or Connect
AVS › AVS Forum › Display Devices › Ultra Hi-End HT Gear ($20,000+) › Different lengths XLR cables…
New Posts  All Forums:Forum Nav:

Different lengths XLR cables…  

post #1 of 17
Thread Starter 
My pre-amp (Krell Showcase ) will be in a rack on the side wall of my theater room, my 3 amps for L/C/R (Krell FPB350 MCX) will be upfront next to each speaker. Can I run three different lengths XLR cables to the amps, my lengths are 12’, 18’ and 24’ or do they all need to be the same length? I did this in order to have the shorts length speaker wire possible.

Thanks,

-Matthew
post #2 of 17
if the lengths were 100' different it would still be not an issue. THe wavelength is EXTREMELY long for that low a frequency. In the neighborhood of about ... well, i am not going to list it, because it would invite far too much scorn and ridicule.

(speed of light/ frequency)

This is not to be confused with that same signal transmission in air. Wherein a few inches can cause a phase shift.
post #3 of 17
Thread Starter 
Thanks.....

-m
post #4 of 17
Quote:
Originally posted by Dizzman
if the lengths were 100' different it would still be not an issue. THe wavelength is EXTREMELY long for that low a frequency. In the neighborhood of about ... well, i am not going to list it, because it would invite far too much scorn and ridicule.

(speed of light/ frequency)

This is not to be confused with that same signal transmission in air. Wherein a few inches can cause a phase shift.
Great, great post, Dizzman!... :)

-THTS
post #5 of 17
I have checked this with my cable manufacturer, Siltech, and they also said it wouldn't make a difference - particularly at the lengths we're talking about.
post #6 of 17
the wavelength of a 10 k sive wave is in the neighborhood of about (i do not have my spreadsheet with me) 40,000'.
post #7 of 17
does this apply just for XLR interconnects? I know that XLR can run very long without any signal drop.
How about RCA interconnect and speaker cables.
Can I have a shorter speaker cable for my main and center?

thanks in adavance
post #8 of 17
Its the same for these cables as well,for reasonable cable lengths.
post #9 of 17
from the perspective of wave propagation, the physics do not change. it is merely frequency and cable velocity of propagation. however some will argue that a longer cable will have more loss. personally i would be quite comfortable putting good money on a test where you have to identify the 10' or the 100' cable (same model to sidestep that argument)
post #10 of 17
Quote:
Originally posted by sholei
does this apply just for XLR interconnects? I know that XLR can run very long without any signal drop.
How about RCA interconnect and speaker cables.
Sheesh, I'm surprised you guys missed this.

There is much more to interconnects than phase shifts and propogation delays. One could argue that phase shifts and propogation delays are minor order effects and noise rejection and preservation of signal strength are the major order effects.

From this standpoint XLR interconnects are vastly superior than RCA. Not because the cabling itself is so much more superior but because RCA interconnects use single-ended drivers vs the differential drivers for XLR connections. Differential drivers have much improved signal to noise ratio and can be driven over much longer distances. Differential drivers also provide a much higher gain (something like 6 db over RCA).

I personally would consider running only XLR interconnects over distances greater than 10 feet or so.

One other minor point, the propogation speed of Electromagnetic waves is the speed of light only in a vacuum. For a copper cable, it's still very very fast though...
post #11 of 17
in a cable it is in the area of about 80% of C, so still a delay of about 1.36 ns /ft. In a vacumm it is about 1.06 ns/ft

As far as the balanced vs unbalanced stuff... yess there is the issue of noise rejection, however the average home is in NO WAY WHATSOEVER noisy enough for this to matter. it also depends on whether both ends of the circuit are balanced. THe way i look at it if you have a noisy environment I deal with the commerical world, everything is sent balanced) In a home, it is possible that you could have some noise, but i think that in any dedicated system like this is, the difference is far more percieved than real.

The 6 dB gain is due to an unbalanced signal being turned into a balanced signal and the natural gain through the two sides of the circuit (+ and -) being added together. Also when dealing with a component with a balanced circuit, it is likely using a +4 (or Pro) line level as opposed to the -10 (or consumer) line level. SO the increased gain is a natural part of the component. this pro level can also be had in an unbalanced output. So even in that case you have a signal that is 14dB higher so any natural noise floor is 14 dB farther down so the component is naturally quieter and louder at the smae time.
post #12 of 17
Quote:
Originally posted by Dizzman
however the average home is in NO WAY WHATSOEVER noisy enough for this to matter.
I respectfully disagree. In the rats-nest cabling world of 5.1 surround sound systems, pretty much every long run (15' or so) of RCA that I've used suffered from some degree of 60hz noise. Replacing the RCA with XLR (when it's been an option) has always yielded dramatically improved results. Balanced XLR really is vastly superior to RCA and more manufacturers should go this route.

Dizzman, rather than confusing the issue you should be encouraging people to use XLR if it's an option for them. In fact if all manufacturers opted for XLR interfaces between pre-amp and amp there would be little need for expensive and esoteric cabling.

Note: edited for grammar.
post #13 of 17
I dropped any pretention of the perfect world when i got raked over the coals at CEDIA because all our switchers use BNC for video and captive screw BALANCED for audio.

However, i did say average, and i still think that the rats nest was likely more the culprit. when building racks and doing systems (whatever the size) the cable routing and manaement can be the most important thing.

But, if a balanced interconnect is available, then it should absolutely be used.
post #14 of 17
It's too bad that the industry hasn't moved to XLR for all interconnects.

As far as rat nest cabling goes, many years ago I had an interesting observation which was that I ended up with noticeable 60hz hum when I very carefully tie-wrapped my cables for neatness. What I found is that wrapping them in loops provided a better way to inductively couple noise into the cables. This problem went away when I removed the coils and let the wire hang randomly (ie become a rats nest). The main thing is to try and keep AC cables away from interconnects.

Even still I had a problem with a 15' subwoofer run recently where I had a lot of 60hz hum from a ground loop that was only resolved by replacing the RCA cable with an XLR cable.
post #15 of 17
with excess cables, wrap them in a figure 8. this alows for the noise to cancel itself out.

The whole process of cable management is in my opinion another of those things that is overlooked in systems all the time.

Chris Gillespies list of overlooked AV system elements...

1. Power. Rewiring the system and installing a new technical ground. Maybe even moving lighting and other nasties to a seperate set of circuits and a different technical ground.

2. Room. Shape, wall coverings, placement of gear. (speakers PROPERLY phase alligned) (projectors EXACTLY in the correct geometric location)

3. Cable/Signal Management. Power cables away (or crossing at 90 degrees) from Audio, excess wire chopped off or neatly coiled in an over/under (figure 8) method.

4. Wine being drunk at proper temp while enjoying system. I mean come on... a burgundy at 68 degrees... PLEASE!
post #16 of 17
Dizzman, thanks for the tip on the figure 8. This would definitely do the trick.

I also agree with all of your other points. Especially 2. Proper room treatment can yield tremendous improvements.
post #17 of 17
Quote:
From this standpoint XLR interconnects are vastly superior than RCA. Not because the cabling itself is so much more superior but because RCA interconnects use single-ended drivers vs the differential drivers for XLR connections.
Yep. It should be mentioned that not all components with XLR jacks use differential drivers. Some use a cheap work-around (like a passive converter you'd get at Radio Shack). Make sure your component has differential drivers (or is fully differential) to get the benefit from XLR cabling.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Ultra Hi-End HT Gear ($20,000+)
This thread is locked  
AVS › AVS Forum › Display Devices › Ultra Hi-End HT Gear ($20,000+) › Different lengths XLR cables…