There isn't any way to adjust the volume through OS X. While it's technically feasible to lower the volume via software (iTunes style) there isn't any way to adjust the volume physically alla a line out.

Don't waste your money on the monster cables, they don't shield against GSM buzz. I ended up giving up and buying a Bose system with small speakers so I could fit them on my desk's hutch. Sticking them up there seems to have them far enough away from my iMac to keep interference at a minimal though, I admit, I'm not terribly thrilled with the sound quality.

Interesting comment about the grounding. I'm in the UK and I've rarely heard GSM buzz through speakers. Here though all of our mains cables are grounded.

go yourself some Bose! They make no noise like this at all (but are expensive).

behringer are cheap china speakers, don't confuse em with the real studio monitor (genelec, PMC, Yamaha, Tannoy, etc...)
Try the Genelec 8020, the smallest and cheaper !!

For sure! I never had a problem with Genelec. But they are expansive (But you never want something els for the rest of your live). And a much better reverence as the speakers u use and certainly better than Bose. If you have the money the 8240a's are great. If you do not have that money Look for 2nd hand or so.

I'm a TV director and spend all day in different TV studios which are all set up with hi-tech audio monitoring gizmos.

we're always battling GSM buzz (this is the UK, so the grounding thing may be a red-herring; everything is grounded here).

in truth, the only sure-fire way to fix it is distance.

if i leave my phone on the control desk - buzz buzz buzz (and i've noticed this is worse since I got my iPhone compared to my old Nokias or SonyEricssons).

but just moving the phone a couple of inches can make all the difference.

you don't need it to be very far away from your speakers (and I guess the cable that runs between them), maybe a foot or two can fix this.

now you have the choice monitors, you need to spend a few bucks on some wall brackets (or build a low bridge or shelf for the back of your desk - or at least stop docking your phone right next to the speaker like in the picture!).

you'll get better sound balance as well.

i know this wasn't really the point of your blog, after all you wanted to know how to fix it, not how to avoid it, but I have a feeling there is no way around it as long as there is a signal passing along a conductive cable somewhere along the line.

good luck!

Thanx for the quote, I'm glad my comment was of use, although as it seems, it didn't resolve you issue completely, which is quite strange. As mentioned in previous posts, the cable going from one to the other speaker is usually high power and therefore should be less affected by GSM signals. Using a shielded cable might help, but I guess the problem is the connector. I therefore would suggest to move the phone around a bit and see, whether the Buzz gets louder near the plugs or the cable.

As for the volume: sorry for mentioned that but the output really isn't adjustable, which is indeed quite annoying.

Electrical outlet:

Go to Home Depot and get a circuit checker. I think they are less than $10. Plug-in the outlet and the little lights tell you if you are grounded or not.

It won't help. My iPhone buzzes with everything. The worst is in my car hooked into my Alpine stereo. When I plug it in, a little warning pops up on the iPhone saying "This device is not compatible with iPhone. Do you want to turn the phone off?" So, maybe there are devices that are compatible. But Apple is letting me know:  turn the phone off! Which I don't.

the Genelec have a built in amp,
You wrote:
I suppose that is because these are proper studio monitors, not consumer-grade "speakers" which may smooth-over some detail in service of a more balanced "mix."

The Behringer ARE consumer grade!
Quality costs!!
I'm not a China xenophobous (I don't know the spelling).
I have a lot of chinese manufactured stuff, but I repeat, if you need quality, pay it! Please don't confuse pro stuff with consumer. It's impossible to completely resolve problems paying only a few dollars, you payed an iPhone many more dollars than 100! Why did you buy it ?? You can have a good phone for less than 100 bucks,
Your article shouldn't be "Battling iPhone's GSM Buzz 3: Behringer MS40 Digital" but "I'm rich only when a new apple device goes out: for the rest I'm a windows user!"

