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I get a rattle with movies but not music


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#1 of 5 noDaveu

noDaveu

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Posted February 11 2011 - 05:10 PM

Hey guys, I'm having trouble getting my sub woofer to sound good with movies.  When I play music, the sound is great and the sub woofer thumps and can shake the walls if I turn it up, but at the same or lower volume levels the sub rattles when reproducing bass from movies.  I have tried adjusting settings and just don't have the "know how" for frequencies to get it sound right.


Equipment -


Receiver - Sony STR-DE675

Speakers - (allTechnics) center  - SB-C22 8ohm 160w music / 80w DIN

                                    front     - SB CR33 2 way 8ohm 140w / 70w

                                    rear      - SB S29 8ohm 80w / 40w

Sub woofer -Sony SA-WM20 active sub


I have read and re-read the stereo manual a number of times making sure I have checked all the settings.  And there are a lot of settings, small/large speakers, distance to listener, balance, level, not to mention all the presets for multi-channel surround.


The settings on stereo specifically for the sub are -

1. Sub woofer level (from  -6dB to +6dB)

2. Low Frequency effect - attenuates the level of the channel output from sub without affecting level of bass frequencies sent to sub from front/center/surround channels via the bass redirection circuitry. (from -20dB to 0dB.  At 0dB outputs full LFE signal at mix level recorded)  Selecting off mutes the sound of the LFE channel from the sub.


Two other settings I don't fully understand are Dynamic range compressor which I just have set to OFF, and Front speaker bass adjustment 99Hz to 1.9 kHz which I assume doesn't effect the sub woofer.


The sub woofer itself has three adjustable settings -

1. Phase - Normal / Reverse

2. Cut off Frequency 50Hz / 200Hz

3. Level - Min / Max


I have set the stereo sub level to -6dB and the cut off to 50Hz and turned the level all the way down.  I have tried the other settings without getting + results.  I'm just not sure what to do.  I cannot justify buying a new stereo as this 5.1 is plenty capable for my needs, and I do not want larger speakers.  I'm hoping I don't need a new sub and given the fact that it sounds fine with music I doubt the problem lies with a broken part.


edit - the rattle is deff coming from the sub and nowhere else.  And if it matters, the speakers are wired directly from the stereo and not from stereo to sub to speakers.


Thanks for any help.



#2 of 5 Robert_J

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Posted February 12 2011 - 02:14 AM

Let's get things set up correctly before we try to diagnose the rattle issue.  Try the following:

1.  Turn the cut-off frequency setting on the sub to 200.  This will effectively remove it from the equation and allow your receiver's crossover to handle all of the bass routing.

2.  Set the sub's phase to normal.

3.  Turn the sub setting on the stereo up to 0.

4.  Set your speakers to Small on the receiver.


Calibration.  How did you set the levels for your system?  Please don't tell me that you set them "by ear" because that isn't accurate.  The Radio Shack SPL meter is the least expensive way to get the speaker levels set if your receiver does not have an auto calibration system built in.


In the mean time, set them by ear and see what happens.  Basically by turning down sub's cut-off frequency you were creating a hole in the audio spectrum between 50hz and whatever your receivers crossover frequency was (80 to 120hz).  I don't know why it sounded good with music because you were leaving the best part out.


If you still have a rattle, your sub may be too small to output the frequencies at the SPL you need.



#3 of 5 noDaveu

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Posted February 12 2011 - 06:41 AM

ok, sub is set to 200Hz, phase to normal.  Speakers center, front and rear set to small.  As far as calibration I'm not sure what you mean if other than balance/level.  I just placed the speakers against the wall evenly spaced from the TV pointed straight at the opposing wall, and left balance at zero.  There is a setting for distance to listener that I measured out and set.  Still getting the noise.  Also tried setting all speakers to Micro and it is a little better but the volume is much lower and it doesn't let the front speakers handle any bass at all.


Also I just noticed this, when I turn it on it flashes something about PCM 48, which I googled and there is some info about possibility of compatibility issues with cables.  My sub is connected by a single RCA style cable.  There are no other connections other than the input/output for front speakers.  If I disconnect the single cable and run the front speaker cables to the sub and then out to the speakers, then turn off the sub woofer in the stereo, will I get the bass frequencies to output from the sub?


I looked through the manual to see if I can turn PCM off but it seems as if it is an automatic thing so I can't compare movies with and without it.


Maybe I just need a newer stereo that will configure itself lol!



#4 of 5 Robert_J

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Posted February 12 2011 - 07:47 AM

Calibration is evening out the levels of each speaker and the sub using an SPL meter rather than your ears.  It also means setting the distance from the main listening position (sweet spot) to each speaker.  Before I had a receiver with auto calibration, I would make my wife sit in the best seat and I'd measure from each speaker to her head.


Micro setting keeps all the bass from the speakers and routes it to the sub.


Looking at your owner's manual, PCM 48 is Pulse Code Modulation 48Khz - http://www.docs.sony...se/STRDE675.PDF How is your DVD/BD player set up?  Is it outputting PCM (stereo) or bitstream (raw)?  Bitstream will allow your receiver to decode full surround sound.  Also, how is your player connected to your receiver?



#5 of 5 noDaveu

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Posted February 13 2011 - 05:56 AM

guys thanks for the help, I have tried adjusting everything every which way and I think that maybe the sub just can't handle it.  I bit the bullet and went ahead and purchased a new Polk speaker package that got a lot of good reviews and has smaller front speakers instead of the mismatch I have right now.  I think it is a higher quality system than what I have now, and I will apply what I have learned here to setting up my new system.  Thanks again guys.