Akg K701 rattle with heavy bass (test file now included!)
Feb 28, 2011 at 12:03 PM Thread Starter Post #1 of 15

Cheeze

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Hi there, I'm hoping to get some opinions on something I've encountered with my pair of K701's recently - any help would be really appreciated. 
 
I've been doing some tests using sine sweeps and have noticed that playing very low bass at very high volumes results in both the left and right ear cup vibrating and rattling against my ears, and a knocking sound to accompany. This disappears as the bass becomes higher. Please note that this isn't distortion or clipping, it's the drivers physically moving and resonating. It also won't be a hair or anything like that, I'm sure it's down to the power and depth of the bass itself.
 
Now, is this vibration/rattle of the driver and casing to be expected when pushing the headphones like this? One sign that perhaps it's normal is that the vibrations occur in both left and right earcups, and it seems unlikely that both would be defective.
 
I can reproduce this in certain music with very low bass but only at very high volumes. Low bass at normal to high volumes in music will occassionally produce a feeling of vibration against my head but without much of an audible effect in itself.
 
 
Any opinions would be great
 
Thanks
 
Feb 28, 2011 at 12:18 PM Post #2 of 15

ardgedee

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It sounds like you're making the driver reach its excursion limit.
 
The driver moves forward and backward to generate soundwaves; there's a maximum length of travel possible, and the rattling/crackling you hear could be the noise of the driver slamming against things. If you bring the frequency down to two or four Hz, you can probably get it to make distinguishable "tick, tick, tick, tick..." noises.
 
Feb 28, 2011 at 4:11 PM Post #5 of 15

Cheeze

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Thankyou for the help so far guys.
 
A quick note - it would be really helpful if anyone with 701's could do a quick test to see if they experience the same rattling using the same test file I used. Basically play the file and increase the volume until rattling begins for the first few steps of tone (or not!). File is here:
 
http://www.dogstar.dantimax.dk/testwavs/3stepoct.zip
 
which is found on this page under the section "sine sweeps" and called "3stepoct.zip":
 
http://www.dogstar.dantimax.dk/testwavs/
 
My system-  arcam cd72t player to beresford caiman dac to rega brio 3 with tape out to NJC monitor audio 2 headphone amp with this spec:
 
Frequency Response: 5hz - >100Khz +/-1.5dB
Total Harmonic Distortion: Approx 0.002%
Dynamic Range: Greater than 110dB
Maximum Power Output:
600ohm (120mW+120mW), 300ohm (215mW+215mW)
32ohm (780mW+780mW), 8ohm (1120mW+1120mW)

Maximum Current Output: 800mA (1A Peak <1sec) 
Amplification Gain Factor: Low: (2x), Medium: (4x), High: (6x)
Output Impedance: 3 Ohms
 
In answer to the first post about limits of travel of the driver- so if I understand correctly, the movement of the driver at such high volumes needs to be very large to produce the long wavelengths of the very low bass at that power level? Therefore it reaches the limits by trying to move back and forth too far in it's effort to produce these long wavelengths. If I'm right in this, it doesn't sound like the headphone is at fault, more that I'm applying more volume/power than the cans are capable of dealing with i.e. Its capable of the bass at that level, just not at that volume. Does this sound correct ardgedee? I have the option of returning for exchange, do you think i could've caused damage with this slamming of the driver? It doesn't sound healthy! Sound at normal levels seems fine by the way, but can I be sure there is absolutely no damage...?
 
Elija- your point about the 200mw power limit. Am I right in saying that if the headphones could accept more power, they'd be able to produce the deep bass at higher volumes without hitting the back and forth driver limits? Is there therefore more room for these movements in higher power headphones?
 
Thanks again for your help!
 
Feb 28, 2011 at 4:21 PM Post #7 of 15

Cheeze

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Well not exactly. That doesn't sound like fun. I was testing the headphones/my ears ability to produce or hear very low bass. It was then that I noticed the rattle at high volumes, and then that I wondered if this is a defect or not. What do you think?
 
Feb 28, 2011 at 4:24 PM Post #8 of 15

TheWuss

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Quote:
What are you trying to achieve by this? It looks mostly like an experiment in how to damage the drivers.



exactly, ardgedee.
 
well, does the headphone distort when you listen to music?
you know that's what headphones are supposed to be used for, right?   
wink.gif
   
biggrin.gif

 
Feb 28, 2011 at 4:29 PM Post #10 of 15

Cheeze

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Yep, I partly agree with you - I have tendencies to worry too much about these technical things and obsess, hence the post I guess. I find it hard to drop things unless I understand them! Nonetheless rest assured that I've listened to a hell of alot of music as well at least...
 
Thanks
 
Feb 28, 2011 at 5:16 PM Post #11 of 15

Cheeze

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Nope, it doesn't rattle at normal listening levels. Thanks, this is probably the sensible answer- accept that under normal use the phones are fine. What are the chances I've damaged do you think? I've probably reproduced the rattling a few times now.
 
Feb 28, 2011 at 8:50 PM Post #13 of 15

Blasto_Brandino

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If your source lets you, cutoff the bass frequencies under about,,, I'd say 15-20 hz that MIGHT help.
 
Feb 28, 2011 at 9:50 PM Post #14 of 15

SP Wild

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The K701 cannot reproduce low sub bass amplitudes as high as what other cans are able to - including HD650, HD800.  I confirmed this with an equaliser and it doesn't take very loud levels before the drivers suffer severe clipping. 

I can EQ the HD800 to handle Denon type bass amplitudes with finesse and ease.  The K701 falls apart when EQing to emulate HD650 type bass amplitudes.  The K701 was never desgned to produce these types of sub bass amplitudes.  I also found via EQ - the K701 bass is not as tight as many believe - the HD650 has a much better controlled bass.  The K701 sounds tighter because its harder to hear the bass imperfections when they are at lower amplitudes.
 
Nov 28, 2012 at 8:16 PM Post #15 of 15

casoninabox

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I have some brand new AKG K701's.
 
I listened to the sample.  I have an Fiio E17 driving them and when it got to 50/60 the first two tones started clipping.  Anything below 50 sounds fine.
 
I can listen to almost all of my music within tolerable levels at 50-60 volume on the E17.
 

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