You may want to go lurk some Amateur Radio operator websites - these guys know how to isolate RF noise from audio equipment and have more tricks up their sleeves than a back lot watch dealer.

http://www.eham.net/

My guess (and yes, I am way too lazy to actually do this myself) is that you could make a pair of faraday cages - one for each speaker, set the speakers in 'em and the problem would be solved. Doesn't do much for the wife/girlfriend acceptance factor of your desk decorations, but it would be effective. I would think that any mesh that the speakers were set in would be acoustically transparent as well.

http://en.wikipedia.org/wiki/Faraday_cage

I work in a recording studio, and I usually keep my phone (nokia) on the mixer. Somethimes more than one (other than nokia). Never Had buzz problems (of course I use Genelec speakers) the main problems are not the cables. but the woofer ( in the speakers) and the amp. You have to know that the pro speakers like genelec has two amplifiers ( one for each speaker) that's why the behringer cunsumer speakers can't reject noises, the left speaker have no amplifier inside so it's not shielded so catches every noise around your room. Try speakers that have an amplifier on every speaker ( both shielded). if you like chinese cheap plastic sound no pro speakers try the behringer truth ... BUT DON'T SAY THAT SOUNDS AMAZING !!!!

I work in a recording studio, and I usually keep my phone (nokia) on the mixer. Somethimes more than one (other than nokia). Never Had buzz problems (of course I use Genelec speakers) the main problems are not the cables. but the woofer ( in the speakers) and the amp. You have to know that the pro speakers like genelec has two amplifiers ( one for each speaker) that's why the behringer cunsumer speakers can't reject noises, the left speaker have no amplifier inside so it's not shielded so catches every noise around your room. Try speakers that have an amplifier on every speaker ( both shielded). if you like chinese cheap plastic sound no pro speakers try the behringer truth ... BUT DON'T SAY THAT SOUNDS AMAZING !!!!

a thought on phone position..

i haven't been reading this whole series, so forgive me if someone has already mentioned something along these lines, but...

any time i have noticed gsm buzz at work, i have found that keeping the phone in the same place but rotating it by 90 degrees can often greatly reduce the amount of buzz in my speakers..

it may turn out that your solution may have to be a combination of not only what speaker hardware you use, but also where you place the speakers and the phone..

In this case, the electrical ground on your A/C receptacle will not have any effect, as these speakers do not have a proper ground anyway.  Proper grounding at the breaker panel may, however, because the ground and neutral become common at that point.  (assuming it's a main panel, and not a sub panel).  I'm really surprised that you're getting interference in the left speaker, as the interconnect happens @ amplified speaker level, and not line level. 

Anyway, have you tried using a "ferrite choke" on any of the lines?  They filter RF interference without impacting audio frequencies.  I found a generic one on Radioshack's website, although there are others that would be higher quality out there.  You can see it here:  http://www.radioshack.com/product/index.jsp?productId=2103222  It should be installed as close to the end of the cable as is possible.

This also might have alleviated the issue with the previous setups if used on the line level cable between the Mac and the speakers, although that part is no longer an issue on count of using the optical out.

I've had problems similar to this before, and one of two things has always fixed them to date:

1. Use a ground remover plug (a little under a dollar at Home Depot) to strip the common ground from your speakers and from any power transformers like laptop adapters that are on the same breaker. Be aware that sometimes a breaker covers more than one room. If that fixes it, make sure to attach each of them to a different ground with a wire.

2. Make a shield-drained cable. You might try just making a cable first, and seeing how it works. www.markertek.com will sell you bulk cable and connectors for cheap. I use Mogami's Neglex Quad, but Canare StarQuad is cheaper and probably sufficient for your purpose. Canare RCA connectors are good. Remember that you'll need two - one for each end. For normal cable-making, you attach the shield to the connector. In making a shield-drained cable, you have to split the jacket a bit further back and bring the shield out through the split. Connect grounding wires to each end.

Hope this helps!

Bla bla bla bla bla bla
Changing cables and connectors doesn't change anything !!!!!

Unplug the input cable from the speaker. The phone should still affect it, meaning you don't need to upgrade cables. My $4000 studio monitors also have this problem.

Grounding your system will have no effect on GSM buzz. The GSM Buzz comes from the energy going between your GSM phone and GSM tower being picked up by the wires(antennas) in your audio system. My GSM phone lives on the other side of my studio whenever I'm recording to avoid this problem.

Why not headphones?????
try speakers with amplifier on both cabinets !!!

Your best bet is to focus on the radio in the phone. I suggest that you will not be able to beat the "calling home" from the GSM radio in the iPhone. You're much better off to find/develop a hack that keeps the phone from calling home except manually. In this way, you'll minimize or eliminate unexpected GSM noise and save some battery life too. I've found the radio in my iphone powerful enough to create GSM noise in TV studios, recording studios and just about anywhere there are audio [analog] cables.

Best,

G