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Interference issues with monitors

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Jonathan Frank
Interference issues with monitors
on Feb 17, 2013 at 4:13:55 pm

I am a video editor that mainly works on theatrical events (so lots of spoken word). I had a pair of KRK VXT4s that I purchased in 2008 when I bought my MacPro and just replaced them last week with KRK Rokit 5s as the VXT4s had developed an interference issue that had steadily increased to the point of utter distraction. It sounds like cell tower/radio/etc. signal interference (bursts of high pitched stuttering) and it would occur regardless of whether the computer was on or not and whether there were cables plugged into speakers or not.

I was going to go with another brand, as I had been reading about shielding issues with KRK, but the sales person at B&H talked me into going back to the KRKs as he felt I had purchased early versions of the VXT4s and the issues had been fixed.

It's been less than a week and I was happy...until today, when the Rokit 5s started acting up and the same interference is starting to occur - softly, but definitely there (and loud enough to be noticeable when trying to edit).

I'm not sure what to do. I'm in an old building in New York City and can't control too much of what goes on externally. I purchased new Mogami cables (TRS to XLR). The speakers are plugged into a PreSonus Firebox, which in turn is connected to my MacPro via firewire 400. The speakers are plugged into an APG power source which should protect against spikes.

Is there anything else I can do? Is there another brand that is better shielded?



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Peter Groom
Re: Interference issues with monitors
on Feb 17, 2013 at 5:02:40 pm

Does problem still come through speakers with no connection to anything except to mains power
Peter

Post Production Dubbing Mixer


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 5:15:06 pm

As I said, it occurs regardless of whether the computer was on or not and whether there were cables plugged into speakers or not. It's not happening 100% of the time - there will be instances of silence (such as now) and then interference will start and will go on for a while (minutes...hours...)

As mentioned, I replaced the connector cables (and upgraded them even).



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Peter Groom
Re: Interference issues with monitors
on Feb 17, 2013 at 5:23:34 pm

Are the mains cables correctly earthed
Peter

Post Production Dubbing Mixer


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 5:27:35 pm

How can one tell? If you mean the electrical, no idea what is on the other side of the outlet nor do I have any way of changing anything. The Cables used are all top of line and new and plugged in according to specifications.



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Craig Alan
Re: Interference issues with monitors
on Feb 17, 2013 at 5:39:12 pm

There might be something you can do. If the electric is not properly grounded, it is most likely against code and could be reported. There are line conditioners you can buy. You might consider a battery back-up box that includes line conditioners. Poor electric lines are not good for your computer gear either.

Maybe you could hire an electrician to test everything for you and make recommendations?

Have you tried plugging the speakers in from a different outlet? Maybe the wires are frayed or shortening or ground got disconnected inside the outlet.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 5:55:53 pm

I live in an old New York City apartment...getting anything done is an impossibility. I would guess that code is not...quite up to snuff. Which is why I have all my computer and sound equipment on a Premium APC Back Up (which is supposed to correct high/low voltage and has a site wiring fault indicator that would scream bloody murder if improper grounding was happening).

If that's not enough of a line conditioner, is there anything you recommend?

Of course right now the speakers are silent (as are the old ones which I plugged into an outlet on a different circuit).

Being in NYC, there are towers everywhere (I see two cell towers on the roof across the street in fact).



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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 6:00:56 pm

And thanks, guys for your help and feedback



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Peter Groom
Re: Interference issues with monitors
on Feb 17, 2013 at 5:40:19 pm

Are they 3 pin at each end?
Put a meter on the cables to check all 3 cores are good.
Having a poor earth would not be good.
Is there any rf nearby. Wireless alarms, mobile phones, masts etc

Post Production Dubbing Mixer


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 5:56:53 pm

As I live in an old NYC apartment with towers every where you look...the answer is yes to any interference possibilities. Hence my wondering if there is a brand with better shielding



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Peter Groom
Re: Interference issues with monitors
on Feb 17, 2013 at 6:01:41 pm

I don't know about better shielding.

Have you tried bypassing the backup device for the speakers to see if the noise is better, worse etc?
Have you tried taking them to a different premises?
I guess you need to establish if the issue is specific to your building first.
Peter

Post Production Dubbing Mixer


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 6:03:47 pm

I've had them plugged into a basic power strip, I've had them plugged into a different APC backup.

