use two parallel cable runs for speaker which is twice as far away? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 11 Old 01-16-2013, 05:22 AM - Thread Starter
Newbie
 
segmentor's Avatar
 
Join Date: Jan 2013
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
I have to wire my surround speakers.

For reasons of misunderstanding I have a quantity of 17AWG cable available for use. In short, the store threw it in with the speakers and told me it's 16AWG suitable for running along the wall edge under the carpet, but it's really 17AWG. I discussed this with the guys in store who still say it's fine for surrounds and it doesn't matter. I'm pedantic though, and I care.

Judging by Roger Russell's much linked-to wire table, 17AWG will do for the left channel. Both speakers are rated at 8 ohms (Polk FXi-A4)

The right speaker requires about 5.5m of cable. (0.09 ohms cable impedance @ 16.61 ohms/km)
The left speaker requires about 12.1m of cable. (0.2 ohms cable impedance)

Is it worth running two pairs of cable from the receiver to the left speaker to halve the resistance, making up for the poor cable gauge?

Will this cause any other issues like different capacitance on the cables to each speaker?

Yes I know I should go out and buy some 14AWG cable and be done with it, but I'd rather use what I have. I also don't know if 14AWG will fit where I need to run it.
segmentor is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 01-16-2013, 05:24 AM
Advanced Member
 
JD in NJ's Avatar
 
Join Date: Jan 2012
Location: Northern NJ
Posts: 645
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 35
You can do this. If you did it in order to try and improve your sound they'd call it "biwiring" and usually there's no reason for it. In your case, it could actually help your system, although as you say the cleaner path would be to install heavier gauge wire.

JD in NJ is offline  
post #3 of 11 Old 01-16-2013, 05:34 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,301
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 690 Post(s)
Liked: 1145
Quote:
Originally Posted by segmentor View Post

I have to wire my surround speakers.

For reasons of misunderstanding I have a quantity of 17AWG cable available for use. In short, the store threw it in with the speakers and told me it's 16AWG suitable for running along the wall edge under the carpet, but it's really 17AWG. I discussed this with the guys in store who still say it's fine for surrounds and it doesn't matter. I'm pedantic though, and I care.

Judging by Roger Russell's much linked-to wire table, 17AWG will do for the left channel. Both speakers are rated at 8 ohms (Polk FXi-A4)

The right speaker requires about 5.5m of cable. (0.09 ohms cable impedance @ 16.61 ohms/km)
The left speaker requires about 12.1m of cable. (0.2 ohms cable impedance)

Is it worth running two pairs of cable from the receiver to the left speaker to halve the resistance, making up for the poor cable gauge?

Will this cause any other issues like different capacitance on the cables to each speaker?

Yes I know I should go out and buy some 14AWG cable and be done with it, but I'd rather use what I have. I also don't know if 14AWG will fit where I need to run it.

It turns out that two parallel runs of 17 gauge should have the exact same resistance as one run of 14 gauge. The extra capacitance should be negligible.

To correctly understand the impact of your cable runs we'd need to know the impedance curves of your speakers, but this is usually moot, even for ca. 30 foot runs.
arnyk is offline  
post #4 of 11 Old 01-16-2013, 08:39 AM
AVS Special Member
 
commsysman's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,254
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked: 250
0.2 ohms of wire resistance, when connected to a 4 ohm speaker, is 5% of the impedance of the speaker.

This simply means that you will have a 5% loss in the wire, and have to turn the volume up 5% higher. Big freaking deal...lol.

With a double run, or 14 gauge wire, you will knock the loss down to 2% or so.
commsysman is offline  
post #5 of 11 Old 01-16-2013, 04:23 PM - Thread Starter
Newbie
 
segmentor's Avatar
 
Join Date: Jan 2013
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Thanks guys.

Commsysman - yep but I'm also aware that the speaker will have a different impedance at different frequencies and although I can't find an impedance graph for the F/XiA4's I'm hoping the 8 ohm rating is close to the 'real' minimum.

Maybe this concept is overkill for 8 ohm speakers; I guess I will try it both ways and see if my ears can tell the difference.
segmentor is offline  
post #6 of 11 Old 01-16-2013, 04:28 PM
AVS Special Member
 
commsysman's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,254
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked: 250
I have looked at impedance graphs for hundreds of speakers, and they almost always have a minimum impedance of somewhere between 3 and 5 ohms, so I always go with the assumption of 4 ohms when considering wiring.

The average impedance is usually between 6 and 8 ohms over the whole frequency range, but the minimum needs to be considered too.
commsysman is offline  
post #7 of 11 Old 01-17-2013, 02:40 AM - Thread Starter
Newbie
 
segmentor's Avatar
 
Join Date: Jan 2013
Posts: 12
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Thanks for the advice; I can't argue with the logic.
segmentor is offline  
post #8 of 11 Old 01-17-2013, 06:20 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,301
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 690 Post(s)
Liked: 1145
Quote:
Originally Posted by commsysman View Post

0.2 ohms of wire resistance, when connected to a 4 ohm speaker, is 5% of the impedance of the speaker.

This simply means that you will have a 5% loss in the wire, and have to turn the volume up 5% higher. Big freaking deal...lol.

With a double run, or 14 gauge wire, you will knock the loss down to 2% or so.

The problem with too-thin hifi speaker wires is not overall sound loss, but differential sound loss at various frequencies.

