Axiom Home Page Forums General Discussion Advice from Axiom Owners Axiom EP500 - Funny noises at 20Hz?

Okay, here is a clarification... I was testing my subwoofer this morning I here is description:

1) The noise that I am hearing sounds like a motorboat. This extraneous sound appears to be coming from the driver (meaning its more of a mechanical sound). This sound is separate and distinct from the actual sine wave.

2)This noise is the most prominent at 20Hz. I was mistaken, but I am able to hear it up to 24Hz. However, at 23-24Hz, this extraneous sound is present but can be intermittent. It also requires higher dB to get this sound (i.e. 95dB nearfield, using a RS Meter).

3) I'm not a subwoofer expert, but the driver excursion is more prominent when this happens, and seems to be related.

As I said, this is my first real subwoofer, and I have no idea what is normal. I have another subwoofer that I'm auditioning and it doesn't make that sound. But its a sealed sub, and doesn't start going until 25Hz.

I will also e-mail Alan to see what he thinks. Thanks guys for your help... You guys are great!

PS My EP500 starts at 19Hz, but doesn't really start going until 20Hz. I guess its the same as everybody else.

I would just call Axiom and talk with them. They will probly send you a replacement if your sub is new.

I had a problem with port noise on my EP 500 and they are sending me a new one.

I talked to somebody from Axiom customer service. They stated that this may be normal for my subwoofer as the Axiom representive occasionally hears the same thing on certain sinewave CD's with his EP500. However, he does not hear it during normal listening. I explained to him that it is very noticeable, and nobody seems to be hearing the same thing. In addition, I tried the Darla scene from Finding Nemo, and the same noise was heard intermittently. All in all, he didn't seem concerned that there was problem.

But he suggested sending it back to Axiom to have them take a look at it. I'll have to pay for shipping. However, it is indeed a defective product, should I be paying for shipping? But then again, in Axiom's view, it may not be a problem. I guess I have to do, what I have to do.

I don't have my 500 yet, but based on what others have said, this does not sound normal. I'm suprised that is the feedback you received from Axiom, are you sure you called the right number?

If your hearing the noise during other music and/or dvd's then it should be a warranty issue, in my opinion. I would call again. Do you recall who you talked to?

You could also send Alan or Amie a PM, to see what they tell you..

Yeah, it was Axiom alright.

The funny thing is, when I got first got my EP500, I noticed the noise from the driver. I called Axiom, and they said it was probably normal. I guess I became more concerned when I heard it during Finding Nemo recently. For the most part, the subwoofer otherwise sounds great.

I would have no problems with this if my findings are consistent with other users. However, this is not the case. One user who shall remain nameless , is known for torturing his subwoofers, and he has not heard this sound.

I have already left Alan and e-mail, and I'll see what he has to say.

I want to state that I have NO DOUBT that this will be worked out. Axiom seems to have an excellent history with customer service.

Its hard to believe that axiom said that sound was normal. When I called them and told them about the port noise I was getting from my sub they immediatly sent out a replacement and are paying for the return of my other sub.

Hi Jinhan,

There is far more information here than in the email you sent me. Anyway, if you use sine waves or pure tone signals to "test" a subwoofer, and keep raising the level, at some point you are going to cause the driver to go into some mode of mechanical or acoustical distortion or resonance.

Certainly the sound you describe isn't "normal" but then again please use program material (movie soundtracks or wideband music) to see if there is any similar sound from your EP500. If there is, then perhaps there may be a driver defect. Single frequency sine waves put enormous stress on drivers that are not encountered in normal playback.

Here is what I told you in the email, for the benefit of others who may hear "funny noises" that they attribute to the subwoofer: '"In many cases like this, the "odd noise" is often a resonance elsewhere in your room. Our hearing acuity diminishes dramatically at low frequences, and below 20 Hz we don't hear pitch so much as sense pressure. The latter may cause sheetrock, blinds, the frame of a couch, springs in upholstered furniture--almost anything-- to briefly buzz or rattle, and it may seem to come from the EP500. Everything has a resonance frequency and because of the tremendous acoustical output of an EP500 as ultra-low frequencies, it may trigger resonances you would never hear from conventional speakers (which typically have little or no output below about 28 Hz).

It's very difficult to locate these in your room. There is no inherent problem like this with an EP500. Tighten the screws around the driver and, like Brent said, check that no wires are vibrating.
Once you find whatever is resonating or vibrating in your room, you may be able to move it or do something. In most cases, there isn't anything you can do. One of the slats in my Venetian blinds vibrates at very low frequencies. I can adjust the shades and it may go away, but then another object my resonate instead. It can be maddening, but it comes with the territory of serious low-frequency subwoofer operation.

Regards,

I just love to hang out here for what I get to learn.

Alan makes strong point here Jinhan.
I've played around with test tones rather extensively in the search for answers on a strange piece of music that was causing some reverberation in one of my M60 drivers. There really was no easy answer to be found. Sometimes particles hit a certain resonance putting molecules into a similar step beat causing detrimental things to happen.
Anyone ever read about the army crossing the bridge while walking in step and causing it to collapse?
There is sound physics behind this.

Ultimately if you cannot honeslty hear it with normal playback material, i would ignore the artifact. Otherwise you may drive yourself mad.

Alan,
Thank you for your detailed answer. I trust your opinion which is why I wanted to ask you before I sent my Axiom EP500 in. I do understand that sinewaves are torture tests for a driver, but if no one else is hearing it at 20Hz at similar levels, then should this be an issue?

I also understand that the sound may be from the house or objects in the house. I hear that as well, but the sound I'm specifically describing is distinctly different. This sound gets louder as I get get closer to the subwoofer. But I accept the fact that household noises may be mistakenly localized to the subwoofer itself.

As I said, during normal HT listening I have only heard it during one movie, in one scene. This is why I chose to reinvestigate this issue. I will gladly continue to test my EP500 with different HT passages in the mean time. As you said, if I don't hear it during HT passages, then it shouldn't be an issue.

I will probably take to a different room, and possibly outside to listen for the same noise.

Thanks again for your reply.

-Jin

PS I never got your reply or Brent's suggestion...