AMP & Passive Subwoofer Recommendations?

ccmichaelson

Active Member
So I was an idiot and pulled the wrong subwoofer wires throughout my home - I used 12 gauge speaker wire versus shielded RG6 and have the classic hum issue because I home ran all wires into central rack location.
 
Thus, I need to purchase a sub amplifier (I believe) so that my Sonos Connect AMP and/or AV receivers can send their line level sub out to a rack mounted amp, which then uses regular speaker wires connected to a passive sub...  Make sense?   Also, I plan to dual-purpose my sub's (either listening to music through my Sonos Connect AMP or via my AVR).  Here's my planned sub wiring scheme:
 
[Sonos/AVR sub out] -> [Nile SAS-1 (ability to have two sources per speaker w/ auto sensing)] -> [Sub AMP] -> [12 gauge speaker wire through wall] -> [Passive Sub AMP]
 
Thoughts?
 
Here do not have sub woofers wired to the Russound's 12 zones.  That said have 14-16 / 4 going to each zone and split to 16/2's plus cat5e's going to same keypad wall box in each room or zone.
 
I recall on your endeavor your mentioning of subwoofers / 12 guage wire when doing your stuff initially.
 
I have two multimedia setups in the house and used microphone shielded cable for the local combination sub woofer / amps being utilized.  One multimedia set up has two speakers (of 5.1 surround) that work with the zoned system and just using an AB switch.
 
I don't see much of a difference between using a separate subwoofer amp to speakers versus source amp to speakers on a long subwoofer speaker run.  Think earlier it was mentioned to try pushing low level audio on to your speaker wires and using a subwoofer with an amplier to see if you hear a hum.  Has that been tried?
 
Is your audio amp properly grounded? Does it have a three prong ac plug? Also if your audio amp is near another device it can receive interference from that device's power supply. Try moving the amp and make sure that it and the outlet that it is plugged into  are well grounded.
 
Mike.
 
If you're woofer is truly passive and does not have a power cord then the hum is coming from an external device and you should think about the source of the hum. It can be originating in the audio amp or it can be induced into the speaker wire on it's path between the amp and the speakers. do the wires pass close to a power source?
 
Mike.
 
pete_c said:
I recall on your endeavor your mentioning of subwoofers / 12 guage wire when doing your stuff initially.
Think earlier it was mentioned to try pushing low level audio on to your speaker wires and using a subwoofer with an amplier to see if you hear a hum.  Has that been tried?
You have a good memory pete...  Yes I pulled 12 gauge speaker wire for all speakers include my sub's.  I currently have an active/amplied subwoofer and if I connect my Sonos Connect AMP sub out to an adapter over my speaker wires I get a hum.  I've tried it in multiple rooms where sub's will be located.  Thus, I believe my only option is to look for a subwoofer amp and co-located it in my rack with my Sonos.
 
mikefamig said:
Is your audio amp properly grounded? Does it have a three prong ac plug? Also if your audio amp is near another device it can receive interference from that device's power supply. Try moving the amp and make sure that it and the outlet that it is plugged into  are well grounded.
 
Mike.
Thanks Mike for ideas.  I tried that as well.  Sonos is well grounded into monster surge protector.  I also tried moving my sonos to a dedicated 30 AMP plug in my house and that didn't work either.  I did my best to keep all my LV wires away from the electrician but I know he came in after I was finished and routed a few wires across mine.
 
mikefamig said:
If you're woofer is truly passive and does not have a power cord then the hum is coming from an external device and you should think about the source of the hum. It can be originating in the audio amp or it can be induced into the speaker wire on it's path between the amp and the speakers. do the wires pass close to a power source?
 
Mike.
I don't yet have a passive woofer...  Given that I can't get my amplified sub to work without a hum I believe I'll need to switch to passive sub's unless you guys come up with a better option. 
 
Initially here did install a dual coaxial microphone cable from the basement to the master bedroom.  I did get an AC hum on that cable and put in filters but do not use it anymore.
 
You shouldn't be getting hum on a short run. 
 
Ahh now see though why though.  Electrical might do this. 
 
Here in the basement did run much LV (including audio) near electrical conduit.  I do not hear any hum on the in wall speakers but never do crank them up.
 
