subsonic rumble question

mlundy57 · « **on:** 20 Feb 2016, 02:43 am »

Last night I turned on the turntable for the first time in a couple of weeks and there was a tremendous amount of subsonic rumble. The woofers started going crazy as soon as the needle dropped. This was not happening the last time I listened to the TT.

As a point of reference, these woofers are 12" GR-Research sub drivers (two per channel) designed to play from the low teens up to 200Hz. The plate amps (Rythmik A370PEQ3's, open baffle version) have a rumble filter which I engaged even though it is normally not used for music, only HT. It helped some but the rumble persisted and was audible between tracks.

The rumble is definitely coming from the TT. When I switched to digital via the computer I could play bass augmented tracks at volumes that rattled the windows with zero distortion.

Any ideas what is going on?

Thanks,

Mike

GentleBender · « **Reply #1 on:** 20 Feb 2016, 11:41 am »

I would start with checking the cartridge. Someone may be of more help if you post some details about your turntable setup.

mlundy57 · « **Reply #2 on:** 20 Feb 2016, 12:17 pm »

Thanks.

The TT is a Pro-Ject RPM 3 Carbon with a Sumiko Bluepoint No. 2 cartdridge. I got it this past Christmas. The setup is stock out of he box with the exception of having added a Pro-Ject leather mat.

I have been using the extreme phono solid state system cleaner and a cartdridge brush for cleaning.

Letitroll98 · « **Reply #3 on:** 20 Feb 2016, 12:26 pm »

Rumble comes from the bearings, either platter or tonearm, or the cartridge suspension. I couldn't imagine the bearings going bad since Christmas, do you have another cartridge to try? Is it rumble or hum?

Stercom · « **Reply #4 on:** 20 Feb 2016, 01:04 pm »

Mike - check that your phono ground wire didn't come loose. Scott

Wayner · « **Reply #5 on:** 20 Feb 2016, 03:30 pm »

Rumble can also be transmitted via the drive belt to the platter from the motor.

ACHiPo · « **Reply #6 on:** 20 Feb 2016, 06:17 pm »

Sounds like low frequency feedback, not rumble per se. I had a similar situation when my turntable was closer to my sub, there was a resonance that built up quickly between the low frequency of the LP/cartridge/sub. Turning on the subsonic filter helped, and listening at a lower volume fixed the problem. I haven't experienced it since relocating my turntable away from my speakers/subs.

stonedeaf · « **Reply #7 on:** 21 Feb 2016, 04:08 am »

I bought the predecessor of your table (The Genie 3 ??) -looks pretty much the same -mine had been a severally abused store demo. I've been workin on tables for decades and after about 10 hours into "fixin"this one decided to set it aside for a future effort (maybe never). The motor seems to be the issue - I kept doing circular e-mails with Europe to ca. to mn . e-mail strings trying to get parts and service info. This thing thumps -well above simply rumble levels -unless you cushion the motor pod with something like room temperature freeze packs .That worked (sorta) except that the motor pod had to be outside the ring (NBD) and the location wasn't stable enough -so bass thumping got traded for higher pitched flutter problems. Please understand this is not a slam on Pro-Ject tables ( I have almost no experience with them) - but this one did what the OP is describing.

mlundy57 · « **Reply #8 on:** 21 Feb 2016, 05:03 am »

Quote from: Stercom on 20 Feb 2016, 01:04 pm

Mike - check that your phono ground wire didn't come loose. Scott

Scott,

Checked the ground cable. It was not completely tight at either end and the the connector at the TT was halfway out. I redid the connections at both ends of the ground cable and made sure they were tight.

Quote from: Wayner on 20 Feb 2016, 03:30 pm

Rumble can also be transmitted via the drive belt to the platter from the motor.

Wayner,

Took the belt off, wiped it down and reinstalled it.

Quote from: stonedeaf on 21 Feb 2016, 04:08 am

I bought the predecessor of your table (The Genie 3 ??) -looks pretty much the same -mine had been a severally abused store demo. I've been workin on tables for decades and after about 10 hours into "fixin"this one decided to set it aside for a future effort (maybe never). The motor seems to be the issue - I kept doing circular e-mails with Europe to ca. to mn . e-mail strings trying to get parts and service info. This thing thumps -well above simply rumble levels -unless you cushion the motor pod with something like room temperature freeze packs .That worked (sorta) except that the motor pod had to be outside the ring (NBD) and the location wasn't stable enough -so bass thumping got traded for higher pitched flutter problems. Please understand this is not a slam on Pro-Ject tables ( I have almost no experience with them) - but this one did what the OP is describing.

stonedeaf,

The motor had been bumped and part of it was touching the side of the ring in the plinth (not sure why that ring is there unless it is a placement guide for proper belt tension). While the drive belt was off I re-positioned the motor in the center of the ring so the motor housing was not touching the plinth.

Not sure which one did it or if it was a combination of the three but the bad behavior is gone. I haven't done a full check-out yet because my wife is in bed so I can't crank the volume up real loud. I'll do that final test tomorrow.

