AVS Discussions
Home Theater Construction => Construction tips => Topic started by: kenreau on November 08, 2016, 05:05:41 PM
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Finally underway with building out my first home theater room. My room is 13' wide x 26' long x 7' high ceiling (basement). I have an adjacent 6' x 6' closet being converted to the HT gear room. I am installing a 7.1.4 Dolby Atmos speaker array using GoldenEar Invisa SP 652s (4 each) in the ceiling and Supersat 50s (4 each) for wall surround speakers.
With the equipment closet off to one side, the speaker cable lengths from AVR to speaker locations are much closer on one side (say 15 feet to right side) and quite far to reach the left channel sides (say 30 feet).
Coming from the dedicated 2 channel music side, I've always ran equal speaker cable lengths to both left and right channel speakers. Is there a consensus for surround effects channels that equal speaker cable lengths for each channel are still good practice? Or, overkill in this situation?
Continuing on to the front L, C &R channel speakers, same question. The furthest channel left speaker is about 40 feet and the nearest right channel is about 25 feet. Should I use just enough speaker cable to reach those? or, run equal cables lengths to all three (approx. 40 feet each)
Thanks
Kenreau
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When we ran ours...we just left a few extra feet, just in case we ever get new equipment or move the speakers. IMO there is no need to make the wires equal.
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I remember on my first home theater build, I ran equal lengths to all five of my speakers. Later I learned that it did not really matter. The time delay difference in even 50' of extra wire is so small that it requires pretty good measuring equipment to show a difference. You will never ever be able to hear a difference.
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Well, the speed of light is 186,000 miles/sec. Electricity through a home generally runs about 1/100 of that speed so we are saying 1,860 miles/sec. Sound travels at 1115 ft/sec roughly which is 0.21 miles/sec. Therefore, the electrons providing the signal to your speaker moves approximately 8,857 times faster to your speaker than the sound travels from your speaker. You would need miles of speaker cable difference in order to make a dent in the timing. So, 20 or even 30 extra feet will make no difference in apparent sound timing reaching your ears.
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The change with differences in length, if any, and if audible, is not (or very rarely) due to propagation delay. The extra wire length adds impedance, that is resistance, capacitance, and inductance, that can both reduce the signal level (easily compensated) and affect the frequency response (magnitude and phase, probably in a minor way, and again room correction can compensate if it is significant). Probably the biggest difference for FR is due to the crossover since most speaker designs assume pretty near an ideal voltage source. Add resistance (ok, impedance for techies), and the crossover "sees" a higher driving source and that can cause the FR to vary from the design target. How much this matters is open for discussion (and measurements, natch).
In practice I doubt you'd hear a difference between 25' and 40' of decent gauge speaker cable.
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A lot of things I learned 20 to 30 years ago have proven to be false. :)