Unbalanced connections to active speakers?

[roog]

I am considering a change to active speakers, I am likely to retain my current system which will mean driving my speakers via unbalanced line level feeds.

Having always kept my unbalanced cables short, I was wondering if there was a practical limit to their length before the signal is noticeably affected?

 

[DVDdoug]

As long as you aren't wiring from room-to-room, or between buildings, I'd consider that a "short" connection and you'll usually be fine.

And if your speakers have a balanced input, the correct unbalanced-to-balanced adapter retains most of the benefits of a fully-balanced connection.

(it doesn't always work the other way around... A balanced-output to an unbalanced input is trickier.)

 

[DSJR]

I used 7 - 8m runs with no issues. The preamp was designed for this (driving remote power amps) and the active speaker maker advised on the usual way of connecting up.

 

[roog]

Mine are unlikely to be longer than 3metres or 10ft so from what you say it sounds like I should be OK

 

[Speedskater]

Actually you could run 1000 foot unbalanced RCA interconnects to a battery powered receiver, with only small level and high frequency response loses.
Often with long interconnect cable runs, the components on each end are powered from different AC circuits. This can result in higher Common Impedance Coupling Noise (power line related hum/buzz). So use coax cables with a heavy braided shield.

 

[sergeauckland]

Use well screened cable like RG6 or UR59 and you should be fine for any sensible domestic length. I used 7m for my Meridian actives with no problems.
S

 

[unpluggged]

Actually you could run 1000 foot unbalanced RCA interconnects to a battery powered receiver

If the cables are coaxial and impedance matching is maintained at both ends of the line.

 

[AnalogSteph]

You may still want to post a rundown of your current system and everything connected to it. It may prove advantageous to use RCA to XLR cables with an integrated R||C on the shield connection.

RCA to XLR Cable ("pseudo-balanced") to buy ?

Also note that in the schematic at the end of the above paper Putzeys is making use of the full XLR connector,ie apart from the usual -+G also connects ground with the XLR's case (through the 4th pin on top usually) on both input and output connectors. (TRS usually does that naturally,by it's...

www.audiosciencereview.com

 

[Speedskater]

If the cables are coaxial and impedance matching is maintained at both ends of the line.

Impedances:
send end - about 2 hundred Ohms or less
receive end - about 2 thousand Ohms or more (often 10,000 Ohms)

 

[unpluggged]

Impedances:
send end - about 2 hundred Ohms or less
receive end - about 2 thousand Ohms or more (often 10,000 Ohms)

I'm talking about characteristic termination impedance, not about ohmic impedance of the input/output stages.

Transmission line - Wikipedia

en.wikipedia.org

 

[antcollinet]

I'm talking about characteristic termination impedance, not about ohmic impedance of the input/output stages.

Transmission line - Wikipedia

en.wikipedia.org

Characteristic impedance matching is a transmission line topic, which is not a thing at audio frequencies (as stated in the article you linked). Analogue interconnects are not impedance matched - and don't need to be.

It only becomes an issue when cable length becomes a significant proportion of the electrical wavelength. The electrical wavelength of 20kHz is in excess of 14 kilometers. Unless your cable length is in excess of a couple of miles or so, you don't need to think about transmission line effects for audio.

 

[antcollinet]

As long as you aren't wiring from room-to-room, or between buildings, I'd consider that a "short" connection and you'll usually be fine.

IME that depends on the system, and level of ground noise. I've experienced ground loop noise with interconnect in the 1 to 2 meter region when a PC is in the mix.

 

[Speedskater]

And even with digital interconnect cables, the 75 Ohm Radio Frequency Characteristic Impedance cables.
The 75 Ohms only matters with long cables (say 30 feet/10 meters or longer).

 

[unpluggged]

Characteristic impedance matching is a transmission line topic, which is not a thing at audio frequencies (as stated in the article you linked). Analogue interconnects are not impedance matched - and don't need to be.

It only becomes an issue when cable length becomes a significant proportion of the electrical wavelength. The electrical wavelength of 20kHz is in excess of 14 kilometers. Unless your cable length is in excess of a couple of miles or so, you don't need to think about transmission line effects for audio.

And even with digital interconnect cables, the 75 Ohm Radio Frequency Characteristic Impedance cables.
The 75 Ohms only matters with long cables (say 30 feet/10 meters or longer).

Yes, you are right. Somehow I overlooked this

 

[dfuller]

I will note that the bigger concern is not EMI but rather ground loop induced noise.

 

[Speedskater]

Well there are audiophiles using unshielded unbalanced interconnects.
And braided shields are much better than foil shields at the problematic interference frequencies.
* * * * * * * * * *
braided shields for interference below 10 megahertz
foil shields for interference above 50 megahertz
either between 10 and 50 megahertz