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Pink Denia
A friend of my husband's installed our inexpensive home theater system as a favor. He has the wires for the speakers (mounted around the room) coming up out of the vents in the floor. Granted, the vents are in a good spot for speaker placement. But is this a fire hazard?
Answer
Under most circumstances the risk of fire due to a short in loudspeaker cables is virtually non-existent.
If your loudspeaker cables use the typical PVC insulation found on most lower-cost or generic A/V cabling then you do run a somewhat higher risk of developing a problem. Prolonged or repeated exposure to elevated temperature and airflow rates can, over time, result in degradation of the PVC insulation in large part due to plasticizer migration and volatility. This can lead to increased brittleness and crazing in the exposed portion of the insulation, which could eventually result in failure of the insulation.
Under these circumstances the most likely result is that the protection circuit that protects the output stage of the audio amplifier would kick-in, or worse, the output stage of the amplifier could self-destruct; depending on how well the unit was designed and built. There are very few (well-designed) audio amplifiers that would pose a fire hazard when the speaker outputs are shorted.
You have a couple of fairly simple choices to effectively mitigate the threat of potential problems: (1) replace the loudspeaker cabling with either a jacketed loudspeaker cabling or use polyolefin (i.e., polypropylene) insulated cables; or (2) install 1/2" to 1" diameter plenum rated or riser-rated halogen-free (aka low smoke zero halogen or LSZH) nonmetallic corrugated flexible conduit (aka âinnerduct,â) over the (speaker) cabling wherever the cabling passes through the air ducting. Electrical and datacom/telecom suppliers, better hardware stores and A/V dealers/installers should have innerduct in stock.
One last item - you can reduce the amount of self-heating that occurs with higher cable resistances by choosing loudspeaker cabling that has a larger wire gauge. Speaker cabling is generally available in stock wire gauge sizes ranging from 4 AWG up to 16 AWG and higher; the lower the number the larger the gauge of wire. As a general rule of thumb you should always use the lowest wire gauge you can afford and never less than a single run of 14 AWG cable. Though rarely a significant issue, self-heating varies in direct proportion to the cableâs resistance, (which increases as the wire gauge decreases, i.e., smaller overall conductor cross-sectional area and/or the cable length increases,) the impedance of the loudspeaker and the power output of the audio amplifier.
Carlon Product Brochures Index
http://www.carlon.com/Brochures.html
Hal-Free Riser-Gard® Nonmetallic Corrugated Flexible Conduit
http://www.carlon.com/Master%20Catalog/Flexible_Raceway_Brochure.pdf
Belden Low Smoke Zero Halogen Speaker Wire and Cable
http://www.belden.com/search/index.cfm?q=halogen+AND+speaker
Understanding In-wall Speaker, Video and Audio Cable Ratings
http://www.bluejeanscable.com/articles/inwallrating.htm
Cabling What You Don't Know Can Kill You
http://www.wireville.com/news/Cabling%20Can%20Kill%20You.html
Cabling Safety in Multi-Story Structures
http://www.wireville.com/news/Cabling%20Safety%20in%20Multi-Story%20Structures.pdf
Wire Management and Life Safety Articles
http://www.hhrobertson.com/ls_docs.cfm
Guide to Low-Voltage and Limited-Energy Systems
http://www.mikeholt.com/documents/lowvoltage/pdf/LowVoltBook.pdf
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Under most circumstances the risk of fire due to a short in loudspeaker cables is virtually non-existent.
If your loudspeaker cables use the typical PVC insulation found on most lower-cost or generic A/V cabling then you do run a somewhat higher risk of developing a problem. Prolonged or repeated exposure to elevated temperature and airflow rates can, over time, result in degradation of the PVC insulation in large part due to plasticizer migration and volatility. This can lead to increased brittleness and crazing in the exposed portion of the insulation, which could eventually result in failure of the insulation.
Under these circumstances the most likely result is that the protection circuit that protects the output stage of the audio amplifier would kick-in, or worse, the output stage of the amplifier could self-destruct; depending on how well the unit was designed and built. There are very few (well-designed) audio amplifiers that would pose a fire hazard when the speaker outputs are shorted.
You have a couple of fairly simple choices to effectively mitigate the threat of potential problems: (1) replace the loudspeaker cabling with either a jacketed loudspeaker cabling or use polyolefin (i.e., polypropylene) insulated cables; or (2) install 1/2" to 1" diameter plenum rated or riser-rated halogen-free (aka low smoke zero halogen or LSZH) nonmetallic corrugated flexible conduit (aka âinnerduct,â) over the (speaker) cabling wherever the cabling passes through the air ducting. Electrical and datacom/telecom suppliers, better hardware stores and A/V dealers/installers should have innerduct in stock.
One last item - you can reduce the amount of self-heating that occurs with higher cable resistances by choosing loudspeaker cabling that has a larger wire gauge. Speaker cabling is generally available in stock wire gauge sizes ranging from 4 AWG up to 16 AWG and higher; the lower the number the larger the gauge of wire. As a general rule of thumb you should always use the lowest wire gauge you can afford and never less than a single run of 14 AWG cable. Though rarely a significant issue, self-heating varies in direct proportion to the cableâs resistance, (which increases as the wire gauge decreases, i.e., smaller overall conductor cross-sectional area and/or the cable length increases,) the impedance of the loudspeaker and the power output of the audio amplifier.
Carlon Product Brochures Index
http://www.carlon.com/Brochures.html
Hal-Free Riser-Gard® Nonmetallic Corrugated Flexible Conduit
http://www.carlon.com/Master%20Catalog/Flexible_Raceway_Brochure.pdf
Belden Low Smoke Zero Halogen Speaker Wire and Cable
http://www.belden.com/search/index.cfm?q=halogen+AND+speaker
Understanding In-wall Speaker, Video and Audio Cable Ratings
http://www.bluejeanscable.com/articles/inwallrating.htm
Cabling What You Don't Know Can Kill You
http://www.wireville.com/news/Cabling%20Can%20Kill%20You.html
Cabling Safety in Multi-Story Structures
http://www.wireville.com/news/Cabling%20Safety%20in%20Multi-Story%20Structures.pdf
Wire Management and Life Safety Articles
http://www.hhrobertson.com/ls_docs.cfm
Guide to Low-Voltage and Limited-Energy Systems
http://www.mikeholt.com/documents/lowvoltage/pdf/LowVoltBook.pdf
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How can i make a sound system in my room with car sound system like (amps, woofers, others)?
Gino C
I would like to create a room with a amphitheater effect that sounds loud but not enough to break windows (at least not to break my room windows). My room is large, about an american master room size. I would like to know if anyone can suggest a guide of how to do it or give your own suggestions. Also what system should i buy that would work in a not car environment, in other words, what do you recommend i buy?
Thank you.
Answer
Car system audio are designed for small area and operate on direct current. The speakers are desinged for short throw, while home speaker are designed for long throw. It will be more expensive to set up a car audio in a home. Forget the idea and get home audio products for your room. Calibration for wattage in a car versus a home in not the same.
Car system audio are designed for small area and operate on direct current. The speakers are desinged for short throw, while home speaker are designed for long throw. It will be more expensive to set up a car audio in a home. Forget the idea and get home audio products for your room. Calibration for wattage in a car versus a home in not the same.
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Title Post: Are my home theater speakers a fire hazard?
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