I'm pretty sure my receiver has always had a hum but it seems like it got louder for a brief period and now it's back to being "quieter". Maybe three or four weeks ago my kids were watching antenna tv, after I put them to bed I went to turn the tv off and noticed the picture on the tv was frozen. I turned the receiver off and the picture started moving and the "loud" humming was first heard. It was at this point that I realized that my receiver was affecting my antenna signal. I turned the receiver back on and the picture froze again. I turned it off and the picture returned to normal.
Just moments ago, I had the signal meter up on the tv and turning the receiver on/off had no impact on the signal whereas a few weeks ago it made the signal drop significantly. The past week or so, it seems like the "loud" humming has stopped and it's back to "normal".

If my memory is correct, it was at this same time that I noticed my sub was humming as well. I don't recall it always humming, if it did it was a very low hum that I never noticed.

I did some googling in regards to the sub, I haven't searched regarding the receiver yet. I found several possible causes it could be and grounding comes up often. I just now attempted to ground the sub by putting a wire in the ground hole in my wall outlet and put the other end against the rca connector on the back of the sub. I also tried touching it against the screws on the back of the sub but they all appear to be wood screws so I don't expect them to ground anything. I would think the rca connector would provide a ground but maybe in wrong? Nothing I did worked, the hum was still there. If I unplug my sub cable while it's powered up the hum persists after it's unplugged. If I power the sub off then turn it back on with no cables connected there is no hum.

I'm a novice when it comes to this stuff so I would appreciate any guidance.

Anyone have any suggestions for me to get rid of the humming?

I have my receiver enclosed by baby gates and all of my cables are managed neatly so troubleshooting is going to be a major pain, so ideally I'm trying to get this corrected the first time so I don't have to get to the back of my receiver multiple times.

I honestly can't remember if my speaker and sub wires are in the same bundle as my power cables, and I can't tell without a lot of work to get back there. I am aware that is one of the things to check for and separate them if they are in fact together.

I have the speaker wire for my rears and the sub cable in the same cable management channel. My sub is plugged into a different outlet from the rest of my devices. Everything else is plugged into a "clean power" power bar.

I appreciate any and all suggestions, thanks in advance

Jumbo, if you have an Axiom sub, did you try loosening the ground screw that is on the amp plate?

[img]https://ibb.co/2PL3t2w[/img]

this is the back of my axiom sub. its an older sub so maybe it doesnt have a dedicated ground? i dont think any of those are a ground

No ground screw on that old sub.

If you have cable connected up to the receiver, try disconnecting it.

BTW, not sure you are aware but you can trade that old sub in for a new one. I'd bet even the least expensive Axiom sub (EP125) is better than that one. I have two EP125s and like them very much. I also have four EP500s, two EP600s and an 800. I really like them all!

I do not have cable (if you mean cable tv) hooked up to the receiver. The tv antenna that i mentioned in my original post is connected to the tv, not the receiver.
I have an old Xbox, a playstation 3, a DVD player and the tv hooked up to the receiver. And naturally, my speakers, an am and fm antenna are hooked up to the receiver. Off the top of my head that's everything that is plugged into it, and everything is connected via hdmi.

I was not aware of the trade up, thanks for pointing that out. I will look into it but it's not likely in the budget at the moment.

Am I correct in assuming the rca connector would provide a ground?
I have no issue opening it up and making a ground connection if necessary, but don't want to waste my time doing that if it's not going to make a difference

I can't advise you to connect the safety ground from your AC receptacle to the RCA jack. I'd expect the RCA jack is not connected to safety ground internally but rather what is called "raised ground". Raised ground usually has a resistor or capacitors or MOVs or even all three connected to ground.

It's a pain, but you may want to try disconnecting everything from the receiver and then sequentially plugging everything back in while you listen for the hum.

If it is a grounding issue I was going to put a proper ground inside the sub, I was just using the rca jack for testing purposes.

When I unplug the sub cable from the sub and its still humming, would that indicate the issue is the sub's ground?
I would expect that if it's humming, once I ground it the humming should stop. Is that a fair assumption?

I'm really trying to avoid disconnecting everything if I can

Could be a leaky filter capacitor in the power supply. You could be more sure of that by cutting open a spare RCA cable, shorting the wires together and connecting the mess to the sub jack. That eliminates any possibility of airborne noise getting in via the sub's RCA jack. It is a high impedance input after all.

Are you using a shielded sub cable?

Can you please elaborate/simplify on this?
Are you suggesting cutting an end off of the cable, then joining the two wires inside together, then plug this shorted device into the rca jack on the sub?

Yes it's a double shielded Monoprice cable

Correct.

What exactly would this test prove?


wouldn't shorting it be a bad idea?

Sorry, I know you know far more about this stuff than I do, but this just doesn't make a whole lot of sense to me

Mojo, you or I would have built specialized connectors to track down these kinds of problems but best to keep it simple ... use a wire ...

Shorting it as I described would be like your receiver putting out zero volts. No harm will be done.

Since the sub is humming without the cable connected, you may have airborne noise entering through the RCA jack. If you short the input and the hum disappears, that means you've shorted the airborne noise. If it still hums, it's likely a leaky power supply capacitor.

