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#287411 - 01/18/10 03:02 PM Bad crossover in M80?
terzaghi Offline
connoisseur

Registered: 04/04/07
Posts: 4870
Loc: Tulsa, Oklahoma
So I spent some time tweaking things this weekend and re-ran Audyssey, looked at other sub placement options, ect.

After running Audyssey I used the real traps test tones and ran a frequency sweep and noticed that there was a pretty bad dip at 150 hz. If I move my SPL meter a foot forward or backward it reads much higher so I assume I must be sitting a dead zone for this frequency...?

Anyway, so the problem: I re-ran the real traps 150-159 hz test tone today to compare the volume at the 150hz mark with and without audyssey. At louder volumes (about 80db) there is a buzzing noise coming from both tweeters on the right m80. I haven't noticed this before but I don't think that I had the test tones as loud the time before.

I swapped tweeters between speakers and confirmed that the problem is not with the tweeters themselves. I called axiom and spoke with JC and he suggested that the crossover is bad. The noise is pretty loud, and always occurs when I hit about -27.5 on the denon volume control at the 150 hz test tone. turn the volume down a notch and it stops, back up and it starts again. This is in the right speaker only. It did not appear to happen at the 160hz mark, at least not at the same volume.

Apparently there have been some minor changes in the crossover design in the m80's since I purchased them 2 years ago. As a result JC said I would have to send in my m80 for repair since they don't want to send me a new one (then my two m80's would have slightly different crossover designs). What I have to do is pay for return shipping to Axiom's US depot. This will cost me about $70 ($40 for axiom to send me a box/packaging stuff that is appropriate for holding the m80's) and $30 for the shipping label itself.

JC also cautioned against using test tones that play the same frequency for a period of time because it could damage the drivers.

I popped in my DVE disk and did a buzz and rattle test on the right speaker from 15hz to 300 hz. Even with the volume cranked way up I don't hear any buzzing.

So, I guess my dilemma is that it appears that one of my speakers makes a loud noise at about the 150hz mark. This noise stops when both tweeters are removed and unplugged. It doesn't appear to be noticeable when listening to music or movies, or even running a frequency sweep test such as the one found on DVE. I am not sure if the dip at 150hz and the buzzing noise are in anyway related because as mentioned when I move my SPL meter forward or backward a small amount the DB level jumps up considerably. Perhaps it is just a null spot at that frequecny and Audyssey tried to bump up the db level at the 150hz mark so much to compensate and then when running the test tone at this frequency it damaged the crossover or something. However, JC said that the test tones could be harmful for a driver, but shouldn't pose a threat to the crossover itself. Perhaps the crossover has been bad all along or perhaps there is no problem at all.



Any thoughts, comments, suggestions? What would you do?

OH yeah, if I send it in it will cost me $70 as mentioned, and I will be without an m80 for about 3 weeks \:\(
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-David

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#287414 - 01/18/10 03:22 PM Re: Bad crossover in M80? [Re: terzaghi]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13572
Loc: Iowa
About a year ago when I was playing around with the realtraps test tones and manually plotting my room, there were certain frequencies that appeared to have a piercing buzzing sound. Not sure if it is what your describing, but it appeared to be related to the room. I've never had an issues with music or movies after those tests.

If you swap the location of your m80's does it still happen? Axiom also asked me if I run a lot of frequency test tones for extended periods of tiime, hinting it might not be good for the drivers.
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#287419 - 01/18/10 03:36 PM Re: Bad crossover in M80? [Re: terzaghi]
Adrian Offline
axiomite

Registered: 12/27/08
Posts: 6888
Loc: It's all about the location.
David, I don't know if you might have talked to Axiom about the possibility of removing the crossover and sending that in for testing(less shipping $$). Could that be an option for you?
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#287420 - 01/18/10 03:49 PM Re: Bad crossover in M80? [Re: Adrian]
terzaghi Offline
connoisseur

Registered: 04/04/07
Posts: 4870
Loc: Tulsa, Oklahoma
Randy, I do not think that there is something buzzing in the room since the sound stops when the tweeters are removed. I had a buzz at about 80 hz which turned out to be a loose spike on the right m80. tightening the feet up eliminated that.

I have confirmed that it is not the tweeter that is causing the problem- it just makes the noise. When swapping tweeters between speakers the noise stays with the right speaker regardless of which tweeters are being used in the left or right speaker. The noise is not a vibration of the right speaker cabinet since I can hold the tweeter in my hand and specifically here the noise coming from the tweeter. The noise stops completely when both tweeters are disconnected.

at 150hz there should be no noise coming from my tweeters. It sounds like the tweeter is indeed trying to reproduce a 150 hz sound, but just buzzes miserably in its attempt. I can't say that I have ever heard this noise before and as far as I know the only way to reproduce it is to play a tone of about 150 hz at fairly loud volume.



_________________________
-David

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#287424 - 01/18/10 04:03 PM Re: Bad crossover in M80? [Re: terzaghi]
terzaghi Offline
connoisseur

Registered: 04/04/07
Posts: 4870
Loc: Tulsa, Oklahoma
Hmmmm.... At the volume I just had set (-26.0 on denon) at 150 hz the tweeter makes the buzzing noise with the audyssey EQ on. When I turn off the Audyssey EQ the noise does not occur. I am going to re-run audyssey and see what happens.


_________________________
-David

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#287428 - 01/18/10 04:20 PM Re: Bad crossover in M80? [Re: terzaghi]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

I'd say it's not the speaker but the signal that's being sent. If it does this without the Audyssey then I would think there's the problem.

Do you hear this in program material?
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#287433 - 01/18/10 04:29 PM Re: Bad crossover in M80? [Re: Wid]
terzaghi Offline
connoisseur

Registered: 04/04/07
Posts: 4870
Loc: Tulsa, Oklahoma
I have never heard it under normal listening conditions.
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-David

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#287435 - 01/18/10 04:31 PM Re: Bad crossover in M80? [Re: terzaghi]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

I personally wouldn't sweat it then.
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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#287445 - 01/18/10 05:42 PM Re: Bad crossover in M80? [Re: Wid]
terzaghi Offline
connoisseur

Registered: 04/04/07
Posts: 4870
Loc: Tulsa, Oklahoma
So I suspect that there was something goofy going on in the processing of Audyssey or something else in the receiver. I also just realized that the "restorer" was set on the mid level (thought it was turned off but had been listening to internet radio earlier). I think perhaps what was happening is that I was playing a frequency which was been boosted by Audyssey since there was a dip at this frequency in the main listening area. Between Audyssey's boost, my restorer boost, and the fairly loud volume something bad happened. Why it was only the right speaker I don't know, but audyssey could have been boosting this frequency in the right speaker more than the left or something.

I moved the speakers and couch a few inches further apart (this is all the room I had to play with) and re-ran audyssey. The dip around 150hz was less pronounced after moving the speakers a bit (only an 8 db dip instead of about 20!) so I don't think audyssey attempted to bump this area up as much this time around. The noise is not reoccurring when playing the 150 hz tone at a similar volume as before. I'm going to assume everything is fine unless the problem crops up again.

_________________________
-David

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#287446 - 01/18/10 05:44 PM Re: Bad crossover in M80? [Re: terzaghi]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

That's good to hear.
_________________________
Rick


"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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