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Slow Wi-Fi Performance on New 27in Imac

1058 Views 10 Replies Latest reply: Apr 6, 2013 3:57 PM by raffinewyork RSS
djmarafi Calculating status...
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Jan 29, 2013 4:03 PM

Hi All,


I recently received delivery of my new 27 inch iMac. A quite noticeable problem that I found was real Wi-Fi slowness.


So I set up a test connecting to the all on Chrome Web Browser


- Computer 1: 2007 15 inch Macbook Pro - OS 10.5.8

     Download: 15.8 Mpbs, Upload: 1.02 Mbps


- Computer 2: 2011 13 inch Macbook Pro - OS 10.6.8

     Download: 16.46 Mpbs, Upload: 1.03 Mbps


- Computer 3: 2013 27 inch iMac - OS 10.8.2

     Download: 3.12 Mbps, Upload: 1.01 Mbps


Can this be explained? Rectified?


Does Apple acknowledge that there seems to be a problem?




iMac (27-inch, Late 2012), OS X Mountain Lion (10.8.2)
  • Kalob Calculating status...
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    Jan 29, 2013 4:26 PM (in response to djmarafi)

    This is strange if it's a new, fresh-out-of-the-box iMac. Assuming the MBPs are connected to the same network (ethernet or WiFi), there shouldn't be a performance difference of this size.


    There's a few variables to consider:


    1.Are you able to connect the iMac via ethernet, turn off the WiFi (from the menubar), then test the web performance?


    2. Verify all of your products are connected to the same network (SSID) and that their IP Addresses are similar.


    3. What type of router are you using? Apple? 3rd party?


    4. Any signs of wireless interference? When you click the WiFi icon in the menubar, how many other network names appear? Where are your computers located in relation to the router?


    5. Test the web performance with other browsers.



    If the issue still seems to be with just the iMac, then first non-destructive step would be to create a new location in System Preferences > Network > Locations > Edit Locations. This will set the network settings to default. Reconnect to your network (if needed) and try your tests again.


    If it is in-fact a new system, then you could consider playing it really safe and simply format the internal drive and do a clean install of OS X. I realize you may have bought it "new" but you never know exactly where a system is coming from and a clean install would rule out any system software on the iMac being the source of the problem.

  • Kalob Level 1 Level 1 (80 points)
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    Jan 29, 2013 5:01 PM (in response to djmarafi)

    Wow. That's interesting.


    For the following, I am keeping in mind that your MBPs seem to function adequately on your WiFi network.

    Are there any major software differences between the iMac and MBPs? Are they all up-to-date?


    If its a clean OS, then here's a few more software ideas:


    1. Is the wireless connection for your iMac strong or does it randomly drop off? Signal Strength? If you hold the OPTION key down a click the WiFi icon in the menubar, you'll see a bit more information about it's WiFi connection. What is the Transmit Rate? How about the MBPs?


    2. If you're connecting to a secure WiFi, did you have any issues with entering the password? Keychains?


    3. What kind of security is set for your network? WEP? WPA?


    4. What if, for temporary, you setup your network with a new/different network name(SSID) and NO SECURITY. Connect all your products to that SSID and then test again.



    If we're thinking hardware:


    1. You could try an SMC reset (basically unplug it for more than 15 seconds...from the back of the iMac too)


    2. I don't think a PRAM reset would benefit your situation.


    3. You could carefully lug that iMac to another location and connect to another network (this could be tough). Maybe the network within the Apple Retail Store (if you have one nearby).

  • Kalob Level 1 Level 1 (80 points)
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    Jan 29, 2013 7:14 PM (in response to djmarafi)

    I'm curious as to why your transmit rate is 130. My iMac shows 300 and it has a single wall in between it and the router.


    I'm using an AirPort Extreme in dual-band(5th gen I believe). 1st network is 802.11n (5GHz only) for all the computers while the 2nd network is 802.11n (2.4GHz) for my other devices (iPhones, game consoles, etc).


    Is there a way for you to test running a 5GHz only network?


    This may be a sidetrack because the proof still exists that your MBPs are getting the same transmit rate of 130 but showing a much faster download speed.


    You may get the most answers (and the best support) by bringing it into an Apple Retail Store, connecting it to their WiFi and testing it. If it works, then it's the combination your home network and that iMac. If it doesn't work, they'll most likely keep the iMac to test it overnight (possibly install a new Airport card if that's the issue).


    I haven't taken the time to check what others are saying online about WiFi issues with any of the new iMacs. Networking can get really complicated if one isn't methodical in diagnosing a problem. I worry that many of the complaints online would be caused from a lack of networking knowledge as apposed to an actual technical issue with the AirPort card in tons of iMacs (but stranger things have happened).


    Let me know what you find out.

  • raffinewyork Calculating status...
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    Mar 28, 2013 5:27 PM (in response to djmarafi)

    I have the same exact problem with the same exact wifi card on my New 27" iMac.  Even the first three octets of the MAC address are the same.  I am connecting to a dual band N router (cisco/linksys), that my equally new MacBook Air (athough with apparently a slightly older wifi card based on the revision) has much better speed with.  I have an old, external wireless N adapter that, when I connect to my iMac, restores my normal speeds.