Let's go with the assumption there is something in the building as I have two sets of speakers of the same brand acting the same way.



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Peter Groom
Re: Interference issues with monitors
on Feb 17, 2013 at 6:09:18 pm

Is not know what you could do if it's an electrical / building thing. I'd suggest trying some other pro end speakers to see if it's a weakness of those speakers.
You may just have to be like most video editors I know and not worry about the audio .
Lol
Peter

Post Production Dubbing Mixer


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John Fishback
Re: Interference issues with monitors
on Feb 17, 2013 at 7:19:23 pm

Do you have an ATT mobile phone? If so, it may be interfering. I heard periodic interference when recording with a U87 mic. I was afraid there was a problem with the mic. Someone mentioned the ATT issue and the next time it cropped up sure enough the talent had an ATT mobile. We switched it off and the interference was gone. Then I started hearing what sounded like weak radio transmissions. I installed in-line RF filters on the mic lines and that interference went away. Good luck Finding interference sources is like finding water leaks. They can come from anywhere.

John

MacPro 8-core 2.8GHz, 16 GB RAM, OS 10.7.4, QT10.1, Kona 3, Dual Cinema 23, ATI Radeon HD 5870, 24" TV-Logic Monitor, ATTO ExpressSAS R380 RAID Adapter, PDE enclosure with 8-drive 6TB RAID 5
FCS 3 (FCP 7.0.3, Motion 4.0.3, Comp 3.5.3, DVDSP 4.2.2, Color 1.5.3)
FCP-X 10.0.7, Motion 5.0.6, Compressor 4.0.6

Pro Tools HD 10 w SYNC IO & 192 Digital I/O, Yamaha DM1000, Millennia Media HV-3C, Neumann U87, Schoeps Mk41 mics, Genelec DSP Monitors, Prima CDQ120 ISDN


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Craig Alan
Re: Interference issues with monitors
on Feb 17, 2013 at 7:14:10 pm

You've tried everything I know, though there are dedicated line conditioning boxes that cost way more than built in stuff in battery back ups. I would try to find an electrician that has worked on production studios/post houses in NY. I think at this point it would be worth the consultation fee. Before that you might try to buy another set of speakers from a different brand that allow for a certain amount of time while you can still return. Like 30 days. Try them out. If the problem is solved then you have an answer. If the interference is regardless of which speakers then you have you have isolated your problem.

If you buy from BH again, you might be able to work out an exchange. It was their guy that recommended the brand you have.

You might ask your neighbors if they are experiencing the same problem. Not everyone is an editor but a lot of folks have either stereo or home movie speakers and or computer speakers - cheaper and less shielded.

Cell tower stuff is usually the speaker wires acting as an antena. The fact that that is not the culprit is interesting.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Jonathan Frank
Re: Interference issues with monitors
on Feb 17, 2013 at 9:43:31 pm

It's been 'fun' trying out suggestions (and new ideas). the 'it's like trying to stop a series of leaks' analogy is perfect.

Putting the old speakers in another room on another circuit renders them silent. Replacing one of the new with one of the old results in noise from the old (but not from the new if it was in a silent phase). Cell phone has been a concern (not sure it's limited to AT&T - which is what I had - as I have been finding phones to interfere on shoots even. Would love a ban on phones in theaters but that's another argument :)

So it's either the electrical in my office or interference that is more prevalent there (which could be anything from the cell towers I see outside my window to my neighbors who run a hair salon in the adjacent apartment...don't ask...). Luckily the newer ones have less a problem (and I'm hoping it stays that way and doesn't increase). And I'm trying to move them further away from my ears so I hear the interference less.

But if anybody has had a similar experience and bought a set of speakers that worked better shielding-wise...let me know (I have 25 days to return these)



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Craig Alan
Re: Interference issues with monitors
on Feb 18, 2013 at 12:12:25 am

Sounds to me like you have a combo of problems. The new ones have better shielding. There is a problem with the circuit and/or plug where you have been setting them up. There is phone interference once they are set up on a quiet properly grounded line. I would still think that cell interference applies to the speaker wire not electrical wire but maybe I'm wrong. Speaker wire I know acts as an antenna for over he air transmissions. So shorter runs sometimes help. And shielding.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Ty Ford
Re: Interference issues with monitors
on Feb 18, 2013 at 1:53:44 am

Hello Jonathan and welcome to the Cow Audio Forum.

