Just a side note, cables running into an active speaker are not speaker cables, they're actually signal cables.
Mac mini > AVI ADM9Ts
5m of copper speaker wire of 2.5mm with have a resistance of approximately 0.017092 ohms
10m of copper speaker wire of 2.5mm with have a resistance of approximately 0.03418 ohms
I don't personally consider this amount of resistance as particulary significant in any part of the audio chain downstream of the sources.
Hmmn. You must have got your EE degree at the same place Chris Covenanter did.
I calc 5M of 2.5mm^2 copper cable at 0.034 ohms, or 0.068 ohms for the round trip.
My Martin Logan's impedance curve dips to a low of 1 ohm, so we are talking about 6.8% of 'voicecoil'. Doubling this to 10M gets the speaker cable to approximately 14% of 'voicecoil' impedance.
That sort of feels significant.
............ and that is why they make 110ohm coax SPDIF cables
I think you are mixing chalk and cheese.
The S/PDIF spec requires 75ohm termination. EBU-AES digital audio was designed for use in studios over existing balanced twisted pair cables, not coax, and has 110ohm termination.
Hmm, my mistake your figures are correct. However, 1ohm is exeptionally low, 10m rather a long cable run and it would be easy and cheap enough to use thicker speaker wire.
Say 4mm cable, then 0.021 ohms.
You can use the Martin Logans as an example, but it's easy enough to get thick speaker cable to counter the low voicecoil impedence and using more sensible and realistic cable lengths still results in insignificant resistance.
So resistance in the speaker cable, whilst not irrelevant, if taken into consideration when buying to suit the speakers, might as well be.
The general rule of thumb is to buy as thick a cable as you can fit into the binding posts for the lowest resistance possible. Use silver if you're feeling flush for a slightly better proposition, but a little OTT.
Well I went to London University, what was then Chelsea College, now part of Kings College. They had the only pure Electronics course in the UK at the time, all the others were Electrical Engineering. It was at the time when semiconductors were just beginning to dominate but I still did a whole year's course on valves and indeed my first self-designed amp was valve based. The technology has changed a lot since but the basic laws haven't!
If as you say you have very low impedance speakers the the impedance of the speaker cable becomes more important. I would guess that most people don't have very low impedance speakers though. Do you really have 10M speaker cables? Must be one hell of a room as that makes the speakers potentially about 60 foot apart! My speaker cables are 2M long.
It also depends on the amp. some older Naim amps would blow up unless thay had at least 3.5 metres of speaker cable, so Naim said, had to be Naim cable as well.
As for lengths for 10m you do not need the speakers 60 feet apart as the hifi is not always in between the speakers, often to the side of both. I have 5m and my speakrs are only 6 feet apart.
Another point how important is it to have both speaker cables the same length?
© 2013 Haymarket Publishing