Members kobe Posted November 19, 2006 Members Share Posted November 19, 2006 i'm currently using 4mm conductor thickness cable for connecting my amps to subs in about 50ft lengths, my question is -If my amp rack has speaker patch leads going from the amp binding post to a rack patch panel, and these patch leads are made up of 1mm thickness conductor and a lenght of about 1 foot will the small gauge patch leads have a detrimental effect on the system? cheers, john Link to comment Share on other sites More sharing options...
Members nobrainer440 Posted November 19, 2006 Members Share Posted November 19, 2006 Short answer: At low power, no. At high power, yes. We just finished having a 4-page debate (er... shouting match) about cable thickness. You can read it here. Link to comment Share on other sites More sharing options...
Members dboomer Posted November 19, 2006 Members Share Posted November 19, 2006 Why such small hook up wire? 1mm is roughly 20 awg. I'd use at least 2mm wire inside the rack (14 awg). Typically the cabinets themselves will have 16 awg hookup wire inside ... and it quickly gets smaller once it hits the speaker. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 19, 2006 Members Share Posted November 19, 2006 All depends on how much power AND the minimum load impedance you operate at. For some applications it may be fine (like acoustic music wher ethe sub may be a small 100 watt 8 ohm box) but, I would look at either 16 or 14 gauge in as much as the cost is insignificant and the mechanical integrity is better. No benefit in going beyond 14ga for such a short run on any reasonable system configuration. Link to comment Share on other sites More sharing options...
Members kobe Posted November 19, 2006 Author Members Share Posted November 19, 2006 Originally posted by nobrainer440 Short answer: At low power, no. At high power, yes.We just finished having a 4-page debate (er... shouting match) about cable thickness. You can read it here. yeah i did read that thread, it go quite scary in there!! lol ok i'm sending about upto 1.5Kwatt down 5 inches of 20 awg cable, I know 20awg is far to small but let me stress it's only 5 inches the 50foot run is down 4mm cable (whatevet the awg for that is!!) john Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 19, 2006 Share Posted November 19, 2006 Originally posted by dboomer Why such small hook up wire? 1mm is roughly 20 awg.I'd use at least 2mm wire inside the rack (14 awg). Typically the cabinets themselves will have 16 awg hookup wire inside ... and it quickly gets smaller once it hits the speaker. ? I think kobe means 4sq. mm, which I believe is about 1/2 way between 10 and 11 ga. 4sq. mm is pretty fat stuff. I believe 4sq. mm is the fattest conductor that will fit in NL4FC and NL4FX cord ends. oh wait a minute... now I see the 1mm stuff (my eyes are just crap, and I never seem to have reading glasses close at-hand... and who's idea is black on a blue background typing field... don't those computer wiz-kids know most of us are varying degrees of colorblind? Psstt: Black on a white background is the highest resolution possible... ok? You know? Like all the boarder stuff which I can clearly read... even at arms length, or even slightly less. Crap... I hate getting old). Yup... that's pretty thin stuff. Yup, you're probably choking your chicken with that doing speaker cable duty... no matter how short it is. I suspose it would be fine for a few 10's of watts, but I doubt that's the application. I'd be kind of concerned about the possibility of spring loaded or screw banana posts cutting right through 1mm wire. I guess feel back there when your system's running hard and see if the conductors are getting warm. If they're getting at-all noticably warm, you're throwing away some potential. Link to comment Share on other sites More sharing options...
Members kobe Posted November 19, 2006 Author Members Share Posted November 19, 2006 Originally posted by Audiopile ?I think kobe means 4sq. mm, which I believe is about 1/2 way between 10 and 11 ga.4sq. mm is pretty fat stuff.I believe 4sq. mm is the fattest conductor that will fit in NL4FC and NL4FX cord ends.oh... now I see the 1mm stuff. Yup... that's pretty thin stuff. Yup, you'd be choking your chicken with that doing speaker cable duty. choking the chicken...ha ha thats a great phrase!! remember than 1mm stuff is only a very short run. john Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2006 Share Posted November 20, 2006 Originally posted by kobe choking the chicken...ha ha thats a great phrase!!remember than 1mm stuff is only a very short run.john Like Andy sez: It's a combination of wattage, load impedance, and length of the run. Admittedly your run is real short, but I suspect the wattage is high enough and the load impedance is low enough that you could benefit from a larger cable size regardless of how short you make it. With that short of runs, the cost difference is minimal, and the PITA factor of dealing with 16ga. or even 14ga. is probably minimal. FWIW:AWG = sq. mm10 = 5.2611 = 4.17 12 = 3.3113 = 2.6214 = 2.0815 = 1.6516 = 1.3117 = 1.0418 = 0.82319 = 0.65320 = 0.518 Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2006 Share Posted November 20, 2006 Originally posted by kobe choking the chicken...ha ha thats a great phrase!! I believe that reference has a notably different meaning here on the other side of the pond... but it seemed descriptive in the context of the subject matter. I guess the end result is about the same... possibly lots of activity, but a fairly single ended result regardless of the context. Link to comment Share on other sites More sharing options...
