Hi everyone,
I'm new to the forum and I signed up because I could use some help.
My problem is that I bought some Behringer Truth 2031A Active monitors. (I know... serves me right for buying Behringer. They're just so cheap I had to roll the dice.) The problem is that they pick up the radio. Even without any cables attached they play the radio so I know it's not a ground issue or loose cables or anything like that. I've even tried opening up the amp on the back and installing RF chokes everywhere there was enough wire to get a few good wraps in. While I had the cabinet and amp open I noticed that the amp construction seems sub par and all of the cables are unshielded. The cabinet and the drivers seem to be decent and they actually sounds pretty good when you're playing music loud enough to cover up Star98.9 FM.
I'm thinking about removing the amps and replacing them with a decent 2 channel amp. I think I need something that can push a 4ohm load with 150watts peak. I guess less watts would be fine and I should probably double check the ohm load. The passive models take 4ohms so I'm assuming the active models use the same parts.
I think I have all the skills I need to pull this off. I'm a decent woodworker and I can solder. But I don't know what I need. I assume I need an amp with a crossover, but I've never used one before so I don't know what to look for. Adding a sub later would be nice so I guess I should get an amp that can drive a sub too. I'm running the speakers through a mixer so XLR inputs would be ideal. I'm assuming that I can build whatever cables I need to attach the amp to the speakers. Probably 1/4" (?). I dunno... that's why I'm here!
Or maybe I should just sell the Behringers and get something else. But the budget's tight. $300 max without having to save up. And that will only get me... another pair of behringers.
Thanks in advance!
Mike
I'm new to the forum and I signed up because I could use some help.
My problem is that I bought some Behringer Truth 2031A Active monitors. (I know... serves me right for buying Behringer. They're just so cheap I had to roll the dice.) The problem is that they pick up the radio. Even without any cables attached they play the radio so I know it's not a ground issue or loose cables or anything like that. I've even tried opening up the amp on the back and installing RF chokes everywhere there was enough wire to get a few good wraps in. While I had the cabinet and amp open I noticed that the amp construction seems sub par and all of the cables are unshielded. The cabinet and the drivers seem to be decent and they actually sounds pretty good when you're playing music loud enough to cover up Star98.9 FM.
I'm thinking about removing the amps and replacing them with a decent 2 channel amp. I think I need something that can push a 4ohm load with 150watts peak. I guess less watts would be fine and I should probably double check the ohm load. The passive models take 4ohms so I'm assuming the active models use the same parts.
I think I have all the skills I need to pull this off. I'm a decent woodworker and I can solder. But I don't know what I need. I assume I need an amp with a crossover, but I've never used one before so I don't know what to look for. Adding a sub later would be nice so I guess I should get an amp that can drive a sub too. I'm running the speakers through a mixer so XLR inputs would be ideal. I'm assuming that I can build whatever cables I need to attach the amp to the speakers. Probably 1/4" (?). I dunno... that's why I'm here!
Or maybe I should just sell the Behringers and get something else. But the budget's tight. $300 max without having to save up. And that will only get me... another pair of behringers.
Thanks in advance!
Mike
Hi there.
A friend of mine lives close to a radio broadcast station and gets a lot of fm through his actives exactely like you do. Do you live near an FM brodcasting station?In many actives the electronics are not fully enclosed in a metal box but only placed on a metal sheet that acts as an heatsink.
you might want first to decouple the bridge rectifier in your speaker so that it acts less as an FM antenna with small values capacitors ( 10 nF ceramics are fine if i remember well, but please check this) and if this does not solve it , to shield the electronics ( think of a faraday cage).
A friend of mine lives close to a radio broadcast station and gets a lot of fm through his actives exactely like you do. Do you live near an FM brodcasting station?In many actives the electronics are not fully enclosed in a metal box but only placed on a metal sheet that acts as an heatsink.
you might want first to decouple the bridge rectifier in your speaker so that it acts less as an FM antenna with small values capacitors ( 10 nF ceramics are fine if i remember well, but please check this) and if this does not solve it , to shield the electronics ( think of a faraday cage).
