallel,so you end up with,Pair 1-2x16ohms=8 ohms Pair 2-2x16ohms=8ohms.Pair 1 is wired in series with pair2, Pair1(8ohms) + Pair2(8ohms)=16 ohms Cabs are sometimes switchable between 4 and 16.The 4 ohms comes from all of the speakers being wired in parallel,16/4=4 ohms. Rule 5.If you do use cabs of different impeadences,the parallel rule works like this-divide 1 byeach value (ie,make 16=1/16,8=1/8 etc),add the fractions together,and then invert the fraction. eg.16 ohm in parallel with 8= 1/16+1/8=3/16 invert=16/3=5.33ohms Rule 6.Look at the example in Rule 5 and notice that when different values are used in parallel,the total impeadence is always smaller than the smallest resistance-5.33ohms Chris........ Link to comment Share on other sites More sharing options...
Members okavipra Posted January 26, 2011 Members Share Posted January 26, 2011 Hey Black,Lets simplify this,it's getting out of hand.My job is an electrician,so I'll handout the no BS approach to amp and speaker impeadence before you get confused and break something..........Rule 1.your amp of x impeadence can run cab of x impeadence or higher.Rule 2.don't do the opposite of rule one unless you like smoke shows from your amp.Suggestion 1.If you use multiple cabs,for amp purposes use the same impeadence cabs so that they will be of equal volume-in a real world they will not be spot on but the difference will be trivial.Rule 3.Most amps use a parallel outs for multi cabs.Check your manual,it should show the connections,and will be marked clearly on the back panel-I have a Laney GH50L that has dedicated multi out's(1x16,2x16/1x8,2x4/1x8).My TSL100 has a 1x16,1x4/2x4,1x8/2x8,with a selector switch.Your pair of 16 ohm cabs will indeed = 8 ohms,you just have to connect them to the appropriate outputs.I'd have a suspicion that the Bogner would have dedicated jacks for connection in full stack mode(2x16ohm quads).......Rule 4.Impeadences in series are added together-eg 8ohm + 8ohm =16 ohms.Impeadences in parallel(if the same value)-divide the value by the number of speakers.eg 2x16 ohms = 16/2 = 8ohms 4x16 ohms = 16/4 =4 ohms16 ohm cabs most often use 4 x 16 ohm speakers wired in series/parallel.eg a pair of speakers each are wired in parallel,so you end up with,Pair 1-2x16ohms=8 ohms Pair 2-2x16ohms=8ohms.Pair 1 is wired in series with pair2, Pair1(8ohms) + Pair2(8ohms)=16 ohmsCabs are sometimes switchable between 4 and 16.The 4 ohms comes from all of the speakers being wired in parallel,16/4=4 ohms.Rule 5.If you do use cabs of different impeadences,the parallel rule works like this-divide 1 byeach value (ie,make 16=1/16,8=1/8 etc),add the fractions together,and then invert the fraction.eg.16 ohm in parallel with 8= 1/16+1/8=3/16invert=16/3=5.33ohmsRule 6.Look at the example in Rule 5 and notice that when different values are used in parallel,the total impeadence is always smaller than the smallest resistance-5.33ohmsChris........ ok, so i just want to ask you one question, i have an ampeg vt 22(combo version of v4) so how should i adjust ohmage if i want to hook it up with 1. 1xevm15l 8omh open back cab and 2. his original 2x12(dont know brand) speaker wired on 8 ohmsthanks in advancep.s. ampeg has 2,4 or 8 ohm options Link to comment Share on other sites More sharing options...
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