Thanks for your help,

Mike

ACHiPo · « **Reply #9 on:** 21 Feb 2016, 07:13 am »

Glad you got it sorted. Happy listening.

mlundy57 · « **Reply #10 on:** 21 Feb 2016, 04:59 pm »

It helped some. The excessive over extension of the drivers is not occurring at normal listening levels but increases as the volume is turned up. At high volumes the cone movement is so bad it literally vibrates the Wedgies (midrange/tweeter modules) off the top of the subs.

Quote from: Letitroll98 on 20 Feb 2016, 12:26 pm

Rumble comes from the bearings, either platter or tonearm, or the cartridge suspension. I couldn't imagine the bearings going bad since Christmas, do you have another cartridge to try? Is it rumble or hum?

Unfortunately, no. The only cartridge I have is the one that came with the TT

Mike

stonedeaf · « **Reply #11 on:** 21 Feb 2016, 05:13 pm »

try putting something soft (really soft) under the motor module and move it off to one side (out of the ring) -frankly as long as you have the proper tension on the belt it will run on speed (sorta) - this will allow you to figure out if the source of this is the motor module or not. I own too many turntables -so my enthusiasm for spending any more time on this problem was limited - but you should be under warranty and if it IS the motor module -send it in for warranty replacement.
But I've got to say that sub-wompers and suspensionless turntable don't strike me as as a match made in heaven.

ACHiPo · « **Reply #12 on:** 21 Feb 2016, 07:18 pm »

Quote from: mlundy57 on 21 Feb 2016, 04:59 pm

It helped some. The excessive over extension of the drivers is not occurring at normal listening levels but increases as the volume is turned up. At high volumes the cone movement is so bad it literally vibrates the Wedgies (midrange/tweeter modules) off the top of the subs.

Unfortunately, no. The only cartridge I have is the one that came with the TT

Mike

The other thing to try is adjusting your subs: frequency roll-off, volume, damping, and placement of the sub(s) to minimize the constructive interference that's causing the problem. If you have or can borrow a mic you can download REW and do it visually, or you can just tweak and observe.

AC

Stercom · « **Reply #13 on:** 21 Feb 2016, 09:37 pm »

Mike - I have a Pro-Ject Extension 10 turntable with a Sumiko Blackbird cartridge. I encountered the exact same problem with the woofers over-extending especially when I turned up the volume. I had recently switched-out my phono interconnects so I assumed that was the problem because the ground wire seemed secure even though I had bumped it while putting in the new interconnects. After much screwing around I finally re-secured the ground cable and it made the subsonic rumble disappear - even at higher volumes. Anyway, I guess I'm simply repeating my previous suggestion but based on my experience I do think that is where the problem is. Scott

stonedeaf · « **Reply #14 on:** 22 Feb 2016, 12:42 am »

I find myself asking this question a lot -BUT-is the rumble/feedback occurring at a volume level that you would actually listen to music at ?

mlundy57 · « **Reply #15 on:** 22 Feb 2016, 04:01 am »

Scott,

I have disconnected and reconnected the interconnects and ground wire at both the TT and phono pre, have switched phono preamps and have installed a new ground cable, all to no avail.

Stonedeaf,

In the small room the TT is currently setup in (10'x13') it is possible to listen to music at a low enough level that the problem doesn't develop. However, in a larger room where more volume is needed that wouldn't be the case.

Also, the bass isn't right. It is no longer full bodied. It somehow sounds off even when the drivers are not going crazy.

The dealer I bought the TT from doesn't do any type of repairs. However, there is another Pro-Ject dealer in town who has somebody who is supposed to be very knowledgeable about them so I will go by and ask if he can take a look at it.

Thanks everybody for all your suggestions. Once I find out what is wrong I'll let you know.

Mike

GentleBender · « **Reply #16 on:** 22 Feb 2016, 10:13 am »

Have you looked closely at the cartridge? Maybe someone inadvertently messed it up while checking out your TT. I was able to save mine during the Christmas holiday when I caught my niece lifting the dust over while reaching for the tonearm. She was curious about it since she had never seen one in person and it gave me a chance to explain a little before the 8 year olds eyes glazed over and lost interest. You could pick up a cheap one from Amazon to test out.

mlundy57 · « **Reply #17 on:** 22 Feb 2016, 03:34 pm »

GentleBender,

I looked as close as I could using magnifying lenses. I couldn't see anything that looked suspicious but then I don't really know what to look for. All I could really tell was that the stylus was clean and everything looked intact but I could have easily overlooked something.

I have taken the TT apart and boxed it up in it's original packaging. I'm hoping to be able to get it to the technician sometime this week.

Mike

bacobits1 · « **Reply #18 on:** 22 Feb 2016, 04:32 pm »

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.

Another thought is that RM9 arm I think it was, I have seen all carbon is super light really hard to hang on to I felt. I didn't care for it.

GentleBender · « **Reply #19 on:** 22 Feb 2016, 04:42 pm »

Sorry to hear you have not found any easy fixes. I don't have any experience with the Pro-ject turntables. I have had a Shure M97xe that I loved, one day it was fine and the next awful. I spend a ton of time recalibrating everything on the TT and couldn't make it sound good again. I put another cartridge on the TT and bam, everything sounded right again.

Try bacobits1's suggestion if you continue to experience problems when your TT is returned. Bacobits1 may be on to something...