Speaker phase shift?

[lesmor]

Thanks to this site I am aware of the myths regarding sound delay using different length of speaker cables which are of no importance.
I am now in the process of running speaker cable in ducting for my 7.1 Home cinema and will be using different Lengths to all channels with piece of mind regarding sound.
To be sure I was not going to damage my amps power stages or cause an imbalance on outputs ,I contacted Yamaha here is their reply , it clarified my concern , but raised another.

You cannot damage the amplifier using different lengths of cable.
The only difference/effects that can be experienced by cables are:
Difference between L & R cable length can sometimes cause phase shift, so it is better to make sure front L & R and surround L & R are similar lengths with each other and very long or thin cable can cause difference in power output, but as stated above cable difference will not damage the amplifier.
Hope this helps.

I know what out of phase is , but phase shift , is this a concern , anyone experienced it ?
Thanks Andy

 

[yepimonfire]

basically phase shift is where one speaker outputs sound sooner or later then the other. it is similar to out-of-phase but out-of-phase is where one driver pulls inward while the other at the same time pushes outward. ideally when two speakers are fed the same signal they should both pull in and out at the same time. phase shift is any deviation of this but instead of one speaker doing the opposite of the other say one driver pushes out and the driver of the second speaker pushes out as well but a half of a millisecond after. most speakers have a slight amount of phase shift between the woofers and the tweeters because most of the time the woofer is slight more recessed into the cabinet then the tweeter. i doubt you will notice very small amounts of phase shift. unless your wiring speakers using one 10' wire and the other a 500' wire.

out of phase is a type of phase shift, just a 180 degree phase shift, so they are similar. if you want to experience phase shift simply take one speaker and place it 1 meter further back then the other speaker.

i know my explanation is a bit rough but it's the best i could come up with. maybe someone else here can explain it better.

 

[WaynePflughaupt]

The phase shift they’re talking about is basically the same thing as the delay myth you mentioned.

The only real concern using mismatched speaker lengths is that longer cables adds resistance, especially if their gauge (thickness) is smaller. This can have an effect on the sound quality of some low impedance speakers (e.g. 4-ohm speakers using 2-ohm drivers), but for the most part it not going to be an issue. Also, the resistance from the longer cable could somewhat lower the volume output for that speaker (that’s the “power output” Yamaha was talking about). But this won’t be an issue unless the differing lengths are pretty severe – say, one being 10 ft. and the other being 75-100 ft. – and the gauge small.

IMO the only speakers you have to be concerned about are the front left and right. They contribute your imaging, which is more critical than the ambience the back speakers are mainly contributing. So I’d try to keep the front L/R speaker lengths the same, within reason. For the rest it really doesn’t matter much.

Regards,
Wayne A. Pflughaupt

 

[yepimonfire]

actually recently i had an issue with not being able to phantom a center well, i checked the lengths of my cables and one was about 5' longer and i chopped it off to match the other and it solved my problem, so it can also effect that.

 

[TLS Guy]

Thanks to this site I am aware of the myths regarding sound delay using different length of speaker cables which are of no importance.
I am now in the process of running speaker cable in ducting for my 7.1 Home cinema and will be using different Lengths to all channels with piece of mind regarding sound.
To be sure I was not going to damage my amps power stages or cause an imbalance on outputs ,I contacted Yamaha here is their reply , it clarified my concern , but raised another.

You cannot damage the amplifier using different lengths of cable.
The only difference/effects that can be experienced by cables are:
Difference between L & R cable length can sometimes cause phase shift, so it is better to make sure front L & R and surround L & R are similar lengths with each other and very long or thin cable can cause difference in power output, but as stated above cable difference will not damage the amplifier.
Hope this helps.

I know what out of phase is , but phase shift , is this a concern , anyone experienced it ?
Thanks Andy

You can not cause phase shift or significant delay, by cable length discrepancies.

When speakers are said to out of phase, that is polarity reversal and the phase shift is 180 degrees. In other words one speaker would be peak positive and the other peak negative at that point and cancellation occur.

However phase shift can be anything from zero (perfect phase) to 360 where one speaker would be a whole cycle ahead or behind the other. Actually you can go further and have phase shifts of multiple whole or partial cycles. Just remember a whole cycle is 360 degrees. Of cause these phase shifts have a time dimension. Lower frequencies have longer wavelengths and so time shifts are greater for lower frequencies as a 360 cycle takes longer to complete.

Unfortunately speakers are awash in phase shifts. For instance a two way forth order electrical crossover has a phase shift of 360 degrees at crossover, which puts the tweeter a whole cycle ahead of the woofer.

 

[highfigh]

WRT to all of the BS about phase shift and cable length, if Audyssey or some other system is used, this should all be moot as soon as that system checks and adjusts for the distance from the speakers to the mic. Even if the Audyssey is within 1mS, it's still not going to be absolutely accurate, regardless of how close to equal the speaker cable have been cut. Then, there's always the issue of first reflections and the inability of most people to hear incredibly small differences in time discrepancies.

 

[yepimonfire]

My dad actually invented a device that could perfectly correct phase shifts between woofers and tweeters and even though the thing had very small differences that supposedly could not be heard, the difference this thing made in the imaging was un-real. he called the device "Soundscape" you can find the patent for it on google patents.

 

[lesmor]

Wow you guys are great such a fast response
You have put my mind at rest , so different cable lenghts it is then
I'LL let the Yamaha YAPQ take care of any anomolies.

Many thanks to you all