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patrickm
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Isolating the cause of low frequency problems

My system exhibits two low frequency problems, and I'm not sure what's causing them or who to turn to for assistance. (The setup: Mac Mini > Ayre QB-9 > Bel Canto S300iu > Revel Studio2)

First and foremost, the sound is quite lean, as if there were small monitors instead of full range speakers. I'm not sure if this is an issue with the speakers themselves (they were demos), the room (always an influence, often major), or the amp (great, but underpowered for the application -- I can afford to upgrade in stages only).

In addition, at moderate volumes, test tones (e.g. from Stereophile's Test CD) below 30Hz or so cause an audible rattle from the speakers. I can't hear it while playing music, but this still worries me.

I got these components over time, from different locations, so there's no one dealer in the picture. Should I call a local store and ask them for an in house consulation (for a fee, of course), or look for a repair shop to do the same? Or should I ask some local audiophiles for their thoughts first (for beer/wine/liquor/eternal thanks)? 

tmsorosk
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Go for the beer

I'd start by inviting some audiophile type friends over for a listen. I doubt the problem is your speakers, i've heard the Studio one and two's  many times in many systems and thought they were excellent, thats assuming they are working as designed. I assume you've checked polarity and have moved the speakers into as many different positions as humanly possible. Next I'd try a beefier amp, borrow one from a friend if possible.

geoffkait
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Sounds like the cabinets need

Sounds like the cabinets need to be braced internally.  Most of the energy is being spent rattling the cabinets instead of pushing the woofers. Hence poor bass response.  

 

Geoff Kait

machina dynamica

tmsorosk
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LOL

Geoff thats a good one, still haven't  stop laughing. Maybe you should simply take a look at how the Studio two is constructed. But then you'd have to admit how dumb your comment was, that won't happen.

geoffkait
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Bracing

Well, they are demos.  Things happen.  I once had a new speaker with a similar problem and internal bracing with a custom fitted 2X4 fixed the problem.  Go figure.  

 

gk, machina dynamica

tmsorosk
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Know doubt about it.

Agreed, I've rebraced or gusseted many speakers , but most were pooly designed. I don't think thats the case here. I've spent much time with the Studio and Salon , I've seen both with all drivers and dampening materiel removed, I also own the Salon's and have made some custom mods, but I really don't know how you could improve on there bracing, ( probably do more harm than good trying ). If thats not enough , check out the follow up review in Stereophile's Vol 32 No.12 and JA's measurements. I believe " text book measurements " were John's words.

If you can't trust John , who can you trust?

 

                                                                                                                                             Regards

patrickm
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Update

Thanks all for the replies so far. I have moved the speakers and my ears all around, listened to MATT tests, etc. and am fairly convinced the room is the primary cause of the low frequency distortions.

As for the rattle, both Revel and the dealer from whom I bought them believe there's nothing wrong. Since the rattle comes out primarily around 32Hz and below, which happens to be the Studio2's port tuning frequency, they think I'm simply overdriving the woofers with Stereophile's test CD. (I'm running the Sterephile Test CD and pointing my Radio Shack SPL meter directly at the speakers from a few feet away, and setting the volume to 75-80dB at that position (using the 1kHz test tone from the CD)). JA, who was kind enough to reply to an email of mine, thinks it's likely a warped voice coil hitting the magnet pole piece (and I'm inclined to trust him). I did remove the woofers and take pictures:

https://www.dropbox.com/sh/hv7v8njkul5yrej/5_m1S7U7cb

Thoughts? Also, that beer/wine/liquor offer still stands for anyone in San Francisco...

A few other notes. One: the rattle's worse the longer the speakers have been played. Two: if I'm playing music for the first time in hours (i.e. the system is "cold") and put my ear to the speakers, the rattle is clearly coming from behind the upper woofer, and much more prominently from the left speaker. Three: all four woofers start to exhibit some level of rattle the longer the speakers have been played. Four: Revel and the dealer have been coy about whether they think there's any permanent damage, and while they think that any existing problems would have been my fault, are willing to replace the drivers. I'm not sure what to make of that.

JoeE SP9
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Drivers

Let them replace the drivers!

Bill B
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yeah,

yeah, something is wrong with the speakers, if you are getting rattling with a mere 75-80 dB.  That's not over-driving them at ALL.

mrvco
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Is it still only rattling

Is it still only rattling with the sub-30hz test tones?

patrickm
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Rattle update

Yes, the rattle appears to be coming out only around 30Hz and below. However, I've avoided taking rigorous measurements, since the dealer and Revel warned me that such low frequencies could (they weren't certain) be damaging the driver. Worried about that possibility, I've erred on the side of caution since then and played the low frequency test tones briefly and at low volumes only.

At various points, some music has sounded a bit fuzzy in the bass, though that problem shows up only intermittetantly. 

geoffkait
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Rattling

If the problem is being caused by the (misaligned) voice coil rubbing something wouldn't you hear a scraping type sound coming directly from the woofer?

 

geoff kait

machina dynamica

patrickm
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Apparently there's no issue

The dealer came by my house the other day and listened to the speakers running those low frequency test tones. He suggested then, and apparently confirmed with Revel, that the sound is just air moving in the cabinet. I'm told that below a certain frequency that's bound to happen: the woofer's trying to move more air than the cabinet can handle, and the noise appears to come more from the upper woofer because there's only one (downard facing) port in each speaker.

I'd like to think that's all true, and this was simply a case of me over-reacting. Thanks all for the feedback.

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