Tonearm microphonics

Dear @handymann : I assume that the ARO told you that those subwoofers positions gives you " flat " bass response, rigth?

Now, in any stereo audio system with passive main speakers and powered subwoofers those main speakers must be running as " satellite " ones, this means running from around 80 hz and up and the subwoofers covering from 80 hz and down.

But even that you could have " flat " response at your seat position you need to test the response at TT position that’s where the problem is happening.

You said that you already " play " with different locations for the subs and this subs position is critical when we want that the subs be perfectly integrated to the stereo audio system.
In my case and after more than a year " playing " with the best location in my room/system is both subwoofers rigth in front of the speakers facing each to other ( not facing at seat position. ), are in a " free " space.

Now, the first and main target when we integrated a pair of powered subs in a " passive " system is that IMD/THD goes really down, first at the main speakers and as consequence of that to the whole audio system.
Second target is to improve the quality level reproduction of the bass range ( that’s the foundation of the MUSIC, it’s where MUSIC belongs. Not at the mid-range. ).
Third target is to add a half or one and half bass octave to the audio system.

Main target when subs are integrated in the system is: that we can’t " hear " those subwoofers, that we be aware of only when the recording ask for, this means that the SPL/volume subs set up must be just PERFECT and stay that way always and not be change it by us depending on the recordings we are listening: NO.

In the other side. the THD of your subwoofers is really high when its specs says around 10% at 50hz at 120db, this figure is not a good one. My Velodyne’s has 0.5% not at 50 hz but at 20 hz ! ! ! . Big and critical differences.

Try to make those tests at TT position and that main speakers only handle the frequency range from 80 hz and up, play again with subs position and critical that SPL/volume on those subs that must be fixed.

Regrads and enjoy the MUSIC NOT DISTORTIONS,
R.

Btw, 85 db at seat position is something that when subs are well integrated in the system produce no single problem. I measured SPL at my seat position over 95 dbs with out be awared of problems down there. My TTs are in between the speakers.

Hi Raul:
I have a couple of Wilson Maxx II's.  They're rated @ 20hz, but they don't quite get there.   If I place my subs in front of the speakers, won't that block my main bass?  I have had the subs facing each other before, but they were behind my speakers.  That placed them too close to the corner and overemphasized the bass.  I saw a picture of a guys room and he had his on each side of his listening chair pointed away from him.  I need to build a couple of diaphragmatic absorbers, as well as a couple QRD-13 dispersion panels.  Won't help my current problem, but may help the over all sound.  Do you incorporate these devices?
I have my sub sourced through my tape out on my Calypso preamp and have the subs rolled off around 35hz, so most of the main bass will go through my main speakers.  I kinda like to play with the sub volume, specially on old LP's where they rolled off the bass to high.  I know it's not "real", but still sounds better to me, than the rolled off sound.  When playing quality LP's and the occasional CD, I set the sub volume and leave it.  I was listening to The Thompson Twins "Through The Gap" the other day with my mains turned down low.  I heard some really good low frequency, I hadn't realized was just coming through the subs, so I think I get them matched up pretty well.  It's fun to just listen to the subs sometimes, just to hear things like that.
Sounds like your subs are really good.  Wish I had shopped around more, but mine are OK.  I'm still open to suggestions.  As I said, wish I could find a filter to block everything from around 15hz and down.

Correct me if I'm wrong, I really don't mind. A cartridge doesn't care where it's signal comes from and if any constituent part of a turntable can resonate, it will. Resonance can be either constructive or destructive

@timeltel,  I respectfully ask you to look up the definition of resonance as it relates to vibrations.  It is a condition that increases the amplitude of vibration greatly and as such cannot be constructive.  What's worse is you are using a mechanism where a vibrating stylus is used to reproduce the recorded sound.  If you care at all about accuracy in sound, you do not want a resonance in the audio band. 

Regards, rotarius:

Thanks for the considerate manner of your post. Please consider: "Constructive" and "Desirable" are not necessarily synonyms.

First, neither are resonance or interference technically the same. However, when considering transducers sometimes resonance can generate interference.

Here're a couple of relatively easy to grasp descriptions from:  

Frank Heile, P.h.D. Physics, Stanford University (quote):  
"Resonance is when a driving force is at a frequency that is close to the natural oscillation frequency of a system. This makes the amplitude of the oscillation of the system greatly increase.

Interference is when two waves at similar frequencies are superimposed which results in either constructive interference when the waves are in phase and add together, or destructive interference when the waves are out of phase and interfere with each other."

And:

Bruce Thompson, former Computer programmer at University of California, Berkeley:
"In some systems it makes sense to use either "interference" or "resonance" to describe what is happening. For example in a trumpet, the waves created by the vibration of the player's lips interfere constructively, creating a resonance effect."

 In a paper presented to the AES, Shure technician C. A. Anderson states:
"Resonance exists because the arm and pickup assembly behaves like an effective mass that is coupled to the record groove by means of a stylus assembly with its own mass, compliance, and mechanical resistance".

If a 1kHz signal recorded to vinyl represents a displacement of 80 microns (according to a study by St. Andrews College), it would be difficult to argue that unwanted vibrations of the tonearm have no influence on the signal. The cantilever doesn't discriminate from which end movement originates, sometimes the tail DOES wag the dog.  ;-)  

When a recorded signal matches the natural resonance of our tonearm/cartridge, Mr. Anderson states the recorded signal can be enhanced by 6 to 20 dBl. He doesn't state such but with out of phase  resonances then distortion, diminution or even cancellation of signal at specific frequencies might be anticipated. Resonances can then be considered as constructive or destructive.


Poem.
by Henry Gibson

Her name was Grace, she was one of the best,
Late last night I put her to the test.
She looked so sweet, pretty and slim.
The night was quiet and the lights were dim.
I set everything up as nicely as I could.
I handled her gently for I knew she was good.
She was just one big thrill and the best in the land.
Then she hummed but it was not for joy.
More effective damping was obviously in demand.

Peace,

Sometimes I forget this is not a technical forum.  I realize in the audiophile world things are a bit different from the plain ol' vibrations from electrical and mechanical components I have been dealing with for the last 20 years.  By all means enjoy your constructive resonance.
Cheers.