Members BillESC Posted November 20, 2006 Members Share Posted November 20, 2006 Electricity is much like plumbing. If you feed a 2" copper pipe with a 1/2" copper pipe, you'll never have more water in the 2" pipe than the 1/2" pipe can deliver. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 20, 2006 Members Share Posted November 20, 2006 Yes, electricity has analogies to plumbing but applying the analogies appropriately can cause some misunderstandings. Provided the power loss in the 6" piece of wire does not endanger the wire's insulation due to temperature rise, the wire's contribution over a 50' length of cable is only 1% of the total voltage drop. The only thing the speaker cares about is the total voltage drop to the speaker. If you look inside the amplifier, you may be surprised at the wire gauge feeding the output jacks, and the PCB traces feeding the speaker outputs. It's all calculated on voltage drop and I**R heating effects. There is a point where the voltage drop will cause an unsafe rise in conductor temperature, so this is the second factor that must be considered. 17 gauge equiv. of 1 sq mm is a bit light IMO for your application, but not catastrophicly so. I would look at 16 gauge equiv. as a minimum and 14 as "ideal". Link to comment Share on other sites More sharing options...
Members BillESC Posted November 20, 2006 Members Share Posted November 20, 2006 Originally posted by agedhorse Provided the power loss in the 6" piece of wire does not endanger the wire's insulation due to temperature rise Seems to me the minute one runs a continous load greater than the ampacity of the cables conductor, voltage drop in inevitable and failure just around the corner. Link to comment Share on other sites More sharing options...
Members nobrainer440 Posted November 20, 2006 Members Share Posted November 20, 2006 Originally posted by agedhorse Yes, electricity has analogies to plumbing but applying the analogies appropriately can cause some misunderstandings.Provided the power loss in the 6" piece of wire does not endanger the wire's insulation due to temperature rise, the wire's contribution over a 50' length of cable is only 1% of the total voltage drop. The only thing the speaker cares about is the total voltage drop to the speaker. If you look inside the amplifier, you may be surprised at the wire gauge feeding the output jacks, and the PCB traces feeding the speaker outputs. It's all calculated on voltage drop and I**R heating effects.There is a point where the voltage drop will cause an unsafe rise in conductor temperature, so this is the second factor that must be considered. 17 gauge equiv. of 1 sq mm is a bit light IMO for your application, but not catastrophicly so. I would look at 16 gauge equiv. as a minimum and 14 as "ideal". This is exactly right. Since the run is short, it wont affect the overall voltage drop all that much, BUT since the diameter is so small, overheating is a very real risk. Link to comment Share on other sites More sharing options...
Members Dogoth Posted November 20, 2006 Members Share Posted November 20, 2006 Originally posted by nobrainer440 This is exactly right. Since the run is short, it wont affect the overall voltage drop all that much, BUT since the diameter is so small, overheating is a very real risk. In The automotive industry they call that a "fusable link":D Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2006 Share Posted November 20, 2006 Originally posted by BillESC Seems to me the minute one runs a continous load greater than the ampacity of the cables conductor, voltage drop in inevitable and failure just around the corner. It's been awhile since I've thought about it... but as I understand it, amps (coulombs of electrons) per unit of time is the limiting factor in wire. Yes, the voltage can be raised so those electrons are at a higher state of energy... but you can still only shove so-many electrons down a given gauge of wire per unit of time... as opposed to the water and waterpipe anology... where the same 1/2 dia. of pipe can carry wildly varying quantities of molecules of water depending on the pressure pushing them along. There isn't necessarily an upper limit of how many water molecules a 1/2" dia. pipe can carry per unit of time... the quantity just keeps increasing the more the pressure is cranked up... although admittedly, the wall thickness might have to be increased to handle the pressure... but it's still a 1/2" pipe... as opposed to wire, where the electron quantity capacity can't be increased in a given guage wire... by adding more insulation... or something... maybe by cooling it? Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 20, 2006 Members Share Posted November 20, 2006 Wire ampacity varies depending on the thermal rating of it's insulation, and the cooling effects of the materials surrounding the wire, including ambient temperature. Material also matters... aluminum wire has a lower ampacity due to lower "per unit" conductivity. Duty cycle also affects the ampacity. Ampacity is independant of applied voltage which is why a piece of 12 gauge wire may carry up to 100kVA (similar to 100,000 watts) of power to a load without a problem under high voltage conditions. 12 gauge (copper) wire can have an ampacity of between 10 amps and 30 amps depending on the application. Nothing is quite as easy or simple as it seems. Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2006 Share Posted November 20, 2006 Originally posted by agedhorse Wire ampacity varies depending on the thermal rating of it's insulation, and the cooling effects of the materials surrounding the wire, including ambient temperature. Material also matters... aluminum wire has a lower ampacity due to lower "per unit" conductivity. Duty cycle also affects the ampacity. Ampacity is independant of applied voltage which is why a piece of 12 gauge wire may carry up to 100kVA (similar to 100,000 watts) of power to a load without a problem under high voltage conditions.12 gauge (copper) wire can have an ampacity of between 10 amps and 30 amps depending on the application.Nothing is quite as easy or simple as it seems. Right, but 12ga. copper wire can still only carry a maximum of 30 amps (30 x 6.28 x 10 to the 18th electrons) per second. The voltage (pressure) can't be increased to push more electrons... unlike water and a waterpipe. Regardless of the voltage... there is a finiate quantity of electrons a given size of electron pipe (wire) can carry. Admittedly, the voltage can be raised so those maximum of 188.4 x 10 to the 18th electrons per second hit harder. With the water and waterpipe anology... with a give diameter of pipe... as the pressure is increased, BOTH the quantity and "hitting power" of water molecules is increased. Once 30 amps of quantity is reached with 12ga. cable, that's it, you can't shove any more quantity of electrons down the wire. Right? I'm just trying to point one major difference between the waterpipe and wire anology. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 20, 2006 Members Share Posted November 20, 2006 No, you can keep increasing the current but the losses in the wire will increase by the square of the current till the wire melts. Actually, it becomes even more non-linear as the temperature increases the wire's resistance increases too but only as the wire gets really hot. For example, in free air, 0-2000 volts, uninsulated copper wire is code-legal to 78 amps for type PFAH ot TFE (teflon) at an opertaing temperature of 482 degrees F, and nickel coated copper conductor. For copper only, 68 amps. This is all provided the voltage drop is acceptable for the application. Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2006 Share Posted November 20, 2006 Originally posted by agedhorse No, you can keep increasing the current but the losses in the wire will increase by the square of the current till the wire melts. aargh... I'm having a hard time wording my concept correctly (comprehensably); however, I agree with everything you're saying. eh...? It doesn't much matter for the OP's topic of discussion anyway. I remember a documentry I saw once on machine shop work. One point of interest was the machining of an impeller for a pump on the space shuttle... this pump was about the size of a 18hp Briggs engine... and "they" mentioned this pump could pump out an olympic sized swimming pool in something like 12 seconds. Oh, BS... there is no way that much water could go through that thing that fast... but I guess with enough horsepower and pressure... yup... I guess it could. Well... with wire, I'd think there's be a point where even submursed in liquid nitrogen, there's a finite amount of current a given size of wire can transfer. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 20, 2006 Members Share Posted November 20, 2006 You are hinting at the thermal non-linear portion of the curve... like the yield point on structural materials. Link to comment Share on other sites More sharing options...
Members where02190 Posted November 20, 2006 Members Share Posted November 20, 2006 Seems pretty silly for a bucks worth of wire to even debate it, since larger wire isn't going to hurt anything. Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 21, 2006 Share Posted November 21, 2006 Originally posted by where02190 Seems pretty silly for a bucks worth of wire to even debate it, since larger wire isn't going to hurt anything. Don't worry about it Nick. I think Kobe already knows what the coffee shop thinks about his subject matter. Andy and I were talking about something that might not concern you (unless you're into eddy currents and constant current impedance testing). We (Andy and I) will probably take discussion privately. Link to comment Share on other sites More sharing options...
Members agedhorse Posted November 21, 2006 Members Share Posted November 21, 2006 Though it may be suitable information for a learning experience for some other forum members? Link to comment Share on other sites More sharing options...
Members nobrainer440 Posted November 21, 2006 Members Share Posted November 21, 2006 Sorry, this is a bit off topic, but out of curiosity, agedhorse, what kind of schooling have you had? You seem have a pretty firm grasp on engineering. I'm a junior in mechanical engineering myself. Link to comment Share on other sites More sharing options...
Members kobe Posted November 21, 2006 Author Members Share Posted November 21, 2006 thanks for the responses guys. some great info about my question, although some is of it is admittedly over the top my head!! i have to confess to not knowing much academically about sound reinforcement but have built up my knowledge by trial and error during the last 4 years during which time I've progressed to a 10KW 24channel system which does me fine and allows me to run sound as my full time job. I'm sure without the help of people like Agedhorse, Audiopile and others i'd be we'll and truly stuck by now so thanks guys. John Kobe Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.