Axiom Home Page Forums General Discussion Home Theater Really need some help w/EP500 "problem"

Hello all- I have spent 3 months getting my Axiom setup calibrated properly and I feel like I'm pretty much done. I currently have the EP500 and while it is amazing, I have notice a "rattling" noise when it hits the REALLY low frequencies and it sounds like the driver itself is rattling kind of "loosely". Again this is only at the lowest Hz levels. I tried to tame this by using an Auralex Gramma isolation riser under the sub. It helped some, but I'm wondering if I should use the spikes or feet or neither on the bottom of the sub for this. What can I do to get rid of this annoying rattling noise?

Here is some logistical info:

M60, VP150, QS8's all set to small
Bass out set to "sub" crossed at 80hz
Yamaha RX V2400
Sub is located inboard of the right M60 about 3 inches from back wall and 2.5 feet from side wall.

Don't know if any of this matters, but I can't think that this rattling noise is how it's supposed to sound is it? Again, only at the real low frequencies.

As always thanks to all of you for the great help you always provide.

If you haven't already called Axiom I would strenuously suggest you do that ASAP. They will be the most up to date on issues...

Stupid question but someone brought this up recently. Are you sure it isn't something in the room itself that rattles, like frame, vase, shelf etc?

Darth:
Have you taken off the grill cover and watched the cone during these low frequencies?

I haven't explored it myself either, but I know that my EP-350's cone goes wild with really far excusions during low and loud passages, and I believe I can often hear the cone itself during these times....

Mark- I took the grill off and have watched and yes, the noise is definitely coming from the driver when it is going "crazy" due to the extra low frequencies. Should it rattle this much even w/the excessive movement? The rattling sounds very artificial during seens like in Star Wars EP IV when the ships are flying overhead etc, or when Vader chokes someone w/the force, that "force noise" rattles quite a bit.

DK, if you mean an actual metallic rattling sound, this shouldn't be happening at any reasonable level(I assume that you calibrated the sub level, either with YPAO or manually), especially with a sub of the quality of the EP500. I'd also suggest discussing it with Axiom, in case there's a defect in your 500.

A few thoughts:

1. Have you checked the screws that hold the driver in place? I've found that over time they can come a little loose which allows the driver to rattle under certain circumstances. I check mine roughly every 6 months and in most cases, some require just a smidge (an engineering term) of a tweak to tighten. If you do this, don't overtighten - they just need to be snug.

2. Can you describe your calibration process in more detail? Did you just set the speaker levels (and how did you set the sub relative to the other speakers) or did you also use sine tones and check the room for response over the lower frequencies? What calibration disk did you use for speaker levels - or did you use the test tones from your receiver/pre-pro?

3. Ever heard port noise? Looks like the port for the EPs is right under the driver so it may be you're getting some chuffing and confusing that with driver noise. At roughtly what SPL relative to reference are you hearing the noise?

BTW - does anyone know what the native tune point of the EP500/EP600 is? A quick scan of the manual didn't disclose it. Also has anyone seen any writeup of the behavior of the DSP in the 500/600 - e.g. what it does and when?

Cheers,

Doug

The audioholics article hinted that the tune point was around 30 Hz, which seems high given how deeply the EP5/600 will play.

The DSP seems to do a few things -- act as an EQ to ensure flat response (not EQ'ed against the room, just based on the cabinet and driver) and monitors signal levels and frequencies to make sure the woofer does not get overdriven. No details on exact algorithms though but if you look at the frequency response curves in the Audioholics reviews you can get some clues. I think the AH reviews are based on tone sweeps rather than broadband signal so it's easy to conclude that the DSP code just rolls off bass response at high SPLs -- reading between the lines I think the code is actually much smarter than you might think from a quick glance at the graphs.

Darth, you should still call Axiom, BEFORE you go looking for that Audioholics article

bridgman - thanks - I'll check out the article.

Darth - how big is your room BTW? Any large openings in addition to the room dimensions?

Doug

The room does open into a hallway that is long and VERY narrow, but other than that it is pretty much a square. (I know that's bad). As far as calibrating, the Sub sits at -8.5 db relative to the mains being at +9.5, so quite a difference there.

>>As far as calibrating, the Sub sits at -8.5 db relative to the mains being at +9.5, so quite a difference there.

As far as I know this difference is just a function of where you have the level control on the sub set. If you were to turn the sub level control down 10 dB you could then change the sub setting on the receiver up 10dB to +1.5dB...

... or better yet you could turn the sub down almost 20 dB and then bring ALL the receiver settings closer to zero

Seriously, there is a small chance that because the sub level control is turned up so high some kind of subsonic noise is getting in and making your cone flap. I don't *think* that is the problem but if you felt up to another "calibrate the sub" exercise it wouldn't hurt to :

- turn the sub down a bunch (whatever 20 dB is on the unmarked dial )

- shift all the speaker settings down the same # of dB (suggest 9.5 to get mains at zero)

- recalibrate, but you shouldn't have to change anything except sub

My M&K V-2B sub does the same thing. During very low frequency playback the driver seems to make some kind of rattling/vibrating noise. I'm not positive, but I think it somes from the driver's surround. Its more-or-less undetectable during music playback, but can be quite audible during explosions or the rumbling of spaceship engines and such in movies. I use my setup for music (at least) 95% of the time so I basicly just ignore it