Kenwood KD owners - try this

[jjh92]

I am tempted to buy a Kenwood KD-500/600 with the composite base because I read it is extremely good at preventing low frequency resonances.

Kenwood KD owners, try the test described below and let me know the results?

All turntables I have owned (B&O 4002, Yamaha PF800 and Yamaha PX-3) have picked up and transmitted low frequency noise through the speakers when I lightly rap my knuckles on the plinth. Do you get this same effect?

PS -It is most evident if you do it in between songs.

 

[bolly]

my 650 does

 

[jjh92]

Thanks Bolly for the info. I had great hope for them but your feedback will save me from buying a unit only to be dissapointed.

 

[bolly]

and I only tapped very lightly with one finger-tip

 

[ZebraBlvd]

I must be missing something about this exercise, and my apologies if I am. But if the table plays fine without a tap/rap to the plinth, then wouldn't the cure be not to tap/rap on the plinth while in play.

 

[dmagalhaes]

That is a pointless way to evaluate a turntable's vibration reducing properties. I have yet to find a table, including my 75# stacked plywood plinth Rek-O-Kut, that does not transmit noise through the cartridge when you tap on the base even lightly. The bases are designed to eliminate or reduce micro vibrations, not heavy blows. That is why you use a stethoscope.

 

[mfhale]

Thanks Bolly for the info. I had great hope for them but your feedback will save me from buying a unit only to be dissapointed.

I don't know that I'd eliminate a darn fine 'table based on this test. On my own, non-scientific cost vs. pleasure continuum, my 550 rates pretty high.

 

[bikehorn]

That's a weak test of a great turntable. I'm firmly holding on to my KD-550 + Rega RB250 combo until either I get robbed or something super spectacular comes along. I have mine on cone feet and it does a good job of protecting itself from the sound of the garage door opening, footsteps, door closings, things like that. Direct impact is something that will affect any turntable and I am sorry to read that you are going to steer clear of what I think is one of the better buys in fully manual decks with removable armboards...just because of some silly knuckle test.

 

[thedelihaus]

Those bases are a composite of polyester, powdered stone (concrete and granite powder are rumored) and other materals. It's very similar to HBMC (high bulk molded compound) that Sony used.

I find it excellent. But it's not going to prevent a finger tap.

I've yetcto hear any plinth do so.

Corain won't. And Corian has aluminum powder in it.

Aluminum and rubber won't.

Perhaps slate would reduce it, but I doubt eliminate it.


Maybe a table that uses suspension in the coupling of the arm and platter and decoupling of the rest of the plinth may help.

 

[Tedrick]

Dude, the knuckle-rap test is for speakers, not turntables :scratch2:.

Besides, who goes around routinely whacking their turntables with their fist, anyway :scratch2:??

If you don't want that Kenny, send it to me. I'd love to have a second one :yes:.

 

[cgutz]

I just picked up a 550 from the local thrift shop and am evaluating it now. Compared to my old NAD5040 it transmits much less noise.

I am fairly impressed by how accoustically dead it is by comparison. But then, the NAD was hollow plastic!

If I can talk my wife out of $110 bucks I think I am buying it.

 

[jjh92]

Thanks all for the feedback, I'm happy to hear that all your turntables do the same thing as mine. I will now continue happily with my fine Yami PX-3 now that I know all turntables do the same thing.

 

[Nat]

AR used to demonstrate the isolation of the XA by hitting a hammer on the plinth, without the arm skipping. Don't know if it was inaudible, though. But it has been my experience that the AR is way way way way less skip prone than its progeny -- all the suspended subchassis Thorens et al.

 

[jjh92]

It was never a question of skipping, only of low frequency coupling to the pickup. None of my turntables ever skipped with light rapping on the plinth.

 

[Pio1980]

I use this test with a fingertip to determine LF resonance, a "thunk" is OK , "boom" isn't. Bass-note-centered boom really bad. It's likely my out-of-use Mod'ed H-K T-60 with damped suspension would be more immune to the plinth tap-tap resonance test than the solid mount plinth DENON T-T /Souther combo but the D/D/LTA is far more tolerant of VLF floor-borne disturbances. They are simply different approaches.
Understand that the presence of a mounted dust cover will contribute to feedback and resonances in most cases.

 

[jjh92]

Dude, the knuckle-rap test is for speakers, not turntables :scratch2:.

Besides, who goes around routinely whacking their turntables with their fist, anyway :scratch2:??

If you don't want that Kenny, send it to me. I'd love to have a second one :yes:.

My recommeded test was a simple way to see if the turntable is susceptable to airbore acoustic feedback. If the knuckle rap is audible, then why wouldn't airborne acoustic feedback be audible (granted its a matter if degree, the knuckle being much higher level). I'm pursuing fine detail improvements, acoustic feedback can smear low frequency clarity.

 

[thedelihaus]

to the original poster-

AR used to demonstrate the isolation of the XA by hitting a hammer on the plinth, without the arm skipping. Don't know if it was inaudible, though. But it has been my experience that the AR is way way way way less skip prone than its progeny -- all the suspended subchassis Thorens et al.

I still wonder if the suspended chassis models from thorens, Linn, AR and even the new Music Hall dual layer plinths, among others, will isolate the table *regarding the knuckle test*.

Below is a good point however---

I use this test with a fingertip to determine LF resonance, a "thunk" is OK , "boom" isn't. Bass-note-centered boom really bad. It's likely my out-of-use Mod'ed H-K T-60 with damped suspension would be more immune to the plinth tap-tap resonance test than the solid mount plinth DENON T-T /Souther combo but the D/D/LTA is far more tolerant of VLF floor-borne disturbances. They are simply different approaches.
Understand that the presence of a mounted dust cover will contribute to feedback and resonances in most cases.

Excellent points. I agree in theory with the suspended table isolating a finger tap better.

I also understand a thunk (solid) sound is normal, while any "whomp" sound (extended, or boomy, hollow like whacking a big barrel) is a sign of under-damped, poor plinthing.

I don't doubt you on the suspended table transmitting more foot-fall issues, as I have heard it mentioned by others, but it does bewilder me a bit.

 

[Pio1980]

It's suspension tuning, a less than solid floor tends to set the suspended table a-bob in the plinth. The iso-footed heavy plinth with the solid-mounted D-D table doesn't respond so. My Army career travels and the variety of living circumstances with as-it-comes flooring dictated a D/D table with an LT arm, a DENON D-D and Souther SLA-3. This combo proved immune to unstable floors in practice and provided much better-than-acceptable sonic and actual performance.

 

[cgutz]

I lived in old corregated Army barracks while in college at Iowa State - 1970's. We had to hang our TT from the ceiling to keep it from skipping when you walked across the floor. Those were the days....

 

[Slowhead]

The composite surround is not the end all. For those who own the kd5-600 and such with the after market arms, set up properly are nice decks. I had kd 5070 and it was okay, solid runner, but not real quiet and it had the composite deck. One time I opened a 3070 and it has a piece of concrete attached to the top plinth. So, mass isn't everything.