    After much testing, I have deduced that it is my router.  Or rather, a problem between the imac's wifi adapter and my router....  strangely enough, however, when I setup my iMac's Wifi as an airport station, so that I can directly connect to it with my macbook, (thereby bypassing all traffic with my router), i STILL get horrendously slow speeds (file transfers).


    Maybe I'll have to fork out some money for applecare to extend my service, so that I can get a replacement when the time comes.  Right now, I doubt I'll get an upgrade, more like a downgrade.


    In any case, it's fail on apple.  WTG guys.  Glad you're paying such close attention to your own bottom line.


    RIP Steve Jobs.  Glad you aren't seeing this.  You don't deserve it.

  • godbout Calculating status...
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    Mar 30, 2013 10:41 AM (in response to djmarafi)



    I got exactly the same issue that you guys are reporting here.


    I got an iMac a couple of days ago and I've found the wifi to be very, very slow. I've checked then with speednet and my MacBook Air, my iPad and my iPhone are all reporting 13Mbps, while my iMac is giving me 1Mbps. I'm using a Time Capsule so I also have a 5Ghz network. I've switched to the 5Ghz network and it gives me 13Mbps.


    Now I'm the only one with a 5Ghz wifi around, but there are A LOT of 2.4Ghz.

    So just to test a bit more, even with my problem "fixed", I've forced the TC to go to channel 13 for the 2.4Ghz. It gave me 13Mbps. With the automatic settings it was on channel 1, there are a couple of them around my appartment on channel 1. I've switched to channel 6 and it gives me 6Mbps.


    So it just seems that the iMac WIFI card is more sensitive to interference (or just ******) than the other Apple products. Still it's kinda crap, if you're not familiar with tweaking, you're kinda screwed. Got a lot of issues on my last Apple products, that's a pity, probably too much demand, quality gets bad.

  • raffinewyork Level 1 Level 1 (0 points)
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    Mar 30, 2013 1:01 PM (in response to godbout)

    I fixed the problem as well by tweaking my router.  I'm using a linksys e1500 with thrid party firmware which provides a boatload of tweaking options and features (dd-wrt latest 3-25-13 build) and I've managed to get excellent rates once again.  However, the imac's wifi does recieve a noisier signal from my router than my macbook air when they are side by side.  It's somewhat negligible, but it is consistently higher. (monited using the network utilities performance scanner under the native Wi-fi Diagnostics app)


    I think a firmware update is in order and you can bet I'll be updating that the moment it's released.  Just glad I didn't have to lug my new imac into an apple store for service.  And have them probably tell me it's my network environment or worse yet, open up my virgin machine and downgrade the adapter with a refurb.


    It's true, there are a ton of other APs in my area (I live in NYC), but the fact that an external wifi adapter and my airbook are recieving a truer signal is notable.


    I would recommend, if your router supports it, to make sure your beacon interval is low (100ms/10 per second),  ack sensitivity shouldn't be exageratingly high, channel detection, transmission rate and band on auto, and of course, use a nice, non dictionary based wpa2 password just for security, since if you're having this problem, you probably have alot of wifi neighbors, and it's fair to assume some teenager is upto no good.


    (upgrading my router to a dual band 750 as soon as amazon ships it, but that's really not the issue here).

  • raffinewyork Level 1 Level 1 (0 points)
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    Mar 30, 2013 1:08 PM (in response to djmarafi)

    I suggest to try reflashing your APs firmware with the latest and set the options as noted above.  If you have the latest firmware, reset your router to factory defaults, then reconfig it in as few saves as possible--I've found that saving too often may corrupt the firmware's config.

    Now, why other devices aren't as sensitive to this, I don't know.  But I don't recommend using applecare support.  They couldn't help me and bringing into a macstore for service will probably result in a non optimal solution.

  • raffinewyork Level 1 Level 1 (0 points)
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    Apr 6, 2013 3:57 PM (in response to raffinewyork)

    I've identified the problem.  It has to do with wifi interference.  Solutions were either to force a maximum MIMO rate on my router, or best yet, find a clear channel for your wifi environment.


    It seems that only these new wifi adapters are this sensitive, possibly auto-lowering transmission levels based on channel noise. 


    As stated, even when I bypassed my router and set up my imac as it's own base station, connected to it with my 2013 macbook air, I still suffered from horribly slow speed.  And further, connecting to the same network/AP with my macbook air, right next to my imac, it did not suffer the fluctuating and slow speeds that my imac did.


    The solution was to either force the highest transmission speed on my router (regardless of a clear channel) or to scan and find a clear channel.  Forcing the highest transmission rate worked fine, except that other devices on my netwrok such as my ipads and iphone could not communicate at those rates, so this was not a good solution for me.


    I set up my AP to use channel 2, 40 MHZ channel width and the lower sideband.  It communicates on Channel 2+1 according to apple's wifi scanner.  My rates still fluctuate a bit, but never too low, and my internet speed tests are consistenly max (30+ MBps d/l).


    Must be some auto-negotiating feature built into this wifi adapter.  Find a clear channel and your troubles should clear.


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