OB Servo Subs & Turntable

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Captainhemo

OB Servo Subs & Turntable
« on: 7 Feb 2017, 11:01 pm »
Has nayone running the  OB servo subs and a turntable run into  low frequency   noise being  passed on to the subs which in turn creates oscilation ?
I know one fellow (OE) who has  similar  issue, he gets around it by turning the subs volume a bit lower while listening to vinyl, he also says using the rumble filter  just  makes it worse.
Is this common with TT's ?  Is there a work around ?

jay

corndog71

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Re: OB Servo Subs & Turntable
« Reply #1 on: 7 Feb 2017, 11:59 pm »
It varies with the record I'm playing.  When it happens I switch the rumble filter on and that usually works for me.  I have my turntable wall mounted which seems to isolate it better than the stands I've tried.

Captainhemo

Re: OB Servo Subs & Turntable
« Reply #2 on: 8 Feb 2017, 02:47 am »
It varies with the record I'm playing.  When it happens I switch the rumble filter on and that usually works for me.  I have my turntable wall mounted which seems to isolate it better than the stands I've tried.

Thanks, I'll pass that on  :thumb:

jay

Danny Richie

Re: OB Servo Subs & Turntable
« Reply #3 on: 8 Feb 2017, 03:05 am »
I have Brian working with me to solve that particular customers issues. Something else is not right on his set up. The rumble filter will pretty much kill any DC issue. So something else is a miss.

Captainhemo

Re: OB Servo Subs & Turntable
« Reply #4 on: 8 Feb 2017, 05:54 am »
Cool, sounds good 

jay

ThePriest

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Re: OB Servo Subs & Turntable
« Reply #5 on: 8 Feb 2017, 12:11 pm »
I have had the same issue, am very careful with volume when I am using my (wall mounted) turntable.
So I too will be happy to hear of improvements.

It really is a tough world: having great sounding bass with excellent frequency extension, thus exciting the oscillation frequency in your beloved turntable  :lol:

Best regards,

The Priest

Shakeydeal

Re: OB Servo Subs & Turntable
« Reply #6 on: 8 Feb 2017, 02:41 pm »
I have a wall mounted TT (Well Tempered Amadeus) and a pair of Super Vs. I have had no issues whatsoever with low frequency oscillation.

Shakey

Danny Richie

Re: OB Servo Subs & Turntable
« Reply #7 on: 8 Feb 2017, 03:03 pm »
Some of those turntables try to pass some really low wavelengths. The rumble filters should handle it all unless there is something else going on. If it is sending an oscillating DC signal then it might be impossible to control. 

Keithh

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Re: OB Servo Subs & Turntable
« Reply #8 on: 8 Feb 2017, 04:33 pm »
Depends on the turntable of me, but I have the 3-8" which are probably much more turntable friendly. The Pro-Ject TT had a lot
of problems with the subs. Herbies feet and  a TT mat helped quite a bit but did not completely eliminate it. Purchased a VPI TT and in
stock condition, with no Herbies, have had no problems.

mlundy57

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Re: OB Servo Subs & Turntable
« Reply #9 on: 8 Feb 2017, 06:07 pm »
I have a Project RPM 3 carbon TT in my system with the dual 12" servo subs. In addition to the rumble filters in the subs my phono preamp also has a rumble filter.

The TT is pretty well isolated. I's on the same equipment stand as all the rest of my audio equipment but I have it triple isolated. On top of the equipment rack I have Herbie's fat dots, a piece of 3/4" MDF is on top of the fat dots. Next comes more fat dots than a 2-1/2" thick piece of maple (woodworking workbench top), more fat dots are placed between the maple and the TT.

Even with all that isolation, I have some older albums that need both rumble filters on. New albums that are in good condition usually don't need the sub's rumble filter.

