[mlundy57]

I had a Basis table that was isolated well I thought. I also had a HSU 12" woofer that wreaked havoc on my room causing feedback and actual skipping. Of course no problem on digital.
It was just overpowering pressurizing the whole space and not a small room, it was far away too. I turned down the Sub all was fine.
What happens when you turn down the Subs? You have 4 big ones there. You could be overloading the space.  A KAB Subsonic filter did not help much. In my case it was all sub.

These subs are open baffle. They don't pressurize the room like a sealed or ported sub does. This system worked perfectly for two months then all of a sudden the problems started.

[bacobits1]

Worked perfectly for a few months.........I don't have an answer for that one.
Turning it down help at all?

[orientalexpress]

i have rumble problem when my turntable is on the stand and i bough one of those wall stand for turntable and the rumble go away.maybe try a better isolate the turntable on the stand with herbie rubber feet kinda help also.good luck,keep us update

[undertow]

This might be a stupid question, however are you using the same test album, and track over and over? Sometimes many of the pressings end up having a lot more subsonic noise than others. I would try a few albums, and simply check your alignment with a protractor, your VTF with a digtal scale to make sure your not way out of whack with the weight range of the sumiko, and the VTA of the cartridge trying to get it as level as possible. It sounds like you may have somewhere lost a little bit of alignment causing a lot more noise to blow thru the cartridge of course amplifying it.

By the way you said you have "Subs" I assume these are active subs separate of your full range speakers. I would shut the subs off just see what happens with the woofers on your standard full range speakers... If they are still huffing, and puffing than you have something going on with the turntable, or feedback of some type, and will need a lot more Isolation of the table which cannot be solved necessarily by Phono amp rumble filters electronically. Acoustic problems are a B*tch with turntables... Another reason to add to the list beyond all the other inconveniences, and cost of analog

Another thing is not 100% sure the pressure effects on the room from "Open Baffle" woofers". Seems this could enhance feedback problems vs. even standard sealed, or ported enclosures.

[stonedeaf]

Ya - double checking the VTF seems like a really good idea.

[*Scotty*]

I suspect that you will have to buy or borrow a Dayton Audio UMM-6 USB mic and download the free REW measurement software and measure how much bass energy you actually have at the turntable location. I suspect that you have acoustic feedback problems rather rumble.
 The situation is weird no matter how you look at it.
Scotty

[mlundy57]

OK, update time

First off , to clarify things a bit I have been using the term subs as shorthand because I haven't come up with an easy way of referring to the bass sections of my speakers, and they do cover the low bass frequencies normally associated with subs. However, they also cover the midbass and upper bass frequencies (14Hz-200Hz). My speakers are full range but each side is comprised of two separate bi-amped units. The upper midrange & treble section is passive and stacks on top of the bass section, which is active. Each bass unit has two 12" GR-Research drivers powered by a Rythmik A370PEQ3 amp. The TT is now where the Marantz AVR and Panamax power conditioner are in the picture.



Now for the TT update:

I took the TT into the local Pro-Ject dealer to check out. It worked fine for him with this caveat, he didn't use my interconnect/ground cable.  He suggested that now that everything had been disconnected to take it back and connect the ground wire first, then reconnect everything else. Just to be safe I used a separate 22ga solid copper wire for the ground. Also, to eliminate any possibility of a bad connection with the spade connector I didn't use one, I wrapped the bare wire around the ground studs at both the TT and the phono amp and securely tightened both ends.

Second, I changed a couple settings on the phono amp (reduced gain to 45dB and capacitance to 47pF).

Finally, since everything was torn down I rebuilt the platform the TT was sitting on. Previously The TT was on a piece of 3/4" MDF that had vibration damping pads between it and the equipment rack. These were not the best pads for this application since they were designed for use with air conditioning units.  Now the platform is two parts with better isolation footers between each one. On top of the equipment shelf I have 9 of Herbie's fat dots. On top of these is the 3/4" MDF shelf. On top of that are four DAMP IT pads I got from the Pro-Ject dealer, a 2" thick piece of birch butcher block forms the top platform. The TT sits on top of the Butcher block. 

Since I did three things at once I can't say for sure how much each contributed to the solution but the end result is that my woofers no longer misbehave. I can crank the volume up to 95dB before they even start to act like they are going to misbehave.

Aaaaahhhhh, music once again 

Mike

[THROWBACK]

It's good to know I'm not the only one who tries three solutions at once. As long as it works, though . . .

[PGS3038]

a quick way to find whether you've got feedback or rumble is to place the stylus onto a non-turning disk, then turn the amp gain up. If it honks, it's feedback.

[bacobits1]

Has to be some kind of room excitement.
Great ya got it fixed.

[mlundy57]

The tech agreed with Scott that it was a grounding issue. Had it been either the platform or the settings the TT would not have worked for two months. That's not to say that building a better isolation platform or changing the settings wasn't a good idea they just weren't the cause of the problem.

The tech said that just redoing the ground will not necessarily solve the problem. I had to unhook everything, including the power supplies then reconnect everything making sure I connected the ground wire first. Like doing a power cycle when you lose your internet connection.

The new isolation set up is significantly superior to the old. With the old setup, footfalls wouldn't bother the TT but if I put a hand on the equipment rack it would effect the playback. Now I would probably have to shove the equipment rack to get a reaction during playback.

To conclude, the actual culprit was the ground and just because the connection feels tight, it doesn't mean you have a good ground connection.

Thanks everybody for your help and suggestions.

Mike

[bacobits1]

"The tech said that just redoing the ground will not necessarily solve the problem. I had to unhook everything, including the power supplies then reconnect everything making sure I connected the ground wire first. Like doing a power cycle when you lose your internet connection."

In 40 years of screwing with this I have never heard of that.

Good for you it's fixed!

Enjoy

[Stercom]

The tech agreed with Scott that it was a grounding issue. Had it been either the platform or the settings the TT would not have worked for two months...,,,

Thanks everybody for your help and suggestions.

Mike