BTW, noise figures for audio equipment are always given with RCA jacks shorted as I described. The manufacturer wants to measure internally generated noise and not what might be generated by the ambient environment and radiated or conducted into the equipment by inputs and outputs.

You can use a wire but then it's like a small antenna. Best to put some mu metal around the shorted RCA jack I say.

P.S. Jumbo might have to hold the wire and then it's like an antenna connected to a capacitor. There's no telling what worm hole Jumbo may open up.

Don’t think that’s would be a problem ... but it’s your show

I just tried it, it didn't make a difference, it's still humming.

It's barely audible but if I put my hand on the driver I can definitely feel it's doing something. I believe the humming coming from it when I first noticed it was louder just like my receiver than it is now. It's possible it's been like this for a while now, it's rarely quiet enough in my house to hear it with little kids running around all day.

So this sounds like a capacitor issue?

If I turn the sub off and then back on again, it doesn't hum at all and it doesn't start humming until the sub receives a signal to do it's thing. Once it's received that signal it wont stop humming until the power to it is shut off.

Is the humming affected by the sub's volume control?

Are you sure the hum returns only when signal is fed? Have you tried waiting a minute or so?

So either I'm going crazy and it's been humming all along, or it just started to him full time this evening.

I'm second guessing myself now, but earlier today I must have tried powering it on and off at least 5 times and I was confident the humming was gone when powered back on and I also tried adjusting the sub volume once and turning the knob made no difference.

Just now I checked it and it's basically humming at all times. I turned the volume up and the humming gets worse, when my volume is up past 50% it starts to make a rumbling sound accompanied by a static/white noise type of sound. A sound similar to being tuned into a radio station that you aren't receiving the signal for. When the volume is below 50% the white noise sound goes away and it's not a rumbling sound, just a steady hum.

What do you make of this?

Before cutting open any devices or cables, does the sub power cord have a ground pin? If so, can you find an extension cord with only a 2 blade electrical plug, meaning one without a ground pin?

I have had humming issues with all 3 Axiom subs I have owned, and the ground screw fix did not work with any. All were fixed by the above.

Your mileage may vary, but it is easier and safer than some of the above suggestions.

The sub power cord does not have a ground pin, it's a 2 blade plug.

Try a few more things:

1. Remove the RCA cable, turn the volume down and listen to the tone of the hum. Now raise the volume and put your finger on the RCA jack. Does the tone decrease in frequency (sound lower in pitch)?

2. Reverse the plug if not polarized. Does hum disappear?

3. Move the sub to another circuit. No need to plug RCA in. Does the hum disappear?

I don't notice any difference in the sound when I put my finger on it.

The plug is polarized so I cannot reverse it.

Tried the sub in three other outlets in different rooms and the sub acts the same everywhere.

The humming doesn't start until the volume knob is in the 40-60% range. Below that, it doesnot appear to be humming

Sounds like a sub amp problem to me. If you really want to try a repair, remove the amp and closely examine the power supply filter capacitors for bulging or leaking. You may also have a leaky transistor in the pre-amp section of the sub amp. None of this is for the uninitiated. Trade it in when you can.

Thanks for all of you help, I really appreciate it.

I'll try to get it apart this weekend at some point amd see what I can find.

I attempted going through the trade up part of the website but my serial number isn't recognized, I'm guessing because it's so old and there doesn't appear to be a model number anywhere on it. I sent a message to axiom yesterday hoping to see what I can get for my sub if anything.

As much as I would like a new sub i don't think the discount will be significant enough to convince my wife I need a new sub.

Does it sound like the driver is ok? I could always replace the plate amp I'm assuming at a cost effective price point.

How long would you estimate a typical sub will last?

I have a similar issue. When I plug in the trigger on both or one EP500 I get a hum, once triggers are removed hum goes away tried removing ground screws did not make a difference.

RJ

You may get 120 bucks on trade-in.

I doubt very much Axiom can provide you with a new amp. They're not building them any longer and parts are likely obsolete.

If the driver plays without warbling, it's likely OK.

There is no "typical" subwoofer. I've known folks whose amps failed within a month. I've had my cheap Sony for almost twenty years. It depends on a lot of factors but mostly on whether the engineer selected parts appropriate for the design. A well-designed sub ought to last at least 15 years.

RJ, I recommended in the past to get rid of extraneous cables. A trigger cable is extraneous. I shut all my subs off when not in use.

I had a similar problem (hum) years ago when I purchased my EP350 Subwoofer. The hum was caused by the tv cable from the wall outlet connection to the cable box. My local cable tv provider installed a ground loop coaxial isolator in the cable between the outlet and cable box inlet. Problem solved.

I took the amp off and I don't see any capacitors or anything that looks damaged other than what appears to be a plastic screw showing some burning on it. If you look at the picture I attached it's the philips screw, I'm not sure what function that screw serves?