What happens if you play Star 98.9 on the speakers? Is there an echo? 🙂
Re-doing these is going to be a challenge. Not only do you need an amp, you need to build a crossover. Probably a passive crossover if you want it in the speaker box.
If you know, or can find the crossover points and slopes already being used, you'll be ahead of the game. It's not going to be a small task to do this "right." Can be done, but it will be real work.
Re-doing these is going to be a challenge. Not only do you need an amp, you need to build a crossover. Probably a passive crossover if you want it in the speaker box.
If you know, or can find the crossover points and slopes already being used, you'll be ahead of the game. It's not going to be a small task to do this "right." Can be done, but it will be real work.
You certainly should be able to measure the crossover and EQ in the existing amps and then try to build that in passively or go with an active crossover with external amps, but that will be beyond your budget. Measuring the amp and then doing a passive design is not too hard if you have the tools, but if you don't then passive is probably beyond what you will be able to do.
Possibly the only benefit by going passive is that you will put the amp ( assuming you want to salvage those from the behringers) into a metal box, outside the speaker, thus shielding them.
I have Genelecs 1031A and tannoys AMS8a. none of these are shielded, see my previous post. I do not have FM on any of these speakers, probably because i live far away enough from a broadcast station, but one day I was shoked to hear loud noises form my genelecs seconds before receiving an sms ( i was very close to the speakers). Indeed my mobile makes it trip if i am close enough. Since then i lined the interior of the recess where the electronics are with thick house aluminium foil that is grounded and linked to the amp plate. I can now make a mobile phone call hands free on top of one of my speakers without hearing a thing through them. Should work with your fm problem and at least that's cents of your money if you want to try...
PS: of course make sure you don't create any short circuit doing this!!
I have Genelecs 1031A and tannoys AMS8a. none of these are shielded, see my previous post. I do not have FM on any of these speakers, probably because i live far away enough from a broadcast station, but one day I was shoked to hear loud noises form my genelecs seconds before receiving an sms ( i was very close to the speakers). Indeed my mobile makes it trip if i am close enough. Since then i lined the interior of the recess where the electronics are with thick house aluminium foil that is grounded and linked to the amp plate. I can now make a mobile phone call hands free on top of one of my speakers without hearing a thing through them. Should work with your fm problem and at least that's cents of your money if you want to try...
PS: of course make sure you don't create any short circuit doing this!!
open the box remove all the dampening material, then glue 2 layers of tinfoil inside the whole box then redo the dampening. =)
Thanks for all the suggestions!
I'll try and hit all the points here in one message.
I do live near a radio tower. I can see it from my front yard. I have a lot of other audio gear in the space (it's a recording studio) and the only time anything else picks up the radio is if there's a loose cable. According to the internets the speakers I own are notorious for picking up the radio so I think I'm dealing with a design flaw or just poor build quality... which Behringer is kind of known for.
I have tried a faraday cage. I wrapped a cardboard box in tinfoil and placed a speaker in the box. It was a good fit but it didn't really help. I guess because the face has to be open to use the speaker there's still an a place for the radio waves to get in. But the good news is that if I wear the box like a hat the aliens can't read my thoughts anymore. Which is comforting...
If I coat the interior of the cabinet with tinfoil that still leaves the amp unshielded. It's attached to the back and if I'm going to use it I'll need to access the power switch so boxing it in is awkward at best. I'd also be a little concerned about ventilation. But I might be over-worrying about that.
I could remove the amps and place them in a faraday cage that I can enclose and use shielded cables to run to the cabinet. Right now that's looking like a good move.
But I guess I'll start by lining the interior of the cabinet with a think layer of tinfoil and just see what happens. But I got a hunch that the problem is in the amp on the back.
Quick question about grounding the tinfoil to the amp plate. If I did that wouldn't the tinfoil just act as an antenna and leak a signal back to the amp through the ground? Because I think the electronics are also grounded to the plate.