From the fine details you have given, I'm thinking that the RF is either coming up the power ground to your monitors or up the hot or cold side, or all three. So, right out of the wall and up the power cord.

Do the power cords have 3 pins? If so try a 3 to 2 converter that eliminates the ground and see if the rf goes away. If it doesn't, than that means the RF may on the hot or cold side of the AC (in addition to the ground).

If this is the case, no amount of shielding will help. It's dirty power.

What may help is a symmetrically balanced power conditioner. Furman makes one:
http://www.bhphotovideo.com/c/product/657354-REG/Furman_P_2400_IT_P_2400_IT...

B&H carries it and they are right in Manhattan. $2400!!!! Not cheap, but the symmetrical balancing does give you something regular power conditioners don't. If you talk nice to them, B&H should let you buy and return it if it doesn't work in your RF Hell Hole. Please keep us advised.

What conditioner are you currently using?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Jonathan Frank
Re: Interference issues with monitors
on Feb 18, 2013 at 7:06:49 pm

Right now the speakers (and the computer) are plugged into an APC pro unit so not sure how much conditioning that actually provides (website is...vague).

$2400 is out of price range.

In reading the fine print on the KRK manuals...it reads like a drug ad on TV (Please make sure no TVs, monitors, dimmers and neon signs are plugged into the same AC outlet in the building...). Dimmer...hmmm...now that is something I hadn't considered....



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Craig Alan
Re: Interference issues with monitors
on Feb 18, 2013 at 7:26:39 pm

So according to them you need a dedicated line for a set of computer monitors. Seriously, I'd go back to BH and get a different brand and test them out under the 30 trial. Return the one that doesn't work. I mentioned above there are fancy line conditioners installed in studios with fat budgets. Ty knows his stuff and the price point makes sense.

I'd also find the local electric panel for your apartment, turn it off, unscrew the outlet you are using and see if the wiring look ok. Nothing frayed, nothing touching that shouldn't be. easy enough to look on-line for the type of wiring connections and follow the diagrams.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Jonathan Frank
Re: Interference issues with monitors
on Feb 18, 2013 at 7:31:23 pm

Yup. I loved that. Dedicated line for monitors. Dedicated line for computer. Dedicated line for TV. Dedicated line for Computer monitor. Yup. Real world scenario :)

I'll look at the wiring - not a bad idea and one I hadn't considered. This apartment is a nightmare electrically speaking (four circuits...one for fridge, one for outlet in dining room, one for light in hall...and one for everything else - all three bedroom/2 baths of it!)

I'm going to see if the dimmer is making things wonky (as it's something I hadn't considered before). But given that it's a very intermittent problem with these speakers, gut says it's something non-electrical (as that would be constant) and a shielding issue.

Which is a shame as I really like the way these speakers sound...



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Craig Alan
Re: Interference issues with monitors
on Feb 18, 2013 at 10:12:04 pm

Hi Ty,

If the RF is traveling through the electrical line, where does it originate? Can an electrical line pick up RF from the air? The way speaker wire can? And if so, why does electrical wire not do this constantly?

In other words what makes a line dirty power vs. clean? And once discovered to be dirty is the only answer a high end conditioning box like the one you are recommending? In the studio installations I've seen where they have these boxes built in, I do not assume that the basic wiring with all the dedicated lines is dirty. I had therefore thought it was just to keep things as clean and constant as possible.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Ty Ford
Re: Interference issues with monitors
on Feb 18, 2013 at 10:34:07 pm

RF may originate anywhere. It comes in over anything conductive, including up the power line or ground system if exposed and not terminated properly.

I had a friend with RF problems in Boston. His DAW was getting regularly occurring hits. Turns out it was the radar at logan airport sweeping past his third story studio.

I had another client who had a recording studio with RF problems in the mics. He knew his ground system was iffy. We tried new cables, different wiring of cables, nothing worked. I went in one night and in trying to move the mic cables to null the RF, I had to move his copy stand. It was a metal music stand. The RF from the tV station 1/4 mile away was being re-radiated by the copy stand. The solution was a wooden copy stand.

