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Fluttery sub-harmonic tones


hydro_pyro

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My RW-10's exhibit a weird sub-harmonic sound with certain tone bass frequencies. Using Yamaha RX-V577. Some bass tones have a fluttery overtone/undertone sound instead of a deep monotone sound. Is this the product of processing in the receiver LFE channel? Or am I hearing weird phasing issues due to direct/reflected paths to my ears?

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My RW-10's exhibit a weird sub-harmonic sound with certain tone bass frequencies. Using Yamaha RX-V577. Some bass tones have a fluttery overtone/undertone sound instead of a deep monotone sound. Is this the product of processing in the receiver LFE channel? Or am I hearing weird phasing issues due to direct/reflected paths to my ears?

It could be the position of the sub in the room. Try the sub crawl and see if this changes your problem.

 

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Position choices are limited. In the corner behind the couch, the flutters seem worse. In the front row next to my mains, it's a little less, but of course less efficient. And strangely, it sounds thin up there if the phase isn't flipped, which doesn't even make sense.

Even sitting right next to the sub, tone bass sounds like it has an artificial subharmonic.

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It sounds like you are describing room modes. If you are standing in a node, you might precieve a big gain in a certain frequency while possibly a nul in another. Doing the sub crawl would help identify if this is the problem even if you don't intend on making a permanent change in sub position. The best sub in the world will provide the same room modes if that is your problem. 

 

The best fix for reducing room modes is to increase the modal density by adding subs in different locations in the room. The second best fix is to move your sub or move your listening position.

 

PS: Room modes are indeed phase issues, so you are probably right about that. Flipping the phase changes the interaction of overlapping frequencies between your sub and the speakers. There is an overlap!

Edited by mustang guy
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Always done it. Didn't do it any less when I ran multiple subs. Is it possible the Yamaha receiver is adding the fluttery undertones?

Multiple subs in completely different locations of the room or close together? Very different things from a room mode standpoint. The idea is to make the room modes more dense. They will still exist. Stacking subs simply makes the nulls and peaks more pronounced.

 

Somebody who uses a Yammy AVR can chime in about the flutter, but unless there is something wrong with the unit I doubt it.

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Leave the sub in the exact same spot, and move yourself around the room and listen to see if it gets better and worse.  I've spent a few dozen hours on subwoofer placement and tuning lately (2 subs in an L-shape room), and what you describe sounds just like what Mustang is saying.  Room modes in a certain position are causing frequencies to null and peak where you hear "flutter".  Phase is the issue, but phase can be changed through settings or by repositioning the sub or the listening position.  

 

Moving the sub just a bit sometimes changes things a lot.   Try moving it a foot left, right, forward and back, and see if it's the same.  I'd guess one move or the other may shed some light on the room modes.

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I just want the bass tones to sound the way they do on the same audio track on any other system.

This reminds me of the sound effect of a Subharmonic bass "enhancer."

It just occurred to me, the RW8 subwoofer hooked to my dining room speakers on the B speaker channels is fed by a speaker-level signal, and it sounds this way too.

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Does the RW8 sound this way when you connect it to the AVR? From what you are describing now, it sound less like room modes and more like a problem with the AVR, a problem with the sub, or you are just expecting a small sub to sound like a larger one.

 

May I ask what speakers you are using and how large and open the room is?

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Update:

 

I did the sub crawl tonight, and you guys were right.  The room is sick, with nasty phase interference everywhere.  I put the sub in the ideal listening position, and the only suitable placement is entirely unsuitable from a cosmetic standpoint. In the entryway by the front door, or in the entry closet where my wife's shoe rack is sitting. ;)

 

i I moved the sub to a second commonly-used listening position, and there's literally NOWHERE in the room where it doesn't sound fluttery.  In fact, placement anywhere in that part of the room produced nasty results.  Putting the sub next to the front mains causes entire phase cancellation to most bass frequencies, but for some reason sounds stronger with the phase flipped, even though my mains are set to "small" and the sub is acting alone without a stereo helper. That doesn't even make sense. 

 

Heres my my sub in the listening position:

 

169C6462-E0DF-4651-9DC0-3BBDDA635DD2.jpg

 

The entryway area across the opposite side of the room is where the sub sounded strongest and flutter-free while located at the listening position:

 

9D0B7D49-F0B0-43A0-8848-402BA8E50DCD.jpg

 

now what do I do?

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The mains and the sub sounding different with the phase flipped makes perfect sense. The cutoff is not a sheer cliff as some folks think. It is a gradual slope. Here is an example:

 

bSL7Mnu.jpg

 

Everything in the overlap is a potential cancellation (comb filter). When you flip the phase, you "reduce" this filtering...

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The RW8 and RW10 do not fit well behind my couch without moving it far away from the wall.  However, I discovered the RW8 will fit INSIDE the couch's middle section where there isn't a recliner. :)  The cushion doesn't sag as far now, but it sounds great in most listening positions.  This will do for now. :)

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