[Captain Humble]

I just moved all of my old albums to a spot where they are readily accessible.  Put on LA LeRoux LP and noticed that the midwoofers on my Odyssey Lorelies were traveling much farther than they travel with CDs at typical SPLs.

I grabbed Heart, Dog and Butterfly, both LP and CD and matched the SPLs and there it is again.  The LP makes the midwoofers travel much further than the CD.  With the CD as a source the midwoofer travel is just about inperceptable but with the LP it travels a bunch.

Does anyone have an explanation for this?  

Thanks.
Jeff

[Marbles]

The woofers are trying to reproduce some low rumble..less than 10 hz notes generally with the turntable.

[Captain Humble]

Marbles,
Is this typical even with high end turntables?

The drivers aren't close to bottoming out, but is it safe to assume that all this extra motion will have a significant impact on the life of the drivers?

My turntable predates the introduction of CDPs.
Technics SL-Q2 direct drive.

Specs for Rumble as follows:
-56 dB (IEC 98A Unweighted)
-78 dB (IEC 98A Weighted)

Are these terrible specs for rumble?

Thanks.

[Marbles]

Marbles,
Is this typical even with high end turntables?

The drivers aren't close to bottoming out, but is it safe to assume that all this extra motion will have a significant impact on the life of the drivers?

My turntable predates the introduction of CDPs.
Technics SL-Q2 direct drive.

Specs for Rumble as follows:
-56 dB (IEC 98A Unweighted)
-78 dB (IEC 98A Weighted)

Are these terrible specs for rumble?

Thanks.

I don't know about the specs, but your assumption is probably correct.  If you look at some late 70 receivers or integrateds you will notice low filters on them.  The rumbling your experiencing is the reason they had them.

If I were you, I would try to isolate your TT better.  You might want to try some panda feet (sorbathane) under the TT.  Maybe some brass cones would work if you have any lying around.

My Teres sits on black diamond racing cones and does not have the problem you are experiencing.

[Carlman]

Marbles,
Is this typical even with high end turntables?

The drivers aren't close to bottoming out, but is it safe to assume that all this extra motion will have a significant impact on the life of the drivers?

Yes, it's typical but can be fixed with isolation/mass loading techniques or a low freq filter cut which I prefer.

To me the detriment is not that it isn't safe or impacts driver life but that it impacts sound quality.  Especially midbass and midrange.  When I apply a filter cut and the cones stop dancing/rumbling, the image becomes much better and the overally accuracy improves a bit.

I also think the amp suffers having to move the cones that much, causing even more muddy bass or lack of detail.

Just my .02

[Captain Humble]

Thanks Gentlemen.

I just tried three Audio Selection cones.  Without pulling the backing off to make them stick, I couldn't balance them by myself so I placed them points up.  No help.  

Unless this is a total misapplication of the cones it might be time to try the low pass filter.

Where do I find one of these things and what frequency should I shoot for?

Thanks,
Jeff

[mcrespo71]

Hi,

Cones or isolation will not help your problem.  You have a mismatch between the mass of your tonearm and the compliance of your cartridge.  The only way to get rid of woofer pump is to change your cartridge or get a subsonic filter.  KABUSA apparently has a good one.  When I had this problem, I used an old audiocontrol eq that had a subsonic filter.  I put the eq in the tape loop and would only use the filter when I needed to.  This is a problem even with very high end TT.  At HE 2004, Jeff Joseph was playing some vinyl on his La Luce TT and there was obvious woofer pump from his speakers.  

Michael

[Wayne1]

The "problem" isn't rumble, which refers to motor or bearing noise. You are seeing a low frequency "noise" caused by slight warps in the vinyl. As your cartridge rides up and down these warps, the mechanical energy is turned into electrical energy.

There is no such thing as perfect vinyl. The amount of content below 12 HZ from surface irregularities is always present..no matter how slight, it is there.

In days gone by, most receivers and preamps had a switchable "subsonic filter" which would eliminate the cones slow movement. The Cornet phono stage, that Marbles and I use, has this "filter" built into it as part of the circuit design.

A subsonic filter at 16HZ 24dB/oct (4th order) should rid your system of cone pumping.

[Captain Humble]

Thanks again guys.

Wayne, do you guys sell these filters?

If not, would you please direct me to someone who does.

I have no idea what these filters look like, or how they are implemented.

Can it be placed between the TT and the amp so that it filters only the signal from the TT?

Thanks,
Jeff

[Wayne1]

I do not sell any filters.

The KAB unit is the only thing I see that is preassembled

http://www.kabusa.com/RF1.HTM

I have never used this and have no experience with it.

Here is a link for a neat looking circuit for a filter.

http://sound.westhost.com/project99.htm

He sells the circuit board alone for a very reasonable price.

This might be the way to go if you are handy at DIY electronics.

He does have a few comments about the KAB unit on that link.

http://www.marchandelec.com/

Marchand Electronics makes an inexpensive 24 db crossover module, the XM-1 that might be able to be used as a subsonic filter. Get in touch with Phil info@marchandelec.com

You might also look into used outboard phono preamps that have a subsonic filter already installed.

