2. analog
  3. 159441-46

Sub Sonics and woofer pumping

I have a VPI prime on bear claws sitting on a maple base. Floor is concrete. I use a Nagaoka MP500 cart with going to an ARC PH3se phono pre, then to a Herron 1A preamp. Amp is an ARC Classic 60. Speakers are Thiel CS 2.4’s. 
I get pretty aggressive woofer pumping with vinyl. 
I’ve lubed my bearings on the table.

my alignment is spot on. 
Tracking force at the upper limits of cart. 
I’ve added the 2nd pivot point to the 3D arm. 
I’ve even switched out the counter wt to a much heavier unit and added a comparable head shell weight to change the total mass of arm. To no avail. 
None of these things have had any effect in reducing the pumping. 
I REALLY don’t want to use a rumble filter. 
I’m left with the conclusion that the cart may not be a match for the arm, even after adding all the extra mass. 

Any thoughts or solutions. 
last_lemming
millercarbon's avatar
millercarbon
12,531 posts
 
Never said one word about feedback. Gave you the steps to figure it out. Try it on the floor. Good luck.
mijostyn's avatar
mijostyn
8,570 posts
 
Last lemming, you have several problems culminating in amplification of rumble. The most significant one is that you are using a very stiff cartridge in a uni pivot arm. Your resonance frequency is too high and you are amplifying rumble inherent in records. You will need to add mass to the head shell. In order to determine how much you will need a test record with resonance tracks like the Hi Fi News Analog Test LP. You want to get that resonance frequency down below 10 Hz. Uni pivot arms are a problem because they have a third degree of freedom and a third resonance point, the rotary one. The best way to avoid issues with rotary resonance is to use a compliant cartridge like an Ortofon 2M series cartridge. They run around 20 X 10-6 cm/dyne. The Nagaoka is 8.5 X 10-6 cm/dyne. It is a great cartridge but it was designed for a heavy gimbal arm. I think you can get the rumble down to acceptable levels by tuning the system. If you can't then there are only three solutions, change the cartridge, change the tonearm, get a rumble filter. My preference would be a new arm. The Nagaoka will work perfectly in an Ortofon arm and they are relatively inexpensive. Soundsmith sells a dandy set of graduated head shell screws. Put the heaviest (Stainless) screws on and tell us what happens! 
last_lemming OP
639 posts
 
I changed out my counter wt from 140 gr to 180 and I added a head shell wt, can’t remember the weight but it was about the size of a dime and about as thick as a nickel. 
No change to the woofer pumping. 
I do have the Soundsmith weights, but they are too short to use on the cart. 
erik_squires
16,368 posts
 
Does the pumping happen with the needle still up??
mijostyn's avatar
mijostyn
8,570 posts
 
Last_lemming are the woofers pumping at normal listening levels or just when you turn it up?
The Nagaoka is very stiff and we really do not know where you are.
It would help if you could get the Hi Fi News Test LP. Then we can know for sure. It also is a lot of fun to test other parameters. Very Useful.
Here,  https://www.amazon.com/Tonearm-Headshell-Cartridge-Weights-turntables/dp/B01B8ONJVI and  https://www.amazon.com/Ultimate-Analogue-Test-Lp/dp/B001GBA71Y/ref=asc_df_B001GBA71Y/?tag=hyprod-20&linkCode=df0&hvadid=312149562874&hvpos=&hvnetw=g&hvrand=501746434509243117&h
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