Axiom Home Page Forums General Discussion Home Theater Bad crossover in M80?

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

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.

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?

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.

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.

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?

I have never heard it under normal listening conditions.

I personally wouldn't sweat it then.

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.

That's good to hear.

or, not hear.

This is just one reason why test tones should be permanently banned from anything audio ... they'll drive a good man to insanity within a matter of days.

You talkin' 'bout me?

If he was talking about you, he wouldn't have used the term "good man."

Well, I was figurin' that as "past tense"...

If y'all only knew just how much you make me laugh every day.

If we knew that, we'd have to have JP commit you.

Speaking of which, it's fascinating to me how different Georgia is from Virginia as far as committing people. In Virginia, I would have to call a local agency. They send out their specialist to give the person a independent evaluation. Then, if the specialist agrees with me, then he goes to a judge to get a detaining order. The police can be called, shown the order, and they take the person away to the hospital. In Georgia, I sign a piece of paper, call the police, show them my signature, and they take the person to the hospital.

So, how many times has your wife had to post bail for you since you moved?

Is that the REAL reason why you moved?

So that's why the bad crossover in the M80!