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bass note distorting only my right speaker (bm6a) at 100 hz Studio Monitors
Old 29th December 2010
  #1
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otobianki74's Avatar
 

bass note distorting only my right speaker (bm6a) at 100 hz

I have a pair of dynaudio bm6as. I was mixing a bass line today and had it solo'd and noticed this overdriven and pushed vibration (though I might say more of a chasis rattle) occurring on the right speaker. I swept the pan left and nothing. I thought it could be some loose screws, so I tightened the back of the right speaker.

no luck. I put an eq on to the track, boosted like 10 db and swept across. as soon as the freq boost hit 100 hz, the right speaker was distorting like crazy. I did a surgical cut at that freq, narrow q, and it seems to have alleviated the problem.

I guess, safe to say something is wrong with the speaker? could it just be that that particular corner of my room is creating addition waves and maybe causing that side to resonate more than the other? I dunno, fishing for advice. it really seems more rattly.

thx.

oto
Old 30th December 2010
  #2
Gear Guru
 
Drumsound's Avatar
Did you swap the speakers physically? That would help you to determine the room, stand, furniture, duct work or speaker.
Old 30th December 2010
  #3
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drBill's Avatar
yup, gotta do some homework before you can discern what's wrong and needing fixing. Could be as simple as a bad patch or loose cable, or as expensive as a new driver.

#1 - I'd swap the input cables to each speaker and see if the sound "moves" to the Left. If it does, it's not your speaker, and further upstream. Logically test each link in the chain and find the problem.
Old 30th December 2010
  #4
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otobianki74's Avatar
 

for sure, will swap cables/speakers and check it out...

I've got a window tomorrow to troubleshoot.

thanks for the obvious pointers I overlooked.
Old 25th September 2013
  #5
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Bump.

Did you ever get to the bottom of this? One of my bm6a's (mk1) has recently started to distort at low-ish volumes as well, coming out of the woofer only. You can slowly raise the level of a test tone and hear the moment when the distortion kicks in, with plenty of headroom to spare. It seems to be most pronounced on tones between 120-200 Hz. I've swapped sides and cables with my good monitor, and even switched out their amplifiers. The problem remains with the one particular cabinet, leading me to believe it's mechanical in nature. Could it be a bad driver or a cracked surround foam?
Old 25th September 2013
  #6
Have you closely inspected the LF driver? A cracked surround foam ring or a loose, vibrating dust cap should be visibly obvious. Unfortunately, a rubbing voice coil (either off center or one with a out of round coil former) is harder to visually detect. Do check the area around the voice coil spyder for any foreign material that may have found its way there. Also, carefully check the area where the voice coil flex leads are attached to the back of the cone. They are usually attached with a "blob" of glue and can sometimes break loose and buzz.

You can remove the LF driver from the front of the cabinet and drive it with an external power amp. If the distortion still happens (or get's worse) when the driver is out of the cabinet and "unloaded" when driven by an external amp, you've answered your question.
Old 25th September 2013
  #7
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Quote:
Originally Posted by Lotus 7 View Post
Have you closely inspected the LF driver? A cracked surround foam ring or a loose, vibrating dust cap should be visibly obvious. Unfortunately, a rubbing voice coil (either off center or one with a out of round coil former) is harder to visually detect. Do check the area around the voice coil spyder for any foreign material that may have found its way there. Also, carefully check the area where the voice coil flex leads are attached to the back of the cone. They are usually attached with a "blob" of glue and can sometimes break loose and buzz.

You can remove the LF driver from the front of the cabinet and drive it with an external power amp. If the distortion still happens (or get's worse) when the driver is out of the cabinet and "unloaded" when driven by an external amp, you've answered your question.
Thanks for the tips. I've now swapped the LF driver between monitors and indeed that's where the problem lies. I've shot canned air in the front and back of the speaker to remove any stray particles, and no luck. Dynaudio dust caps are fixed in place, and the foam surround "appears" to be fine, with the cone feeling solidly glued to it all the way around. When I gently move the cone in and out, there is no scraping or unusual resistance, but the buzz remains. I can't seem to find what part of the speaker is causing it. Oh well, I guess it's time to order a new woofer.
Old 26th September 2013
  #8
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Was advised by Dynaudio support that it's likely a voice coil issue, which they will not service or sell individual components for, and to order a new woofer. There you have it.
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