Mike

bdp24

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Re: OB Servo Subs & Turntable
« Reply #10 on: 8 Feb 2017, 08:06 pm »
It could also be that the sub is making audible what was already there but unheard (because the owners speakers don't reproduce the very low frequencies that the sub does)---the low-frequency resonance created by a mis-match between cartridge compliance and tonearm mass. A cartridge and arm need to be paired such that their combined low-frequency resonance is located between 8-12Hz, 10Hz being optimum. If the cartridges compliance is too high for the effective moving mass of the arm, or conversely the arms emm too low for the cartridges compliance, the resulting resonant frequency of the pairing will be too low, below 8Hz. The lower the frequency, the worse. A very low-frequency resonance can cause tonearm instability, power amp distortion, and woofer pumping.
« Last Edit: 11 Feb 2017, 06:40 pm by bdp24 »

Captainhemo

Re: OB Servo Subs & Turntable
« Reply #11 on: 9 Feb 2017, 04:14 pm »
I'm not TT guy so I don't a whole  lot about his  gear but  I do know it is supposed to be world class and it was all setup by Jeffrey Catalano of High Water Sound so there should not be asetup issue ...
Trying lots of different setting but still  gettng  major oscillation  when turning up  the gain

jay

Danny Richie

Re: OB Servo Subs & Turntable
« Reply #12 on: 9 Feb 2017, 05:02 pm »
Okay, I just went over this with Brian at Rythmik Audio.

The fact that you can turn on the rumble filter and the oscillation gets worse confirms that you have a mechanical feedback issue. It can also be confirmed by moving the woofers further away from the turn table.

Captainhemo

Re: OB Servo Subs & Turntable
« Reply #13 on: 9 Feb 2017, 06:13 pm »
He does have the  subs inboard of his mains,  I'll pas this on to him



jay

tmaslar

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Re: OB Servo Subs & Turntable
« Reply #14 on: 11 Feb 2017, 04:19 pm »
I have the same problem with my Merrill Heirloom table with Morch DP-6 arm and Micro Benz Wood body cartridge. The arm tube used is the one recommended by Morch...So I doubt I would have a mechanical  mismatch. My table is wall mounted on a Target wall mount. The table is located in a stairwell behind the system and behind a door so it is pretty well isolated from the system.

bdp24

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Re: OB Servo Subs & Turntable
« Reply #15 on: 11 Feb 2017, 06:39 pm »
I have the same problem with my Merrill Heirloom table with Morch DP-6 arm and Micro Benz Wood body cartridge. The arm tube used is the one recommended by Morch...So I doubt I would have a mechanical  mismatch. My table is wall mounted on a Target wall mount. The table is located in a stairwell behind the system and behind a door so it is pretty well isolated from the system.

Hmm. The Morch is a very low mass arm, the Benz a rather low compliance cartridge. Have you put the numbers into the resonance calculator on the Vinyl Engine site? It could be that you have a mismatch, the arms low mass and the cartridges low compliance creating a very low frequency resonance.

Skiman

Re: OB Servo Subs & Turntable
« Reply #16 on: 11 Feb 2017, 06:51 pm »
Shouldn't room treatment, in particular corner bass traps help?

tmaslar

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Re: OB Servo Subs & Turntable
« Reply #17 on: 11 Feb 2017, 08:43 pm »
Turns out that engaging the rumble filter does solve my problem. I know that when I purchased the arm tube from Morch the mass of the "Green Dot" arm tube was supposed to be the correct mass arm tube to match the Benz woody according to Morch.

Captainhemo

Re: OB Servo Subs & Turntable
« Reply #18 on: 12 May 2017, 11:57 pm »
hey  folks, just a quick follow up  on  this topic...
After trying  pretty much everything we could think of,   the customer went ahead and  ordered a set of Townshend Isolation Bars for his subs.   Here's  a copy of  his email:
"I just received my Townshend Isolation Bars and stuck them under my subs. My oscillation issue is 100% cured, even at the sub amps full volume! It doesn’t matter if the rumble filter is on or off or where I set the frequency switch or any of the controls. Highly recommended for all those vinyl guys with subs."



jay

bdp24

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Re: OB Servo Subs & Turntable
« Reply #19 on: 13 May 2017, 01:48 am »
A set of the Townshend Seismic Pods (the things bolted onto the ends of the bars pictured above---they are available separately) are at the top of my list of "buy as soon as possible" items. They're not cheap, but they are worth their price. There is a new product that may give them some tough competition, the Isoacoustics Iso-Puck.