If the tinfoil doesn't work I'll do some research and try to understand C37's suggestion of decoupling the bridge rectifier. You lost me there but I'm going to assume that it was a great suggestion since you obviously know more about electronics than I do. Unless you just made that up. In which case you totally got me!
Thanks again!
I'll post the results soon.
I'll try and hit all the points here in one message.
I do live near a radio tower. I can see it from my front yard. I have a lot of other audio gear in the space (it's a recording studio) and the only time anything else picks up the radio is if there's a loose cable. According to the internets the speakers I own are notorious for picking up the radio so I think I'm dealing with a design flaw or just poor build quality... which Behringer is kind of known for.
I have tried a faraday cage. I wrapped a cardboard box in tinfoil and placed a speaker in the box. It was a good fit but it didn't really help. I guess because the face has to be open to use the speaker there's still an a place for the radio waves to get in. But the good news is that if I wear the box like a hat the aliens can't read my thoughts anymore. Which is comforting...
If I coat the interior of the cabinet with tinfoil that still leaves the amp unshielded. It's attached to the back and if I'm going to use it I'll need to access the power switch so boxing it in is awkward at best. I'd also be a little concerned about ventilation. But I might be over-worrying about that.
I could remove the amps and place them in a faraday cage that I can enclose and use shielded cables to run to the cabinet. Right now that's looking like a good move.
But I guess I'll start by lining the interior of the cabinet with a think layer of tinfoil and just see what happens. But I got a hunch that the problem is in the amp on the back.
Quick question about grounding the tinfoil to the amp plate. If I did that wouldn't the tinfoil just act as an antenna and leak a signal back to the amp through the ground? Because I think the electronics are also grounded to the plate.
If the tinfoil doesn't work I'll do some research and try to understand C37's suggestion of decoupling the bridge rectifier. You lost me there but I'm going to assume that it was a great suggestion since you obviously know more about electronics than I do. Unless you just made that up. In which case you totally got me!
Thanks again!
I'll post the results soon.
My understanding of shielding is that the shield must be grounded. Did you ground your faraday cage?
Another possibility is to pull the amps off the back of speakers, install them in an appropriately shielded enclosure, and install normal speaker terminals in the speaker.
Another possibility is to pull the amps off the back of speakers, install them in an appropriately shielded enclosure, and install normal speaker terminals in the speaker.
Theoretical Sucess!
I did not ground my faraday cage until about 10 minutes ago.
And it turns out you do need to ground it.
I put the loudest radio... um I mean speaker... in the tinfoil covered cardboard box and ran a wire to the amp plate and when I touched the other end to the tinfoil >boom< no more radio! That's promising!
Now I just need to decide if I should remove the amp and build a new home for it or just shield the back of the speaker cabinet. I'll report back when I get something working.
Thanks everybody! I know there's a lot of other people out there with the same problem to this particular model of speaker so hopefully this thread will be the gift that keeps on giving. I'll try to document the steps I take to fix it for those guys.
w00t!
I did not ground my faraday cage until about 10 minutes ago.
And it turns out you do need to ground it.
I put the loudest radio... um I mean speaker... in the tinfoil covered cardboard box and ran a wire to the amp plate and when I touched the other end to the tinfoil >boom< no more radio! That's promising!
Now I just need to decide if I should remove the amp and build a new home for it or just shield the back of the speaker cabinet. I'll report back when I get something working.
Thanks everybody! I know there's a lot of other people out there with the same problem to this particular model of speaker so hopefully this thread will be the gift that keeps on giving. I'll try to document the steps I take to fix it for those guys.
w00t!
exciting when you get success eh?
but now you have to put all of these problems out of your head and without prejudice and upset give us a an honest account of how, for the little money they cost, they actually do sound.
but now you have to put all of these problems out of your head and without prejudice and upset give us a an honest account of how, for the little money they cost, they actually do sound.
Do you have grounded AC plug? If not, it could help to use a grounded mains and see if it does the job.
