Audio Link between 2 buildings circa 150m apart

[TonyMitchell]

I've got to quote to provide a PA system in a church for a memorial service, with a separate system in the village hall, circa 150 metres from the church, for the overspill (small church/popular guy/both :blink: )

 

I'm advised there are no roads between the two buildings, therefore cabling is an option.

 

Initial thoughts were daisy chaining 8 or 9 x 20mtr balanced mic cables, or using a Brikworm to send over CAT5.

 

Any advice/experiences would be welcomed.

 

Many thanks

 

Tony

[bruce]

Any old copper will do the job :blink:

 

Seriously. Twisted is better, of course, but I've done this sort of thing over old BT phone lines in the past!

 

I'd get a drum of the cheapest cat5 (30-40 pounds for 300m), pick any pair, wire an XLR onto each end. Pins 2/3 only - don't connect the ground. As long as the source and destination are balanced, it should be fine.

[J Pearce]

Balanced audio should be fine over that distance, though you probably want to avoid connections.

 

You'll probably struggle to hire in a 150m single length lead, so buying a 300m drum of cheap cat5 (£30ish) and writing it off afterwards (or salvaging good bits for re-use) is likely the way forwards.

 

You shouldn't need baluns to send balanced line level audio over cat5, though transformer isolation (DI box?) might be advisable as the two systems are likely on different mains supplies.

[Dmills]

Transformers on at least one end, particularly if the power to either site is TN-C-S (Think about the possible issues with bringing connections across the equipotential zone boundary).

Given transformer isolated balanced lines, cat 5 does fine and is cheap as chips.

 

Regards, Dan.

[TonyMitchell]

Many thanks for the fast replies, gents. Much appreciated and excellent as always.

 

Tony

[Bobbsy]

Just to summarise the posts to date and add a bit of emphasis to a couple of points:

 

1. A run of 150 metres is easily within the range of standard balanced audio.

 

2. Use continuous runs of cable without connectors hidden away in the trunking. Hidden connectors are potential points of failure.

 

3. Twisted cables like CAT5 (but used for balanced audio, not data, are cost effective and good at rejecting interference.

 

4. Transformer isolation at one end will quite likely be needed since the two buildings with be on different mains supplies and earths.

 

Bob

[billy jim]

I've done a job like this before, we just sent a speaker cable to the other end, plugged it in and linked out into the other speaker- you're not really going to need stereo sound, and no one will notice anyway! So yeh, I would amplify in the main room, and send a nice long speaker cable to the other end.

[mervaka]

on a 150m run? :/

 

the amp should be in the same building as the speakers, at least.. using cat5 there's no reason not to send a second channel down.

[paulears]

I've done a job like this before, we just sent a speaker cable to the other end, plugged it in and linked out into the other speaker- you're not really going to need stereo sound, and no one will notice anyway! So yeh, I would amplify in the main room, and send a nice long speaker cable to the other end.

 

Sorry Billy Jim - but there's a couple of really big problems here. 150m of speaker cable is going to mean a huge amount of loss. You could do it on 100V systems, but the OP wants line level, not speaker levels. On top of that, 150m of speaker sized cable is rather an expensive way of doing this.

 

Everyones suggesting balanced line level, via twisted pair - the same way the telcoms companies do it (and have done for ever!) - sorry, but the speaker level thing is just a bit daft!

[billy jim]

Was just shouting up the way we did it- worked fine for us!

[Rob_Beech]

Was it 150m?

 

 

A quick check on VDC tells me that 150m of speaker cable is going to be around £400 including the vat. This is 2x4mm. Now it's still going to present us with a loss at 4mm.

This is bearing in mind that its circa 150m away. This means the cable run may be 200m. This would be closer to £550 including the vat.

 

 

For £550 inc vat, you could buy an amp, 200m of cat 5, a repeater, the necessary connectors to terminate, a soldering iron and accessories to do the job, bacon sarnies for everyone involved with the job and hire a car to pick up the stuff to do it.

 

You could then donate the other £200 to the church.

[bruce]

More importantly, running a long speaker cable gives you no local control over volume levels at the remote site.

 

With any job, there will always be several ways to do it - the right way, the wrong way, and various shades of grey in between. Running a long speaker cable definitely falls into the "very dark grey" zone - it may work, but it's certainly not the best way to do this.

[billy jim]

Come to think of it- the cable run was nowhere near 150m! Apologies!

[Dan Gruner]

Just run some Cat5 cable between each location and use a DI box (something like a BSS AR133) at the receiving end. Connect pins 2 and 3 (NOT pin 1 the ground) - ie pick a pair in the cat5 cable - or use 2 pairs and 2 DI boxes for stereo. Please make sure the sending end has a proper balanced output as well!

 

If you have 150m of good quality mic cable feel free to use this instead of the cat 5 - 150m is nothing for balanced audio. Do still use a DI box at the receiving end though.

 

Dan