SPKR cable for 4x1200 amp @4r ? |
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valve head777
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1780 |
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Thanks Ceharden
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Freedom of choice, choice of freedom.
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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so the 10m long cable is effectively 20m conductor.
Source: https://commons.wikimedia.org/wiki/File:Copper_cable_resistance.jpg From the 2.5mm^2 wire it is 0.28R From the 4mm^2 wire it is 0.175R while the 6mm^2 wire is 0.117R Since the Damping Factor(Df) = Z_load / Z source (source: https://en.wikipedia.org/wiki/Damping_factor ) and the cable itself added to the source impedance, even with the best amplifier with 0 output impedance (infinite Df) you could have the following possible best damping factors for the 10m long cable: 2.5mm^2 : < 14.28 ( it would be as low as just 7! with 2R load ) 4mm^2 : < 22.85 6mm^2: < 34.2 Do not you think how this physics is such a shameful when you have Df > 5000 amplifier?! ;-D It is obvious too why low impedance system is bad idea on higher power levels. Edited by U.Viktor - 29 January 2017 at 4:19pm |
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Dutchman
Registered User Joined: 23 March 2013 Location: GENT Status: Offline Points: 365 |
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Hahaha, too funny this thread. Copper is copper!
2.5mm² will do just fine 90 procent of the time!! Almost every big PA company has 2.5mm² cables for mains (16A) or for speaker use.
Damping factor doesn't exist!! |
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We need more SPL!
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Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
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Even if you took the resistance of 0.28 from the 2.59 mm cable into factor, it would basically mean the 1207.56 watts (69.5 volts @ 4 ohms) would be reduced to 1118.11 watts which, offers a dB differential of -0.3 dB loss in terms of SPL. I would imagine Safetyman can determine if a dB gain of 0.3 dB in larger cable is worth it or not. Best Regards, Edited by Elliot Thompson - 29 January 2017 at 5:51pm |
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Elliot Thompson
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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7199 |
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That's a big statement there. Damping factor does exist, but maybe not as important as some people state. I think that Rod Elliott has an article somewhere on his site and IIRC concludes that a (real) damping factor of 50 or so is ok for most applications. "In general I'm also in the 2.5mmsq camp. However I did used to notice when doing live gigs that having about 15m of cable to one stack and less than 5m to the other (amps on one side of the stage), the stereo image was slightly shifted towards the shorter cables." +1 I've noticed that as well on one of my systems. I generally just boost the gain of the far side by a couple of dB on the LMS and it's fine. You do have to be dead center to really notice anything. Edited by Earplug - 29 January 2017 at 6:17pm |
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Earplugs Are For Wimps!
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Safetyman
Young Croc Joined: 08 February 2009 Location: Brighton, East Sussex Status: Offline Points: 555 |
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Thanks to all, much appreciated.
My 'normal' cable is Van Damme Pro Touring 2x2.5 twinax, as well as some 5-6 metre lengths of their 2x4mm version. The amplifier is one of Andy's XT6004EQ's, which on recorded music at least, has never been on more than half power ( it is just too loud above that ). I have ordered some Klotz SY225 as, having used their 1.5 version for tops on my small EV system, it sounded rather better than the 2x2.5 Van Damme Pro Touring. Hoping that the 2x2.5 Klotz will sound ok, too. Yes, I get it, that keeping the cables as short as possible, of equal length and with both stacks equidistant from the amp rack is preferable . Not always possible, though, as the last thing you want are muso's falling -over the cabling or the rack as they move about the stage area in low light. Doubling up the cables sounds like an idea I might try in the future, if all else fails. |
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Protect your hearing, and feel the music.
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Jasonstry
Young Croc Joined: 11 September 2007 Location: Cannock. J11 M6 Status: Offline Points: 1367 |
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I use 4mm for my main PA and I have two reasons for doing that nobody can argue with. The first one is that I was given a load of it (mostly VDC) for nothing and the second is that I am a small operator so the weight isn't an issue. If either of those things hadn't been true I would be using 2.5mm. I plan to add another two high/mids soon and will need more speaker leads. I will be using 4 core 2.5g HO7RNF.
Hope that helps! |
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Down with signatures!
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B_Bender
Registered User Joined: 28 October 2016 Location: Surrey Status: Offline Points: 118 |
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You're telling us that one speaker cable 'sounds better' than another speaker cable over short runs?
I needed some comedy on a monday morning, thanks for the laugh!
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Safetyman
Young Croc Joined: 08 February 2009 Location: Brighton, East Sussex Status: Offline Points: 555 |
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Glad it 'made your day' LOL
Edited by Safetyman - 30 January 2017 at 9:35am |
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Protect your hearing, and feel the music.
MU South East Roving Safety Rep. |
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concept-10
Young Croc Joined: 17 May 2016 Status: Offline Points: 1292 |
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A PKN amlifier is so good and so much better than anything else that you can hear the difference in cables lol
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U.Viktor
Young Croc Joined: 04 May 2010 Status: Offline Points: 716 |
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Well , if you have an "INUKE-category" power stage (with so variable source impedance..) likely will not hear the difference between 2.5 and 4mm^2 cables without very sensitive ears.. However if you want to bring out the best sound from your drivers, it would need a good power source and the influence of cabling is noticeable mainly NOT in SPL but in sound quality. The amplifier is a living "coupled system" with the moving coils of drivers, and things like cable resistance has effect on the system behavior! |
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snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3118 |
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maybe I am missing something here but I've never understood why damping factor matters for amplifiers other than valve amps.
if I were to connect a resistive test load to an amplifier then we would understand the resistance of the resistor as being the load impedance. but when that resistance is a speaker cable it is said to be part of the source impedance. WHAT? doesn't the resistance of the voice coil make other smaller resistances in the circuit irrelevant? damping factor is about behaviour at driver resonance. at resonance the impedance of a loudspeaker is very much higher than its nominal value. so aren't damping factors calculated using nominal values out by a factor of ten? isn't a more significant value the ratio of acoustical impedance (at resonance) to electrical resistance (voice coil + cable + source impedance)?
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