[img]https://ibb.co/fMMmXq7[/img]

Years ago I was given a Reel sub that didn't work, the driver and amp were bad. My brother gave me a sub that used to be in his car that he no longer used so I bought a plate amp from parts express and put everything together in the Reel sub box. It made for a cheap sub that has worked well for me in my basement. I just tried attaching the driver from my axiom sub to that amp and there is no hum so if the "trade up" option is still to expensive, I'm thinking I can just buy another plate amp since my driver seems to be ok still. I'm thinking this route would likely be much cheaper.

There doesn't appear to be any clear info on my axiom amp or driver in regards to wattage.

On the amp it says: 120V~ 60 Hz
On the driver it says: 10ACB-4-80LY120-20

I'm trying to look for a replacement plate amp but I'm not sure of the specs on my driver. I searched for "10ACB-4-80LY120-20" but haven't been able to find any info yet.

I'm guessing 10ACM means 10"
4 means 4 ohms
80 & 120 are the watt range???
not sure what the 20 would mean

Am I grasping at straws or am I onto something?

a guess from the serial number that it is an EP175....if I read that correctly.
Use that and your date of purchase in the trade up calculation, skipping the serial number portion.

I'm a novice myself but could it be a case of a blown subwoofer? That could lead to distorted sounds from what I know here.

Jumbo, the yellow plastic screw is a trim pot and it does look a little crispy. There is something suspicious going on there. To the right of it is a transistor and a capacitor (C19). Have a good look at that capacitor - to me it looks fried. Or it could be the transistor was getting hot and that discolored the plastic on the trim pot and the capacitor.

That number you found on the driver may as well be a message from an alien civilization.

You can't just buy any old amp and mate it to a driver. It's not just about impedance and power.

I looked at that capacitor again, it looks perfectly fine to me.

I heard back from Axiom today and BBIBH is correct, my sub is an EP175. The trade up value exceeded my expectations. I think with some convincing of my wife I might be able to get her on board with an EP125. At the moment, I have this sub in a small living room but there is a good chance we will be purchasing my in-laws house in the next 2-3 years. If/when that happens, this sub would be getting installed in a much larger room. I haven't actually measured it but I would estimate it's close to the 20x12x8 size that is ideal for the EP175, however the ceiling is much taller, its probably 8' on the ends but it peaks up to probably around 16' in the middle of the room. Do you think an EP125 would be sufficient for a room that large? I've never used a sub that was "undersized" for the room it was in so I'm not sure what it would sound like. I use the sub primarily for watching tv/movies, I don't care nearly as much about it when it comes to music. I enjoy the full surround experience when it comes to my tv.

Mojo, why do you say, "you can't just buy any old amp and mate it to a driver." Is that not essentially what people who build their own subs do? Do you not just buy an amp that matches the specs of the driver?

Hi Jumbo

The EP125 will help a lot, even in a 20 x 12 x 8 room.

Jumbo, controlling a woofer to achieve articulate bass is more than just nominal impedance and rated power. Otherwise, the only thing that's achieved is one-note boom as in car subs.

The 125v4 is practically identical in sound pressure and low frequency reach as your older EP175. One will do just fine for your 2000 cu ft space. Take advantage of Axiom's generous trade-in offer, choose the wood finish you want and enjoy.

This is the review of the EP125v4 I think I provided to Axiom but don't see on the product page:

"I run 2.2 using dual EP125v4 in cherry chestnut with M2 on-walls in my 1920 cu. ft. living room. They are tight, smooth and totally musical. Victor Wooten, Kraftwerk, Dan Fogelberg, Yazoo, Queen, Red Hot Chili Peppers...all full, tight, nice mid-bass and controlled lows even at volumes that I'd never play. Clapton's Change the World has such a wonderful pop and articulation.

The 125v4 has a really nice mid-bass touch but it doesn't sacrifice the textured growling I have with my sealed Axiom subs. It's not like a one-note mid-bass punch. The sound is very nice. Very engaging.

The 125 would be very good for movie effects as well as music in a smaller room like my living room. It's a very good double-duty sub. It's such a small size too. With its trapezoidal shape, it's easy to fit it under side tables, etc. I like having them out in the open though where I can take in the cherry chestnut.

I like the 125v4 better on some tracks than the 500v4. For example, Another one bites the dust sounds better to me on the dual 125v4/M2OW combo than on the dual 500v4 and 800v4 I have in my main room with the active LFR1100. The bass is far more engaging on the 125v4 for some tunes. It has to do with the perceived greater mid-bass but not so "peaky" that it is of the one-note type that can be distracting or over-whelming.

These subs have made a previously good presentation even better. Now it just sounds so much cleaner and more tactile."

I wonder what happened.

I'm going to trade up for an ep 125. Going to do so this weekend.

Would you guys say the ep 175 is worth the extra $200?

I can't say because I've never listened to it. However, based on the specs, it'll sound the same as the 125 except play a bit deeper. Since you're into movies, that might matter to you. Note it's the same amp power.

I wonder what happened.

I ordered a 125. My wife wants to renovate our kitchen now so that money would be put to better use there. As much as I would have liked to get the 175, it just didn't make sense to do so right now.

Good deal. You can always trade it in later. I think you'll like it.