There are different kinds of dirt. That's why I asked Jonathan exactly WHICH box he is using so I can figure out what kind of filtering it does. He may not need the $2400 solution, but my point was, he could probably get B&H to sell him that with a return guarantee..or get them to loan him one to find out if that was the problem.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Jonathan Frank
Re: Interference issues with monitors
on Feb 18, 2013 at 10:40:28 pm

If you use the words "loan" and "B&H" in the same breath (especially in regards to a $2400 device)...I'm thinking you've never been there (even though they have a good return policy, doing so is...not necessarily the easiest thing depending on whom is working the desk that day). This is a company that doesn't even put gear to try out unless the manufacturer has paid them to do so... So forgive me if I'm not about to rush out and buy something that expensive unless it's a last resort as it is definitely a 'you put a microscopic ding in it? you bought it...' type of affair sometimes...

I have an APC XS-1300



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Ty Ford
Re: Interference issues with monitors
on Feb 18, 2013 at 11:03:22 pm

Jonathan,

If you have this: http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BX...

It doesn't do any filtering. Just spike suppression and battery backup.

If you have dirty power it will not filter that out.

If you run on its battery, do you have the same problems?

I have a contact in NYC. Waiting to hear back.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Jonathan Frank
Re: Interference issues with monitors
on Feb 19, 2013 at 4:18:53 pm

Great suggestion regarding running off battery (of course the speaker is behaving itself right now...)

Thanks! That will at least clear up if it's electrical or interference from another source



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Craig Alan
Re: Interference issues with monitors
on Feb 18, 2013 at 11:19:20 pm

That's true Jonathan. What I suggest is you find a service rep there that deals with profession audio gear.

First find out who there best rep is for this type of gear. Tell them you have a small post house and need help isolating an RF problem. Then establish an email relationship. Explain your RF problem and that you are looking for solutions. Everyone knows in the audio field that it can come down to trial and error. Then deal only with this rep. Make sure he is in when you stop by. Keep all packing material. Take pictures as you go when you unpack it. Use scissors to cut open sealed plastic but leave cut piece attached. Nothing sells still new as a neatly repacked item. BH is the biggest vendor for the entertainment industry for a reason. They do honor the warranties and exchange policy and do not sell grey market stuff. On the other hand, they really are mostly not helpful when it comes to helping anyone buy what they need or technical support. But know what you want and they are the biggest if not the best.

Since you are getting different degrees of Rf in different outlets in the apartment, I suspect that maybe something can be done with the room wiring and a cheaper conditioner. For sure check out the wiring behind the outlet covers. And listen to Ty's suggestion to figure out if it is the ground wire.

Also a different brand of speaker just might do the trick.

MacPro4,1 2.66GHz 8 core 12gigs of ram. GPU: Nvidia Geoforce GT120 with Vram 512. OS X 10.6.x; Camcorders: Panasonic AG-HPX170, Sony Z7U, Canon HV30/40, Sony vx2000/PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.


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Jonathan Frank
Re: Interference issues with monitors
on Feb 18, 2013 at 7:08:05 pm

at 6', the Mogami's are as short as I can safely make them (and for the price they cost, they should shield against alien and government transmissions so I can take off my tin foil hat..)



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Ty Ford
Re: Interference issues with monitors
on Feb 18, 2013 at 7:35:20 pm

Jonathan.

APC pro what model number?

Dimmers won't bring in RF they'll buzz.

If the wiring is old and you have different appliances and an elevator in the building, all of that could be dumping into your power.

Wall dimmers in someone else's apartment could be the cause.

Saying no to going to B&H to find out if you can see if their box will help is the worst sort of denial.

Do you want to find and fix the problem or not?

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford's Blog


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Jonathan Frank
Re: Interference issues with monitors
on Feb 18, 2013 at 7:39:38 pm

It's not denial...it's being practical (especially since I really doubt it's an electrical issue as it's not a constant problem)

If I had a spare $2400...but right now given what my accountant told me I owe for taxes, that's not an option - or rather it's a last resort (buying more expensive speakers/monitors like Genelec 80s to see if they have better shielding...much better option). Especially as right now it's not a huge interference issue and is largely ignorable (unlike the other KRKs which got to the point that I couldn't listen to anything)



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