Yup and what Mike mentions about grounding.  Here too my multimedia stuff is on it's own breaker.  For the electrical outlets here use that extra green wire to the ground on the outlet going to the metal box.  I do not know if that matters.
 
You could also see how noisy your electrical is using a toner if you wanted to.  Think this has been asked before but are the speaker wires loosey goosey or are they stapled down.  It would be great if you could use the wires to pull catXX cable or coaxial cable.  Well you mentioned RG6.  That should be noise free.
 
ccmichaelson said:
I don't yet have a passive woofer...  Given that I can't get my amplified sub to work without a hum I believe I'll need to switch to passive sub's unless you guys come up with a better option. 
 
Make sure that your sub woofer and the audio amp are both plugged into the same AC circuit. Otherwise you may be getting what is called a ground loop causing the 60 cycle hum. If possible get an extension cord and try plugging them into the same AC outlet as a test.
 
Mike.
 
mikefamig said:
Make sure that your sub woofer and the audio amp are both plugged into the same AC circuit. Otherwise you may be getting what is called a ground loop causing the 60 cycle hum. If possible get an extension cord and try plugging them into the same AC outlet as a test.
 
I just pulled a long extension cord and plugged my sub into the same surge protector where my amp is plugged into and the hum is still present.  The hum isn't horrible and I can only hear it when the sonos connect amp isn't playing anything and the sub woofer is turned on.
 
ccmichaelson said:
I just pulled a long extension cord and plugged my sub into the same surge protector where my amp is plugged into and the hum is still present.  The hum isn't horrible and I can only hear it when the sonos connect amp isn't playing anything and the sub woofer is turned on.
If there was no change then I would say it's not a ground loop and go on to the next step. Pete made a good suggestion to try a short wire. You are trying to determine if the source of the hum is the audio amplifier, the sub=woofer amplifier or noise induced into the wire from one. the other or some other source.
 
Does the sub woofer hum when it is powered on and not attached to the speaker wire at all?
 
Does it hum with attached to the speaker wire alone and that wire is detached from the audio amp?
 
Does it hum when connected to the audio amp wit a short speaker wire or shielded rg cable?
 
I would experiment with different scenarios and see what it leads to.
 
Mike.
 
The short wire works just fine...  Also, the long run RG6 pulled into the same room works fine too so I know it's the speaker wire runs, which are about 50 - 125' in length and while I tried my best to stay away from the HV wires my electrician found some shortcuts and crossed over my wires in a few spots...
 
I really think the only way to solve the problem is to purchase passive sub's and amp(s)...  Not the end of the world but just not what I envisioned is all.  thanks all for your assistance.  If you happen to know of decent passive sub's (floor standing type) and/or sub amplifiers by all means speak up.
 
i don't understand how that will help. If there is noise on the line then won't the amps at the woofer just amplify the noise?
 
mikefamig said:
i don't understand how that will help. If there is noise on the line then won't the amps at the woofer just amplify the noise?
 
According to a variety of folks I've spoken too and threads on avsforum.com, subwoofer wire type should be shielded RG6 (a.k.a coax) because I guess sub level audio can pickup interference whereas regular audio (non-sub) does not.  For instance, I have 6 sonos connect amp's powering 24 polk audio speakers using the standard 12 gauge speaker wire and the sound is flawless.  However, sub audio apparently is "sensitive" to interference and I'm being told that if I purchase a sub amplifier and a passive sub, I can co-locate the sub amp with my sonos connect amp's and use the existing in-wall speaker wire with a passive subwoofer at the other end and the hum/interference goes away completely.
 
I think you've been given good advice about using a passive subwoofer connected to an amp back at the other end.
 
An active subwoofer takes a line level audio signal in and it gets amplified locally to power the subwoofer.  The line level signal is very low power - similar to the audio signals from a CD or DVD player to your amplifier.  They must be connected through shielded cables.
 
The hum that gets picked up by an unshielded cable is also low power, and the amp in an active subwoofer will amplify that just as nicely as the audio signal.
 
On the other hand, if you locate the amp back at the Sonos end, the audio signal coming out of the amp will be high powered to drive the passive subwoofer directly.  Any hum picked up by the unshielded cable won't be able to be heard because it just doesn't have enough power to drive a passive speaker.
 
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