You'll find all interesting details in the spec sheet. (Interestingly the spec sheet for the passives contains far less information.)
Specifically:
Woofer 80 W RMS, 320 W Peak, 4 ohm
Tweeter 25 W RMS, 100 W Peak, 4 ohm
Crossover 4-th order Linkwitz-Riley @ 2 kHz
Specifically:
Woofer 80 W RMS, 320 W Peak, 4 ohm
Tweeter 25 W RMS, 100 W Peak, 4 ohm
Crossover 4-th order Linkwitz-Riley @ 2 kHz
The power is grounded properly. The Behringers just pick up the radio. If I take them further away from the broadcast tower they're fine.
As for Terry J's request for a review - That actually influenced my decision to just shield the back instead of removing the amp. When I got to thinking about it I decided that I'm not going to cut any cables because eventually I'll want to sell them when I have some more money for better speakers.
But in all fairness the Behringers are good for the money. Just keep in mind that they're cheap. I paid $279 for a pair on eBay. I've heard of other people replacing the amp and they said the difference in quality is night and day when you use a good amp. The cabinet and drivers seem to be decent. But the amp gives you that "this was made in a sweat shop" kind of vibe when you open it up. Hot glue, cheap parts and loose cables everywhere. If I had to do it over I'd buy the passives. And it looks like peteran found the specs to match it with a good amp. Thanks!
I've been mixing on them for about 2 years now and they'll get the job done. But the mix doesn't always translate to other systems accurately so I almost always have to go back and tweak a few things after I listen to it outside of the control room. Bass seems to be a problem frequency. I though it was my control room acoustics that were throwing it off and it partially was. The funny thing is now that I've treated the space the mix is more accurate (still not perfect) but the radio is driving me crazy! It didn't bother me as much when the white noise from the highway and the air conditioner drowned it out.
So my 2 cents would be:
Buy something better if you can afford it and you need something accurate.
But if you just need something decent that won't break the bank buy the passives and match them with a decent amp.
As for Terry J's request for a review - That actually influenced my decision to just shield the back instead of removing the amp. When I got to thinking about it I decided that I'm not going to cut any cables because eventually I'll want to sell them when I have some more money for better speakers.
But in all fairness the Behringers are good for the money. Just keep in mind that they're cheap. I paid $279 for a pair on eBay. I've heard of other people replacing the amp and they said the difference in quality is night and day when you use a good amp. The cabinet and drivers seem to be decent. But the amp gives you that "this was made in a sweat shop" kind of vibe when you open it up. Hot glue, cheap parts and loose cables everywhere. If I had to do it over I'd buy the passives. And it looks like peteran found the specs to match it with a good amp. Thanks!
I've been mixing on them for about 2 years now and they'll get the job done. But the mix doesn't always translate to other systems accurately so I almost always have to go back and tweak a few things after I listen to it outside of the control room. Bass seems to be a problem frequency. I though it was my control room acoustics that were throwing it off and it partially was. The funny thing is now that I've treated the space the mix is more accurate (still not perfect) but the radio is driving me crazy! It didn't bother me as much when the white noise from the highway and the air conditioner drowned it out.
So my 2 cents would be:
Buy something better if you can afford it and you need something accurate.
But if you just need something decent that won't break the bank buy the passives and match them with a decent amp.
The Sounds of Silence
Problem solved.
Now the speakers look bad but they sound great.
First I lined the inside of each cabinet with a few layers of tinfoil and replaced all the padding. Loose speaker wire in the cabinet was also wrapped around a ferrite ring.
This fixed one speaker but the other was still pretty bad so...
I found a shoebox that fit the back of the amp perfectly. Using a hot glue gun and packing tape I covered the box with a few layers of tinfoil and added access points for the power switch and cables.
That was enough to silence the other speaker.
The cardboard box is tight enough to stay in place just from friction. It's incredibly functional but it's also really ugly. I think I'll cover it with some vinyl or fabric. Maybe my wife will knit a cover for it.
