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Connecting subwoofer with speaker wire
I have a room which I attempted to pre-wire for home theater. There is
a regular speaker wire behind the wall which I intended to use for the subwoofer. Now that I have the equipment, I realize that the receiver has an RCA type subwoofer output only. Since I did not have the foresight to run a shielded cable behind the wall, I'm wondering what will happen if I just solder RCA connectors to each end of the speaker wire to make the subwoofer connection. |
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#4
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mhkatz wrote:
I have a room which I attempted to pre-wire for home theater. There is a regular speaker wire behind the wall which I intended to use for the subwoofer. Now that I have the equipment, I realize that the receiver has an RCA type subwoofer output only. In the absense of specific detail, we are assuming that you mean that your receiver has only a line-level output rather than a speaker output? Since I did not have the foresight to run a shielded cable behind the wall, I'm wondering what will happen if I just solder RCA connectors to each end of the speaker wire to make the subwoofer connection. I would expect the noise (principally hum) to be too great to make this practical. Of course, you could get lucky, but don't bet on it. The obvious solution would be to have the subwoofer amp back next to your receiver, and use your in-wall speaker wires as (are you ready for it? :-) *speaker wires*.' Of course, this assumes that you have not already acquired a powered sub-woofer which wants line-level input. |
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#5
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On Wed, 5 Oct 2005 15:10:52 -0700, "Richard Crowley"
wrote: I would expect the noise (principally hum) to be too great to make this practical. Of course, you could get lucky, but don't bet on it. Not too hard to try, though. Just throw any spare receiver/speaker on the end of the line, and see what comes out. |
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#7
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In .com, on 10/05/05
at 07:11 PM, said: Try a test. Cut an old RCA patch cable in half and strip insulation from the shield and the center conductor at the two cut ends. Connect the shield (the outside wrap or braid of wire) to the speaker wire such that the shield at the other end is connected to the same conductor, then connect both center conductors to the remaining speaker wire conductor. For this test you are allowed to make a simple twisted wire junction. Turn the system on gingerly, keeping the subwoofer volume as low as possible. Adjust the subwoofer output of your receiver as high as possible. If the system sounds OK, make the connections permanent. (solder or use some sort of crimp) If there is trouble (very likely), get back to us and we can suggest some solutions. Your likelyhood of success will increase if you can plug your whole system (including, TV, Cable Box, Audio System, and Subwoofer) into the same electrical outlet. If you have hum, disconnect the cable feed from the cable box. Has the subsided? If so, there are "hum breakers" that can be added to the cable feed that will help. Can you tell me more about what you mean by "balanced conversion" if that still makes sense now that I've described the situation more completely. "Balanced" is a different way of sending signals over longer, more difficult paths without picking-up unwanted electrical noise. My suggestion above is very risky in tems of picking-up noise. It is unlikely that my scheme will work, but it might and it is so cheap and easy to try that you should run the test before you run out and waste some gas trying to track down gadgets. Converting to balanced will entail adding a small little gadget at each end of the cable to the subwoofer. There is a modest expense involved. That's why I suggest my test above. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
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"dizzy" wrote in message news  On Wed, 5 Oct 2005 15:10:52 -0700, "Richard Crowley" wrote: I would expect the noise (principally hum) to be too great to make this practical. Of course, you could get lucky, but don't bet on it. Not too hard to try, though. Just throw any spare receiver/speaker on the end of the line, and see what comes out. Correct. And if the test fails, your next (relatively inexpensive) step *could* be to try and install the correct wire in the wall using the exising speaker wire as a "pull wire". Of course, if you attached the speaker wires to any of the studs, or some other nonsense, this becomes un-doable. Barring that, however, and assuming you have enough "wiggle room" for the entire length of the run, give it a try. Another tip; any time you pull a wire through a wall or floor or ceiling, also pull a spare wire or some other (strong) fiber as a pull wire for the next time you want to run something through the same channel, either for additional use, or if you need to upgrade something. If you don't know how to use a ull wire, let us know. Kendall |
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#9
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writes:
I have a room which I attempted to pre-wire for home theater. There is a regular speaker wire behind the wall which I intended to use for the subwoofer. Now that I have the equipment, I realize that the receiver has an RCA type subwoofer output only. That's typical on modern systems. You should have expected it in the beginning. Since I did not have the foresight to run a shielded cable behind the wall, I'm wondering what will happen if I just solder RCA connectors to each end of the speaker wire to make the subwoofer connection. If you just solder the RCA connectors to the speaker wire ends, you will get the sound going from receiver to subwoofer. But because the wires is not shielded, this wire will very easily pick up all kinds of interference starting from mains frequency humming pickup (50Hz or 60 Hz and the harmonics if it) anding to pickung noise from electrical (clicks when lights/equipment are switched on/off) and radio frequency interference (noise from nearby cellular phone etc..). You can try the connection and find out. The best approach to correct the problem is to wire right type of cable in place of the existing wire. If you have wired your cable to installation tube, relacing the wiring with a new one should not be too hard (use old speaker wire to pull in new wire or wires). If you need to use the existing wire and the noise is a problem, then one approach would be to use a balanced line approach: Convert the signal to the balanced in the receiver end (audio transformer, professional distribution amplifier, small mixer etc) then using blaanced received on the subwoofer end (XLR connector if it has those, through audio transformer to RCA, usign small mixer with balanced inputs etc..). Balanced line signals will travel acceptably even through unshielded wires. Balancing is the trick. Another idea if your subwoofer has speaker level sound inputs: Put a small audio power amplifier between your receiver RCA output and the speaker wire on the wall. This will convert the signal to strong speaker line signal that will survive in the noisy enviroment in unshielded cable (the toughness has to do with the stronger signal level and lower output impedance compared to line level signal). The at the subwoofer end kust wire the signal to "speaker level" input of the subwoofer instead of that RCA input. If your subwoofer does not have "speaker level" inputs, you can try car audio "speaker to line" adapter. -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/ |
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#10
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In article .com, wrote:
Sorry if I wasn't specific enough. It is a powered subwoofer and the speaker wire would be carrying a signal, not driving the speaker. I called Yamaha (it is a Yamaha receiver) and their tech support guy told me that my solution might possibly work if I get some kind of line conditioner to remove any noise from the signal. He could not give me any more detail on what I would need. Can you tell me more about what you mean by "balanced conversion" if that still makes sense now that I've described the situation more completely. Radio Shack part number 273-1374 is a 600 ohm isolation transformer. You attach the input to the drive, normally a speaker output. A line level output is probably not going to have a low enough impedance to drive it. So you get another maybe 10 watt amp and attach the amp input to your sub out. The amp will attach to the transformer input. Its better to have the transformer near the sub. The output will feed the sub. The gain on the auxilarry amp may have to be fiddled with, and will otherwise have no bass or treble boost. The polarity may also have to be reversed if the aux amplifier iverted the signal. Since the 600 ohm transformer feeds a higher impedance input, its response will be much better than its specs indicate. This will give noise free performance. I have used this system, however you might want to check out part # 270-054 which is a RCA ground loop isolator from Radio Shack. I have never used this, but if you connect the ends of the wires to the RCA input, it will feed directly into your sub. There are several products for car stereo which you can adapt to your situation if you do a little searching. greg GregS wrote: In article , wrote: wrote: : I have a room which I attempted to pre-wire for home theater. There is : a regular speaker wire behind the wall which I intended to use for the : subwoofer. Now that I have the equipment, I realize that the receiver : has an RCA type subwoofer output only. Since I did not have the : foresight to run a shielded cable behind the wall, I'm wondering what : will happen if I just solder RCA connectors to each end of the speaker : wire to make the subwoofer connection. Are you sure the rca output is for directly driving a sub as opposed to connecting to an amp/powered sub? I think this is line level. Try the connection and find out. A balanced line receiver may work or even better, using a balanced conversion on both ends. If you use a small amp and as I suggested to another post, using a small Radio Shack isolation transformer to feed the subwoofer RCA input, will also work without producing any hum from stray fields or ground loops. greg |
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#11
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(GregS) writes:
In article .com, wrote: Sorry if I wasn't specific enough. It is a powered subwoofer and the speaker wire would be carrying a signal, not driving the speaker. I called Yamaha (it is a Yamaha receiver) and their tech support guy told me that my solution might possibly work if I get some kind of line conditioner to remove any noise from the signal. He could not give me any more detail on what I would need. Can you tell me more about what you mean by "balanced conversion" if that still makes sense now that I've described the situation more completely. Radio Shack part number 273-1374 is a 600 ohm isolation transformer. You attach the input to the drive, normally a speaker output. A line level output is probably not going to have a low enough impedance to drive it. True. So you get another maybe 10 watt amp and attach the amp input to your sub out. The amp will attach to the transformer input. Its better to have the transformer near the sub. The output will feed the sub. True for the idea. The problem could be that the technical specifications of that Radio Shack transformer do not look very good for subwoofer application From http://support.radioshack.com/suppor.../doc9/9888.htm 1:1 Audio Transformer (273-1374) Specifications Faxback Doc. # 9888 Coil Turns Ratio:............................................ ..........1:1 DC Resistance: Secondary:........................................ ......60 Ohms +/- 10% Impedance:........................................ ............600-900 Ohms Frequency Response:........................................3 00 Hz to 5 kHz Insulation Resistance:.....................More than 100 megohms at 250VDC The frequency response is specified from 300 Hz to 5 kHz. That transformer is not expected to work well with subwoofer frequencies (20 Hz to 100-150 Hz typically). Attenuation of the lowest frequencoes and with strong input signals (amplified line signals) I would expect serious distortions at lowest frequencies. Ttransformer approach works as descrubed above, but I would look for a better transformer with more suitable specifications. The gain on the auxilarry amp may have to be fiddled with, and will otherwise have no bass or treble boost. The polarity may also have to be reversed if the aux amplifier iverted the signal. Since the 600 ohm transformer feeds a higher impedance input, its response will be much better than its specs indicate. This will give noise free performance. The specifications on frequiency response would be with high inpedance load on output and low impedance input better than listed on the specs. That's true. But still might not be adequate for hifi subwoofer. And then there is that risk of transformer satutation at low frequencies at high signal levels. This is quite tiny transformer, it can't handle high signal levels at low frequencies. I have used this system, Do you have any specifications to give how well it worked. Especially at lowest frequencies. however you might want to check out part # 270-054 which is a RCA ground loop isolator from Radio Shack. I have never used this, but if you connect the ends of the wires to the RCA input, it will feed directly into your sub. There are several products for car stereo which you can adapt to your situation if you do a little searching. I have never used this particular products. But I have used similar devices from several manufacturers (some look pretty much the same as the one in the Radio Shack web page picture). This kind of RCA isolators generally work much better than those small 600:600 ohm transformers in audio applications. When connected to normal RCA line level sources, they typically attenuate the lowest frequencies somewhat, but not very much. You can get frequency rensponse from 40 Hz and up wery well on units I have worked with... with very low impedance signal source and not too stong signals lower than that to 20 Hz or so. -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/ |
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#12
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In article , Tomi Holger Engdahl wrote:
(GregS) writes: In article .com, wrote: Sorry if I wasn't specific enough. It is a powered subwoofer and the speaker wire would be carrying a signal, not driving the speaker. I called Yamaha (it is a Yamaha receiver) and their tech support guy told me that my solution might possibly work if I get some kind of line conditioner to remove any noise from the signal. He could not give me any more detail on what I would need. Can you tell me more about what you mean by "balanced conversion" if that still makes sense now that I've described the situation more completely. Radio Shack part number 273-1374 is a 600 ohm isolation transformer. You attach the input to the drive, normally a speaker output. A line level output is probably not going to have a low enough impedance to drive it. True. So you get another maybe 10 watt amp and attach the amp input to your sub out. The amp will attach to the transformer input. Its better to have the transformer near the sub. The output will feed the sub. True for the idea. The problem could be that the technical specifications of that Radio Shack transformer do not look very good for subwoofer application From http://support.radioshack.com/suppor.../doc9/9888.htm 1:1 Audio Transformer (273-1374) Specifications Faxback Doc. # 9888 Coil Turns Ratio:............................................ ..........1:1 DC Resistance: Secondary:........................................ ......60 Ohms +/- 10% Impedance:....................................... .............600-900 Ohms Frequency Response:........................................3 00 Hz to 5 kHz Insulation Resistance:.....................More than 100 megohms at 250VDC The frequency response is specified from 300 Hz to 5 kHz. That transformer is not expected to work well with subwoofer frequencies (20 Hz to 100-150 Hz typically). Attenuation of the lowest frequencoes and with strong input signals (amplified line signals) I would expect serious distortions at lowest frequencies. Ttransformer approach works as descrubed above, but I would look for a better transformer with more suitable specifications. The gain on the auxilarry amp may have to be fiddled with, and will otherwise have no bass or treble boost. The polarity may also have to be reversed if the aux amplifier iverted the signal. Since the 600 ohm transformer feeds a higher impedance input, its response will be much better than its specs indicate. This will give noise