If the problem were due to overall sound loss, the too-thin cable could be compensated for over a wide range by simply turning up the volume a little more.

Most speakers, as is correctly pointed out in post 6 have a frequency range where their impedance is minimum, while the impedance of the same speaker is much higher over broad ranges at other frequencies.

The cable's resistance usually causes far more loss in the range of frequencies where the speaker's impedance is minimum or close to minimum. The cable's losses over the range where the speaker's impedance is higher is often much less.

The difference in the cable's loss in different frequency reanges is the essence of the problem. If the difference in the losses is large enough then the sound of the speaker may be audibly colored by the cable's excess resistance.

This same problem can be caused by certain tubed amplifiers that may provide even higher source impedances than the wire that we are talking about right now.

5% loss corresponds to a 0.5 dB loss which is possibly audible, but rarely if ever an actual serious sound quality problem. Modern AVRs with automated system optimization facilities may address problems like this or even far worse as part of their normal operation.

Therefore the basic advice that a speaker cable with only 0.2 ohms or less resistance will cause no serious problems with a reasonable worst case speaker that dips down to 4 ohms is basically good.

However I thought this was a good opportunity to clarify the basic goal of the discussion, which is to produce high fidelity and minimize audible coloration.
arnyk is offline  
post #9 of 11 Old 01-17-2013, 07:35 AM
AVS Special Member
 
commsysman's Avatar
 
Join Date: Dec 2007
Location: Southern California
Posts: 5,254
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 113 Post(s)
Liked: 250
If you carefully analyze what you just said, you will realize that you are talking nonsense.

If speaker wire has a resistance of 0.2 ohms, which is much higher than most will be, that will give you a 5% loss at a frequency where the speaker is 4 ohms, and a 1 % loss at a frequency where the speaker is 20 ohms.

So....in one case the speaker is getting 95% of the power and in the second case it is getting 99%. Do you think anyone can hear a 4% change in volume between the two frequencies? Absolutely not!!

It is well-documented by extensive hearing research that no one can hear that kind of minute difference.

Quote:
Originally Posted by arnyk View Post

The problem with too-thin hifi speaker wires is not overall sound loss, but differential sound loss at various frequencies.
If the problem were due to overall sound loss, the too-thin cable could be compensated for over a wide range by simply turning up the volume a little more.
Most speakers, as is correctly pointed out in post 6 have a frequency range where their impedance is minimum, while the impedance of the same speaker is much higher over broad ranges at other frequencies.
The cable's resistance usually causes far more loss in the range of frequencies where the speaker's impedance is minimum or close to minimum. The cable's losses over the range where the speaker's impedance is higher is often much less.

The difference in the cable's loss in different frequency reanges is the essence of the problem. If the difference in the losses is large enough then the sound of the speaker may be audibly colored by the cable's excess resistance.

This same problem can be caused by certain tubed amplifiers that may provide even higher source impedances than the wire that we are talking about right now.

5% loss corresponds to a 0.5 dB loss which is possibly audible, but rarely if ever an actual serious sound quality problem. Modern AVRs with automated system optimization facilities may address problems like this or even far worse as part of their normal operation.

Therefore the basic advice that a speaker cable with only 0.2 ohms or less resistance will cause no serious problems with a reasonable worst case speaker that dips down to 4 ohms is basically good.

However I thought this was a good opportunity to clarify the basic goal of the discussion, which is to produce high fidelity and minimize audible coloration.
commsysman is offline  
post #10 of 11 Old 01-17-2013, 07:43 AM
AVS Special Member
 
SAM64's Avatar
 
Join Date: Apr 2011
Posts: 1,581
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 70
Quote:
If you carefully analyze what you just said, you will realize that you are talking nonsense.

This is hilarious...then he goes on to repeat his bad math, again....proving that he has absolutely no idea.
SAM64 is offline  
post #11 of 11 Old 01-17-2013, 08:42 AM
AVS Addicted Member
 
arnyk's Avatar
 
Join Date: Oct 2002
Location: Grosse Pointe Woods, MI
Posts: 14,301
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 690 Post(s)
Liked: 1145
Quote:
Originally Posted by commsysman View Post

If you carefully analyze what you just said, you will realize that you are talking nonsense.

If speaker wire has a resistance of 0.2 ohms, which is much higher than most will be, that will give you a 5% loss at a frequency where the speaker is 4 ohms, and a 1 % loss at a frequency where the speaker is 20 ohms.

So....in one case the speaker is getting 95% of the power and in the second case it is getting 99%. Do you think anyone can hear a 4% change in volume between the two frequencies? Absolutely not!!

It is well-documented by extensive hearing research that no one can hear that kind of minute difference.

For reference, a 5% loss is about the same as a 0.5 dB loss. It is well-documented that under some conditions a 0.5 dB loss is audible. I've duplicated this test result myself under double-blind conditions.

However, something I wrote seems to be itself lost. I wrote:

"5% loss corresponds to a 0.5 dB loss which is possibly audible, but rarely if ever an actual serious sound quality problem."

I also wrote:

"Therefore the basic advice that a speaker cable with only 0.2 ohms or less resistance will cause no serious problems with a reasonable worst case speaker that dips down to 4 ohms is basically good."

In short, I agreed with the general point you made in your post.

So, you are arguing with yourself! ;-)
arnyk is offline  
Reply Audio theory, Setup and Chat

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off