[AC2011]

Hi -


I plan to build a custom rack for my gear (under the stairwell) - this will make it so that the receiver, etc. is to my left as I sit and look at the TV.


When running my in-wall wiring, do I need to be very concerned with matching the length runs to the surrounds? For example, the left surround would really only require about a 7 - 10ft run, but the right surround would require something more like 35ft. So, should I do a matching 35ft run to the left surround as well?


Same would go for the L/C/R, as each would technically require a couple of extra feet as you move left to right - should I just figure the longest run required and do the same for all 3?


I assume that I don't have to match the longest run to ALL 5 (or 7) speakers?



Thanks.

 

[Kal Rubinson]

No need. Make sure you use cable gauge adequate for the longest run and the others will be OK. In one of my systems, all the cables are of identical length. In my other system, they range from 6' for the FL to nearly 40' for the SR. No issues with either system.

 

[Glimmie]

There are no timing issues in analog audio systems. Yes electrical energy does travel through cable at approx 66% light speed, but at 20khz, well do the math. Thousands of feet doesn't make even a hint of a difference hearing wise.


Some may point out the timing of physical tweeter placement against the woofer placement in speaker design. But that's acoustical delay, not electrical delay. And as sound travels at 750mph, much, much slower so it's a big difference vs electrical energy.


Now I would try to keep the lengths within 20 feet of each other on the LCR speakers due to wire resistance. This can have a slight effect on bass dampening factor due to cable resistance and inductance.

 

[mtbdudex]



Quote:
Originally Posted by AC2011 /forum/post/20891122


Hi -


I plan to build a custom rack for my gear (under the stairwell) - this will make it so that the receiver, etc. is to my left as I sit and look at the TV.


When running my in-wall wiring, do I need to be very concerned with matching the length runs to the surrounds? For example, the left surround would really only require about a 7 - 10ft run, but the right surround would require something more like 35ft. So, should I do a matching 35ft run to the left surround as well?


Same would go for the L/C/R, as each would technically require a couple of extra feet as you move left to right - should I just figure the longest run required and do the same for all 3?


I assume that I don't have to match the longest run to ALL 5 (or 7) speakers?



Thanks.

Quote:
Originally Posted by Glimmie /forum/post/20891348


There are no timing issues in analog audio systems. Yes electrical energy does travel through cable at approx 66% light speed, but at 20khz, well do the math. Thousands of feet doesn't make even a hint of a difference hearing wise.


Some may point out the timing of physical tweeter placement against the woofer placement in speaker design. But that's acoustical delay, not electrical delay. And as sound travels at 750mph, much, much slower so it's a big difference vs electrical energy.


Now I would try to keep the lengths within 20 feet of each other on the LCR speakers due to wire resistance. This can have a slight effect on bass dampening factor due to cable resistance and inductance.

Back in fall 2007 I did online research, asked this exact Q, and was told to keep the lengths within 10% for "cable resistance and inductance" load on the amp as Glimmie stated above.


I followed the advice....routed the extra wire away from 120v ac in the walls.


Front wall, AV closet is on RH side.

Biggest "waste" of wire is LH RR side surround vs RH RR side surround....like 40feet of wire....


I sleep good at night knowing my HT wires resistance and inductance load on the amp is in balance

 

[htcritic]



Quote:
Originally Posted by mtbdudex /forum/post/20893660


...I sleep good at night knowing my HT wires resistance and inductance load on the amp is in balance

This is just plain silly.


So, really. You'd actually not sleep if your speaker wire lengths were not matched. Really.


Hey, if you believe it and it allows you to actually sleep, great. But to suggest to someone looking for data that matched lengths of speaker wire is better than the length actually needed is, well, silly.

 

[SAM64]



Quote:
I sleep good at night knowing my HT wires resistance and inductance load on the amp is in balance

Why ignore capacitance?

Quote:
routed the extra wire away from 120v ac in the walls.

Do you really think you get much current induced into such a low impedance circuit?

 

[Glimmie]



Quote:
Originally Posted by htcritic /forum/post/20894148


This is just plain silly.


So, really. You'd actually not sleep if your speaker wire lengths were not matched. Really.


Hey, if you believe it and it allows you to actually sleep, great. But to suggest to someone looking for data that matched lengths of speaker wire is better than the length actually needed is, well, silly.

We aren't saying critical matched length. 10-20 feet difference is hardly matched. But there is a real issue with the inductance on long runs if one channel is say 5 feet and the other is 50 feet with say 16ga wire. It's not night and day but still measurable.


Also note the poster is a PE. Probably not an electrical PE but any PE is a stamp of highly significant overall engineering knowledge and education. Plus you must have some EE knowledge to pass the FE exam which is the first step. So let's show a little respect here. And note that it's illegal to put the PE suffix after your name unless you are actually licensed.


Me? I'm not a licensed PE but do hold a BSEE and 27 years in broadcast system engineering. So laugh away.

 

[Glimmie]



Quote:
Originally Posted by SAM64 /forum/post/20894711


Why ignore capacitance?

because at the impedances we are dealing with, it doesn't have significant influence.

Quote:
Do you really think you get much current induced into such a low impedance circuit?

