CAT5e as speaker wire?

[ketch90]

I work in the technology department of a school district, and we are currently putting SmartBoards into classrooms. Each classroom is also getting speakers mounted in the ceiling tiles, with four speakers and two channels on the output source. The contractors are using Category 5-E network cable for the passive speaker connections, using pairs at the source and splitting to individual wires to accommodate the number of speakers. The amp is 5 watts for each channel at 4 ohms.

What are the properties of network cable that make it good for speaker wire? Is it a good alternative, or is it just a cheap replacement? Any ideas on how many watts it can handle? Thanks for any answers.

 

[lsiberian]

http://www.audioholics.com/education/cables/myth-vs-reality-2013-putting-cat5e-based-a-v-structured-wiring-in-its-place

 

[highfigh]

I work in the technology department of a school district, and we are currently putting SmartBoards into classrooms. Each classroom is also getting speakers mounted in the ceiling tiles, with four speakers and two channels on the output source. The contractors are using Category 5-E network cable for the passive speaker connections, using pairs at the source and splitting to individual wires to accommodate the number of speakers. The amp is 5 watts for each channel at 4 ohms.

Is it a good alternative, or is it just a cheap replacement? Any ideas on how many watts it can handle? Thanks for any answers.

How long are the runs from the head end to the farthest room? That's asking for trouble is they think one little skinny 24 ga wire will last a long time, but they probably don't care.

If the runs are long enough, it'll take 5W just to make up for the voltage drop. If they're using a 70V system, nah- I wouldn't even use one pair of Cat5e for that. What they're doing should be reported to the school's contact person and explained that it's not sufficient. One strand breaks and that speaker is dead. That's not a good way to do this job.

As far as this question "What are the properties of network cable that make it good for speaker wire?", the answer is:

It has none.

 

[ketch90]

The wire runs from one end of the room to the other, no more than 40 or 50 feet from the amp to the farthest speaker for each room. I guess I wasn't clear, each room has an amp.

 

[highfigh]

The wire runs from one end of the room to the other, no more than 40 or 50 feet from the amp to the farthest speaker for each room. I guess I wasn't clear, each room has an amp.

I still wouldn't use any UTP (Cat3, 4, 5, 6, 7) for speaker runs. If they need 500' for the whole job, they can get a box of 16/2 CL2 rated wire from their supplier for $75, of it's good wire. They're just being incredibly cheap and may be using up what they have left over from other jobs. I would look at the bid to see what was specified by the school and compare that with what they're using.

5W or not, it's not made to be used as speaker wire and definitely not by using only one strand for + and -.

 

[ketch90]

I'm not sure if I explained properly. At the amp, there is a twisted pair of wires, where each strand goes to a single speaker.

 

[krzywica]

You mean as in 1 CAT5E cable could do 4 individual speakers correct? As there are 4 pairs or 8 "strands" of wire?

If this is the case they are doing a lousy job at best and are most likely ripping the school off.

 

[ketch90]

Well since most of the rooms are done, I guess I have to wait until wires start to go before I can tell my boss that they made a fairly large mistake. However, once a single strand goes, we would have to change the wires on all four speakers in the room because otherwise we would just have more and more wires going up to the ceiling. What guage wire should I suggest we get?

 

[Rickster71]

Are you sure it's not a 70v system?

 

[ketch90]

Are you sure it's not a 70v system?

Taken from the SMART Technology site:

Audio Output - 5 W × 4 at 4 ohms
Power Requirement - 15V DC at 2.7A

 

[highfigh]

I'm not sure if I explained properly. At the amp, there is a twisted pair of wires, where each strand goes to a single speaker.

Are these pairs separate or do they have a common jacket? The jacket will often have text indicating the type of cable (Cat5e, Cat4, Cat6, Cat7) and Class (CL-2, CL-3) as well as the wire gauge.

Is it this model?
http://www2.smarttech.com/st/en-US/Products/SMART+classroom+audio+system/

I guess, in thinking about it, it's possible for this to be designed for Cat5e because it's only a listening aid, not a system designed for actual public address. If the speakers have a jack that looks like an ethernet port, they may split the pairs at the amp but with the low cost of Cat5e cable, they should just have 4 jacks with one cable to each speaker, so they could use all four pairs. If the twisted pair has no jacket, it may not meet code. The building code for schools and institutions is much more strict that residential.

Again, if you can look at the project scope and specs, check for what was supposed to be used for cabling to find out if they're using something else.

 

[Rickster71]

Now that I understand the system they are using, and that it's a Max of 5 watts for 40 feet, I don't see a problem.

A single 24 ga wire has the ampacity of about half an amp.
It depends on how many pairs are in the CAT5 they are using, and how many they are doubling up.
Four 24-ga wires are 1620 circular mills, that's almost 18AWG.

'If' they use four 24-gauge wires they can carry 4 x 0.577 amps. That is just a little over 2.3 Amps.