free performance. The specifications on frequiency response would be with high inpedance load on output and low impedance input better than listed on the specs. That's true. But still might not be adequate for hifi subwoofer. And then there is that risk of transformer satutation at low frequencies at high signal levels. This is quite tiny transformer, it can't handle high signal levels at low frequencies. I feel the specs would be using a 600 ohm output load. Like I say, I have used this type of setup on a few systems. I have not measured the response. On my TV setup, the audio sounds pretty good. I tapped off the speaker leads, to feed the receiver. I did this because it was the only easy wasy to control the volume with the remote. Plenty of bass, but I would predict some low frequency rolloff at some point. Expecting to get no reduction at 20 Hz would be asking too much. I ran about 80 feet of line in a bar to drive a remote system. Worked well. greg I have used this system, Do you have any specifications to give how well it worked. Especially at lowest frequencies. however you might want to check out part # 270-054 which is a RCA ground loop isolator from Radio Shack. I have never used this, but if you connect the ends of the wires to the RCA input, it will feed directly into your sub. There are several products for car stereo which you can adapt to your situation if you do a little searching. I have never used this particular products. But I have used similar devices from several manufacturers (some look pretty much the same as the one in the Radio Shack web page picture). This kind of RCA isolators generally work much better than those small 600:600 ohm transformers in audio applications. When connected to normal RCA line level sources, they typically attenuate the lowest frequencies somewhat, but not very much. You can get frequency rensponse from 40 Hz and up wery well on units I have worked with... with very low impedance signal source and not too stong signals lower than that to 20 Hz or so. |
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#13
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Greg,
Generally, 600-Ohm transformers are made for telephone bandwidth. Radio Shack used to make a double (stereo) transformer that handled the entire audio range pretty well. It was cylindrical, about two inches long, and about an inch in diameter. Unmounted. Had a cable at each end, each with two RCA plugs. I happened to look for it just the other day on their web site, and it seems to have disappeared. Meanwhile, the OP can just hook it up using the unshielded wire, as someone suggested, being careful to maintain which is the shield conductor at each end. If the output impedance of the receiver's sub output is low, and they're often just a few Ohms, it will likely work fine. -- Earl ------------------------------------------------------ "GregS" wrote in message ... In article .com, wrote: Sorry if I wasn't specific enough. It is a powered subwoofer and the speaker wire would be carrying a signal, not driving the speaker. I called Yamaha (it is a Yamaha receiver) and their tech support guy told me that my solution might possibly work if I get some kind of line conditioner to remove any noise from the signal. He could not give me any more detail on what I would need. Can you tell me more about what you mean by "balanced conversion" if that still makes sense now that I've described the situation more completely. Radio Shack part number 273-1374 is a 600 ohm isolation transformer. You attach the input to the drive, normally a speaker output. A line level output is probably not going to have a low enough impedance to drive it. So you get another maybe 10 watt amp and attach the amp input to your sub out. The amp will attach to the transformer input. Its better to have the transformer near the sub. The output will feed the sub. The gain on the auxilarry amp may have to be fiddled with, and will otherwise have no bass or treble boost. The polarity may also have to be reversed if the aux amplifier iverted the signal. Since the 600 ohm transformer feeds a higher impedance input, its response will be much better than its specs indicate. This will give noise free performance. I have used this system, however you might want to check out part # 270-054 which is a RCA ground loop isolator from Radio Shack. I have never used this, but if you connect the ends of the wires to the RCA input, it will feed directly into your sub. There are several products for car stereo which you can adapt to your situation if you do a little searching. greg GregS wrote: In article , wrote: wrote: : I have a room which I attempted to pre-wire for home theater. There is : a regular speaker wire behind the wall which I intended to use for the : subwoofer. Now that I have the equipment, I realize that the receiver : has an RCA type subwoofer output only. Since I did not have the : foresight to run a shielded cable behind the wall, I'm wondering what : will happen if I just solder RCA connectors to each end of the speaker : wire to make the subwoofer connection. Are you sure the rca output is for directly driving a sub as opposed to connecting to an amp/powered sub? I think this is line level. Try the connection and find out. A balanced line receiver may work or even better, using a balanced conversion on both ends. If you use a small amp and as I suggested to another post, using a small Radio Shack isolation transformer to feed the subwoofer RCA input, will also work without producing any hum from stray fields or ground loops. greg |
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#14
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#15
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