Now that I will agree on, passive speaker cables are pretty much immune to this.

 

[Joe Skubinski]

It's not the current it's induced potential. You need to consider susceptibility in the electronics, such as the feedback loop.

 

[Glimmie]



Quote:
Originally Posted by Joe Skubinski /forum/post/0


It's not the current it's induced potential. You need to consider susceptibility in the electronics, such as the feedback loop.

Huh? If the impedance is too low for an induced potential to ingress, then how will the amps feedback loop even see it? Plus, the feed back loop is a voltage divider of at least 100:1.


Joe, stick to marketing and let the engineers worry about real electrical engineering.

 

[Joe Skubinski]

So you would have no problem with say running 30 meters of a zip cord style speaker cable parallel to a typical home's AC wiring? I take it you did this in your own HT room build, speaker cable runs all bundled together with the power.

I agree with you on keeping cable lengths similar at least across the front three, typically recommend staying within a 25% difference.

Quote:
Originally Posted by Glimmie /forum/post/20895961


Huh? If the impedance is too low for an induced potential to ingress, then how will the amps feedback loop even see it? Plus, the feed back loop is a voltage divider of at least 100:1.


Joe, stick to marketing and let the engineers worry about real electrical engineering.

 

[htcritic]



Quote:
Originally Posted by Glimmie /forum/post/20895221


... But there is a real issue with the inductance on long runs if one channel is say 5 feet and the other is 50 feet with say 16ga wire. It's not night and day but still measurable....

Granted. But I'd also say that running 50' of 16 ga wire is as silly as stating that speaker wire lengths alter sq. There have to be some givens and some qualifications. The poster did not mention 16 ga, you did.


He implied that without matching speaker wire lengths (I assumed he used proper gauge) he wouldn't sleep at night.

 

[SAM64]



Quote:
Originally Posted by Joe Skubinski /forum/post/20895783


It's not the current it's induced potential. You need to consider susceptibility in the electronics, such as the feedback loop.

JS reveals his level of "knowledge" again

 

[CharlesJ]



Quote:
Originally Posted by htcritic /forum/post/20896956


.J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures ....

One's imagination can help, no?

 

[Glimmie]

No I wouldn't just on principle. But still it would not induce audible noise. Might also be an NEC violation mixing class 1 &. 2 circuits for that distance.

 

[Glimmie]



Quote:
Originally Posted by Joe Skubinski /forum/post/0


So you would have no problem with say running 30 meters of a zip cord style speaker cable parallel to a typical home's AC wiring? I take it you did this in your own HT room build, speaker cable runs all bundled together with the power.

I agree with you on keeping cable lengths similar at least across the front three, typically recommend staying within a 25% difference.

No I wouldn't just on principle. But still it would not induce audible noise. Might also be an NEC violation mixing class 1 &. 2 circuits for that distance.

 

[Speedskater]

Might also be an NEC violation mixing class 1 &. 2 circuits for that distance.


Small typo here, as CL1, CL2 & CL3 are all low voltage wires.


Let's try:


Might also be an NEC violation mixing AC power with class 1,2 or 3 circuits for that distance.

 

[Glimmie]



Quote:
Originally Posted by Speedskater /forum/post/0


Might also be an NEC violation mixing class 1 &. 2 circuits for that distance.


Small typo here, as CL1, CL2 & CL3 are all low voltage wires.


Let's try:


Might also be an NEC violation mixing AC power with class 1,2 or 3 circuits for that distance.

But class1 is AC line power.


Google it.

 

[Speedskater]

But class1 is AC line power.


You are correct!

I remembered that long after turning the PC off for the night.


CL1 are control wires (for things like air conditioners) that can be run with the AC power lines.

725.1 Scope.

This article covers remote-control, signaling,

and power-limited circuits that are not an integral part of a

device or appliance.

FPN: The circuits described herein are characterized by

usage and electrical power limitations that differentiate

them from electric light and power circuits; therefore, alternative

requirements to those of Chapters 1 through 4 are

given with regard to minimum wire sizes, derating factors,

overcurrent protection, insulation requirements, and wiring

methods and materials.


Class 1 Circuit.

The portion of the wiring system between

the load side of the overcurrent device or power-limited

supply and the connected equipment.

FPN: See 725.21 for voltage and power limitations of

Class I circuits.

 

[Ivan Beaver]



Quote:
Originally Posted by CharlesJ /forum/post/20899338


Originally Posted by htcritic

.J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures ....




One's imagination can help, no?

It depends on what you call "measured". You can do very simple measurements (such as 1/3rd oct RTA)-which don't revel very much, or you can do measurements that revel much more than our ears can resolve.


For example-how many loudspeaker "measurements" do you see that show amplitude AND phase? Not very many-even for manufacturers data sheets. And I would argue that the phase response is more important and the amplitude-but amplitude iw usually the most you get-if you even get an accurate measurement of that (depending on room conditions and the influence the room has on the measurement)


Just because somebody says they have "measured" a loudspeaker does not really say very much.


TRUE complete measurements would take days and a nice measurement rig AND measurement condeitions AND the knowledge to operate the rig and get good results. Most of which the average person "measuring" loudspeakers does not have.