Anyway that's a confirmed fix for the Behringer 2031As.
I might still try to replace the amps with a better one. Probably something with an active crossover and a sub. But for now the Behringers are quiet and I don't feel the need to replace them right away.
Thanks everybody!
Problem solved.
Now the speakers look bad but they sound great.
First I lined the inside of each cabinet with a few layers of tinfoil and replaced all the padding. Loose speaker wire in the cabinet was also wrapped around a ferrite ring.
This fixed one speaker but the other was still pretty bad so...
I found a shoebox that fit the back of the amp perfectly. Using a hot glue gun and packing tape I covered the box with a few layers of tinfoil and added access points for the power switch and cables.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
That was enough to silence the other speaker.
The cardboard box is tight enough to stay in place just from friction. It's incredibly functional but it's also really ugly. I think I'll cover it with some vinyl or fabric. Maybe my wife will knit a cover for it.
Anyway that's a confirmed fix for the Behringer 2031As.
I might still try to replace the amps with a better one. Probably something with an active crossover and a sub. But for now the Behringers are quiet and I don't feel the need to replace them right away.
Thanks everybody!
I had an amp that picked up short wave radio.
I simply put a 100pF across the input to the amp and the problem went away.
The amplifier input is acting as a radio detector circuit.
The 100pF shorts out the radio frequencies to ground.
I simply put a 100pF across the input to the amp and the problem went away.
The amplifier input is acting as a radio detector circuit.
The 100pF shorts out the radio frequencies to ground.
combine the cap with a 'grid stopper' resistor (or whatever the SS equvalent is called - base stopper, gate stopper??))
Hi Stereomaster,
Ok-So the electonics in behringers are piggy backed . How are they attached to the main body of the loudspeaker? is it through a metal plate or just to the MDF of the L/S?
How did you make the ground connection? Soldering? ( Alu foil is *very* tricky to solder- forget it...). check a) if there is no 360° metal on the piggy back , it's not a faraday cage ! and b) if the grounding of your boxed foil is still there ( it might have fallen off/ teared off depending on how you did it).
Other suggestions from the two post above are also worth a try... Are you inputting balanced in or not?
Ok-So the electonics in behringers are piggy backed . How are they attached to the main body of the loudspeaker? is it through a metal plate or just to the MDF of the L/S?
How did you make the ground connection? Soldering? ( Alu foil is *very* tricky to solder- forget it...). check a) if there is no 360° metal on the piggy back , it's not a faraday cage ! and b) if the grounding of your boxed foil is still there ( it might have fallen off/ teared off depending on how you did it).
Other suggestions from the two post above are also worth a try... Are you inputting balanced in or not?
Attachments
The amp is attached directly to the MDF and when you remove the amp all of the electronics are exposed. The foil does not totally encase the amp. There's access for the on/off switch and cables. The underside of the amp is shielded-ish from inside the cabinet which is also covered in foil. But the foil box covering the amp does not encircle the amp. It's grounded to the amp plate. Which I am assuming is grounded to the 3rd prong of the power cable. I'm using XLR input cables but the radio plays even with no cables plugged into the amp. It's a stand alone radio.
And here's another piece of the puzzle...
The amp has hi/low mutes (tweeter & woofer) and when I mute the highs the radio becomes much louder. That seems to suggest that the problem is somewhere past the input in the signal chain.
So can I place a capacitor anywhere in the signal chain?
There's lots of room in the wires going to and from the magnet.
And if I could remove the tinfoil box that would be super duper.
Thanks for all the support.
You guys rawk.
Mike
And here's another piece of the puzzle...
The amp has hi/low mutes (tweeter & woofer) and when I mute the highs the radio becomes much louder. That seems to suggest that the problem is somewhere past the input in the signal chain.
So can I place a capacitor anywhere in the signal chain?
There's lots of room in the wires going to and from the magnet.
And if I could remove the tinfoil box that would be super duper.
Thanks for all the support.
You guys rawk.
Mike
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