[Tonto Yoder]

I'll second Marbles on this one--you may have what's often described as woofer flutter. I've experienced the same thing.  A certain frequency on the LP excites the tonearm/cart which reproduces the frequency which comes back through the speakers which again excites the arm/cart and on and on.

Isolation might help or sometimes just physically moving the TT to another spot helps (that worked for me).

http://db.audioasylum.com/cgi/search.mpl?forum=vinyl&searchtext=woofer+flutter

[Captain Humble]

The Kabusa website describes installation of the KAB RF1 filter as follows:
“Place it in between the phono preamp and control amp or in a process
loop. It requires no attendance. It is happy to remain powered up at all
times.”

I sent an email to To:   INFO@KABUSA.COM
Subject:  Questions regarding KAB RF1

I have 2 systems.
1. A turntable feeding a H/T receiver.
Here it would connect in the tape loop.
2. A turntable feeding a 2 channel preamp that in turn feeds monoblock
    poweramps. (It's actually an Odyssey Dual Mono but I didn't want to   try an explain this configuration.)
          If the 2 channel amp has a tape loop it could go there.
          It can also go in the path from the preamp to the mono blocks.
          Unless the amplifier requires more than say 4 VRMS for full
          power. Most amps need only 2 VRMS or less.

Let me know if you need more info

Kevin

Preserving The Sounds Of A Lifetime
Website http://www.kabusa.com
Phone (908) 754-1479
Fax (908) 222-3442
Mail KAB Electro-Acoustics
P.O.Box 2922
Plainfield, NJ 07062-0922

My two systems are integrated, so naturally I would prefer to connect the TT to my Odyssey Tempest preamp that has a tape loop, H/T pass through and a second set of outputs. If I place the KAB RF1 between the Tempest and the Dual Monos I'll be filtering all sources including H/T, CDP, FM etc. Since I have no issues with any of my other sources I really don't like the idea of filtering them.

The Tempest does have a tape loop but I don't understand how I to hook it up through the tape loop.  
Can anyone explain this configuration please?

I don't see why running a turntable should be so complicated.  I'm leaning toward Tonto Yoder's solution which is to simply move the TT.  Problem is the only other spot I've got for it is my garage.  

Thanks to all of you that responded.
Jeff

[Tonto Yoder]

Tape loops can be labelled differently on different gear, but you basically connect interconnects from a "Tape Out" jack to the inputs of the filter and another interconnect from filter outputs to the "Tape In" or "Tape Monitor" jacks.  You might be able to A/B filter/no-filter by switching from "Source" to "Monitor".  And you could listen to the TT direct when playing LP's that don't cause rumble/flutter/pump/feedback. Of course, when listening to CD's or whatever, you'd use the "Source" setting and the KAB wouldn't be in the circuit.

[Captain Humble]

Thanks Tonto.

So the TT will still plug into the phono in on the Tempest preamp.

The pream tape knob has 2 positions:
Select & Tape

Then I just toggle to engage or disengage the filter?

Thanks again.
Jeff

[Tonto Yoder]

Yeah, the TT still has to go through the preamp for the RIAA equalization (and probably a small amount of amplification/gain). Put the selector on "Phono" and the "Monitor"  knob on "Tape" and you're listening to LP's filtered by the KAB. Selector on "Phono" and "Monitor" on "Select" and you're listening directly to the TT. (I'm not intimately familiar with the Tempest, but I'm pretty sure that's how it'll work).

Hopefully, things will sound pretty identical whether the monitor knob is at "Select" or "Tape" (minus the annoying rumble)

[Captain Humble]

Thanks for the explanation Tonto.

[ginger]

As explained above the cone movement is due to record warp and this can be inferred by the fact that 33 RPM is about 1/2 Hz.

The CORRECT place to tackle this problem is in the phono preamp. Originally RIAA compensation was specified as:
Low Pass Filter with time constant = 75 us (2122Hz)
High Pass Filter with time constant = 318 us (500Hz)
Low Pass Filter with time constant = 3180 us (50Hz)

The culprit here is the 50Hz Low Pass - The gain of the RIAA stage is at absolute maximum below the 50 Hz corner.

That is at low frequencies the gain is at maximum, above 50 Hz the gain rolls off until the 500Hz corner where you get a "shelving" or flattening effect where the 500Hz High Pass conteracts the 50Hz Low Pass. This continues up to 2122Hz where the gain rolls off again due to the low pass filter at that frequency.

To cope with the gain being at maximum below 50 Hz IEC published a modification to the RIAA Specification which added a 20Hz High Pass Filter as well, such that the gain was rolled off below 20Hz. This was precisely to address the problem you have described. Earlier Phono preamps will NOT have this additional filter, any phono preamp post 1990 SHOULD have it and if it doesn't then I would begin to wonder what other defects it might have.

This is what is referred to when you see a phono preamp described as having an "IEC modified RIAA response".

Most phono preamp designs are easily modified to add the extra 20Hz High Pass Filter.

Cheers,
Ginger (Electronic Design Engineer)